áç
XRT72L53
PRELIMINARY
THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
MAY 2001
REV. P1.1.8
GENERAL DESCRIPTION
The XRT72L53, 3 Channel DS3/E3 Framer IC is designed to accept User Data from the Terminal Equipment and insert this data into the Payload bit-fields
within an Outbound DS3/E3 Data Stream. Further,
the Framer IC is also designed to receive an Inbound
DS3/E3 Data Stream (from the Remote Terminal
Equipment) and extract out the User Data.
The XRT72L53 DS3/E3 Framer device is designed to
support full-duplex data flow between Terminal Equipment and an LIU (Line Interface Unit) IC. The Framer
Device will transmit, receive and process data in the
DS3-C-bit Parity, DS3-M13, E3-ITU-T G.751 and E3ITU-T G.832 (November 1995 and October 1998 Revisions) Framing Formats.
The XRT72L53 DS3/E3 Framer IC consists of three
Transmit sections, three Receiver sections, three Performance Monitor Sections and a Microprocessor interface.
the local terminal equipment to receive data from remote terminal equipment.
The Microprocessor Interface is used to configure the
Framer in different operating modes and monitor the
performance of the Framer.
The Performance Monitor Sections consist of a large
number of Reset-upon-Read and Read-Only registers that contain cumulative and One-Second statistics that reflect the performance/health of the three
channels of the Framer IC/system.
FEATURES
• Transmits, Receives and Processes data in the
DS3-C-bit Parity, DS3-M13, E3-ITU-T G.751 and
E3-ITU-T G.832 Framing Formats.
• 3 Channel HDLC Controller - Tx and Rx
• Interfaces to all Popular Microprocessors
• Integrated Framer Performance Monitor
• Available in a 272 Ball PBGA package
The Transmit Sections, include a Transmit Payload
Data Input Interface block, a Transmit Overhead Data
Input Interface block, a Transmit HDLC Controller, a
Transmit DS3/E3 Framer block and a Transmit LIU Interface Block which allows the Terminal Equipment to
transmit data to a remote terminal.
• 3.3V Power Supply, 5V Tolerant I/O
The Receive Sections, consist of a Receive LIU Interface, a Receive DS3/E3 Framer, a Receive HDLC
Controller, a Receive Payload Data Output Interface,
and a Receive Overhead Data Interface which allows
• PCM Test Equipment
• Operating Temperature -40°C to +85°C
APPLICATIONS
• Network Interface Units
• CSU/DSU Equipment.
• Fiber Optic Terminals
• DS3/E3 Frame Relay Equipment
FIGURE 1. BLOCK DIAGRAM OF THE XRT72L53
TestMode
NibbleLnTF
TxOHEnable
TxOHClk
TxOHFrame
TxAISEn
TxOH
TxOHIns
Typical Channel n
Where n = 0, 1 & 2
T3/E3
Transmit
Overhead
Interface
T3/E3
transmit
Input
T3/E3 Transmit
Framer
HDLC
controller
TxLineClk[n:0]
TxPOS[n:0]
TxNEG[n:0]
RxLineClk[n:0]
RxPOS[n:0]
RxNEG[n:0]
ExtLOS
RxOHEnable[n:0]
RxOHClk[n:0]
RxOH[n:0]
RxRed[n:0]
RxOHFrame[n:0]
RxOOF[n:0]
LIU
Interface/
Controller
T3/E3
Receive
Overhead
Interface
T3 FEAC & Data
Link Controller
T3/E3 Receive
Framer
Performance
Monitor
Interrupt
Controller
T3/E3
Receive
Output
uP
Interface
HDLC
controller
TxOHInd[n:0]
TxNibFrame[n:0]
TxFrame[n:0]
TxNibClk[n:0]
TxLnClk[n:0]
TxFrameRef[n:0]
TxNib[n:0]
TxSer[n:0]
A(11:0)
D(7:0)
ALE_AS
WR_R/W
CS
RDY_DTCK
Reset
INT
MOTO
RD_DS
RxClk[n:0]
RxOHind[n:0]
RxFrame[n:0]
RxNib[n:0]
RxSer[n:0]
RxOUTClk[n:0]
Exar Corporation 48720 Kato Road, Fremont CA, 94538 • (510) 668-7000 • FAX (510) 668-7017 • www.exar.com
áç
XRT72L53
THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. P1.1.8
FIGURE 2. PIN OUT OF THE XRT72L53
(See pin list for pin names and function)
Y1
Y
W1
W
V1
V
U1
T1
G
T2
T3
R1
VDD
G
VDD
G
VDD
G
U
T4
T
VDD
VDD
R
P1
P
N1
G
G
M1
L1
L2
L3
K1
G
G
G
G
L4
G
G
G
G
VDD
G
G
G
G
K
G
G
G
G
J
J1
H1
M
VDD
G
L
18
L
19
L
20
G
G1
F1
N
H
G
XRT72L53
VDD
L
VDD
F
E1
E
D1
G
VDD
G
VDD
G
VDD
G
D
C1
C
B1
B
A1
A
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
ORDERING INFORMATION
PART NUMBER
PACKAGE TYPE
OPERATING TEMPERATURE RANGE
XRT72L53
27x27 mm 272 Ball PBGA
-40°C to +85°C
2
áç
XRT72L53
THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. P1.1.7
PIN DESCRIPTIONS
PIN DESCRIPTION NO CONNECTION PINS
PIN #
PIN NAME
TYPE
J18
K1
K2
L2
L4
L19
M2
M4
N2
P1
P4
R1
R2
T2
T4
U1
U2
U7
U16
U18
V2
V3
V4
V5
V8
V9
V10
V11
V12
V13
V14
V15
V18
V19
W7
W14
W17
W18
Y1
Y2
Y3
Y5
Y6
Y8
Y9
Y11
Y12
Y13
Y16
Y17
Y20
NC
NC
NC
NC
NC
NC
NC
NC
NC
NC
NC
NC
NC
NC
NC
NC
NC
NC
NC
NC
NC
NC
NC
NC
NC
NC
NC
NC
NC
NC
NC
NC
NC
NC
NC
NC
NC
NC
NC
NC
NC
NC
NC
NC
NC
NC
NC
NC
NC
NC
NC
*****
DESCRIPTION
No Connection
The pins listed here are not connected in the XRT72L53.
3
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XRT72L53
THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. P1.1.7
PIN DESCRIPTION CONNECTED PINS
PIN #
PIN NAME
TYPE
DESCRIPTION
A1
TxLev[1]
O
Transmit Line Build-Out Enable/Disable Select output pin - Channel 1:
See Description for Pin C3
A2
EncoDis[1]
O
HDB3/B3ZS Encoder Enable/Disable output pin - Channel 1:
See Description for Pin B2
A3
RxOOF[0]
O
Receive Out of Frame Indicator - Channel 0:
The Receive Section of Channel 0, within the XRT72L53 Framer IC will
assert this output signal whenever it has declared an Out of Frame
(OOF) condition with the incoming DS3 or E3 frames. This signal is
negated when the framer correctly locates the framing alignment bits or
bytes and correctly aligns itself with the incoming DS3 or E3 frames.
A4
RxRed[1]
O
Receive Red Alarm Indicator - Channel 1:
See Description for Pin B5
A5
REQ[0]
O
Receive Equalization Enable/Disable Select output pin - Channel 0(to be connected to the DS3/E3 Line Interface Unit IC):
This output pin is intended to be connected to either the REQ, REQDIS
or REQEN input pin of the DS3/E3 LIU. The user can control the state
of this output pin by writing a '0' or '1' to Bit 5 (REQ) within the Line
Interface Driver Register (Address = 0x80).
This output pin permits the user to have control over the state of the
Receive Equalizer block(s) within the corresponding DS3/E3 LIU IC.
Writing a "1" to Bit 5 of the Line Interface Drive Register (Address =
0x80) will cause this output pin to toggle "High". Writing a "0" to this bitfield will cause this output pin to toggle "Low".
NOTE: This output pin can also be used as a “General Purpose Output”
pin.
A6
LLOOP[1]
O
Local Loop-back Output pin - Channel 1 (to be connected to the
LLOOP input pin of the DS3/E3 LIU IC):
See Description for Pin C7
A7
RLOOP[1]
O
Remote Loop-back Output pin - Channel 1 (to be connected to the
RLOOP input pin of the DS3/E3 LIU IC):
See Description for Pin B7
A8
ExtLOS[1]
I
Receive LOS (Loss of Signal) Input - Channel 1:
See Description for Pin D9
A9
RxOHClk[1]/
RxHDLCClk[1]
O
Receive Overhead Data Output Clock signal/Receive HDLC Controller Output Clock signal - Channel 1:
See Description for Pin D12
A10
TxOHClk[1]
O
Transmit Overhead Clock Output - Channel 1:
See Description for Pin A14
A11
TxOHFrame[1]/
TxHDLCClk[1]
O
Transmit Overhead Framing Pulse/Transmit HDLC Controller Output clock signal - Channel 1:
See Description for Pin C13
A12
TxOH[1]/
TxHDLCDat5[1]
I
Transmit Overhead Input pin/Transmit HDLC Controller Data Input
- Bit 5 (Channel 1):
See Description for Pin A15
4
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XRT72L53
THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. P1.1.7
PIN DESCRIPTION CONNECTED PINS
PIN #
PIN NAME
TYPE
DESCRIPTION
A13
RxOHFrame[0]/
O
Receive Overhead Frame Boundary Indicator/Receive HDLC Controller Data Output - Bit 4
The exact functionality of this output pin depends upon whether Channel 0 has been configured to operate in the “High Speed HDLC Controller” Mode, or not.
Non-High Speed HDLC Controller Mode - Receive Overhead Frame
Boundary Indicator:
This output pin pulses "High" whenever the Receive Overhead Data
Output Interface” block outputs the first overhead bit (or nibble) of a new
DS3 or E3 frame.
High Speed HDLC Controller Mode - Receive HDLC Data Output Bit 4:
This pin functions as bit 4, within the byte-wide Receive HDLC Controller output interface (RxHDLCDat[7:0]), whenever Channel 0 has been
configured to operate in the “High Speed HDLC Controller” Mode.
RxHDLCDat4[0]
A14
TxOHClk[0]
O
Transmit Overhead Clock output - Channel 0:
This output signal serves two purposes:
1. The Transmit Overhead Data Input Interface block will provide a rising
clock edge on this signal, one bit-period prior to the start to the instant
that the “Transmit Overhead Data Input Interface” block (associated with
Channel 1) is processing an overhead bit.
2. The Transmit Overhead Data Input Interface will sample the data at
the “TxOH[0]” input pin, on the falling edge of this clock signal (provided
that the “TxOHIns[0]” input pin is “HIGH”).
NOTE: The Transmit Overhead Data Input Interface block will supply a
clock edge for all overhead bits within the DS3 or E3 frame (via the
“TxOHClk[0]” output signal). This includes those overhead bits that the
“Transmit Overhead Data Input Interface” will not accept from the Terminal Equipment.
A15
TxOH[0]/
I
Transmit Overhead Input Pin/Transmit HDLC Controller Data Input
- Bit 5 (Channel 0):
The exact functionality of this input pin depends upon whether Channel
0 has been configured to operate in the “High-Speed HDLC Controller”
Mode, or not.
TxHDLCDat5[0]
Non-High Speed HDLC Controller Mode - Transmit Overhead Input
pin - Channel 0:
The Transmit Overhead Data Input Interface accepts the overhead data
via this input pin, and inserts into the overhead bit position within the
very next outbound DS3 or E3 frame. If the TxOHIns pin is pulled
"High", then the Transmit Overhead Data Input Interface will sample the
data at this input pin (TxOH[0]), on the falling edge of the TxOHClk[0]
output pin. Conversely, if the TxOHIns[0] pin is pulled "Low", then the
Transmit Overhead Data Input Interface will NOT sample the data at this
input pin (TxOH[0]). Consequently, this data will be ignored.
High Speed HDLC Controller Mode - Transmit HDLC Data Input Bit 5:
This pin functions as bit 5, within the byte-wide Transmit HDLC Controller input interface (TxHDLCDat[7:0]), whenever Channel 0 has been
configured to operate in the “High Speed HDLC Controller” Mode.
5
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XRT72L53
THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. P1.1.7
PIN DESCRIPTION CONNECTED PINS
PIN #
PIN NAME
TYPE
DESCRIPTION
A16
TxNib2[1]/
TxHDLCDat2[1]
I
Transmit Nibble-Parallel Data Input - Bit 2/Transmit HDLC Data
Input - Bit 2; Channel 1:
See Description for Pin C20
A17
RxSer[1]/
RxIdle[1]
O
Receive Serial Output/Receive Flag Sequence Indicator - Channel
1:
See Description for Pin F19
A18
TxOHInd[1]/
TxHDLCDat6[1]
O
I
Transmit Overhead Data Indicator output/Transmit HDLC Data
Input - Bit 6; Channel 1:
See Description for Pin E19
A19
RxOHInd[1]
O
Receive Overhead Bit Indicator output - Channel 1:
See Description for Pin G18
A20
RxClk[1]
O
Receive Clock Output signal for Serial and Nibble-Parallel Data
Interface - Channel 1:
See Description for Pin D20
B1
TDI
I
Test Data In:
Boundary Scan Test data input.
B2
EncoDis[0]
O
Encoder (HDB3/B3ZS) Disable Output pin - Channel 0 (intended to
be connected to either the ENCODIS or the ENDECDIS input to the
DS3/E3 Line Interface Unit IC):
This output pin is intended to be connected to either the Encodis or
ENDECDIS input pin of the DS3/E3 Line Interface Unit IC. The user can
control the state of this output pin by writing a "0" or "1" to Bit 3 (Encodis) within the Line Interface Driver Register (Address = 0x80). If the
user commands this signal to toggle "High" then it will disable the B3ZS/
HDB3 encoder circuitry within the DS3/E3 LIU IC. Conversely, if the
user commands this output signal to toggle "Low", then the B3ZS/HDB3
Encoder circuitry, within the DS3/E3 LIU IC will be enabled.
Writing a "1" to Bit 3 of the Line Interface Driver Register (Address =
0x80) will cause this output pin to toggle "High". Writing a "0" to this bitfield will cause this output pin to toggle "Low".
The user is advised to disable the B3ZS/HDB3 encoder (within the DS3/
E3 LIU IC) if Channel 0, within the XRT72L53 Framer IC has been configured to operate in the B3ZS/HDB3 line code.
NOTE: .This output pin can be used as a “General Purpose” Output pin.
B3
RxLOS[1]
O
Receive LOS (Loss of Signal) Indicator Output - Channel 1:
See Description for Pin C4
B4
RxAIS[1]
O
Receive AIS (Alarm Indication Signal) Indicator Output - Channel
1:
See Description for Pin C5
B5
RxRed[0]
O
Receive Red Alarm Indicator Output - Channel 0:
The Framer toggles this output pin “high” to denote that one of the following events has been detected by the Receive Framer block, within
Channel 0:
LOS - Loss of Signal Condition
OOF - Out of Frame Condition
AIS - Alarm Indication Signal Detection
6
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XRT72L53
THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. P1.1.7
PIN DESCRIPTION CONNECTED PINS
PIN #
PIN NAME
TYPE
DESCRIPTION
B6
Req[1]
O
Receive Equalization Enable/Disable Select output pin - Channel 1:
See Description for Pin A5
B7
RLOOP[0]
O
Remote Loopback Output Pin - Channel 0 (to be connected to DS3/
E3 Line Interface Unit IC):
This output pin is intended to be connected to the RLOOP input pin of
the DS3/E3 Line Interface Unit IC. The user can command this signal to
toggle "High" and, in turn, force the DS3/E3 Line Interface Unit IC into
either the Remote or Digital Local- Loopback modes (depending upon
the state of the LLOOP[0] pin. Conversely, the user can command this
signal to toggle "Low" and allow the XRT7300 device to operate in the
normal mode.
Writing a "1" to bit 1 of the Line Interface Drive Register (Address =
0x80) will cause this output pin to toggle "High". Writing a "0" to this bitfield will cause the RLOOP output to toggle "Low".
NOTE: This output pin can be used as a General Purpose Output pin.
B8
RLOL[0]
I
Receive Loss of Lock Indicator input pin - Channel 0 (from the
DS3/E3 Line Interface Unit IC):
This input pin is intended to be connected to the RLOL (Receive Loss of
Lock) output pin of the DS3/E3 Line Interface Unit IC. The user can
monitor the state of this pin by reading the state of Bit 1 (RLOL) within
the Line Interface Scan Register (Address = 0x81).
If this input pin is "Low", then it means that the clock recovery phaselocked-loop circuitry, within the LIU device is properly locked onto the
incoming DS3 E3 data-stream; and is properly recovering clock and
data from this DS3/E3 data-stream. However, if this input pin is "High",
then it means that the phase-locked-loop circuitry, within the LIU device
has lost lock with the incoming DS3 or E3 data-stream, and is not properly recovering clock and data.
If the customer is not using an “Exar XRT73L0X Family of DS3/E3 LIU
ICs, then this input pin can be used for other purposes.
B9
DMO[1]
I
Drive Monitor Output input pin - Channel 1 (from the DS3/E3 LIU
IC):
See Description for Pin C9
B10
RxOH[1]/
RxHDLCDat6[1]
O
Receive Overhead Data Output port/Receive HDLC Data Output Bit 6; Channel 1:
See Description for Pin C12
B11
TxOHIns[1]/
TxHDLCDat4[1]
I
Transmit Overhead Data Insert Input/Transmit HDLC Data Input Bit 4 - Channel 1:
See Description for Pin C14
B12
TxAISEn[1]
I
Transmit AIS Command Input - Channel 1:
See Description for Pin B15
7
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XRT72L53
THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. P1.1.7
PIN DESCRIPTION CONNECTED PINS
PIN #
PIN NAME
TYPE
DESCRIPTION
B13
RxOHEnable[0]/
O
Receive Overhead Enable Indicator/Receive HDLC Controller Data
Output - Bit 5; Channel 0:
The exact functionality of this output pin depends upon whether Channel 0 has been configured to operate in the “High-Speed HDLC Controller” Mode, or not.
Non-High Speed HDLC Controller Mode - Receive Overhead
Enable Indicator - Channel 0:
The XRT72L53 will assert this output signal for one “RxOutClk” period
when it is safe for the Terminal Equipment to sample the data on the
“RxOH” output pin.
High-Speed HDLC Controller Mode - Receive HDLC Controller Data
Ouptut - Bit 5, Channel 0:
This pin functions as bit 5, within the byte-wide Receive HDLC Controller output interface (RxHDLCDat[7:0]), whenever Channel 0 has been
configured to operate in the “High-Speed HDLC Controller” Mode.
RxHDLCDat5[0]
B14
TxOHEnable[0]/
O
I
TxHDLCDat7[0]
Transmit Overhead Input Enable/Transmit HDLC Controller Data
Output - Bit 7; Channel 0:
The exact functionality of this bit-field depends upon whether Channel 0
has been configured to operate in the “High-Speed HDLC Controller”
Mode, or not.
Non-High Speed HDLC Controller Mode - Transmit Overhead Input
Enable Output - Channel 0:
Channel 0, within the XRT72L53 device, will assert this signal, for one
“TxInClk[0]” period, just prior to the instant that the “Transmit Overhead
Data Input Interface” will be sampling and processing an overhead bit.
If the Terminal Equipment intends to insert its own value for an overhead bit, into the outbound DS3 or E3 frame, it is expected to sample
the state of this signal, upon the falling edge of “TxInClk”. Upon sampling the “TxOHEnable” high, the Terminal Equipment should (1) place
the desired value of the overhead bit, onto the “TxOH” input pin and (2)
assert the “TxOHIns” input pin. The Transmit Overhead Data Input Interface” block will sample and latch the data on the “TxOH” signal, upon
the rising edge of the very next “TxInClk” input signal.
High-Speed HDLC Controller Mode - Transmit HDLC Data Input Bit 7; Channel 0:
This pin functions as bit 5, within the byte-wide Transmit HDLC Controller input interface (TxHDLCDat[7:0]), whenever Channel 0 has been
configured to operate in the “High-Speed HDLC Controller” Mode.
B15
TxAISEn[0]
I
Transmit AIS Command Input - Channel 0:
Setting this input pin "High" configures the Transmit Section of Channel
0 to generate and transmit an AIS Pattern.
Setting this input pin "Low" configures the Transmit Section to generate
E3 or DS3 traffic in a normal manner.
B16
TxNib3[1]/
TxHDLCDat3[1]
I
Transmit Nibble-Parallel Payload Data Input - Bit 3/Transmit HDLC
Data Input - Bit 3; Channel 1:
See Description for Pin D19
8
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XRT72L53
THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. P1.1.7
PIN DESCRIPTION CONNECTED PINS
PIN #
PIN NAME
TYPE
DESCRIPTION
B17
TxNibFrame[1]/
ValFCS[1]
O
Transmit Frame Boundary Indicator - Nibble-Parallel Interface/
Transmit HDLC - VALID FRAME CHECK SEQUENCE Indicator Channel 1:
See Description for Pin G17
B18
RxFrame[1]
O
Receive Boundary of DS3 or E3 Frame Output Indicator - Channel
1:
See Description for Pin F20
B19
RxNib0[1]/
RxHDLCDat0[1]
O
Receive Nibble Output - Bit 0/Receive HDLC Data Output - Bit 0;
Channel 1:
See Description for Pin G19
B20
RxNib2[1]/
RxHDLCDat2[1]
O
Receive Nibble Output - Bit 2/Receive HDLC Data Output - Bit 2;
Channel 1:
See Description for Pin H18
C1
TxPOS[0]
O
Transmit Positive Polarity Pulse output - Channel 0:
The exact role of this output pin depends upon whether Channel 0 is
operating in the Single-Rail or Dual-Rail Mode.
Single-Rail Mode:
This output pin functions as the Single-Rail output signal for the outbound DS3 or E3 data stream. The signal, at this output pin, will be
updated on the user-selected edge of the TxLineClk signal.
Dual-Rail Mode:
This output pin functions as one of the two dual rail output signals that
commands the sequence of pulses to be driven on the line. TxNEG[0] is
the other output pin. This input is typically connected to the TPDATA
input of the external DS3 or E3 Line Interface Unit IC. When this output
is asserted, it will command the LIU to generate a positive polarity pulse
on the line
C2
TCK
I
Test Clock:
Boundary Scan clock input.
9
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XRT72L53
THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. P1.1.7
PIN DESCRIPTION CONNECTED PINS
PIN #
PIN NAME
TYPE
DESCRIPTION
C3
TxLev[0]
O
Transmit Line Build-Out Enable/Disable Select Output - Channel 0
(to be connected to the DS3/E3 Line Interface Unit IC):
This output pin is intended to be connected to the TxLev input pin of the
DS3/E3 Line Interface Unit IC. The user can control the state of this output pin by writing a "0" or a "1" to Bit 2 (TxLev) within the Line Interface
Driver Register (Address = 0x80).
Writing a "1" to Bit 2 of the Line Interface Drive Register (Address =
0x80) will cause this output pin to toggle "High". Writing a "0" to this bitfield will cause this output pin to toggle "Low".
For DS3 Application:
If the user commands this signal to toggle "High" then the Transmit Line
Build-Out circuit (within the DS3/E3 LIU device) will be disabled. In this
mode, the LIU device will output unshaped (e.g., square) pulses onto
the line (via the TTIP and TRING output pins).
Conversely, if the user commands this signal to toggle "Low" then the
Transmit Line Build-Out circuit (within the DS3/E3 LIU device) will be
disabled. In this mode, the LIU device will output shaped (e.g., more
rounded) pulses onto the line (via the TTIP and TRING output pins).
In order to comply with the DSX-3 Isolated Pulse Template Requirement
(per Bellcore GR-499-CORE), the user is advised to command this output pin to be "High" if the cable length (between the transmit output of
the XRT7300 device and the DSX-3 Cross-Connect System) is greater
than 225 feet. Conversely, the user is advised to command this output
pin to be "Low" if the cable length (between the transmit output of the
XRT7300 device and the DSX-3Cross Connect System) is less than
225 feet.
For E3 Applications:
This pin can be used as a General Purpose Output pin. The Transmit
Line Build-Out circuitry (within the XRT7300 device) is not active for E3
applications.
C4
RxLOS[0]
O
Receive Loss of Signal Output Indicator - Channel 0:
This pin is asserted when the Receive Section of Channel 0 encounters
a string of 180 consecutive 0's (for DS3 operation) or 32 consecutive 0's
(for E3 operation) via the RxPOS[0] and RxNEG[0] pins.
This pin will be negated once the Receive Section has detected at least
60 pulses within 180 bit-periods (for DS3 operation); or the Receive
Section has detected a string of 32 consecutive bits, that does not contain a string of 4 consecutive "0s" (for E3 operation).
C5
RxAIS[0]
O
Receive Alarm Indication Signal Output pin - Channel 0:
Channel 0 will assert this pin to indicate that the Alarm Indication Signal
(AIS) has been identified in the Receive DS3 or E3 data stream.
For DS3 Applications:
Channel 0 will assert this pin to indicate that the Alarm Indication Signal
(AIS) has been identified in the Receive DS3 data stream. An AIS is
detected if the payload consists of the recurring pattern of 1010... and
this pattern persists for 63 M-frames. An additional requirement for AIS
indication is that the C-bits are set to 0, and the X-bits are set to 1. This
pin will be negated when a sufficient number of frames, not exhibiting
the "1010..." pattern in the payload has been detected.
For E3 Applications:
Channel 0 will declare an AIS condition, if it detects two consecutive E3
frames, each containing 7 or less "0s".
10
áç
XRT72L53
THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. P1.1.7
PIN DESCRIPTION CONNECTED PINS
PIN #
PIN NAME
TYPE
DESCRIPTION
C6
TAOS[0]
O
Transmit All Ones Signal (TAOS) Command Input - Channel 0 (for
the DS3/E3 LIU IC):
This output pin is intended to be connected to the TAOS input pin of the
DS3/E3 Line Interface Unit IC. The user can control the state of this output pin by writing a '0' or '1' to Bit 4 (TAOS) of the Line Interface Drive
Register (Address = 0x80). If the user commands this signal to toggle
"High" then it will force the Line Interface Unit IC to transmit an "All
Ones" pattern onto the line. Conversely, if the user commands this output signal to toggle "Low" then the DS3/E3 Line Interface Unit IC will
proceed to transmit data based upon the pattern that it receives via the
TxPOS[0] and TxNEG[0] output pins.
Writing a "1" to Bit 4 of the Line Interface Drive Register (Address =
0x80) will cause this output pin to toggle "High". Writing a "0" to this bitfield will cause this output pin to toggle "Low".
If the customer is not using an Exar “XRT73L0X Family of DS3/E3 LIU
ICs then this output pin can be used for a variety of other purposes.
C7
LLOOP[0]
O
Local Loopback Output Pin - Channel 0 (to be connected to the
DS3/E3 Line Interface Unit IC):
This output pin is intended to be connected to the LLOOP input pin of
the DS3/E3 LIU IC. The user can command this signal to toggle "High"
and, in turn, force the LIU into the Local Loopback mode.
Writing a "1" to bit 1 of the Line Interface Drive Register (Address =
0x80) will cause this output pin to toggle "High". Writing a "0" to this bitfield will cause the RLOOP output to toggle "Low".
NOTE: This output pin can be used as a General Purpose Output.
C8
RLOL[1]
I
Receive Loss of Lock Indicator input - Channel 1 (from the DS3/E3
LIU IC):
See Description for Pin B8
C9
DMO[0]
I
Drive Monitor Output Input pin - Channel 0 (from the DS3/E3 Line
Interface Unit IC):
This input pin is intended to be tied to the DMO output pin of the DS3/
E3 Line Interface Unit IC. The user can determine the state of this input
pin by reading Bit 2 (DMO) within the Line Interface Scan Register
(Address = 0x81). If this input signal is "High", then it means that the
drive monitor circuitry (within the DS3/E3 Line Interface Unit IC) has not
detected any bipolar signals at the MTIP and MRING inputs within the
last 128 (32 bit-periods. If this input signal is "Low", then it means that
bipolar signals are being detected at the MTIP and MRING input pins of
the DS3/E3 LIU device.
NOTE: This input pin can be used as a General Purpose Input pin.
C10
RxOHFrame[1]/
RxHDLCDat4[1]
O
Receive Overhead Frame Boundary Indicator/Receive HDLC Controller Data Output - Bit 4; Channel 1:
See Description for Pin A13
C11
TxOHEnable[1]/
TxHDLCDat7[1]
O
I
Transmit Overhead Data Input Enable/Transmit HDLC Controller
Data Output - Bit 7; Channel 1:
See Description for Pin B14
11
áç
XRT72L53
THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. P1.1.7
PIN DESCRIPTION CONNECTED PINS
PIN #
PIN NAME
TYPE
DESCRIPTION
C12
RxOH[0]/
O
Receive Overhead Data Output/Receive HDLC Data Output - Bit 6;
Channel 0:
The exact function of this input pin depends upon whether Channel 0
has been configured to operate in the High Speed HDLC Controller
Mode, or not.
Non-High Speed HDLC Controller Mode - Receive Overhead Data
Output - Channel 0:
All overhead bits, which are received via the Receive Section of the
Framer IC; will be output via this output pin, upon the rising edge of
RxOHClk.
High Speed HDLC Controller Mode - Receive HDLC Data Output Bit 6:
This pin functions as bit 6, within the byte-wide Receive HDLC Controller input interface (RxHDLCDat[7:0]), whenever Channel 0 has been
configured to operate in the “High-Speed HDLC Controller” Mode.
O
Transmit Overhead Data Framing Pulse/Transmit HDLC Output
Clock - Channel 0:
The exact function of this input pin depends upon whether Channel 0
has been configured to operate in the High-Speed HDLC Controller
Mode, or not.
Non-High Speed HDLC Controller Mode - Transmit Overhead Data
Framing Pulse:
This output pin pulses "High" when the Transmit Overhead Data Input
Interface block is expecting the first Overhead bit, within a DS3 or E3
frame to be applied to the TxOH input pin.
This pin is "High" for one clock period of TxOHClk.
High-Speed HDLC Controller Mode -Transmit HDLC Output Clock:
This pin functions as a demand and latching clock for the Transmit
HDLC Controller input interface, when Channel 0 has been configured
to operate in the “High-Speed HDLC Controller” Mode.
RxHDLCDat6[0]
C13
TxOHFrame[0]/
TxHDLCClk[0]
12
áç
XRT72L53
THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. P1.1.7
PIN DESCRIPTION CONNECTED PINS
PIN #
PIN NAME
TYPE
DESCRIPTION
C14
TxOHIns[0]/
I
Transmit Overhead Data Insert Input/Transmit HDLC Data Input Bit 4; Channel 0:
The exact functionality of this input pin depends upon whether Channel
0 has been configured to operate in the “High-Speed HDLC Controller”
Mode or not.
Non-High Speed HDLC Controller Mode:
Asserting this input signal (e.g., setting it "High") enables the Transmit
Overhead Data Input Interface (of Channel 0) to accept overhead data
from the Terminal Equipment. In other words, while this input pin is
"High", the Transmit Overhead Data Input Interface will sample the data
at the TxOH[0] input pin, on the falling edge of the TxOHClk[0] output
signal.
Conversely, setting this pin "Low" configures the Transmit Overhead
Data Input Interface to NOT sample (e.g., ignore) the data at the
TxOH[0] input pin, on the falling edge of the TxOHClk[0] output signal.
NOTE: If the Terminal Equipment attempts to insert an overhead bit that
cannot be accepted by the Transmit Overhead Data Input Interface
(e.g., if the Terminal Equipment asserts the TxOHIns signal, at a time
when one of these non-insertable overhead bits are being processed);
that particular insertion effort will be ignored.
High-Speed HDLC Controller Mode - Transmit HDLC Data Input Bit 4; Channel 0:
This pin functions as bit 4, within the byte-wide Transmit HDLC Controller input interface (TxHDLCDat[7:0]), whenever Channel 0 has been
configured to operate in the “High-Speed HDLC Controller Mode.
TxHDLCDat4[0]
C15
TxNib1[1]/
TxHDLCDat1[1]
I
Transmit Nibble-Parallel Payload Data Input - Bit 1/Transmit HDLC
Data Input - Bit 1; Channel 1:
See Description for Pin E17
C16
TxSer[1]/
SndMsg[1]
I
Transmit Serial Payload Data Input/Transmit HDLC Controller SEND MESSAGE input - Channel 1:
See Description for Pin E18
C17
TxFrame[1]
O
Transmit End of DS3 or E3 Frame Indicator - Channel 1:
See Description for Pin E20
C18
RxNib1[1]/
RxHDLCDat[1]
O
Receive Nibble Output - Bit 1/Receive HDLC Data Output - Bit 1;
Channel 1:
See Description for Pin G20
C19
RxNib3[1]/
RxHDLCDat3[1]
O
Receive Nibble Output - Bit 3/Receive HDLC Data Output - Bit 3;
Channel 1:
See Description for Pin H19
13
áç
XRT72L53
THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. P1.1.7
PIN DESCRIPTION CONNECTED PINS
PIN #
PIN NAME
TYPE
DESCRIPTION
C20
TxNib2[0]/
I
Transmit Nibble-Parallel Payload Data Input - Bit 2/Transmit HDLC
Data Input - Bit 2; Channel 0:
The exact function of this input pin depends upon whether Channel 0
has been configured to operate in the “High-Speed HDLC Controller”
Mode, or not.
Non-High Speed HDLC Controller Mode - Transmit Nibble-Parallel
Payload Data Input -Bit 2; Channel 0:
The Terminal Equipment is expected to input data, that is intended to be
transmitted to the remote terminal, over an E3 or DS3 transport
medium. The Framer IC will take data, applied to this pin, and insert it
into an outbound E3 or DS3 frame. The XRT72L53 will sample the data
that is at these input pins, upon the rising edge of the TxNibClk signal.
NOTE: This input pin is active only if the Nibble-Parallel Mode has been
selected.
High Speed HDLC Controller Mode - Transmit HDLC Data Input Bit 2:
This pin functions as bit 2, within the byte-wide Transmit HDLC Controller input interface (TxHDLCDat[7:0]), whenever Channel 0 has been
configured to operate in the “High-Speed HDLC Controller” Mode.
TxHDLCDat2[0]
D1
TxNEG[0]
O
Transmit Negative Polarity Pulse output - Channel 0:
The exact role of this output pin depends upon whether Channel 0 is
operating in the Single-Rail or Dual-Rail Mode.
Single-Rail Mode:
This output signal pulses "High" for one bit period, at the end of each
outbound DS3 or E3 frame. This output signal is kept at a logic "Low" for
all of the remaining bit-periods of the outbound DS3 or E3 frames
Dual-Rail Mode:
This output pin functions as one of the two dual-rail output signals that
commands the sequence of pulses to be driven on the line. TxPOS[0] is
the other output pin. This input is typically connected to the TNDATA
input of the external DS3/E3 Line Interface Unit IC. When this output is
asserted, it will command the LIU to generate a negative polarity pulse
on the line.
D2
TRST
I
JTAG Reset Pin:
Resets Boundary Scan Logic.
NOTE: For normal operation this input pin should be tied “low”.
D3
TMS
I
Test Mode Select: Boundary Scan Mode Select input.
NOTE: For normal operation, this input pin should be tied “low”
D4
GND
****
D5
RxOOF[1]
O
D6
VDD
****
D7
TAOS[1]
O
D8
GND
****
Ground
Receive Out of Frame Indicator - Channel 1:
See Description for Pin A3
Power Supply +3.3v ± 5%
Transmit All Ones Signal (TAOS) Command Input - Channel 1 (fto
be connected to the “TAOS” input of the DS3/E3 LIU IC):
See Description for Pin C6
Ground
14
áç
XRT72L53
THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. P1.1.7
PIN DESCRIPTION CONNECTED PINS
PIN #
PIN NAME
TYPE
DESCRIPTION
D9
ExtLOS[0]
I
Receive LOS (Loss of Signal) Indicator Input - Channel 0 (from the
DS3/E3 LIU IC):
This input pin is intended to be connected to the RLOS (Receive Loss
of Signal) output pin of the DS3/E3 Line Interface Unit IC. The user can
monitor the state of this pin by reading the state of Bit 0 (RLOS0) within
the Line Interface Scan Register (Address = 0x81).
If this input pin is "Low", then it means that the LIU device is currently
NOT declaring an LOS (Loss of Signal) condition. However, if this input
pin is "High", then it means that the LIU device is currently declaring an
LOS (Loss of Signal) condition.
Asserting the RLOS input pin will cause the Receive Section of Channel
0 to declare an LOS (Loss of Signal) condition. Therefore, this input pin
should not be used as a general purpose input.
D10
RxOHEnable[1]/
RxHDLCDat5[1]
O
Receive Overhead Enable Indicator/Receive HDLC Controller Data
Output - Bit 5; Channel 1:
See Description for Pin B13
D11
VDD
****
D12
RxOHClk[0]/
O
Power Supply +3.3v ± 5%
Receive Overhead Output Clock Signal/Receive HDLC Controller
Output Clock - Channel 0:
The exact function of this output pin depends upon whether Channel 0,
within the XRT72L53 device has been configured to operate in the
“High Speed HDLC Controller” Mode, or not.
Non-High Speed HDLC Controller Mode - Receive Overhead Output Clock Signal - Channel 0:
Channel 0, within the XRT72L53 device will output the Overhead bits
(within the incoming DS3 or E3 frames), via the RxOH[0] output pin,
upon the falling edge of this clock signal.
As a consequence, the user's data link equipment should use the rising
edge of this clock signal to sample the data on both the RxOH[0] and
RxOHFrame[0] output pins.
NOTE: This clock signal is always active.
High Speed HDLC Controller Mode - Receive HDLC Output Clock Channel 0:
When the HDLC controller is on, RxHDLCDat is updated by the 72L53
on this clock signal.
RxHDLCClk[0]
D13
GND
****
D14
TxNib0[1]/
TxHDLCDat0[1]
I
D15
VDD
****
D16
TxNIBClk[1]/
SndFCS[1]
O
I
D17
GND
****
Ground
Transmit Nibble-Parallel Payload Data Input - Bit 0/Transmit HDLC
Data Input - Bit 0; Channel 1:
See Description for Pin D18
Power Supply +3.3v ± 5%
Transmit Nibble Clock output signal/Transmit HDLC - SEND Frame
Check Sequence - Channel 1:
See Description for Pin F18
Ground
15
áç
XRT72L53
THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. P1.1.7
PIN DESCRIPTION CONNECTED PINS
PIN #
PIN NAME
TYPE
DESCRIPTION
D18
TxNib0[0]/
I
Transmit Nibble-Parallel Payload Data Input - Bit 0/Transmit HDLC
Data Input - Bit 0; Channel 0:
The exact function of this input pin depends upon whether Channel 0
has been configured to operate in the “High-Speed HDLC Controller”
Mode, or not.
Non-High-Speed HDLC Controller Mode - Transmit Nibble-Parallel
Payload Data Input -Bit 0:
The Terminal Equipment is expected to input data, that is intended to be
transmitted to the remote terminal, over an E3 or DS3 transport
medium. Channel 0 will take data, applied to this pin (along with that
applied to TxNib1[0], TxNib2[0], and TxNib3[0]), and insert it into an
outbound E3 or DS3 frame. Channel 0 will sample the data that is at
these input pins, upon the rising edge of the TxNibClk[0] signal.
NOTE: This input pin is active only if the Nibble-Parallel Mode has been
selected.
High-Speed HDLC Controller Mode - Transmit HDLC Data Input Bit 0:
This pin functions as bit 0, within the byte-wide Transmit HDLC Controller input interface (TxHDLCDat[7:0]), whenever Channel 0 has been
configured to operate in the “High-Speed HDLC Controller” Mode.
I
Transmit Nibble-Parallel Payload Data Input - Bit 3/Transmit HDLC
Data Input - Bit 3; Channel 0:
The exact function of this input pin depends upon whether Channel 0
has been configured to operate in the “High-Speed HDLC Controller”
Mode, or not.
TxHDLCDat0[0]
D19
TxNib3[0]/
TxHDLCDat3[0]
Non-High Speed HDLC Controller Mode - Transmit Nibble Parallel
Payload Data Input - Bit 3; Channel 0:
The Terminal Equipment is expected to input data, that is intended to be
transmitted to the remote terminal, over an E3 or DS3 transport
medium. The Framer IC will take data, applied to this pin (along with
TxNib1, TxNib2, and TxNib3), and insert it into an outbound E3 or DS3
frame. The XRT72L53 will sample the data that is at these input pins,
upon the rising edge of the TxNibClk signal.
NOTE: This input pin is active only if the Nibble-Parallel Mode has been
selected.
High Speed HDLC Controller Mode - Transmit HDLC Data Input Bit 3:
This pin accepts bit 3 TxHDLC data when the HDLC controller is turned
on.
16
áç
XRT72L53
THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. P1.1.7
PIN DESCRIPTION CONNECTED PINS
PIN #
PIN NAME
TYPE
DESCRIPTION
D20
RxClk[0]
O
Receive Clock Output Signal for Serial and Nibble/Parallel Data
Interface - Channel 0:
The exact behavior of this signal depends upon whether the XRT72L53
is operating in the Serial or in the Nibble-Parallel-Mode.
Serial Mode Operation:
In the serial mode, this signal is a 44.736MHz clock output signal (for
DS3 applications) or 34.368MHz clock output signal (for E3 applications). The Receive Payload Data Output Interface will update the data
via the RxSer[0] output pin, upon the rising edge of this clock signal.
The user is advised to design (or configure) the Terminal Equipment to
sample the data on the RxSer[0] pin, upon the falling edge of this clock
signal.
Nibble-Parallel Mode Operation:
In this Nibble-Parallel Mode, Channel 0 will derive this clock signal, from
the RxLineClk[0] signal. Channel 0 will pulse this clock signal 1176
times for each inbound DS3 frame (or 1074 times for each inbound “E3/
ITU-T G.832” frame, or 384 times for each inbound “E3/ITU-T G.751
frame). The Receive Payload Data Output Interface will update the data,
on the RxNib[3:0][0] output pins upon the falling edge of this clock signal.
The user is advised to design (or configure) the Terminal Equipment to
sample the data on the RxNib[3:0][0] output pins, upon the rising edge
of this clock signal
E1
TxFrameRef[0]
I
Transmit Framer Reference Input - Channel 0:
This input pin functions as the Transmit Frame Generation reference
signal, if Channel 0 has been configured to operate in the Local-Time/
Frame Slave Mode. If Channel 0 has been configured to operate in the
Local-Time/Frame-Slave Mode, then the user's terminal equipment is
expected to apply a pulse (to this input pin) once every 106.4 microseconds (for DS3 applications); once every 125 microseconds (for E3, ITUT G.832 applications) or once every 44.7 microseconds (for E3, ITU-T
G.751 applications).
In the Local-Time/Frame-Slave Mode, the Transmit Section of Channel
0 will initiate its generation of a new outbound DS3 or E3 frame, upon
the rising edge of this signal.
NOTE: The user can configure the XRT72L53 Framer IC to operate in
the Local Time/Frame Slave Mode by writing "xxxx xx01" into the
Framer Operating Mode Register (Address = 0x00).
E2
TxLineClk[0]
O
Transmit Line Interface Clock output - Channel 0:
This clock signal is output to the Line Interface Framer, along with the
TxPOS[0] and TxNEG[0] signals. The purpose of this output clock signal is to provide the LIU with timing information that it can use to generate the AMI pulses and deliver them over the transmission medium to
the Remote Terminal Equipment. The user can configure the source of
this clock to be either the RxLineClk[0] (from the Receiver portion of
Channel 0) or the TxInClk[0] input. The nominal frequency of this clock
signal is 34.368 MHz (for E3 applications), or 44.736MHz for DS3 applications.
17
áç
XRT72L53
THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. P1.1.7
PIN DESCRIPTION CONNECTED PINS
PIN #
PIN NAME
TYPE
DESCRIPTION
E3
RxOutClk[0]/
O
Receive Out Clock - Transmit Payload Data Input Interface Clock
for Loop-Timing/Receive HDLC Data - Bit 7; Channel 0:
The exact function of this output pin depends upon whether Channel 0
has been configured to operate in the “High-Speed HDLC Controller”
Mode or not.
Non-High-Speed HDLC Controller Mode - Receive Out Clock Transmit Payload Data Input Interface Clock for Loop-Timing applications - Channel 0:
This clock signal functions as the Terminal Interface clock source, if
Channel 0 is operating in the loop-timing mode.
In this mode, the Transmitting Terminal Equipment is expected to input
data to the Transmit Section of Channel 0, via the “TxSer[0]” input pin,
upon the rising edge of this clock signal. Channel 0 will use the rising
edge of this clock signal to sample the data at the TxSer[0] input.
NOTE: This clock signal is a buffered version of the RxLineClk[0] signal.
Receive HDLC Data Output - Bit 7:
This pin functions as bit 7 within the byte-wide Receive HDLC Controller
output interface (RxHDLCDat[7:0]); whenever Channel 0 has been configured to operate in the “High-Speed HDLC Controller” Mode.
RxHDLCDat7[0]
E4
TDO
O
Test Data Out: Boundary Scan test data output.
E17
TxNib1[0]/
I
Transmit Nibble-Parallel Payload Data Input - Bit 1/Transmit HDLC
Data Input - Bit 2; Channel 0:
The exact function of this input pin depends upon whether Channel 0
has been configured to operate in the “High-Speed HDLC Controller”
Mode, or not.
Non-High Speed HDLC Controller Mode - Transmit Nibble-Parallel
Payload Data Input -Bit 1:
The Terminal Equipment is expected to input data, that is intended to be
transmitted to the remote terminal, over an E3 or DS3 transport
medium, to this input pin. The Framer IC will take data, applied to this
pin, and insert it into an outbound E3 or DS3 frame. The Transmit Section of Channel 0 will sample the data that is at these input pins, upon
the rising edge of the TxNibClk[0] signal.
NOTE: This input pin is active only if the Nibble-Parallel Mode has been
selected.
Transmit HDLC Data Input - Bit 1:
This pin functions as bit 1 within the byte-wide Transmit HDLC Controller input interface (TxHDLCDat[7:0]); whenever Channel 0 has been
configured to operate in the “High-Speed HDLC Controller” Mode.
TxHDLCDat1[0]
18
áç
XRT72L53
THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. P1.1.7
PIN DESCRIPTION CONNECTED PINS
PIN #
PIN NAME
TYPE
DESCRIPTION
E18
TxSer[0]/
I
Transmit Serial Payload Data Input pin/Transmit HDLC Controller SEND MESSAGE Input pin - Channel 0:
The exact function of this input pin depends upon whether Channel 0
has been configured to operate in the “High-Speed HDLC Controller”
Mode or not.
Non-High-Speed HDLC Controller Mode - Transmit Serial Payload
Data Input Pin - Channel 0:
The Terminal Equipment is expected to input data, that is intended to be
transmitted to the remote terminal, over an E3 or DS3 transport
medium, to this input pin. The Transmit Section of Channel 0 will take
data, applied to this pin, and insert it into an outbound E3 or DS3 frame.
If Channel 0 has been configured to operate in the Local Time Mode,
then it will sample the data (on this pin) upon the rising edge of TxInClk[0]. If Channel 0 has been configured to operate in the Loop-Time
Mode, then it will sample the data (on this pin) upon the rising edge of
RxOutClk[0].
NOTE: This input pin is active only if the Serial Mode has been selected.
High-Speed HDLC Controller Mode - Transmit HDLC SEND MESSAGE Input - Channel 0:
The Terminal Equipment is expected to pull this input pin high during
the entire duration of the HDLC packet (including FCS bytes) to be
transmitted, when the HDLC controller is turned on.
O
Transmit Overhead Data Indicator Output/Transmit HDLC Data
Input - 6:
The exact function of this pin depends upon whether Channel0 has
been configured to operate in the “High-Speed HDLC Controller” Mode,
or not.
Non-High-Speed HDLC Controller Mode -Transmit Overhead Data
Indicator Output - Channel 0:
This output pin will pulse "High" one-bit period prior to the time that the
Transmit Section of Channel 0 will be processing an Overhead bit. The
purpose of this output pin is to warn the Terminal Equipment that, during the very next bit-period, Channel 0 is going to be processing an
Overhead bit and will be ignoring any data that is applied to the
TxSer[0] input pin.
NOTE: For DS3 applications, this output pin is only active if Channel 0 is
operating in the Serial Mode. This output pin will be pulled "Low" if
Channel 0 is operating in the Nibble-Parallel Mode.
Transmit HDLC Data Input - Bit 6:
This input pin functions as bit 6, within the byte-wide Transmit HDLC
Controller Input interface (TxHDLCDat[7:0]), whenever Channel 0 has
been configured to operate in the “High-Speed HDLC Controller” Mode.
SndMsg[0]
E19
TxOHInd[0]/
I
TxHDLCDat6[0]
E20
TxFrame[0]
O
Transmit End of DS3 or E3 Frame Indicator - Channel 0:
The Transmit Section of Channel 0 will pulse this output pin "High" (for
one bit-period), when the Transmit Payload Data Input Interface is processing the last bit of a given DS3 or E3 frame.
The purpose of this output pin is to alert the Terminal Equipment that it
needs to begin transmission of a new DS3 or E3 frame to Channel 0
(e.g., to permit Channel 0, within the XRT72L53 device to maintain
Transmit DS3/E3 framing alignment control over the Terminal Equipment).
19
áç
XRT72L53
THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. P1.1.7
PIN DESCRIPTION CONNECTED PINS
PIN #
PIN NAME
TYPE
DESCRIPTION
F1
RxLineClk[0]
I
Receiver LIU (Recovered) Clock Input - Channel 0:
This input signal serves three purposes:
1. The Receive Section of Channel 0 uses it to sample and latch the
signals at the RxPOS[0] and RxNEG[0] input pins (into the Receive
Framer circuitry).
2. This input signal functions as the timing reference for the Receive
Framer block, within Channel 0.
3. The Transmit Framer block (within Channel 0) can be configured to
use this input signal as its timing reference.
This signal is the recovered clock from the external DS3/E3 LIU (Line
Interface Unit) IC, which is derived from the incoming DS3/E3 data.
F2
RxPOS[0]
I
Receive Positive Data Input - Channel 0:
The exact role of this input pin depends upon whether Channel 0 is
operating in the Single-Rail or Dual-Rail Mode.
Single-Rail Mode:
This input pin functions as the Single-Rail input for the incoming E3 data
stream. The signal at this input pin will be sampled and latched (into the
Receive DS3/E3 Framer block within Channel 0) on the user-selected
edge of the RxLineClk[0] signal.
Dual-Rail Mode:
This input functions as one of the dual rail inputs for the incoming AMI/
HDB3/B3ZS encoded DS3 or E3 data that has been received from an
external Line Interface Unit (LIU) IC. RxNEG[0] functions as the other
dual rail input for the channel. When this input pin is asserted, it means
that the LIU has received a positive polarity pulse from the line.
F3
RxNEG[0]
I
Receive Negative Data Input - Channel 0:
The exact role of this input pin depends upon whether Channel 0 is
operating in the Single-Rail or Dual-Rail Mode.
Single-Rail Mode:
This input pin is inactive, and should be pulled “low” when Channel 0 is
operating in the Single-Rail Mode.
Dual-Rail Mode:
This input pin functions as one of the dual rail inputs for the incoming
AMI/HDB3/B3ZS encoded DS3 or E3 data that has been received from
an external Line Interface Unit (LIU) IC. RxPOS[0] functions as the
other dual rail input for the Channel. When this input pin is asserted, it
means that the LIU has received a negative polarity pulse from the line.
F4
VDD
****
Power Supply +3.3v ± 5%
F17
VDD
****
Power Supply +3.3v ± 5%
20
áç
XRT72L53
THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. P1.1.7
PIN DESCRIPTION CONNECTED PINS
PIN #
PIN NAME
TYPE
DESCRIPTION
F18
TxNIBClk[0]/
O
SndFCS[0]
I
Transmit Nibble Clock Output Signal/Transmit HDLC - SEND
FRAME CHECK SEQUENCE Input - Channel 0:
The exact function of this input pin depends upon whether Channel 0
has been configured to operate in the “High-Speed HDLC Controller”
Mode, or not.
Non-High Speed HDLC Controller Mode - Transmit Nibble Clock
output signal - Channel 0:
If the user opts to operate Channel 0 in the “Nibble-Parallel” mode, then
the XRT72L53 Framer IC will derive this clock signal from either the
“TxInClk[0]” or the “RxLineClk[0]” signal (depending upon which signal
is selected as the timing reference).
The user is advised to configure the Terminal Equipment to output the
“outbound” payload data (to the XRT72L53 Framer IC) onto the
“TxNib[3:0][0]” input pins, upon the rising edge of this clock signal.
NOTES:
1. For DS3 applications, the XRT72L53 Framer IC will output 1176
clock edges (to the Terminal Equipment) for each “outbound”
DS3 frame.
2. For E3, ITU-T G.832 applications, the XRT72L53 Framer IC will
output 1074 clock edges (to the Terminal Equipment) for each
“outbound” E3 frame.
3. For E3, ITU-T G.751 applications, the XRT72L53 Framer IC will
output 384 clock edges (fo the Terminal Equipment) for each
“outbound” E3 frame.
High-Speed HDLC Controller Mode - SEND FRAME CHECK
SEQUENCE Input - Channel 0:
The Terminal Equipment is expected to pull this input pin “High” whenever the “FCS bytes” are being transmitted, after transmitting a valid
HDLC message.
RxSer[0]/
O
F19
RxIdle[0]
Receive Serial Output/Receive Flag Sequence Output - Channel 0
The exact function of this output pin depends upon whether Channel 0
is operating in the “High-Speed HDLC Controller” Mode, or not.
Non High Speed HDLC Controller Mode - Channel 0:
If the user opts to operate Channel 0 in the serial mode, then the chip
will output the payload data, of the incoming DS3 or E3 frames, via this
pin. Channel 0 will output this data upon the rising edge of RxClk[0].
The user is advised to design the Terminal Equipment such that it will
sample this data on the falling edge of RxClk[0].
NOTE: This signal is only active if the NibInt input pin is pulled "Low".
High Speed HDLC Controller Mode - Receive Flag Sequence Indicator - Channel 0:
This pin will go high indicating the idle period of sent HDLC data packets. Also, in combination with ValFCS[0] it can indicate error conditions.
21
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XRT72L53
THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. P1.1.7
PIN DESCRIPTION CONNECTED PINS
PIN #
PIN NAME
TYPE
DESCRIPTION
F20
RxFrame[0]
O
Receive Boundary of DS3 or E3 Frame Output Indicator - Channel
0:
The exact functionality of this output pin depends upon whether Channel 0 is operating in the “Serial” or “Nibble-Parallel” Mode.
Serial Mode Operation:
The Receive Section of Channel 0 will pulse this output pin “high” (for
one bit-period) when the “Receive Payload Data Output Interface” block
is driving the very first bit of a given DS3 or E3 frame, onto the
“RxSer[0]” output pin.
Nibble-Parallel Operation:
The Receive Section of Channel 0 will pulse this output pin “high” (for
one nibble-period), when the “Receive Payload Data Output Interface”
block is driving the very first nibble of a given DS3 or E3 frame, onto the
“RxNib[3:0][0] output pins.
G1
TxInClk[1]
I
Transmit Framer Reference Clock Input - Channel 1:
See Description for Pin G4
G2
RxNEG[1]
I
Receive Negative Data Input - Channel 1:
See Description for Pin F3
G3
TxFrameRef[1]
I
Transmit Framer Reference Input - Channel 1:
See Description for Pin E1
G4
TxInClk[0]
I
Transmit Framer Reference Clock Input - Channel 0:
This input pin functions as the Timing Reference for the Transmit Section of Channel 0, within the XRT72L53 Framer IC; if the device has
been configured to operate in the Local-Time Mode. Further, if Channel
0 has been configured to operate in the Local-Time Mode, the Transmit
Payload Data Input Interface will sample the data at the TxSer[0] input
pin, upon the rising edge of TxInClk[0].
For E3 applications, the user should apply a 34.368MHz clock signal to
this input. Likewise, for DS3 applications, the user should apply a
44.736MHz clock signal to this input pin.
Channel 0, within the XRT72L53 Framer IC can be configured to operate in the Local-Time mode by writing "xxxx xx01" or "xxxx xx1x" into
the Framer Operating Mode register (Address = 0x00)
22
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XRT72L53
THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. P1.1.7
PIN DESCRIPTION CONNECTED PINS
PIN #
PIN NAME
TYPE
DESCRIPTION
G17
TxNibFrame[0]/
O
Transmit Frame Boundary Indicator - Nibble-Parallel Interface/
Transmit HDLC Controller - VALID FRAME CHECK SEQUENCE output - Channel 0:
The exact function of this input pin depends upon whether Channel 0
has been configured to operate in the “High-Speed HDLC Controller”
Mode or not.
Non-High-Speed HDLC Controller Mode - Transmit Frame Boundary Indicator - Nibble/Parallel Interface:
This output pin pulses "High" when the last nibble of a given DS3 or E3
frame is expected at the TxNib[3:0][0] input pins.
The purpose of this output pin is to alert the Terminal Equipment that it
needs to begin transmission of a new DS3 or E3 frame to the
XRT72L53 device.
Transmit HDLC - VALID FRAME CHECK SEQUENCE output - Channel 0:
When the HDLC is on, this pin will pulse high, as it completes its reception of an HDLC frames, in order denote reception of an HDLC frame
with a “VALID” FCS value.
O
Receive Overhead Bit Indicator - Channel 0:
The exact functionality of this output pin depends upon whether the
XRT72L53 Framer IC is operating in the “Serial” or “Nibble-Parallel”
Mode.
Serial Mode Operation:
ValFCS[0]
G18
RxOHInd[0]
This output pin pulses "High" (for one bit-period) whenever an overhead
bit is being output via the RxSer output pin, by the Receive Payload
Data Output Interface block.
Nibble-Parallel Mode Operation:
This output pin pulses “high” (for one nibble-period) whenever an “overhead” nibble is being output via the “RxNib[3:0] output pins, by the
“Receive Payload Data Output Interface” block.
NOTE: The purpose of this output pin is to alert the Receive Terminal
Equipment that an overhead bit is being output via the RxSer output pin,
and that this data should be ignored.
23
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XRT72L53
THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. P1.1.7
PIN DESCRIPTION CONNECTED PINS
PIN #
PIN NAME
TYPE
DESCRIPTION
G19
RxNib0[0]/
O
Receive Nibble Output - Bit 0/Receive HDLC Data - Bit 0, Channel
0:
The exact function of this input pin depends upon whether Channel 0 is
operating in the “High-Speed HDLC Controller” Mode, or not.
Non-High Speed HDLC Controller Mode - Receive Nibble Output Bit 0:
The Receive Section of Channel 0 will output Received data (from the
Remote Terminal) to the local Terminal Equipment via this pin along
with RxNib1[0], RxNib2[0] and RxNib3[0].
The data at this pin is updated on the rising edge of the RxClk[0] output
signal.
NOTE: This output pin is active only if the Nibble-Parallel Mode has
been selected.
Receive HDLC Data Output - Bit 0:
This output pin functions as Bit 0 (the LSB) within the byte-wide Receive
HDLC Controller output interface (RxHDLCDat[7:0]), whenever Channel
0 has been configured to operate in the “High-Speed HDLC Controller”
Mode.
RxHDLCDat0[0]
G20
RxNib1[0]/
O
Receive Nibble Output - Bit 1/Receive HDLC Data - Bit 1; Channel
0:
The exact function of this input pin depends upon whether Channel 0 is
operating in the “High-Speed HDLC Controller” Mode, or not.
Non-High-Speed HDLC Controller Mode - Receive Nibble Output Bit 1:
The Receive Section of Channel 0 will output Received data (from the
Remote Terminal) to the local Terminal Equipment via this pin along
with RxNib0[0], RxNib2[0] and RxNib3[0].
The data at this pin is updated on the rising edge of the RxClk[0] output
signal.
NOTE: This output pin is active only if the Nibble-Parallel Mode has
been selected.
Receive HDLC Data Output - Bit 1:
This output pin functions as Bit 1 within the byte-wide Receive HDLC
Controller output interface (RxHDLCDat[7:0]), whenever Channel 0 has
been configured to operate in the “High-Speed HDLC Controller” Mode.
RxHDLCDat1[0]
H1
TxLineClk[1]
O
Transmit Line Interface Clock output - Channel 1:
See Description for Pin E2
H2
RxLineClk[1]
I
Receiver LIU (Recovered) Clock input - Channel 1:
See Description for Pin F1
H3
RxPOS[1]
I
Receive Positive Data Input - Channel 1:
See Description for Pin F2
H4
GND
****
Ground
H17
GND
****
Ground
24
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XRT72L53
THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. P1.1.7
PIN DESCRIPTION CONNECTED PINS
PIN #
PIN NAME
TYPE
DESCRIPTION
H18
RxNib2[0]/
O
Receive Nibble Output - Bit 2/Receive HDLC Data Output - Bit 2;
Channel 0:
The exact function of this bit-field depends upon whether Channel 0 has
been configured to operate in the “High-Speed HDLC Controller” Mode,
or not.
Non-High-Speed HDLC Controller Mode - Receive Nibble Output Bit 2:
The Receive Section of Channel 0 will output Received data (from the
Remote Terminal) to the local Terminal Equipment via this pin along
with RxNib0[0], RxNib1[0] and RxNib2[0].
The data at this pin is updated on the rising edge of the RxClk[0] output
signal.
NOTE: This output pin is active only if the Nibble-Parallel Mode has
been selected.
High-Speed HDLC Controller Mode - Receive HDLC Data Output Bit 2:
This pin functions as bit 2, within the byte-wide Receive HDLC Controller output interface (RxHDLCDat[7:0]) whenever Channel 0 has been
configured to operate in the “High-Speed HDLC Controller” Mode.
RxHDLCDat2[0]
H19
RxNib3[0]/
O
Receive Nibble Output - Bit 2/Receive HDLC Data Output - Bit 3;
Channel 0:
The exact function of this bit-field depends upon whether Channel 0 has
been configured to operate in the “High-Speed HDLC Controller” Mode,
or not.
Non-High-Speed HDLC Controller Mode - Receive Nibble Output Bit 3:
The Receive Section of Channel 0 will output Received data (from the
Remote Terminal) to the local Terminal Equipment via this pin along
with RxNib0[0], RxNib1[0] and RxNib2[0].
The data at this pin is updated on the rising edge of the RxClk[0] output
signal.
NOTE: This output pin is active only if the Nibble-Parallel Mode has
been selected.
High-Speed HDLC Controller Mode - Receive HDLC Data Output Bit 3:
This pin functions as bit 3, within the byte-wide Receive HDLC Controller output interface (RxHDLCDat[7:0]) whenever Channel 0 has been
configured to operate in the “High-Speed HDLC Controller” Mode.
RxHDLCDat3[0]
H20
Int
O
Interrupt Request Output:
This open-drain, active-low output signal will be asserted when the
Framer device is requesting interrupt service from the local microprocessor. This output pin should typically be connected to the Interrupt
Request input of the local microprocessor.
J1
TxFrameRef[2]
I
Transmit Framer Reference Input - Channel 1:
See Description for Pin E1
25
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XRT72L53
THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. P1.1.7
PIN DESCRIPTION CONNECTED PINS
PIN #
PIN NAME
TYPE
DESCRIPTION
J2
RxOutClk[1]/
RxHDLCDat7[1]
O
Receive Out Clock - Transmit Payload Data Input Interface Clock
for Loop-Timing/Receive HDLC Data Output Bit 7 - Channel 1:
See Description for Pin E3
J3
TxNEG[1]
O
Transmit Negative Polarity Pulse input - Channel 1:
See Description for Pin D1
J4
TxPOS[1]
O
Transmit Positive Polarity Pulse Input - Channel 1:
See Description for Pin C1
J9
GND
****
Ground
J10
GND
****
Ground
J11
GND
****
Ground
J12
GND
****
Ground
J17
Rdy_Dtck
O
READY or DTACK:
This active-low output pin will function as the READY output, when the
microprocessor interface is running in the Intel Mode; and will function
as the DTACK output, when the microprocessor interface is running in
the Motorola Mode.
Intel Mode - READY Output:
When the Framer negates this output pin (e.g., toggles it "Low"), it indicates (to the µP) that the current READ or WRITE cycle is to be
extended until this signal is asserted (e.g., toggled "High").
Motorola Mode - DTACK (Data Transfer Acknowledge) Output:
The Framer device will assert this pin in order to inform the local microprocessor that the present READ or WRITE cycle is nearly complete. If
the Framer device requires that the current READ or WRITE cycle be
extended, then the Framer will delay its assertion of this signal. The
68000 family of µPs requires this signal from its peripheral devices, in
order to quickly and properly complete a READ or WRITE cycle.
J19
D[7]
I/O
MSB of Bi-Directional Data Bus (Microprocessor Interface Section):
This pin, along with pins D0 - D6, function as the Microprocessor Interface bi-directional data bus, and is intended to be interfaced to the local
microprocessor.
J20
D[6]
I/O
See Description for Pin J19
K3
RxNEG[2]
I
K4
VDD
****
Power Supply +3.3v ± 5%
K9
GND
****
Ground
K10
GND
****
Ground
K11
GND
****
Ground
K12
GND
****
Ground
K17
D[5]
I/O
Bi-Directional Data Bus pin:
See Description for Pin J19
Receive Negative Data Input - Channel 2:
See Description for Pin F3
26
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XRT72L53
THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. P1.1.7
PIN DESCRIPTION CONNECTED PINS
PIN #
PIN NAME
TYPE
DESCRIPTION
K18
D[4]
I/O
Bi-Directional Data Bus pin:
See Description for Pin J19
K19
D[3]
I/O
Bi-Directional Data Bus pin:
See Description for Pin J19
K20
D[2]
I/O
Bi-Directional Data Bus pin:
See Description for Pin J19
L1
TxInClk[2]
I
Transmit Framer Reference Clock Input - Channel 2:
See Description for Pin G4
L3
RxPOS[2]
I
Receive Positive Data Input - Channel 2:
See Description for Pin F2
L9
GND
****
Ground
L10
GND
****
Ground
L11
GND
****
Ground
L12
GND
****
Ground
L17
VDD
****
Power Supply +3.3v ± 5%
L18
D[0]
I/O
LSB of Bi-Directional Data Bus pins:
See Description for Pin J19
L20
D[1]
I/O
Bi-Directional Data Bus pin:
See Description for Pin J19
M1
RxLineClk[2]
I
Receive (Recovered) LIU Clock signal - Channel 2:
See Description for Pin F1
M3
TxPOS[2]
O
Transmit Positive Polarity Data output - Channel 2:
See Description for Pin C1
M9
GND
****
Ground
M10
GND
****
Ground
M11
GND
****
Ground
M12
GND
****
Ground
M17
A[7]
I
Address Bus pin:
See Description for Pin M20
M18
A[8]
I
Address Bus pin:
See Description for Pin M20
M19
A[9]
I
Address Bus pin:
See Description for Pin M20
M20
A[10]
I
Address Bus Input (Microprocessor Interface) - MSB (Most Significant Bit):
This input pin, along with inputs A0 - A9 are used to select the on-chip
Framer register and RAM space for READ/WRITE operations with the
local microprocessor.
27
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XRT72L53
THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. P1.1.7
PIN DESCRIPTION CONNECTED PINS
PIN #
PIN NAME
TYPE
DESCRIPTION
N1
TxNEG[2]
O
Transmit Negative Polarity Data output - Channel 2:
See Description for Pin D1
N3
TxLineClk[2]
O
Transmit Line Interface Clock output - Channel 2:
See Description for Pin E2
N4
GND
****
Ground
N17
GND
****
Ground
N18
A[4]
I
Address Bus pin:
See Description for Pin M20
N19
A[5]
I
Address Bus pin:
See Description for Pin M20
N20
A[6]
I
Address Bus pin:
See Description for Pin M20
P2
RxOutClk[2]/
RxHDLCDat7[2]
O
Receive Out Clock - Transmit Payload Data Input Interface Clock
for Loop-Timing/Receive HDLC Data - Bit 7; Channel 2:
See Description for Pin E3
P3
DMO[2]
I
Drive Monitor Output input pin - Channel 2 (from the DS3/E3 LIU
IC):
See Description for Pin C9
P17
WR_RW
I
Write Data Strobe (Intel Mode):
If the microprocessor interface is operating in the Intel Mode, then this
active-low input pin functions as the WR (Write Strobe) input signal from
the µP. Once this active-low signal is asserted, then the Framer will latch
the contents of the µP Data Bus, into the addressed register (or RAM
location) within the Framer IC. In the Intel Mode, data gets latched on
the rising edge of WR
R/W Input Pin (Motorola Mode):
When the Microprocessor Interface Section is operating in the Motorola
Mode, then this pin is functionally equivalent to the R/W pin. In the
Motorola Mode, a READ operation occurs if this pin is at a logic "1".
Similarly, a WRITE operation occurs if this pin is at a logic "0".
P18
A[1]
I
Address Bus pin:
See Description for Pin M20
P19
A[2]
I
Address Bus pin:
See Description for Pin M20
P20
A[3]
I
Address Bus pin:
See Description for Pin M20
R3
ExtLOS[2]
I
Receive LOS (Loss of Signal) Indicator Input - Channel 2 (from
DS3/E3 LIU IC):
See Description for Pin D9
R4
VDD
****
Power Supply +3.3v ± 5%
R17
VDD
****
Power Supply +3.3v ± 5%
28
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XRT72L53
THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. P1.1.7
PIN DESCRIPTION CONNECTED PINS
PIN #
PIN NAME
TYPE
DESCRIPTION
R18
CS
I
Chip Select Input:
This active-low input signal selects the Microprocessor Interface Section of the Framer device and enables READ/WRITE operations
between the Local Microprocessor and the Framer on-chip registers
and RAM locations.
R19
ALE_AS
I
Address Latch Enable/Address Strobe:
This input is used to latch the address (present at the Microprocessor
Interface Address Bus, A(10:0)) into the Framer Microprocessor Interface circuitry and to indicate the start of a READ/WRITE cycle. This
input is active-high in the Intel Mode (MOTO = "Low") and active-low in
the Motorola Mode (MOTO = "High").
R20
A[0]
I
Address Bus Input (Microprocessor Interface) - LSB (Least Significant Bit):
(Please see description for A(10))
T1
RLOL[2]
I
Receive Loss of Lock Indicator Input - Channel 2 (from the DS3/E3
LIU IC):
See Description for Pin B8
T3
RxOOF[2]
O
Receive Out of Frame Indicator - Channel 2:
See Description for Pin A3
T17
RxClk[2]
O
Receive Clock Output signal for Serial and Nibble-Parallel Data
Interface - Channel 2:
See Description for Pin D20
T18
NibbleIntf
I
Nibble Interface Select Input Pin:
This input pin allows the user to configure the Transmit Payload Data
Input Interface and the Receive Payload Data Output Interface to operate in either the Serial-Mode or the Nibble/Parallel-Mode.
Setting this input pin "High" configures the Transmit and Receive Terminal Interfaces to operate in the Nibble/Parallel-Mode. In this mode, the
“Transmit Payload Data Input Interface” block will accept the “outbound”
payload data (from the Terminal Equipment) in a “nibble-parallel” manner via the “TxNib[3:0]” input pins. Further, the “Receive Payload Data
Output Interface” block will output the “inbound” payload data (to the
Terminal Equipment) in a “nibble-parallel” manner via the “RxNib[3:0]”
output pin.
Setting this input pin "Low" configures the Transmit and Receive Terminal Interfaces to operate in the Serial Mode. In this mode, the “Transmit
Payload Data Input Interface” block will accept the “outbound” payload
data (from the Terminal Equipment) in a “serial” manner via the “TxSer”
input pin. Further, the “Receive Payload Data Output Interface” block
will output the “inbound” payload data (to the Terminal Equipment) in a
“serial” manner via the “RxSer” output pin.
T19
Reset
I
Reset Input:
When this "active-low" signal is asserted, the Framer device will be
asynchronously reset. Additionally, all outputs will be "tri-stated", and all
on-chip registers will be reset to their default values.
29
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XRT72L53
THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. P1.1.7
PIN DESCRIPTION CONNECTED PINS
PIN #
PIN NAME
TYPE
DESCRIPTION
T20
MOTO
I
Motorola/Intel Processor Interface Select Mode:
This input pin allows the user to configure the Microprocessor Interface
to interface with either a Motorola-type or Intel-type microprocessor/
microcontroller. Tying this input pin to VDD, configures the microprocessor interface to operate in the Motorola mode (e.g., the Framer device
can be readily interfaced to a Motorola type local microprocessor). Tying
this input pin to GND configures the Microprocessor Interface to operate
in the Intel Mode (e.g., the Framer device can be readily interfaced to a
“Intel type local microprocessor).
U3
RxAIS[2]
O
Receive AIS (Alarm Indication Signal) Indicator - Channel 2:
See Description for Pin C5
U4
GND
****
U5
RLOOP[2]
O
U6
VDD
****
Power Supply +3.3v ± 5%
U8
GND
****
Ground
U9
RxOHEnable[2]/
RxHDLCDat5[2]
O
U10
VDD
****
U11
TxSer[2]/
SndMsg[2]
I
Transmit Serial Payload Data Input pin/Transmit HDLC Controller SEND MESSAGE Input pin - Channel 2:
See Description for Pin E18
U12
TxNib2[2]/
TxHDLCDat2[2]
I
Transmit Nibble-Parallel Payload Data Input - Bit 2/Transmit HDLC
Data Input - Bit 2; Channel 2:
See Description for Pin C20
U13
GND
****
U14
TxFrame[2]
O
U15
VDD
****
Power Supply +3.3v ± 5%
U17
GND
****
Ground
U19
RxFrame[2]
O
Receive Boundary of DS3 or E3 Frame Output Indicator - Channel
2:
See Description for Pin F20
U20
TestMode
***
Factory Test Pin:
The user should tie this pin to Ground.
V1
RxLOS[2]
O
Receive Loss of Signal Output Indicator - Channel 2:
See Description for Pin C4
V6
TxAISEn[2]
I
Transmit AIS Command Input - Channel 2:
See Description for Pin B15
Ground
Remote Looback Output pin - Channel 2 (to be connected to the
DS3/E3 LIU IC):
See Description for Pin B7
Receive Overhead Enable Indicator/Receive HDLC Controller Data
Output - Bit 5; Channel 2:
See Description for Pin B13
Power Supply +3.3v ± 5%
Ground
Transmit End of DS3 or E3 Frame Indicator - Channel 2:
See Description for Pin E20
30
áç
XRT72L53
THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. P1.1.7
PIN DESCRIPTION CONNECTED PINS
PIN #
PIN NAME
TYPE
DESCRIPTION
V7
TxOH[2]/
TxHDLCDat5[2]
I
Transmit Overhead Data Input pin/Transmit HDLC Controller Data
Input - Bit 5; Channel 2:
See Description for Pin A15
V16
RxNib3[2]/
RxHDLCDat3[2]
O
Receive Nibble Output - Bit 2/Receive HDLC Controller Data Output - Bit 3; Channel 2:
See Description for Pin H19
V17
RxNib1[2]/
RxHDLCDat1[2]
O
Receive Nibble Output - Bit 1/Receive HDLC Controller Data Output - Bit 1; Channel 2:
See Description for Pin G20
V20
Rd_DS
I
Read Data Strobe (Intel Mode):
If the microprocessor interface is operating in the Intel Mode, then this
input will function as the RD (READ STROBE) input signal from the
local µP. Once this active-low signal is asserted, then the Framer will
place the contents of the addressed registers (within the Framer) on the
Microprocessor Data Bus (D(7:0)). When this signal is negated, the
Data Bus will be tri-stated.
Data Strobe (Motorola Mode):
If the microprocessor interface is operating in the Motorola mode, then
this pin will function as the active-low Data Strobe signal.
W1
LLOOP[2]
O
Local Loopback Output pin - Channel 2 (to be connected the
LLOOP input of the DS3/E3 LIU IC):
See Description for Pin C7
W2
TAOS[2]
O
Transmit All Ones Signal (TAOS) Command Input - Channel 2 (to
be connected to the TAOS input of the DS3/E3 LIU IC):
See Description for Pin C6
W3
RxRed[2]
O
Receive Red Alarm Indicator output - Channel 2:
See Description for Pin B5
W4
TxLev[2]
O
Transmit Line Build-Out Enable/Disable Select Output - Channel 2
(to be connected to the DS3/E3 LIU IC):
See Description for Pin C3
W5
Req[2]
O
Receive Equalization Enable/Disable Select output pin - Channel 2
(to be connected to the DS3/E3 LIU IC):
See Description for Pin A5
W6
TxOHIns[2]/
TxHDLCDat4[2]
I
Transmit Overhead Data Insert Input/Transmit HDLC Data Input Bit 4; Channel 2:
See Description for Pin C14
W8
RxOHFrame[2]/
RxHDLCDat4[2]
O
Receive Overhead Frame Boundary Indicator/Receive HDLC Data
Output - Bit 4; Channel 2:
See Description for Pin A13
W9
RxOHClk[2]/
RxHDLCClk[2]
O
Receive Overhead Data Clock signal/Receive HDLC Controller Output Clock - Channel 2:
See Description for Pin D12
W10
TxOHClk[2]
O
Transmit Overhead Data Clock Output - Channel 2:
See Description for Pin A14
31
áç
XRT72L53
THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. P1.1.7
PIN DESCRIPTION CONNECTED PINS
PIN #
PIN NAME
TYPE
DESCRIPTION
W11
TxOHFrame[2]/
TxHDLCClk[2]
O
Transmit Overhead Data Framing Pulse/Transmit HDLC Output
Clock - Channel 0:
See Description for Pin C13
W12
TxNib3[2]/
TxHDLCDat3[2]
I
Transmit Nibble-Parallel Payload Data Input - Bit 3/Transmit HDLC
Data Input - Bit 3; Channel 2:
See Description for Pin D19
W13
TxNib1[2]/
TxHDLCDat1[2]
I
Transmit Nibble-Parallel Payload Data Input - Bit 1/Transmit HDLC
Data Input - Bit 1; Channel 2:
See Description for Pin E17
W15
TxNIBClk[2]/
SndFCS[2]
O
I
Transmit Nibble Clock Output Signal/Transmit HDLC - SEND
FRAME CHECK SEQUENCE Input - Channel 2:
See Description for Pin F18
W16
TxNibFrame[2]/
ValFCS[2]
O
Transmit Frame Boundary Indicator - Nibble-Parallel Interface/
Transmit HDLC Controller - VALID FRAME CHECK SEQUENCE output - Channel 2:
See Description for Pin G17
W19
RxSer[2]/
RxIdle[2]
O
Receive Serial Output/Receive Flag Sequence Output - Channel 2:
See Description for Pin F19
W20
RxOHInd[2]
O
Receive Overhead Bit Indicator - Channel 2:
See Description for Pin G18
Y4
EncoDis[2]
O
Encoder (B3ZS/HDB3) Disable Output pin - Channel 2 (intended to
be connected to the DS3/E3 LIU IC):
See Description for Pin B2
Y7
RxOH[2]/
RxHDLCDat6[2]
O
Receive Overhead Data Output/Receive HDLC Controller Data Output - Bit 6; Channel 2:
See Description for Pin C12
Y10
TxOHEnable[2]/
TxHDLCDat7[2]
O
I
Transmit Overhead Input Enable/Transmit HDLC Controller Data
Output - Bit 7; Channel 0:
See Description for Pin B14
Y14
TxNib0[2]/
TxHDLCDat0[2]
I
Transmit Nibble-Parallel Payload Data Input - Bit 0/Transmit HDLC
Data Input - Bit 0; Channel 2:
See Description for Pin D18
Y15
TxOHInd[2]/
TxHDLCDat6[2]
O
I
Transmit Overhead Data Indicator Output/Transmit HDLC Data
Input - Bit 6; Channel 2:
See Description for Pin E19
Y18
RxNib2[2]/
RxHDLCDat2[2]
O
Receive Nibble Output - Bit 2/Receive HDLC Data - Bit 2; Channel
2:
See Description for Pin H18
Y19
RxNib0[2]/
RxHDLCDat0[2]
O
Receive Nibble Output - Bit 0/Receive HDLC Data - Bit 0; Channel
2:
See Description for Pin G19
32
áç
XRT72L53
THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. P1.1.8
ELECTRICAL CHARACTERISTICS
ABSOLUTE MAXIMUMS
Power Supply......................................... -0.3V to +3.6V
Power Dissipation PBGA Package........................ 1.6W
Storage Temperature ...............................-55°C to 150°C
Input Voltage (Any Pin) .....................-0.3V to VDD + 0.3V
voltage at Any Pin .......................... -0.3V to VDD + 0.3V
Input Current (Any Pin) ...................................... + 100mA
DC ELECTRICAL CHARACTERISTICS
Test Conditions: TA = 25°C, VDD = 3.3V + 5% unless otherwise specified
SYMBOL
PARAMETER
MIN.
ICC
Power Supply Current
VIL
Input Low voltage
VIH
Input High Voltage
VOL
Output Low Voltage
VOH
Output High Voltage
2.4
IIH
Input High Voltage Current
-10
IIL
Input Low Voltage Current
-1
TYP.
MAX.
190
UNITS
CONDITIONS
mA
All Channels on
0.3*VDD
V
0.7*VDD
V
0.4
V
IOL = -1.6mA
V
IOH = 40µA
10
µA
VIH = VDD
1
µA
VIL = GND
AC ELECTRICAL CHARACTERISTICS
Test Conditions: TA = 25°C, VDD = 3.3V + 5% unless otherwise specified
SYMBOL
PARAMETER
MIN.
TYP.
MAX.
UNITS
CONDITIONS
Transmit Payload Data Input Interface - Loop-Timed/Serial Mode (See Figure 3)
t1
Payload data (TxSer) set-up time to rising edge of
RxOutClk
12
ns
t2
Payload data (TxSer) hold time, from rising edge of
RxOutClk
0
ns
t3
RxOutClk to TxFrame output delay
5
ns
t4
RxOutClk to TxOHInd output delay
6
ns
Transmit Payload Data Input Interface - Local Timed/Serial Mode (See Figure 4)
t5
Payload data (TxSer) set-up time to rising edge of
TxInClk
4
ns
t6
Payload data (TxSer) hold time, from rising edge of
TxInClk
0
ns
t7
TxFrameRef set-up time to rising edge of TxInClk
2
ns
Framer IC is
Frame Slave
t8
TxFrameRef hold-time, from rising edge of TxInClk
0
ns
Frame IC is
Frame Slave
t9
TxInClk to TxOHInd output delay
15
33
ns
áç
XRT72L53
THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. P1.1.8
AC ELECTRICAL CHARACTERISTICS
Test Conditions: TA = 25°C, VDD = 3.3V + 5% unless otherwise specified
SYMBOL
t10
PARAMETER
MIN.
TYP.
MAX.
UNITS
13
ns
TxInClk to TxFrame output delay
CONDITIONS
Transmit Payload Data Input Interface - Looped-Timed/Nibble Mode (See Figure 5)
t13A
Max Delay of Rising Edge of TxNibClk to Data Valid
on TxNib[3:0]
DS3
E3
20
27
ns
ns
DS3 Applications
E3 Applications
25
ns
DS3 Applications
31
ns
E3 Applications
20
ns
DS3 Applications
27
ns
E3 Applications
Transmit Payload Data Input Interface - Looped-Timed/Nibble Mode (See Figure 5)
t13
TxNibClk to TxNibFrame output delay
Transmit Payload Data Input Interface - Local-Timed/Nibble Mode (See Figure 6)
t14
Max Input Delay from TxNicClk to TxNib
t15
Payload Nibble hold time, from latching edge of
TxNibClk
0
t16
TxFrameRef set-up time, to latching edge of TxInClk
t17
TxFrameRef hold time, from latching edge of TxNibClk
0
t18
TxNibClk to TxNibFrame output delay time
20
34
ns
20
ns
DS3 Applications
27
ns
E3 Applications
Framer IC is
Frame Slave
ns
Frame IC is
Frame Slave
25
ns
DS3 Applications
31
ns
E3 Applications
áç
XRT72L53
THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. P1.1.8
AC ELECTRICAL CHARACTERISTICS (CONT.)
Test Conditions: TA = 25°C, VDD = 3.3V + 5% unless otherwise specified
SYMBOL
PARAMETER
MIN.
TYP.
MAX.
UNITS
CONDITIONS
111
ns
DS3 Applications
0
ns
E3, ITU-T G.832
Applications
0
ns
E3, ITU-T G.751
Applications
194
ns
DS3 Applications
305
ns
E3, ITU-T G.832
Applications
17
ns
E3, ITU-T G.751
Applications
48
ns
DS3 Applications
110
ns
E3, ITU-T G.832
Applications
ns
E3, ITU-T G.751
Applications
194
ns
DS3 Applications
305
ns
E3, ITU-T G.832
Applications
17
ns
E3, ITU-T G.751
Applications
48
ns
DS3 Applications
110
ns
E3, ITU-T G.832
Applications
7
ns
E3, ITU-T G.751
Applications
254
ns
DS3 Applications
72
ns
E3, ITU-T G.832
Applications
15
ns
E3, ITU-T G.751
Applications
Transmit Overhead Input Interface Timing - Method 1 (Figure 7)
t21
t22
t23
TxOHClk to TxOHFrame output delay
TxOHIns set-up time, to falling edge of TxOHClk
TxOHIns hold time, from falling edge of TxOHClk
7
t24
t25
TxOH data set-up time, to falling edge of TxOHClk
TxOH data hold time, from falling edge of TxOHClk
Transmit Overhead Data Input Interface - Method 2 (Figure 8)
t26
TXOHIns to TxInClk (falling edge) set-up Time
35
áç
XRT72L53
THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. P1.1.8
AC ELECTRICAL CHARACTERISTICS (CONT.)
Test Conditions: TA = 25°C, VDD = 3.3V + 5% unless otherwise specified
SYMBOL
t27
t28
t29
t29A
PARAMETER
MIN.
TxInClk clock (falling) edge to TxOHIns hold-time
TXOHIns to TxInClk (falling edge) set-up Time
TxInClk clock (falling) edge to TxOHIns hold-time
TxOHEnable to TxOHIns/TxOH Delay
TYP.
MAX.
UNITS
CONDITIONS
0
ns
DS3 Applications
0
ns
E3, ITU-T G.832
Applications
0
ns
E3, ITU-T G.751
Applications
254
ns
DS3 Applications
72
ns
E3, ITU-T G.832
Applications
15
ns
E3, ITU-T G.751
Applications
0
ns
DS3 Applications
0
ns
E3, ITU-T G.832
Applications
0
ns
E3, ITU-T G.751
Applications
1
ns
Transmit LIU Interface Timing (see Figure 9 and Figure 10)
t30
Rising edge of TxLineClk to rising edge of TxPOS
or TxNEG output signal.
(Framer is configured to output data on TxPOS and
TxNEG on rising edge of TxLineClk
2.0
ns
t31
Falling edge of TxLineClk to rising edge of TxPOS or
TxNEG
(Framer is configured to output data via TxPOS and
TxNEG on falling edge of TxLineClk)
2.4
ns
fTxLineClk
Period of TxLineClk clock signal
44.736
MHz
DS3 Applications
fTxLineClk
Period of TxLineClk clock signal
34.368
Mhz
E3 Applications
t32
Period of TxLineClk
22.36
ns
DS3 Applications
t32
Period of TxLineClk
29.10
ns
E3 Applications
Receive LIU Interface Timing (see Figure 11 and Figure 12)
t38
RxPOS or RxNEG set-up time to rising edge of
RxLineClk.
(Framer is configured to sample data on RxPOS and
RxNEG input pins, on the rising edge of RxLineClk)
0
ns
t39
RxPOS or RxNEG hold time, from rising edge of
RxLineClk
(Framer is configured to sample data on RxPOS and
RxNEG input pins, on the rising edge of RxLineClk)
4
ns
36
áç
XRT72L53
THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. P1.1.8
AC ELECTRICAL CHARACTERISTICS (CONT.)
Test Conditions: TA = 25°C, VDD = 3.3V + 5% unless otherwise specified
SYMBOL
PARAMETER
MIN.
t40
RxPOS or RxNEG set-up time to falling edge of
RxLineClk.
(Framer is configured to sample data on RxPOS and
RxNEG input pins, on the falling edge of RxLineClk)
0
ns
t41
RxPOS or RxNEG hold time, from falling edge of
RxLineClk
(Framer is configured to sample data on RxPOS and
RxNEG input pins, on the falling edge of RxLineClk)
3
ns
TYP.
MAX.
UNITS
CONDITIONS
Receive Payload Data Output Inteface Timing - Serial Mode Operation (See Figure 13)
t50
t51
t52
Rising edge of RxClk to Payload Data (RxSer) output delay
Rising edge of RxClk to RxFrame output delay
Rising edge of RxClk to RxOHInd output delay.
13
ns
DS3 Applications
16
ns
E3 Applications
13
ns
DS3 Applications
16
ns
E3 Applications
13
ns
DS3 Applications
16
ns
E3 Applications
Receive Payload Data Output Interface Timing - Nibble Mode Operation (see Figure 14)
t53
Falling edge of RxClk to rising edge of RxFrame output delay
t54
Falling edge of RxClk to rising edge of RxNib[3:0]
output delay
2.1
ns
2
ns
Receive Overhead Data Output Interface Timing - Method 1 - Using RxOHEnable (see Figure 15)
t59A
t59B
Falling edge of RxOHClk to RxFrame output
Falling edge of RxClk to RxOH output delay
20
23
ns
DS3 Applications
25
0
ns
E3 Applications
20
23
ns
DS3 Applications
25
0
ns
E3 Applications
Receive Overheadf Data Output Interface Timing - Method 2 - Using RxOHEnable (see Figure 16)
t60
Rising edge of RxOutClk to rising edge of
RxOHEnable delay.
t60A
Rising edge of RxOHFrame to rising edge of
RxOHEnable delay
t60B
2
RxOH Data Valid to rising edge of
RxOHEnable delay
37
9.4
ns
88
ns
DS3 Applications
224
ns
E3, ITU-T G.832
Applications
28
ns
E3, ITU-T G.751
Applications
88
ns
DS3 Applications
85
ns
E3, ITU-T G.832
Applications
28
ns
E3, ITU-T G.751
Applications
áç
XRT72L53
THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. P1.1.8
AC ELECTRICAL CHARACTERISTICS (CONT.)
Test Conditions: TA = 25°C, VDD = 3.3V + 5% unless otherwise specified
SYMBOL
PARAMETER
MIN.
TYP.
MAX.
UNITS
Microprocessor Interface - Intel (See Figure 17)
t64
A10 - A0 Setup Time to ALE_AS Low
0
ns
t65
A10 - A0 Hold Time from ALE_AS Low.
1
ns
Intel Type Read Operations (See Figure 17 and Figure 19)
t66
RD_DS, WR_R/W Pulse Width
87
ns
t67
Data Valid from RD_DS Low.
32
ns
t68
Data Bus Floating from RD_DS High
9
ns
t69
ALE to RD Time
3
ns
t701
RD Time to NOT READY (e.g., RDY_DTCK toggling
Low)
16
ns
t70
RD to READY Time (e.g., RDY_DTCK toggling high)
80
ns
t76
Minimum Time between Read Burst Access (e.g.,
the rising edge of RD to falling edge of RD)
33
ns
Intel Type Write Operations (Figure 18 and Figure 20)
t71
Data Setup Time to WR_R/W High
0
ns
t72
Data Hold Time from WR_R/W High
3
ns
t73
High Time between Reads and/or Writes
33
ns
t74
ALE to WR Time
3
ns
t77
Min Time between Write Burst Access (e.g., the rising edge of WR to the falling edge of WR)
33
ns
t770
CS Assertion to falling edge of WR_RW
28
ns
Microprocessor Interface - Motorola Read Operations (See Figure 21)
t78
A10 - A0 Setup Time to falling edge of ALE_AS
0
ns
t79
Rising edge of RD_DS to rising edge of RDY_DTCK
delay
16
ns
t80
Rising edge of RDY_DTCK to tri-state of D[7:0]
0
ns
Microprocessor Interface - Motorola Read & Write Operations (See Figure 22)
t78
A10 - A0 Setup Time to falling edge of ALE_AS
0
ns
t81
D[7:0] Set-up time to falling edge of RD_DS
0
ns
t82
Rising edge of RD_DS to rising edge of RDY_DTCK
delay
13
ns
Reset Pulse Width - Both Motorola and Intel Operations (See Figure 25)
t90
Reset pulse width
200
38
ns
CONDITIONS
áç
XRT72L53
THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. P1.1.8
1.0 TIMING DIAGRAMS
FIGURE 3. TIMING DIAGRAM FOR TRANSMIT PAYLOAD INPUT INTERFACE, WHEN THE XRT72L53 DEVICE IS OPERATDS3 AND LOOP-TIMING MODES
ING IN BOTH THE
XRT72L5x Transmit Payload Data I/F Signals
t3
t2
t1
RxOutClk
TxSer
Payload[4702]
Payload[4703]
X-Bit
Payload[0]
TxFrame
TxOH_Ind
t4
DS3 Frame Number N + 1
DS3 Frame Number N
FIGURE 4. TIMING DIAGRAM FOR THE TRANSMIT PAYLOAD INPUT INTERFACE, WHEN THE XRT72L53 DEVICE IS
OPERATING IN BOTH THE DS3 AND LOCAL-TIMING MODES
XRT72L5x Transmit Payload Data I/F Signals
t6
t8
t5
t7
TxInClk
TxSer
Payload[4702]
Payload[4703]
X-Bit
Payload[1]
TxFrameRef
TxOH_Ind
t9
t10
DS3 Frame Number N
39
DS3 Frame Number N + 1
áç
XRT72L53
THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. P1.1.8
FIGURE 5. TIMING DIAGRAM FOR THE TRANSMIT PAYLOAD DATA INPUT INTERFACE, WHEN THE XRT72L53 DEVICE
IS OPERATING IN BOTH THE DS3/NIBBLE AND LOOPED-TIMING MODES
t13A
t11
t12
RxOutClk
TxNibClk
Nibble [1175]
TxNib[3:0]
Nibble [0]
TxNibFrame
t13
Sampling Edge of XRT72L5x Device
FIGURE 6. TIMING DIAGRAM FOR THE TRANSMIT PAYLOAD DATA INPUT INTERFACE, WHEN THE XRT72L53 DEVICE
IS OPERATING IN THE DS3/NIBBLE AND LOCAL-TIMING MODES
t15
t14
TxInClk
TxNibClk
TxNib[3:0]
TxNibFrame
TxFrameRef
Nibble [1175]
Nibble [0]
t18
t17
t16
DS3 Frame Number N
DS3 Frame Number N + 1
Sampling Edge of the XRT72L5x Device
40
áç
XRT72L53
THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. P1.1.8
FIGURE 7. TIMING DIAGRAM FOR THE TRANSMIT OVERHEAD DATA INPUT INTERFACE (METHOD 1 ACCESS)
t21
t22
t23
TxOHClk
TxOHFrame
TxOHIns
TxOH
X bit = 0
Remaining Overhead Bits with DS3 Frame
X bit = 0
t24 t25
FIGURE 8. TIMING DIAGRAM FOR THE TRANSMIT OVERHEAD DATA INPUT INTERFACE (METHOD 2 ACCESS)
t26
t27
TxInClk
TxOHEnable Pulse # 8
TxOHFrame
TxOHEnable
TxOHIns
t29A
TxOH
X bit = 0
t28
t29
XRT72L5x samples TxOH
here.
41
X bit = 0
áç
XRT72L53
THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. P1.1.8
FIGURE 9. TRANSMIT LIU INTERFACE TIMING - FRAMER IS CONFIGURED TO UPDATE "TXPOS" AND "TXNEG" ON
THE RISING EDGE OF "TXLINECLK"
t32
TxLineClk
t30
t33
TxPOS
TxNEG
FIGURE 10. TRANSMIT LIU INTERFACE TIMING - FRAMER IS CONFIGURED TO UPDATE "TXPOS" AND "TXNEG" ON
THE FALLING EDGE OF "TXLINECLK"
t32
TxLineClk
t31
t33
TxPOS
TxNEG
42
XRT72L53
THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
áç
PRELIMINARY
REV. P1.1.8
FIGURE 11. RECEIVE LIU INTERFACE TIMING - FRAMER IS CONFIGURED TO SAMPLE "RXPOS" AND "RXNEG" ON
THE RISING EDGE OF "RXLINECLK"
RxLineClk
t40
t41
RxPOS
RxNEG
FIGURE 12. RECEIVER LIU INTERFACE TIMING - FRAMER IS CONFIGURED TO SAMPLE "RXPOS" AND "RXNEG" ON
THE FALLING EDGE OF "RXLINECLK"
t42
RxLineClk
t38
t39
RxPOS
RxNEG
43
áç
XRT72L53
THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. P1.1.8
FIGURE 13. RECEIVE PAYLOAD DATA OUTPUT INTERFACE TIMING
XRT72L5x Receive Payload Data I/F Signals
t50
RxClk
RxSer
Payload[4702]
Payload[4703]
X-Bit
Payload[0]
t51
RxFrame
t52
RxOHInd
FIGURE 14. RECEIVE PAYLOAD DATA OUTPUT INTERFACE TIMING (NIBBLE MODE OPERATION)
XRT72L5x Receive Payload Data I/F Signals
t54
RxOutClk
RxClk
RxNib[3:0]
Nibble [0]
RxFrame
DS3 Frame Number N
DS3 Frame Number N + 1
t53
Recommended Sampling Edge of Terminal
Equipment
44
Nibble [1]
áç
XRT72L53
THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. P1.1.8
FIGURE 15. RECEIVE OVERHEAD DATA OUTPUT INTERFACE TIMING (METHOD 1 - USING RXOHCLK)
t59A
RxOHClk
RxOHFrame
X
RxOH
F1
AIC
F0
FEAC
t59B
FIGURE 16. RECEIVE OVERHEAD DATA OUTPUT INTERFACE TIMING (METHOD 2 - USING RXOHENABLE)
t60
RxOutClk
t60A
RxOHEnable
RxOHFrame
t60B
RxOH
UDL
F1
X1
45
F1
AIC
áç
XRT72L53
THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. P1.1.8
FIGURE 17. MICROPROCESSOR INTERFACE TIMING - INTEL TYPE PROGRAMMED I/O READ OPERATIONS
t64
t65
ALE_AS
A[10:0]
Address of Target
CS
t68
t67
D[7:0]
Valid
Not Valid
RD_DS
t69
WR_R/W
t66
t701
RDY_DTCK
t70
FIGURE 18. MICROPROCESSOR INTERFACE TIMING - INTEL TYPE PROGRAMMED I/O WRITE OPERATIONS
t64
t65
ALE_AS
A[10:0]
CS
D[7:0]
Address of Target
t770
t71
t72
Data to be
RD_DS
t73
t66
WR_R/W
46
áç
XRT72L53
THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. P1.1.8
FIGURE 19. MICROPROCESSOR INTERFACE TIMING - INTEL TYPE READ BURST ACCESS OPERATION
t76
ALE_AS
A[10:0]
Address of “Initial” Target Register (Offset = 0x00)
t68
CS
D[7:0]
Not Valid
Valid Data at Offset =0x01
Not Valid
Valid Data at Offset =0x02
RD_DS
WR_R/W
RDY_DTCK
t70
FIGURE 20. MICROPROCESSOR INTERFACE TIMING - INTEL TYPE WRITE BURST ACCESS OPERATION
ALE_AS
A(10:0)
Address of Initial Target Register (offset = 0x00)
CS
D(7:0)
RD_DS
Not Valid
Valid Data at
Offset = 0x01
Not Valid
t68
WR_R/W
t76
47
Valid Data at
Offset = 0x02
áç
XRT72L53
THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. P1.1.8
FIGURE 21. MICROPROCESSOR INTERFACE TIMING - MOTOROLA TYPE PROGRAMMED I/O READ OPERATION
t78
ALE_AS
A(10:0)
Address of Target Register
CS
Not Valid
D(7:0)
Valid Data
RD_DS
WR_R/W
t79
RDY_DTCK
t80
FIGURE 22. MICROPROCESSOR INTERFACE TIMING - MOTOROLA TYPE PROGRAMMED I/O WRITE OPERATION
t78
ALE_AS
A(10:0)
Address of Target Register
CS
D(7:0)
Data to be Written
RD_DS
t81
WR_R/W
RDY_DTCK
t82
48
XRT72L53
THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
áç
PRELIMINARY
REV. P1.1.8
FIGURE 23. MICROPROCESSOR INTERFACE TIMING - RESET PULSE WIDTH
t90
Reset
49
áç
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2.0 THE MICROPROCESSOR INTERFACE
BLOCK
The Microprocessor Interface section supports communication between the local microprocessor (µP)
and the Framer IC. In particular, the Microprocessor
Interface section supports the following operations
between the local microprocessor and the Framer.
The relationship between the states of A9 and A10,
and the corresponding Configuration Register bank,
is tabulated below.
TABLE 1: THE RELATIONSHIP BETWEEN ADDRESS BITS
A9, A10 AND THE SELECTED CONFIGURATION
REGISTER BANK
• Channel Selection
A10
A9
• The writing of configuration data into the Framer
on-chip (addressable) registers.
0
0
Channel 0
• The writing of an outbound PMDL (Path Maintenance Data Link) message into the Transmit LAPD
Message buffer (within the Framer IC).
0
1
Channel 1
1
0
Channel 2
1
1
Not Valid
• The Framer IC's generation of an Interrupt Request
to the µP.
CONFIGURATION REGISTER BANK SELECTED
The remaining Address Bus pins [A8 through A0] are
used to select the individual configuration registers
(within the selected configuration register bank) for
Read/Write access.
• The µP's servicing of the interrupt request from the
Framer IC.
• The monitoring of the system's health by periodically reading the on-chip Performance Monitor registers.
Looking at this Another Way
Each of the three (3) Configuration Register Banks,
within the XRT72L53 DS3/E3 Framer IC has an identical set of configuration registers. However, address
pins A9 and A10 impose the following address location offset, for each of the Configuration Register
Bank within the address space of the XRT72L53.
• The reading of an inbound PMDL Message from
the Receive LAPD Message Buffer (within the
Framer IC).
Each of these operations (between the local microprocessor and the Framer IC) will be discussed in
some detail, throughout this data sheet.
2.1 CHANNEL SELECTION WITHIN THE XRT72L53
The XRT72L53 3-Channel DS3/E3 Clear Channel
Framer IC consists of three independent banks of
Configuration registers. Each of these banks are
identical and correspond to each of the three channels within the XRT72L53. The XRT72L53 is used to
select and access any one of these Configuration
Register Banks, via the two (2) Most Significant Address Pins, A9 and A10.
CONFIGURATION REGISTER ADDRESS OFFSET (WITHIN THE
BANK - CHANNEL NUMBER XRT72L53 ADDRESS SPACE)
0
0x000
1
0x200
2
0x400
Figure 24 presents a simple block diagram of the Microprocessor Interface Section, within the Framer IC.
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FIGURE 24. SIMPLE BLOCK DIAGRAM OF THE MICROPROCESSOR INTERFACE BLOCK, WITHIN THE FRAMER IC
A(10:0)
WR_R/W
Rd_DS
CS
ALE_AS
Reset
Int
D[7:0]
MOTO
RDY_DTCK
Microprocessor
&
Programable Registers
2.2 THE MICROPROCESSOR INTERFACE BLOCK SIG-
operate in the Motorola Mode or in the Intel mode.
When the Microprocessor Interface is operating in the
Motorola mode, then some of the control signals
function in a manner as required by the Motorola
68000 family of microprocessors. Likewise, when the
Microprocessor Interface is operating in the Intel
Mode, then some of these Control Signals function in
a manner as required by the Intel 80xx family of microprocessors.
NAL
The Framer IC may be configured into a wide variety
of different operating modes and have its performance monitored by software through a standard (local housekeeping) microprocessor, using data, address and control signals.
The local µP configures the Framer IC (into a desired
operating mode) by writing data into specific addressable, on-chip Read/Write registers, or on-chip RAM.
The microprocessor interface provides the signals
which are required for a general purpose microprocessor to read or write data into these registers. The
Microprocessor Interface also supports polled and interrupt driven environments. These interface signals
are described below in Table 2, Table 3, and Table 4.
The microprocessor interface can be configured to
Table 2 lists and describes those Microprocessor Interface signals whose role is constant across the two
modes. Table 3 describes the role of some of these
signals when the Microprocessor Interface is operating in the Intel Mode. Likewise, Table 4 describes the
role of these signals when the Microprocessor Interface is operating in the Motorola Mode.
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TABLE 2: DESCRIPTION OF THE MICROPROCESSOR INTERFACE SIGNALS THAT EXHIBIT CONSTANT ROLES IN BOTH
THE INTEL AND MOTOROLA MODES
PIN NAME
TYPE
DESCRIPTION
MOTO
I
Selection input for Intel/Motorola µP Interface.
Setting this pin to a logic "High" configures the Microprocessor Interface to operate in the Motorola
mode. Likewise, setting this pin to a logic "Low" configures the Microprocessor Interface to operate
in the Intel Mode.
D[7:0]
I/O
A[10:0]
I
Eleven Bit Address Bus input:
This Eleven bit Address Bus is provided to allow the user to select an on-chip register or on-chip
RAM location and Select the desired Framer Channel to address.
CS
I
Chip Select input.
This active-”Low” signal selects the Microprocessor Interface of the UNI device and enables read/
write operations with the on-chip registers/on-chip RAM.
INT
O
Interrupt Request Output:
This open-drain/active-low output signal will inform the local µP that the UNI has an interrupt condition that needs servicing.
Bi-Directional Data Bus for register read or write operations
TABLE 3: PIN DESCRIPTION OF MICROPROCESSOR INTERFACE SIGNALS - WHILE THE MICROPROCESSOR INTERFACE
IS OPERATING IN THE INTEL MODE
PIN NAME
EQUIVALENT PIN
IN INTEL
TYPE
DESCRIPTION
ENVIRONMENT
ALE_AS
ALE
I
Address-Latch Enable: This active-”High” signal is used to latch the contents on
the address bus, A[10:0]. The contents of the Address Bus are latched into the
A[10:0] inputs on the falling edge of ALE_AS. Additionally, this signal can be
used to indicate the start of a burst cycle.
RD_DS
RD*
I
Read Signal: This active-”Low” input functions as the read signal from the local
µP. When this signal goes "Low", the UNI Microprocessor Interface will place the
contents of the addressed register on the Data Bus pins (D[15:0]). The Data Bus
will be tri-stated once this input signal returns "High".
WR_R/W
WR*
I
Write Signal: This active-low input functions as the write signal from the local
µP. The contents of the Data Bus (D[15:0]) will be written into the addressed register (via A[10:0]), on the rising edge of this signal.
RDY_DTCK
READY*
O
Ready Output: This active-low signal is provided by the UNI device, and indicates that the current read or write cycle is to be extended until this signal is
asserted. The local µP will typically insert WAIT states until this signal is
asserted. This output will toggle "Low" when the device is ready for the next Read
or Write cycle.
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TABLE 4: PIN DESCRIPTION OF THE MICROPROCESSOR INTERFACE SIGNALS WHILE THE MICROPROCESSOR
INTERFACE IS OPERATING IN THE MOTOROLA MODE
PIN NAME
EQUIVALENT PIN
IN MOTOROLA
TYPE
DESCRIPTION
ENVIRONMENT
ALE_AS
AS*
I
Address Strobe: This active-low signal is used to latch the contents on the
address bus input pins: A[10:0] into the Microprocessor Interface circuitry. The
contents of the Address Bus are latched into the UNI device on the rising edge of
the ALE_AS signal. This signal can also be used to indicate the start of a burst
cycle.
RD_DS
DS*
I
Data Strobe: This signal latches the contents of the bi-directional data bus pins
into the Addressed Register (within the UNI) during a Write Cycle.
WR_R/W
R/W*
I
Read/Write* Input: When this pin is "High", it indicates a Read Cycle. When this
pin is "Low", it indicates a Write cycle.
RDY_DTCK
DTACK*
O
Data Transfer Acknowledge: The UNI device asserts DTACK* in order to inform
the CPU that the present READ or WRITE cycle is nearly complete. The 68000
family of CPU’s requires this signal from its peripheral devices, in order to quickly
and properly complete a READ or WRITE cycle.
2.3 INTERFACING THE XRT72L53 DS3/E3 FRAMER
TO THE LOCAL µC/µP VIA THE MICROPROCESSOR
INTERFACE BLOCK
The Microprocessor Interface block, within the Framer
is very flexible and provides the following options to
the user.
in this mode, the µC/µP can read or write data into
both even and odd numbered addresses within the
Framer address space.
Reading Performance Monitor (PMON) Registers
• To interface the Framer to a µC/µP over an 8-bit
wide bi-directional data bus.
The only issue that the user should be aware of (while
operating in the 8-bit mode) occurs whenever the µC/
µP needs to read the contents of one of the PMON
(Performance Monitor) registers.
• To interface the Framer to an Intel-type or Motorolatype µC/µP.
The XRT72L53 DS3/E3 Framer consists of the following PMON Registers.
• To transfer data (between the Framer IC and the
µC/µP) via the Programmed I/O or Burst Mode
• PMON LCV Event Count Register
Each of the options are discussed in detail below.
Section 2.3.1 will discussed the issues associated
with interfacing the Framer to a µC/µP over an 8-bit
bi-directional data bus. Afterwards, Section 2.3.2 will
discuss Data Access (e.g., Programmed I/O and
Burst) Mode when interfaced to both Motorola-type
and Intel-type µC/µP.
• PMON Received FEBE Event Count Register
2.3.1 Interfacing the XRT72L53 DS3/E3 Framer
to the Microprocessor over an 8 bit wide bi-directional Data Bus
The XRT72L53 DS3/E3 Framer Microprocessor Interface is used to interface it to a µC/µP over an 8-bit
wide bi-directional data bus.
• PMON Received Idle Cell Count Register
2.3.1.1 Interfacing the Framer to the µC/µP
over an 8-bit wide bi-directional data bus.
In general, interfacing the Framer to an 8-bit µC/µP is
quite straight-forward. This is because most of the
registers, within the Framer, are 8-bits wide. Further,
Unlike most of the registers within the Framer, the
PMON registers are 16-bit registers (or 16-bits wide).
Table 5 lists each of these PMON registers as consisting of two 8-bit registers. One of these 8-bit register is labeled MSB (or Most Significant Byte) and the
other register is labeled LSB (or Least Significant
• PMON Framing Error Event Count Register
• PMON Parity Error Event Count Register
• PMON Received Single-Bit HEC Error Count Register
• PMON Received Multiple-Bit HEC Error Count
Register
• PMON Received Valid Cell Count Register
• PMON Discarded Cell Count Register
• PMON Transmitted Idle Cell Count Register
• PMON Transmitted Valid Cell Count Register.
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2.3.2 Data Access Modes
As mentioned earlier, the Microprocessor Interface
block supports data transfer between the Framer and
the µC/µP (e.g., Read and Write operations) via two
modes: the Programmed I/O and the Burst Modes.
Each of these Data Access Modes are discussed in
detail below.
Byte). When an 8-bit PMON Register is concatenated
with its companion 8-bit PMON Register, one obtains
the full 16-bit expression within that PMON Register.
The consequence of having these 16-bit registers is
that an 8-bit µC/µP will have to perform two consecutive read operations in order to read in the full 16-bit
expression contained within a given PMON register.
To complicate matters, these PMON Registers are
Reset-Upon-Read registers. More specifically, these
PMON Register are Reset-Upon-Read in the sense
that, the entire 16-bit contents, within a given PMON
Register is reset, as soon as an 8-bit µC/µP reads in
either byte of this two-byte (e.g., 16 bit) expression.
2.3.2.1 Data Access using Programmed I/O
Programmed I/O is the conventional manner in which
a microprocessor exchanges data with a peripheral.
However, it is also the slowest method of data exchange between the Framer and the µC/µP.
The next two sections present detailed information on
Programmed I/O Access, when the XRT72L53 DS3/
E3 Framer is operating in the Intel Mode or in the Motorola Mode.
For example;
Consider that an 8-bit µC/µP needs to read in the
PMON LCV Event Count Register. In order to accomplish this task, the 8-bit µC/µP is going to have to read
in the contents of PMON LCV Event Count Register MSB (located at Address = 0x50) and the contents of
the PMON LCV Event Count Register - LSB (located
at Address = 0x51). These two eight-bit registers,
when concatenated together, make up the PMON
LCV Event Count Register.
2.3.2.1.1 Programmed I/O Access in the Intel
Mode
If the XRT72L53 DS3/E3 Framer is interfaced to an
Intel-type µC/µP (e.g., the 80x86 family, etc.), then it
should be configured to operate in the Intel mode (by
tying the MOTO pin to ground). Intel-type Read and
Write operations are described below.
If the 8-bit µC/µP reads in the PMON LCV Event
Count-LSB register first, then the entire PMON LCV
Event Count register will be reset to “0x0000”. As a
consequence, if the 8-bit µC/µP attempts to read in
the PMON LCV Event Count-MSB register in the very
next read cycle, it will read in the value “0x00”.
2.3.2.1.1.1 The Intel Mode Read Cycle
Whenever an Intel-type µC/µP wishes to read the
contents of a register or some location within the Receive LAPD Message buffer or the Receive OAM Cell
Buffer, (within the Framer), it should do the following.
1. Place the address of the target register or buffer
location (within the Framer) on the Address Bus
input pins A[10:0].
2. While the µC/µP is placing this address value on
the Address Bus, the Address Decoding circuitry
(within the user's system) should assert the CS
(Chip Select) pin of the Framer, by toggling it
"Low". This action enables further communication
between the µC/µP and the Framer Microprocessor Interface block.
3. Toggle the ALE_AS (Address Latch Enable) input
pin "High". This step enables the Address Bus
input drivers, within the Microprocessor Interface
block of the Framer.
4. After allowing the data on the Address Bus pins
to settle (by waiting the appropriate Address Data
Setup time), the µC/µP should toggle the
ALE_AS pin "Low". This step causes the Framer
to latch the contents of the Address Bus into its
internal circuitry. At this point, the address of the
register or buffer locations (within the Framer),
has now been selected.
5. Next, the µC/µP should indicate that this current
bus cycle is a Read Operation by toggling the
The PMON Holding Register
In order to resolve this Reset-Upon-Read problem,
the XRT72L53 DS3/E3 Framer includes a special
register, which permits 8-bit µC/µP to read in the full
16-bit contents of these PMON registers. This special
register is called the PMON Holding Register and is
located at 0x6c within the Framer Address space.
The operation of the PMON Holding register is as follows. Whenever an 8-bit µC/µP reads in one of the
bytes (of the 2-byte PMON register), the contents of
the unread (e.g., other) byte will be stored in the
PMON Holding Register. Therefore, the 8-bit µC/µP
must then read in the contents of the PMON Holding
Register in the very next read operation.
In Summary: Whenever an 8-bit µC/µP needs to
read a PMON Register, it must execute the following steps.
Step 1: Read in the contents of a given 8-bit PMON
Register (it does not matter whether the µC/µP reads
in the MSB or the LSB register).
Step 2: Read in the contents of the PMON Holding
Register (located at Address = 0x6c). This register
will contain the contents of the other byte.
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7. After some settling time, the data on the bi-directional data bus will stabilize and can be read by
the µC/µP. The XRT72L53 DS3/E3 Framer will
indicate that this data can be read by toggling the
RDY_DTCK (READY) signal "High".
8. After the µC/µP detects the RDY_DTCK signal
(from the XRT72L53 DS3/E3 Framer), it can then
terminate the Read Cycle by toggling the RD_DS
(Read Strobe) input pin "High".
Figure 25 presents a timing diagram which illustrates
the behavior of the Microprocessor Interface signals,
during an Intel-type Programmed I/O Read Operation.
RD_DS (Read Strobe) input pin "Low". This
action also enables the bi-directional data bus
output drivers of the Framer. At this point, the bidirectional data bus output drivers will proceed to
drive the contents of the latched addressed register (or buffer location) onto the bi-directional data
bus, D[7:0].
6. Immediately after the µC/µP toggles the Read
Strobe signal "Low", the Framer will toggle the
RDY_DTCK output pin "Low". The Framer does
this in order to inform the µC/µP that the data (to
be read from the data bus) is NOT READY to be
latched into the µC/µP.
FIGURE 25. BEHAVIOR OF MICROPROCESSOR INTERFACE SIGNALS DURING AN INTEL-TYPE PROGRAMMED I/O READ
OPERATION
ALE_AS
A(10:0)
Address of target Register
CS
D(7:0)
Not Valid
Valid
RD_DS
WR_R/W
RDY_DTCK
2.3.2.1.1.2 The Intel Mode Write Cycle
Whenever an Intel-type µC/µP wishes to write a byte
or word of data into a register or buffer location, within
the Framer, it should do the following.
4. After allowing the data on the Address Bus pins
to settle (by waiting the appropriate Address
Setup time), the µC/µP should toggle the
ALE_AS input pin "Low". This step causes the
Framer to latch the contents of the Address Bus
into its internal circuitry. At this point, the address
of the register or buffer location (within the
Framer), has now been selected.
5. Next, the µC/µP should indicate that this current
bus cycle is a Write Operation by toggling the
WR_R/W (Write Strobe) input pin "Low". This
action also enables the bi-directional data bus
input drivers of the Framer.
6. The µC/µP should then place the byte or word
that it intends to write into the target register, on
the bi-directional data bus, D[7:0].
7. After waiting the appropriate amount of time for
the data (on the bi-directional data bus) to settle,
1. Assert the ALE_AS (Address Latch Enable) input
pin by toggling it "High". When the µC/µP asserts
the ALE_AS input pin, it enables the Address Bus
Input Drivers within the Framer chip.
2. Place the address of the target register or buffer
location (within the Framer), on the Address Bus
input pins, A[10:0].
3. While the µC/µP is placing this address value
onto the Address Bus, the Address Decoding circuitry (within the user's system) should assert the
CS input pin of the Framer by toggling it "Low".
This step enables further communication
between the µC/µP and the Framer Microprocessor Interface block.
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b. It terminates the write cycle.
the µC/µP should toggle the WR_R/W (Write
Strobe) input pin "High". This action accomplishes two things:
a. It latches the contents of the bi-directional data
bus into the XRT72L53 DS3/E3 Framer Microprocessor Interface block.
Figure 26 presents a timing diagram which illustrates
the behavior of the Microprocessor Interface signals,
during an Intel-type Programmed I/O Write Operation.
FIGURE 26. BEHAVIOR OF THE MICROPROCESSOR INTERFACE SIGNALS, DURING AN INTEL-TYPE PROGRAMMED I/O
WRITE OPERATION
ALE_AS
A(10:0)
Address of Target Register
CS
D(7:0)
Data to be Written
RD_DS
WR_R/W
RDY_DTCK
2.3.2.1.2 Programmed I/O Access in the Motorola Mode
If the XRT72L53 DS3/E3 Framer is interfaced to a
Motorola-type µC/µP (e.g., the MC680X0 family, etc.),
it should be configured to operate in the Motorola
mode (by tying the MOTO pin to Vcc). Motorola-type
Programmed I/O Read and Write operations are described below.
4. After allowing the data on the Address Bus pins
to settle (by waiting the appropriate Address
Setup time), the µC/µP should toggle the
ALE_AS input pin "High". This step causes the
Framer to latch the contents of the Address Bus
into its internal circuitry. At this point, the address
of the register or buffer location (within the
Framer) has now been selected.
5. Further, the µC/µP should indicate that this cycle
is a Read cycle by setting the WR_R/W (R/W*)
input pin "High".
6. Next the µC/µP should initiate the current bus
cycle by toggling the RD_DS (Data Strobe) input
pin "Low". This step enables the bi-directional
data bus output drivers, within the XRT72L53
DS3/E3 Framer. At this point, the bi-directional
data bus output drivers will proceed to driver the
contents of the Address register onto the bi-directional data bus, D[7:0].
7. After some settling time, the data on the bi-directional data bus will stabilize and can be read by
the µC/µP. The XRT72L53 DS3/E3 Framer will
indicate that this data can be read by asserting
the RDY_DTCK (DTACK) signal.
8. After the µC/µP detects the RDY_DTCK signal
(from the XRT72L53 DS3/E3 Framer) it will termi-
2.3.2.1.2.1 The Motorola Mode Read Cycle
Whenever a Motorola-type µC/µP wishes to read the
contents of a register or some location within the Receive LAPD Message or Receive OAM Cell Buffer,
(within the Framer) it should do the following.
1. Assert the ALE_AS (Address-Strobe) input pin by
toggling it low. This step enables the Address Bus
input drivers, within the Microprocessor Interface
Block of the Framer IC.
2. Place the address of the target register (or buffer
location) within the Framer, on the Address Bus
input pins, A[10:0].
3. At the same time, the Address Decoding circuitry
(within the user's system) should assert the CS
(Chip Select) input pin of the Framer, by toggling
it "Low". This action enables further communication between the µC/µP and the Framer Microprocessor Interface block.
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during a Motorola-type Programmed I/O Read Operation.
nate the Read Cycle by toggling the RD_DS
(Data Strobe) input pin "High".
Figure 27 presents a timing diagram which illustrates
the behavior of the Microprocessor Interface signals
FIGURE 27. ILLUSTRATION OF THE BEHAVIOR OF MICROPROCESSOR INTERFACE SIGNALS, DURING A MOTOROLAPROGRAMMED I/O READ OPERATION
TYPE
ALE_AS
A(10:0)
Address of target Register
CS
D(7:0)
Not Valid
Valid Data
RD_DS
WR_R/W
RDY_DTCK
2.3.2.1.2.2 The Motorola Mode Write Cycle
Whenever a Motorola-type µC/µP wishes to write a
byte or word of data into a register or buffer location,
within the Framer, it should do the following.
6. The µC/µP should then place the byte or word
that it intends to write into the target register, on
the bi-directional data bus, D[7:0].
7. Next, the µC/µP should initiate the bus cycle by
toggling the RD_DS (Data Strobe) input pin
"Low". When the XRT72L53 DS3/E3 Framer
senses that the WR_R/W (R/W*) input pin is
"High" and that the RD_DS (Data Strobe) input
pin has toggled "Low", it will enable the input drivers of the bi-directional data bus, D[7:0].
8. After waiting the appropriate time, for this newly
placed data to settle on the bi-directional data
bus (e.g., the Data Setup time) the Framer will
assert the RDY_DTCK output signal.
9. After the µC/µP detects the RDY_DTCK signal
(from the Framer), the µC/µP should toggle the
RD_DS input pin "High". This action accomplishes two things.
a. It latches the contents of the bi-directional data
bus into the XRT72L53 DS3/E3 Microprocessor
Interface block.
1. Assert the ALE_AS (Address Select) input pin by
toggling it "Low". This step enables the Address
Bus input drivers (within the Framer chip).
2. Place the address of the target register or buffer
location (within the Framer), on the Address Bus
input pins, A[10:0].
3. While the µC/µP is placing this address value
onto the Address Bus, the Address-Decoding circuitry (within the user's system) should assert the
CS (Chip Select) input pins of the Framer by toggling it "Low". This step enables further communication between the µC/µP and the Framer Microprocessor Interface block.
4. After allowing the data on the Address Bus pins
to settle (by waiting the appropriate Address
Setup time), the µC/µP should toggle the
ALE_AS input pin "High". This step causes the
Framer to latch the contents of the Address Bus
into its own circuitry. At this point, the Address of
the register or buffer location (within the Framer),
has now been selected.
5. Further, the µC/µP should indicate that this current bus cycle is a Write operation by toggling the
WR_R/W (R/W*) input pin "Low".
b. It terminates the Write cycle.
Figure 28 presents a timing diagram which illustrates
the behavior of the Microprocessor Interface signals,
during a Motorola-type Programmed I/O Write Operation.
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FIGURE 28. ILLUSTRATION OF THE BEHAVIOR OF THE MICROPROCESSOR INTERFACE SIGNAL, DURING A MOTOROLAPROGRAMMED I/O WRITE OPERATION
TYPE
ALE_AS
A(10:0)
Address of target Register
CS
D(7:0)
Data to be Written
RD_DS
WR_R/W
RDY_DTCK
2.3.2.2.1 Burst I/O Access in the Intel Mode
If the XRT72L53 DS3/E3 Framer is interfaced to an
Intel-type µC/µP (e.g., the 80x86 family, etc.), then it
should be configured to operate in the Intel mode (by
tying the MOTO pin to ground). Intel-type Read and
Write Burst I/O Access operations are described below.
2.3.2.2 Data Access using Burst Mode I/O
Burst Mode I/O access is a much faster way to transfer data between the µC/µP and the Microprocessor
Interface (of the XRT72L53 DS3/E3 Framer), than
Programmed I/O. The reason why Burst Mode I/O is
faster is explained below.
Data is placed upon the Address Bus input pins
A[10:0] only for the very first access, within a given
burst access. The remaining read or write operations
(within this burst access) do not require the placement of the Address Data on the Address Data Bus.
As a consequence, the user does not have to wait
through the Address Setup and Hold times for each of
these Read/Write operation, within the Burst Access.
2.3.2.2.1.1 The Intel-Mode Read Burst Access
Whenever an Intel-type µC/µP wishes to read the
contents of numerous registers or buffer locations
over a contiguous range of addresses, then it should
do the following.
a.
It is important to note that there are some limitations
associated with Burst Mode I/O Operations.
Perform the initial read operation of the burst
access.
b. Perform the remaining read operations of the
burst access.
1. All cycles within the Burst Access, must be either
all Read or all Write cycles. No mixing of Read
and Write cycles is permitted.
2. A Burst Access can only be used when Read or
Write operations are to be employed over a contiguous range of address locations, within the
Framer.
3. The very first Read or Write cycle, within a burst
access, must start at the lowest address value, of
the range of addresses to be accessed. Subsequent operations will automatically be incremented to the very next higher address value.
Examples of Burst Mode I/O operations are presented below for read and write operations, with both Intel-type and Motorola-type µC/µP.
c. Terminate the burst access operation.
Each of these operations within the burst access are
described below.
2.3.2.2.1.1.1 The Initial Read Operation
The initial read operation of an Intel-type read burst
access is accomplished by executing a Programmed
I/O Read Cycle as summarized below.
A.0 Execute a Single Ordinary (Programmed I/
O) Read Cycle, as described in steps A.1
through A.7 below.
A.1 Place the address of the initial-target register or
buffer location (within the Framer) on the
Address Bus input pins A[10:0].
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A.2 While the µC/µP is placing this address value
onto the Address Bus, the Address Decoding
circuitry (within the user's system) should
assert the CS input pin of the Framer, by toggling it "Low". This step enables further communication between the µC/µP and the Framer
Microprocessor Interface block.
output drivers of the Framer. At this point, the
bi-directional data bus output drivers will proceed to drive the contents of the addressed
register onto the bi-directional data bus, D[7:0].
A.6 Immediately after the µC/µP toggles the Read
Strobe signal "Low", the Framer will toggle the
RDY_DTCK (READY) output pin "Low". The
Framer does this in order to inform the µC/µP
that the data (to be read from the data bus) is
NOT READY to be latched into the µC/µP.
A.3 Assert the ALE_AS (Address Latch Enable) pin
by toggling it "High". This step enables the
Address Bus input drivers, within the Microprocessor Interface block of the Framer.
A.7 After some settling time, the data on the bidirectional data bus will stabilize and can be
read by the µC/µP. The XRT72L53 DS3/E3
Framer will indicate that this data is ready to be
read, by toggling the RDY_DTCK (Ready) signal "High".
A.4 After allowing the data on the Address Bus pins
to settle (by waiting the appropriate Address
Data Setup time), the µC/µP should then toggle
the ALE_AS pin "Low". This step latches the
contents, on the Address Bus pins, A[10:0], into
the XRT72L53 DS3/E3 Framer Microprocessor
Interface block. At this point, the initial address
of the burst access has now been selected.
A.8 After the µC/µP detects the RDY_DTCK signal
(from the XRT72L53 DS3/E3 Framer IC), it can
then will terminate the Read cycle by toggling
the RD_DS (Read Strobe) input pin "High".
NOTE: The ALE_AS input pin should remain "Low" for the
remainder of this Burst Access operation.
Figure 29 presents an illustration of the behavior of
the Microprocessor Interface Signals, during the initial
Read Operation, within a Burst I/O Cycle for an Inteltype µC/µP.
A.5 Next, the µC/µP should indicate that this current bus cycle is a Read Operation by toggling
the RD_DS (Read Strobe) input pin "Low". This
action also enables the bi-directional data bus
FIGURE 29. BEHAVIOR OF THE MICROPROCESSOR INTERFACE SIGNALS, DURING THE INITIAL READ OPERATION OF A
BURST CYCLE (INTEL TYPE PROCESSOR)
ALE_AS
A(10:0)
Address of "Initial" Target Register (Offset = 0x00)
CS
Not Valid
D(7:0)
Valid Data of
Offset = 0x00
RD_DS
WR_R/W
RDY_DTCK
label indicates that the µC/µP is reading the very first
register (or buffer location) in this burst access operation.
At the completion of this initial read cycle, the µC/µP
has read in the contents of the first register or buffer
location (within the XRT72L53 DS3/E3 Framer) for
this particular burst I/O access operation. In order to
illustrate how this burst access operation works, the
byte (or word) of data, that is being read in Figure 29,
has been labeled Valid Data at Offset = “0x00”. This
2.3.2.2.1.1.2 The Subsequent Read Operations
The procedure that the µC/µP must use to perform
the remaining read cycles, within this Burst Access
operation, is presented below.
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B.0 Execute each subsequent Read Cycles, as
described in steps 1 through 3 below.
(READY) output pin "Low" to indicate its NOT
READY status.
B.1 Without toggling the ALE_AS input pin (e.g.,
keeping it "Low"), toggle the RD_DS input pin
"Low". This step accomplishes the following.
B.3 After some settling time, the data on the bidirectional data bus will stabilize and can be
read by the µC/µP. The XRT72L53 DS3/E3
Framer will indicate that this data is ready to be
read by toggling the RDY_DTCK (READY) signal "High".
a. The Framer will internally increments the latched
address value (within the Microprocessor Interface circuitry).
B.4 After the µC/µP detects the RDY_DTCK signal
(from the XRT72L53 DS3/E3 Framer), it can
then terminates the Read cycle by toggling the
RD_DS (Read Strobe) input pin "High".
b. The output drivers of the bi-directional data bus,
D[7:0] are enabled. At some time later, the register or buffer location corresponding to the incremented latched address value will be driven onto
the bi-directional data bus.
For subsequent read operations, within this burst cycle, the µC/µP simply repeats steps 1 through 3, as illustrated in Figure 30.
B.2 Immediately after the Read Strobe pin toggles
"Low" the Framer IC will toggle the RDY_DTCK
FIGURE 30. BEHAVIOR OF THE MICROPROCESSOR INTERFACE SIGNALS, DURING SUBSEQUENT READ OPERATIONS
BURST I/O CYCLE
WITHIN THE
ALE_AS
A(10:0)
Address of "Initial" Target Register (Offset = 0x00)
CS
D(7:0)
Not Valid
Valid Data at
Offset = 0x01
Not Valid
Valid Data at
Offset = 0x02
RD_DS
WR_R/W
RDY_DTCK
The Burst Access Operation will be terminated upon
the rising edge of the ALE_AS input signal. At this
point the Framer will cease to internally increment the
latched address value. Further, the µC/µP is now free
to execute either a Programmed I/O access or to start
another Burst Access Operation with the XRT72L53
DS3/E3 Framer.
In addition to the behavior of the Microprocessor Interface signals, Figure 30 also illustrates other points
regarding the Burst Access Operation.
a. The Framer internally increments the address
value, from the original latched value shown in
Figure 29. This is illustrated by the data, appearing on the data bus, (for the first read access)
being labeled Valid Data at Offset = 0x01 and that
for the second read access being labeled Valid
Data at Offset = 0x02.
2.3.2.2.1.2 The Intel-Mode Write Burst Access
Whenever an Intel-type µC/µP wishes to write data into a contiguous range of addresses, then it should do
the following.
b. The Framer performs this address incrementing
process even though there are no changes in the
Address Bus Data, A[10:0].
2.3.2.2.1.1.3
Operation
a. Perform the initial write operation of the burst
access.
Terminating the Burst Access
b. Perform the remaining write operations, of the
burst access.
c. Terminate the burst access operation.
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the XRT72L53 DS3/E3 Framer Microprocessor
Interface block. At this point, the initial address
of the burst access has now been selected.
Each of these operations within the burst access are
described below.
2.3.2.2.1.2.1 The Initial Write Operation
The initial write operation of an Intel-type Write Burst
Access is accomplished by executing a Programmed
I/O write cycle as summarized below.
NOTE: The ALE_AS input pin should remain "Low" for the
remainder of this Burst I/O Access operation.
A.5 Next, the µC/µP should indicate that this current bus cycle is a Write operation by keeping
the RD_DS pin "High" and toggling the WR_R/
W (Write Strobe) pin "Low". This action also
enables the bi-directional data bus input drivers
of the Framer.
A.0 Execute a Single Ordinary (Programmed I/
O) Write cycle, as described in Steps A.1
through A.7 below.
A.1 Place the address of the initial target register
(or buffer location) within the Framer, on the
Address Bus pins, A[10:0].
A.6 The µC/µP places the byte (or word) that it
intends to write into the target register on the
bi-directional data bus, D[7:0].
A.2 At the same time, the Address-Decoding circuitry (within the user's system) should assert
the CS (Chip Select) input pin of the Framer, by
toggling it "Low". This step enables further
communication between the µC/µP and the
Framer Microprocessor Interface block.
A.7 After waiting the appropriate amount of time, for
the data (on the bi-directional data bus) to settle, the µC/µP should toggle the WR_R/W (Write
Strobe) input pin "High". This action accomplishes two things.
A.3 Assert the ALE_AS (Address Latch Enable)
input pin "High". This step enables the Address
Bus input drivers, within the Microprocessor
Interface Block of the Framer.
a. It latches the contents of the bi-directional data
bus into the XRT72L53 DS3/E3 Framer Microprocessor Interface Block.
b. It terminates the write cycle.
A.4 After allowing the data on the Address Bus pins
to settle (by waiting the appropriate Address
Setup time), the µC/µP should then toggle the
ALE_AS input pin "Low". This step latches the
contents, on the Address Bus pins, A[10:0], into
Figure 31 presents a timing diagram which illustrates
the behavior of the Microprocessor Interface signals,
during the initial write operation within a Burst Access, for an Intel-type µC/µP.
FIGURE 31. BEHAVIOR OF THE MICROPROCESSOR INTERFACE SIGNALS, DURING THE INITIAL WRITE OPERATION OF
BURST CYCLE (INTEL-TYPE PROCESSOR)
A
ALE_AS
A(10:0)
Address of "Initial" Target Register (Offset = 0x00)
CS
Data to be Written
(Offset = 0x00)
D(7:0)
RD_DS
WR_R/W
RDY_DTCK
illustrate this point, the byte (or word) of data, that is
being written in Figure 31 has been labeled Data to
be Written (Offset = 0x00).
At the completion of this initial write cycle, the µC/µP
has written a byte or word into the first register or
buffer location (within the XRT72L53 DS3/E3 Framer)
for this particular burst access operation. In order to
2.3.2.2.1.2.2
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The Subsequent Write Operations
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a. It enables the input drivers of the bi-directional
data bus.
The procedure that the µC/µP must use to perform
the remaining write cycles, within this burst access
operation, is presented below.
b. It causes the Framer to internally increment the
value of the latched address.
B.0 Execute each subsequent write cycle, as
described in steps B.1 through B.3.
B.3 After waiting the appropriate amount of settling
time the data, in the internal data bus, will stabilize and is ready to be latched into the Framer
Microprocessor Interface block. At this point,
the µC/µP should latch the data into the Framer
by toggling the WR_R/W input pin "High".
B.1 Without toggling the ALE_AS input pin (e.g.,
keeping it "Low"), apply the value of the next
byte or word (to be written into the Framer) to
the bi-directional data bus pins, D[7:0].
B.2 Toggle the WR_R/W (Write Strobe) input pin
"Low". This step accomplishes two things.
For subsequent write operations, within this burst I/O
access, the µC/µP simply repeats steps B.1 through
B.3, as illustrated in Figure 32.
FIGURE 32. BEHAVIOR OF THE MICROPROCESSOR INTERFACE SIGNALS, DURING SUBSEQUENT WRITE OPERATIONS
BURST I/O CYCLE
WITHIN THE
ALE_AS
A(10:0)
Address of "Initial" Target Register (Offset = 0x00)
CS
D(7:0)
Data Written at Offset = 0x01
Data Written at Offset = 0x02
RD_DS
WR_R/W
RDY_DTCK
2.3.2.2.1.2.3 Terminating the Burst I/O Access
Burst Access Operation will be terminated upon the
rising edge of the ALE_AS input signal. At this point
the Framer will cease to internally increment the
latched address value. Further, the µC/µP is now free
to execute either a Programmed I/O access or to start
another Burst Access Operation with the XRT72L53
DS3/E3 Framer.
Whenever a Motorola-type µC/µP wishes to read the
contents of numerous registers or buffer locations
over a contiguous range of addresses, then it should
do the following.
a. Perform the initial Read operation of the burst
access.
b. Perform the remaining read operations in the
burst access.
2.3.2.2.2 Burst I/O Access in the Motorola
Mode
If the XRT72L53 DS3/E3 Framer is interfaced to a
Motorola-type µC/µP (e.g., the MC680x0 family, etc.),
then it should be configured to operate in the Motorola mode (by tying the MOTO pin to VCC). Motorolatype Read and Write Burst I/O Access operations are
described below.
c. Terminate the burst access operation.
Each of these operations, within the Burst Access are
discussed below.
2.3.2.2.2.1.1 The Initial Read Operation
The initial read operation of a Motorola-type read
burst access is accomplished by executing a Programmed I/O Read cycle, as summarized below.
2.3.2.2.2.1 The Motorola-Mode Read Burst I/O
Access Operation
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A.0 Execute a Single Ordinary (Programmed I/
O) Read Cycle, as described in steps A.1
through A.8 below.
A.5 Further, the µC/µP should indicate that this
cycle is a Read cycle by setting the WR_R/W
(R/W*) input pin "High".
A.1 Assert the ALE_AS (AS*) input pin by toggling
it "Low". This step enables the Address Bus
input drivers (within the XRT72L53 DS3/E3
Framer) within the Framer Microprocessor
Interface Block.
A.6 Next the µC/µP should initiate the current bus
cycle by toggling the RD_DS (Data Strobe)
input pin "Low". This step will enable the bidirectional data bus output drivers, within the
XRT72L53 DS3/E3 Framer. At this point, the bidirectional data bus output drivers will proceed
to driver the contents of the Address register
onto the bi-directional data bus.
A.2 Place the address of the initial target register or
buffer location (within the Framer), on the
Address Bus input pins, A[10:0].
A.7 After some settling time, the data on the bidirectional data bus will stabilize and can be
read by the µC/µP. The XRT72L53 DS3/E3
Framer will indicate that this data can be read
by asserting the RDY_DTCK (DTACK) signal.
A.3 At the same time, the Address-Decoding circuitry (within the user's system) should assert
the CS (Chip Select) input pins of the Framer
by toggling it "Low". This action enables further
communication between the µC/µP and the
Framer Microprocessor Interface block.
A.8 After the µC/µP detects the RDY_DTCK signal
(from the XRT72L53 DS3/E3 Framer) it will terminate the Read Cycle by toggling the RD_DS
(Data Strobe) input pin "High".
A.4 After allowing the data on the Address Bus pins
to settle (by waiting the appropriate Address
Setup time), the µC/µP should toggle the
ALE_AS input pin "High". This step causes the
Framer to latch the contents of the Address Bus
into its internal circuitry. At this point, the initial
address of the burst access has now been
selected.
Figure 33 presents an illustration of the behavior of
the Microprocessor Interface Signals during the initial
Read Operation, within a Burst I/O Cycle, for a Motorola-type µC/µP.
FIGURE 33. BEHAVIOR OF THE MICROPROCESSOR INTERFACE SIGNALS, DURING THE INITIAL READ OPERATION OF A
BURST CYCLE (MOTOROLA TYPE PROCESSOR)
ALE_AS
A(10:0)
Address of "Initial" Target Register (Offset = 0x00)
CS
Not Valid
D(7:0)
Valid Data at
Offset = 0x00
RD_DS
WR_R/W
RDY_DTCK
beled Valid Data at Offset = “0x00”. This indicates
that the µC/µP is reading the very first register (or
buffer location) in this burst access.
At the completion of this initial read cycle, the µC/µP
has read in the contents of the first register or buffer
location (within the XRT72L53 DS3/E3 Framer) for
this particular burst access operation. In order to illustrate how this burst I/O cycle works, the byte (or word)
of data, that is being read in Figure 33 has been la-
2.3.2.2.2.1.2
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The Subsequent Read Operations
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The procedure that the µC/µP must use to perform
the remaining read cycles, within this Burst Access
operation, is presented below.
NOTE: In order to insure that the XRT72L53 DS3/E3
Framer will interpret this signal as being a Read signal, the
µC/µP should keep the WR_R/W input pin "High".
B.0 Execute each subsequent Read Cycle, as
described in steps B.1 through B.3, below.
B.2 After some settling time, the data on the bidirectional data bus will stabilize and can be
read by the µC/µP. The XRT72L53 DS3/E3
Framer will indicate that this data is ready to be
read by asserting the RDY_DTCK (DTACK*)
signal.
B.1 Without toggling the ALE_AS input pin (e.g.,
keeping it "High"), toggle the RD_DS (Data
Strobe) input pin "Low". This step accomplishes the following.
B.3 After the µC/µP detects the RDY_DTCK signal
(from the XRT72L53 DS3/E3 Framer), it terminates the Read cycle by toggling the RD_DS
(Data Strobe) input pin "High".
a. The Framer internally increments the latched
address value (within the Microprocessor Interface circuitry).
b. The output drivers of the bi-directional data bus
(D[7:0]) are enabled. At some time later, the register or buffer location corresponding to the incremented latched address value will be driven onto
the bi-directional data bus.
For subsequent read operations, within this burst cycle, the µC/µP simply repeats steps B.1 through B.3,
as illustrated in Figure 34.
FIGURE 34. BEHAVIOR THE MICROPROCESSOR INTERFACE SIGNALS, DURING SUBSEQUENT READ OPERATIONS
BURST I/O CYCLE (MOTOROLA-TYPE µC/µP)
WITHIN THE
ALE_AS
A(10:0)
Address of "Initial" Target Register (Offset = 0x00)
CS
D(7:0)
Not Valid
Valid Data at
Offset = 0x01
Not Valid
Valid Data at
Offset = 0x02
RD_DS
WR_R/W
RDY_DTCK
2.3.2.2.2.1.3 Terminating the Burst Access
Operation
The Burst I/O Access will be terminated upon the falling edge of the ALE_AS input signal. At this point the
Framer will cease to internally increment the latched
address value. Further, the µC/µP is now free to execute either a Programmed I/O access or to start another Burst Access Operation with the XRT72L53
DS3/E3 Framer.
over a contiguous range of addresses, then it should
do the following.
a. Perform the initial write operation of the burst
access.
b. Perform the remaining write operations, of the
burst access.
c. Terminate the burst access operation.
Each of these operations within the burst access are
described below.
2.3.2.2.2.2 The Motorola-Mode Write Burst
Access
Whenever a Motorola-type µC/µP wishes to write the
contents of numerous registers or buffer locations
2.3.2.2.2.2.1 The Initial Write Operation
The initial write operation of a Motorola-type Write
Burst Access is accomplished by executing a Programmed I/O Write Cycle as summarized below.
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A.0 Execute a Single Ordinary (Programmed I/
O) Write cycle, as described in Steps A.1
through A.7 below.
A.6 The µC/µP should then place the byte or word
that it intends to write into the target register, on
the bi-directional data bus, D[7:0].
A.1 Assert the ALE_AS (Address Strobe) input pin
by toggling it "Low". This step enables the
Address Bus input drivers (within the
XRT72L53 DS3/E3 Framer).
A.7 Next, the µC/µP should initiate the bus cycle by
toggling the RD_DS (Data Strobe) input pin
"Low". When the XRT72L53 DS3/E3 Framer
senses that the WR_R/W input pin is "Low", and
that the RD_DS input pin has toggled "Low" it
will enable the input drivers of the bi-directional
data bus, D[7:0].
A.2 Place the address of the initial target register or
buffer location (within the Framer), on the
Address Bus input pins, A[10:0].
A.8 After waiting the appropriate amount of time, for
this newly placed data to settle on the bi-directional data bus (e.g., the Data Setup time) the
Framer will assert the RDY_DTCK (DTACK)
output signal.
A.3 At the same time, the Address-Decoding circuitry (within the user's system) should assert
the CS input pin of the Framer by toggling it
"Low". This step enables further communication between the µC/µP and the Framer Microprocessor Interface block.
A.9 After the µP/µC detects the RDY_DTCK signal
(from the Framer) it should toggle the RD_DS
input pin "High". This action accomplishes two
things:
A.4 After allowing the data on the Address Bus pins
to settle (by waiting the appropriate Address
Setup time), the µC/µP should toggle the
ALE_AS input pin "High". This step causes the
Framer to latch the contents of the Address Bus
into its own circuitry. At this point, the initial
address of the burst access has now been
selected.
a. It latches the contents of the bi-directional data
bus into the XRT72L53 DS3/E3 Framer Microprocessor Interface block.
b. It terminates the Write cycle.
Figure 35 presents a timing diagram which illustrates
the behavior of the Microprocessor Interface signals,
during the Initial write operation within a Burst Access, for a Motorola-type µC/µP.
A.5 Further, the µC/µP should indicate that this current bus cycle is a Write operation by toggling
the WR_R/W (R/W*) input pin "Low".
FIGURE 35. BEHAVIOR OF THE MICROPROCESSOR INTERFACE SIGNALS, DURING THE INITIAL WRITE OPERATION OF
BURST CYCLE (MOTOROLA-TYPE PROCESSOR)
A
ALE_AS
A(10:0)
Address of "Initial" Target Register (Offset = 0x00)
CS
D(7:0)
Data to be Written
(Offset = 0x00)
RD_DS
WR_R/W
RDY_DTCK
trate how this burst I/O cycle works, the byte (or word)
of data, that is being written in Figure 35 has been labeled Data to be Written (Offset = 0x00).
At the completion of this initial write cycle, the µC/µP
has written a byte or word into the first register or
buffer location (within the XRT72L53 DS3/E3 Framer)
for this particular burst I/O access. In order to illus65
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REV. P1.1.7
b. The input drivers of the bi-directional data bus are
enabled.
2.3.2.2.2.2.2 The Subsequent Write Operations
The procedure that the µC/µP must use to perform
the remaining write cycles, within this burst access
operation, is presented below.
NOTE: In order to insure that the XRT72L53 DS3/E3
Framer will interpret this signal as being a Write signal, the
µC/µP should keep the WR_R/W input pin "Low".
B.0 Execute each subsequent write cycle, as
described in Steps B.1 through B.3
B.2 Toggle the RD_DS (Data Strobe) input pin
"Low". This step accomplishes the following.
B.3 After some settling time, the data, in the internal data bus, will stabilize and is ready to be
latched into the Framer Microprocessor Interface block. The Microprocessor Interface block
will indicate that this data is ready to be latched
by asserting the RDY_DTCK (DTACK) output
signal. At this point, the µC/µP should latch the
data into the Framer by toggling the RD_DS
input pin "High".
a. The Framer internally increments the latched
address value (within the Microprocessor Interface).
For subsequent write operations, within this burst I/O
access, the µC/µP simply repeats steps B.1 through
B.3 as illustrated in Figure 36.
B.1 Without toggling the ALE_AS (Address Strobe)
input pin (e.g., keeping it "High"), apply the
value of the next byte or word (to be written into
the Framer) to the bi-directional data bus pins,
D[7:0].
FIGURE 36. BEHAVIOR OF THE MICROPROCESSOR INTERFACE SIGNALS, DURING SUBSEQUENT WRITE OPERATIONS
BURST I/O CYCLE (MOTOROLA-TYPE µC/µP)
WITH THE
ALE_AS
A(10:0)
Address of "Initial" Target Register (Offset = 0x00)
CS
D(7:0)
Data Written at Offset = 0x01
Data Written at Offset = 0x02
RD_DS
WR_R/W
RDY_DTCK
• Perform status monitoring
2.3.2.2.2.2.3 Terminating the Burst I/O Access
The Burst I/O Access will be terminated upon the falling edge of the ALE_AS input signal. At this point the
Framer will cease to internally increment the latched
address value. Further, the µC/µP is now free to execute either a Programmed I/O access or to start another Burst I/O Access with the XRT72L53 DS3/E3
Framer.
• Enable/Disable and service Interrupt Conditions
All of these things are accomplished by reading from
and writing to the many on-chip registers within the
Framer. Table 5 lists each of these registers and their
corresponding address locations within the Framer
Address space.
2.4 ON-CHIP REGISTER ORGANIZATION
The Microprocessor Interface section, within the
Framer allows the user to do the following.
2.4.1 Framer Register Addressing
The array of on-chip registers consists of a variety of
register types. These registers are denoted in
Table 5, as follows.
• Configure the Framer into a wide variety of operating modes.
R/O - Read Only Registers.
R/W - Read/Write Registers
• Employ various features of the Framer.
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The bit-format and definitions for each of these registers are presented in Section 3.3.2
RUR - Reset-upon-Read Registers
Additionally, some of these registers consists of both
R/O and R/W bit-fields. These registers are denoted
in Table 5 as Combination of R/W and R/O.
TABLE 5: REGISTER ADDRESSING OF THE FRAMER PROGRAMMER REGISTERS
ADDRESS
REGISTER NAME
POWER UP DEFAULT VALUE
REGISTER TYPE
0x00
Operating Mode register
b00100011
R/W
0x01
I/O Control Register
b10100000
R/W, R/O
0x02
Part Number Register
b00000001
R/O
0x03
Version Number Register
b00000011
R/O
0x04
Block Interrupt Enable Register
b00000000
R/W
0x05
Block Interrupt Status Register
b00000000
R/O
b00000000
R/W, R/O
0x06-0x0B Reserved
0x0C
Test Register
0x0D-0x0F Reserved
0x10
RxDS3 Configuration & Status Register
RxE3 Configuration & Status Register 1 - G.832
RxE3 Configuration & Status Register 1 - G.751
b00010000
b00000010
b00000010
R/W, R/O
0x11
RxDS3 Status Register
RxE3 Configuration & Status Register 2 - G.832
RxE3 Configuration & Status Register 2 - G.751
b00000000
b01100111
b01100111
R/W, R/O
0x12
RxDS3 Interrupt Enable Register
RxE3 Interrupt Enable Registers -1 G.832
RxE3 Interrupt Enable Registers - 1 G.751
b00000000
b00000000
b00000000
R/W, R/O
0x13
RxDS3 Interrupt Status Register
RxE3 Interrupt Enable Register -2 G.832
RxE3 Interrupt Enable Register - 2 G.751
b00000000
b00000000
b00000000
R/W, R/O
0x14
RxDS3 Sync Detect Enable Register
RxE3 Interrupt Status Register 1 - G.832
RxE3 Interrupt Status Register 1 - G.751
b00011111
b00000000
b00000000
RUR, R/O
0x15
RxE3 Interrupt Status Register 2 - G.832
RxE3 Interrupt Status Register 2 - G.751
b00000000
b00000000
RUR, R/O
0x16
RxDS3 FEAC Register
b01111110
R/O
0x17
RxDS3 FEAC Interrupt Enable/Status Register
b00000000
R/O
0x18
RxDS3 LAPD Control Register
RxE3 LAPD Control Register
b00000000
R/W, RUR
0x19
RxDS3 LAPD Status Register
RxE3 LAPD Status Register
b00000000
b00000000
R/O
0x1A
RxE3 NR Byte Register - G.832
RxE3 Service Bit Register G.751
b00000000
b00000000
R/O
0x1B
RxE3 GC Byte Register - G.832
b00000000
R/O
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TABLE 5: REGISTER ADDRESSING OF THE FRAMER PROGRAMMER REGISTERS
ADDRESS
REGISTER NAME
POWER UP DEFAULT VALUE
REGISTER TYPE
0x1C
RxE3 TTB-0 Register - G.832
b00000000
R/O
0x1D
RxE3 TTB-1 Register - G.832
b00000000
R/O
0x1E
RxE3 TTB-2 Register - G.832
b00000000
R/O
0x1F
RxE3 TTB-3 Register - G.832
b00000000
R/O
0x20
RxE3 TTB-4 Register - G.832
b00000000
R/O
0x21
RxE3 TTB-5 Register - G.832
b00000000
R/O
0x22
RxE3 TTB-6 Register - G.832
b00000000
R/O
0x23
RxE3 TTB-7 Register - G.832
b00000000
R/O
0x24
RxE3 TTB-8 Register - G.832
b00000000
R/O
0x25
RxE3 TTB-9 Register - G.832
b00000000
R/O
0x26
RxE3 TTB-10 Register - G.832
b00000000
R/O
0x27
RxE3 TTB-11 Register - G.832
b00000000
R/O
0x28
RxE3 TTB-12 Register - G.832
b00000000
R/O
0x29
RxE3 TTB-13 Register - G.832
b00000000
R/O
0x2A
RxE3 TTB-14 Register - G.832
b00000000
R/O
0x2B
RxE3 TTB-15 Register - G.832
b00000000
R/O
0x2C
RxSSM Register - G.832
b0xxx0000
R/W, R/O
b00000000
R/O
0x2C - 0x2F Reserved
0x30
TxDS3 Configuration Register
TxE3 Configuration Register - G.832
TxE3 Configuration Register - G.751
b00000111
b00000000
b00000000
R/W
0x31
TxDS3 FEAC Configuration and Status Register
b00000000
R/O, R/W, RUR
0x32
TxDS3 FEAC Register
b01111110
R/W
0x33
TxDS3 LAPD Configuration Register
TxE3 LAPD Configuration Register
b00000000
b00000000
R/W
0x34
TxDS3 LAPD Status/Interrupt Register
TxE3 LAPD Status/Interrupt Register
b00000000
b00000000
R/W, R/O, RUR
0x35
TxDS3 M-Bit Mask Register
TxE3 GC Byte Register - G.832
TxE3 Service Bits Register - G.751
b00000000
b00000000
b00000000
R/W
0x36
TxDS3 F-Bit Mask Register 1
TxE3 MA Byte Register - G.832
b00000000
b00000000
R/W
0x37
TxDS3 F-Bit Mask Register 2
TxE3 NR Byte Register - G.832
b00000000
b00000000
R/W
0x38
TxDS3 F-Bit Mask Register 3
TxE3 TTB-0 Register - G.832
b00000000
b00000000
R/W
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TABLE 5: REGISTER ADDRESSING OF THE FRAMER PROGRAMMER REGISTERS
ADDRESS
REGISTER NAME
POWER UP DEFAULT VALUE
REGISTER TYPE
0x39
TxDS3 F-Bit Mask Register 4
TxE3 TTB-1 Register - G.832
b00000000
b00000000
R/W
0x3A
TxE3 TTB-2 Register - G.832
b00000000
R/W
0x3B
TxE3 TTB-3 Register - G.832
b00000000
R/W
0x3C
TxE3 TTB-4 Register - G.832
b00000000
R/W
0x3D
TxE3 TTB-5 Register - G.832
b00000000
R/W
0x3E
TxE3 TTB-6 Register - G.832
b00000000
R/W
0x3F
TxE3 TTB-7 Register - G.832
b00000000
R/W
0x40
TxE3 TTB-8 Register - G.832
b00000000
R/W
0x41
TxE3 TTB-9 Register - G.832
b00000000
R/W
0x42
TxE3 TTB-10 Register - G.832
b00000000
R/W
0x43
TxE3 TTB-11 Register - G.832
b00000000
R/W
0x44
TxE3 TTB-12 Register - G.832
b00000000
R/W
0x45
TxE3 TTB-13 Register - G.832
b00000000
R/W
0x46
TxE3 TTB-14 Register - G.832
b00000000
R/W
0x47
TxE3 TTB-15 Register - G.832
b00000000
R/W
0x48
TxE3 FA1 Error Mask Register - G.832
TxE3 FAS Error Mask Upper Register - G.751
b00000000
b00000000
R/W
0x49
TxE3 FA2 Error Mask Register - G.832
TxE3 FAS Error Mask Lower Register - G.751
b00000000
b00000000
R/W
0x4A
TxE3 BIP-8 Mask Register - G.832
TxE3 BIP-4 Mask Register - G.751
b00000000
b00000000
R/W
0x4B
TxSSM Register - G.832
b0xxx0000
R/W
0x4C-0x4F Reserved
0x50
PMON LCV Event Count Register - MSB
b00000000
RUR
0x51
PMON LCV Event Count Register - LSB
b00000000
RUR
0x52
PMON Framing Bit Error Event Count Register - MSB
b00000000
RUR
0x53
PMON Framing Bit Error Event Count Register - LSB
b00000000
RUR
0x54
PMON Parity Error Event Count Register - MSB
b00000000
RUR
0x55
PMON Parity Error Event Count Register - LSB
b00000000
RUR
0x56
PMON FEBE Event Count Register - MSB
b00000000
RUR
0x57
PMON FEBE Event Count Register - LSB
b00000000
RUR
0x58
PMON CP Bit Error Event Count Register - MSB
b00000000
RUR
0x59
PMON CP Bit Error Event Count Register - LSB
b00000000
RUR
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TABLE 5: REGISTER ADDRESSING OF THE FRAMER PROGRAMMER REGISTERS
ADDRESS
REGISTER NAME
POWER UP DEFAULT VALUE
REGISTER TYPE
b00000000
R/O
0x5A - 0x67 Reserved
0x68
PRBS Bit Error Counter - MSB
b00000000
RUR
0x69
PRBS Bit Error Counter - LSB
b00000000
RUR
b00000000
R/O
0x6A-0x6B Reserved
0x6C
PMON Holding Register
b00000000
RUR
0x6D
One-Second Error Status Register
b00000000
R/O
0x6E
LCV One-Second Accumulator Register - MSB
b00000000
R/O
0x6F
LCV One-Second Accumulator Register - LSB
b00000000
R/O
0x70
Frame Parity Error One-Second Accumulator Register MSB (BIP-8 in G.832)
b00000000
R/O
0x71
Frame Parity Error One-Second Accumulator Register LSB (BIP-8 in G.832)
b00000000
R/O
0x72
Frame CP Bit Error - One-Second Accumulator Register MSB
b00000000
R/O
0x73
Frame CP Bit Error - One-Second Accumulator Register LSB
b00000000
R/O
0x74 - 0x7F Reserved
0x80
Line Interface Drive Register
b00001000
R/W
0x81
Line Interface Scan Register
b00000000
R/O
0x82
HDLC Control Register
b00000000
R/W
bxxxxxxx
R/W
bxxxxxxx
R/W
0x83 - 0x85 Reserved
0x86 - 0xDD Transmit LAPD Message Buffer (RAM)
0xDE 0x135
Receive LAPD Message Buffer (RAM)
bits. Finally, the functional description, associated with each
register bit-field is presented, along with a reference to a
Section Number, within this Data Sheet, that provides a
more in-depth discussion of the functions associated with
this register bit-field.
2.4.2 Framer Register Description
This section provides a function description of each
bit-field within each of the on-chip Framer Registers.
NOTE: For all on-chip registers, a table containing the bitformat of the register is presented. Additionally, these tables
also contain the default values for each of these register
2.4.2.1
Framer Operating Mode Register
FRAMER OPERATING MODE REGISTER (ADDRESS = 0X00)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
Local Loopback
DS3/E3*
Internal
LOS
Enable
RESET
Interrupt
Enable Reset
Frame Format
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
1
0
1
0
1
1
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BIT 0
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Bit 7 - Local Loopback Mode
This Read/Write bit-field is used to configure the
XRT72L53 Framer chip to automatically disable all Interrupts that are activated.
This Read/Write bit-field is used to command the
Framer chip to operate in the Local Loopback Mode.
Setting this bit-field to "0" configures the XRT72L53
Framer chip to NOT disable the Interrupt Enable Status, of any interrupts, following their activation.
Setting this bit-field to "0", configures the Framer chip
to operate in the Normal Mode. Setting this bit-field to
"1", configures the Framer chip to operate in the Local-Loopback Mode.
Setting this bit to "1" configures the XRT72L53 Framer chip to automatically disable any interrupt that is
activated.
NOTE: For a detailed description of the Local Loopback
Mode, please see Section 6.0
NOTE: For more information on this feature, please see
Section 1.6.1.
Bit 6 - DS3/E3* Select
This Read/Write bit-field is used to command the
Framer chip to operate in either the DS3 Mode or the
E3 Mode.
Bit 2 - Frame Format Select
This Read/Write bit-field, along with the DS3/E3 select bit-field (bit 6 in this register) is used to select the
Framing Format that the XRT72L53 will operate in.
The following table relates the states of this bit-field
(bit 2) and that of bit 6 to the selected framing format
for this chip.
Setting this bit-field to "0", configures the Framer chip
to operate in the E3 Mode. Setting this bit-field to "1",
configures the Framer chip to operate in the DS3
Mode.
Bit 5 - Internal LOS Enable Select
BIT 6 - DS3/E3
SELECT
This Read/Write bit-field is used to configure the
Framer chip to either declare an LOS condition,
based upon the Internal Circuit's criteria or not.
Setting this bit-field to "0", configures the Framer chip
to NOT declare an LOS condition, based upon its
own internal criteria.
Setting this bit-field to "1", configures the Framer chip
to declare an LOS condition based upon its own internal criteria.
BIT 2 - FRAME SELECTED FRAMING
FORMAT SELECT
FORMAT
0
0
E3, ITU-T G.751
0
1
E3, ITU-T G.832
1
0
DS3, C-bit Parity
1
1
DS3, M13
Bits 1 & 0 - TimRefSel[1:0] - Timing Reference Select
NOTES:
1. The XRT72L53 Framer Chip will declare an LOS
condition, anytime the RLOS input pin (pin 78) is
set "High", independent of the setting of this bitfield.
2. For more information on the XRT72L53 Framer's
internal criteria for Loss of Signal please see Section 3.3.2.5.
These two Read/Write bit-fields is used to select both
a Framing Reference and Timing Reference for the
Transmit Section of the XRT72L53. The following table relates the states of these two bit-fields to the selected Framing and Timing references.
Bit 4 - RESET:
This Read/Write bit-field is used to command the
XRT72L53 Framer chip into the Reset state. If the
XRT72L53 Framer chip is commanded into the Reset
state, all of its internal register bits will automatically
be set to their default condition.
Setting this bit-field to "0" configures the XRT72L53
Framer chip to operate normally. Setting this bit-field
to "1" configures the XRT72L53 Framer chip to go into the Reset Mode.
Bit 3 - Interrupt Enable Reset
TIMREFSEL[1:0]
FRAMING
REFERENCE
00
Asynchronous
RxLineClk Input
Signal
01
TxFrameRef
TxInClk Input signal
10
Asynchronous
TxInClk Input signal
11
Asynchronous
TxInClk Input signal
TIMING REFERENCE
NOTE: For more information on Framing and Timing References, please see Section 3.2.
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2.4.2.2
I/O Control Register
I/O CONTROL REGISTER (ADDRESS = 0X01)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
Disable
TxLOC
LOC
Disable
RxLOC
AMI/
ZeroSup*
Unipolar/
Bipolar*
TxLine
Clk
Invert
RxLine
Clk
Invert
Reframe
R/W
RO
R/W
R/W
R/W
R/W
R/W
R/W
1
0
1
0
0
0
0
0
operating in the DS3 Mode, then the chip will transmit and receive data using the B3ZS Line Code.
2. If the XRT72L53 is configured to transmit and
receive data, using a Zero-Suppression code, while
operating in the E3 Mode, then the chip will transmit and receive data using the HDB3 Line Code.
3. This bit-field will be ignored if bit 3 (Unipolar/Bipolar*) of this Register is set to "1" (for Unipolar
Mode).
Bit 7 - Disable TxLOC
This Read/Write bit-field is used to enable or disable
the Transmit Loss of Clock feature.
Setting this bit-field to "0" enables the Transmit Loss
of Clock feature. Conversely, setting this bit-field to "1"
disables the Transmit Loss of Clock feature.
NOTE: For more details into the Transmit Loss of Clock feature, please see Section 1.4.
Bit 6 - LOC (Loss of Clock) Status
Bit 3 - Unipolar/Bipolar*
This Read-Only bit-field reflects the Loss of Clock
status for the XRT72L53. The XRT72L53 will set this
bit-field to "0" under normal operation conditions.
Conversely, if the XRT72L53 has experiences a Loss
of Clock event, then it will set this bit-field to "1".
This Read/Write bit-field is used to configure the
XRT72L53 to transmit data to and receive data from
an LIU IC, in either the Single-Rail or Dual-Rail format.
Setting this bit-field to "0" configures the XRT72L53 to
operate in the Bipolar or Dual-Rail Format. In this
mode, the Transmit Section of the XRT72L53 will output data to the LIU via both the TxPOS and TxNEG
output pins. Additionally, the Receive Section of the
will receive data from the LIU via both the RxPOS and
RxNEG output pins.
NOTE: For more details into the Loss of Clock status,
please see Section 1.4.
Bit 5 - Disable RxLOC
This Read/Write bit-field is used to enable or disable
the Receive Loss of Clock feature.
Setting this bit-field to "0" enables the Receive Loss
of Clock feature. Conversely, setting this bit-field to "1"
disables the Receive Loss of Clock feature.
Setting this bit-field to "1" configures the XRT72L53 to
operate in the Unipolar or Single-Rail Format. In this
mode, the Transmit Section of the XRT72L53 will output data to the LIU, in a binary data stream manner
via the TxPOS output pin. Additionally, the Receive
Section of the device will receive data from the LIU, in
a binary data stream manner, via the RxPOS input
pin.
NOTE: For more details into the Receive Loss of Clock feature, please see Section 1.4.
Bit 4 - AMI/ZeroSup*
This Read/Write bit-field is used to configure the
XRT72L53 to transmit and receive data via the AMI
(Alternate Mark Inversion) line code or via a ZeroSuppression (e.g, B3ZS/HDB3) line code.
NOTE: For more information on the transmission and
reception of data in the Single-Rail or Dual-Rail format,
please see Section 3.2.5.
Setting this bit-field to "0" configures the XRT72L53 to
transmit and receive data via a Zero-Suppression line
code.
Bit 2 - TxLineClk Invert
This Read/Write bit-field is used to configure the
XRT72L53 to output data, via the TxPOS and TxNEG
output pins, on the rising or falling edge of TxLineClk.
Setting this bit-field to "1" configures the XRT72L53 to
transmit and receive data via the Alternate Mark Inversion line code.
Setting this bit-field to "0" configures the XRT72L53 to
output data, via the TxPOS and TxNEG output pins,
on the rising edge of TxLineClk.
NOTES:
1. If the XRT72L53 is configured to transmit and
receive data, using a Zero-Suppression code, while
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Setting this bit-field to "1" configures the XRT72L53 to
output data, via the TxPOS and TxNEG output pins,
on the falling edge of TxLineClk.
Setting this bit-field to "1" configures the XRT72L53 to
latch the data on the RxPOS and RxNEG input pins,
into the device, data, on the falling edge of RxLineClk.
Bit 1 - RxLineClk Invert
Bit 0 - Reframe
This Read/Write bit-field is used to configure the
XRT72L53 to latch data on the RxPOS and RxNEG
input pins, into the XRT72L53, on the rising or falling
edge of RxLineClk.
This Read/Write bit-field is used to configure the Receive Section of the XRT72L53 to start a new frame
search. A "0" to "1" transition, in this bit-field will force
the chip to start a new frame search.
Setting this bit-field to "0" configures the XRT72L53 to
latch the data on the RxPOS and RxNEG input pins,
into the device, on the rising edge of RxLineClk.
2.4.2.3
Part Number Register
PART NUMBER REGISTER (ADDRESS = 0X02)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
Part Number Value
RO
RO
RO
RO
RO
RO
RO
RO
0
0
0
0
1
0
0
1
2.4.2.4 Version Number Register
The Version Number register permits the user’s software to identify the revision number of the part. The
very first revision of the part will contain the value
“0x01”.
The Part Number register can be used by Systemlevel software to identify this particular device as the
XRT72L53 3-Channel DS3/E3 Framer IC. The value
of the Part Number register, within this device is
“0x09”.
VERSION NUMBER REGISTER (ADDRESS = 0X03)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
Version Number Value
RO
RO
RO
RO
RO
RO
RO
RO
0
0
0
0
0
0
0
1
2.4.2.5
Block Interrupt Enable Register
BLOCK INTERRUPT ENABLE REGISTER (ADDRESS = 0X04)
BIT 7
BIT 6
BIT 5
RxDS3/E3
Interrupt
Enable
BIT 4
BIT 3
BIT 2
Not Used
BIT 1
BIT 0
TxDS3/E3
Interrupt
Enable
One-Second
Interrupt
Enable
R/W
RO
RO
RO
RO
RO
R/W
R/W
0
0
0
0
0
0
0
0
Bit 7 - RxDS3/E3 Interrupt Enable
Setting this bit-field to "1" enables the Receive Section related Interrupts (within the XRT72L53) at the
block level.
This Read/Write bit-field is used to enable or disable
all Receive Section related interrupts (within the
XRT72L53), at the Block Level.
NOTE: Setting this bit-field to "1" does not enable all
Receive Section related Interrupts. Each of these interrupts
can still be disabled at the Source Level. However, setting
Setting this bit-field to "0" disables all Receive Section
related Interrupts within the XRT72L53.
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this bit-field to "0" does disable all Receive Section related
Interrupts.
still be disabled at the Source Level. However, setting this
bit-field to "0" does disable all Transmit Section related
Interrupts.
Bit 1 - TxDS3/E3 Interrupt Enable
Bit 0 - One-Second Interrupt Enable
This Read/Write bit-field is used to enable or disable
all Transmit Section related interrupts (within the
XRT72L53), at the Block Level.
Setting this bit-field to "0" disables all Transmit Section related Interrupts within the XRT72L53.
This Read/Write bit-field is used to enable or disable
the One-Second Interrupt, within the XRT72L53. If
this interrupt is enabled, then the XRT72L53 will generate interrupts to the µC/µP at one-second intervals.
Setting this bit-field to "1" enables the Transmit Section related Interrupts (within the XRT72L53) at the
block level.
Setting this bit-field to "0" disables the One-Second
Interrupt. Conversely, setting this bit-field to "1" enables the One-Second Interrupt.
2.4.2.6
NOTE: Setting this bit-field to "1" does not enable all Transmit Section related Interrupts. Each of these interrupts can
Block Interrupt Status Register
BLOCK INTERRUPT STATUS REGISTER (ADDRESS = 0X05)
BIT 7
BIT 6
BIT 5
RxDS3/E3
Interrupt
Status
BIT 4
BIT 3
BIT 2
Not Used
BIT 1
BIT 0
TxDS3/E3
Interrupt
Status
One-Second
Interrupt
Status
RO
RO
RO
RO
RO
RO
RO
RUR
0
0
0
0
0
0
0
0
Bit 7 - RxDS3/E3 Interrupt Status Indicator
ly, if this bit-field is set to "1", then there is at least one
Transmit Section related interrupt, awaiting service.
This Read-Only bit-field indicates whether or not a
Receive-Section related interrupt has been requested
and is awaiting service.
NOTE: If this bit-field is set to "1", then the µC/µP must
read the Source-Level Interrupt Status register, in order to
clear this bit-field.
If this bit-field is set to "0", then there are no ReceiveSection related interrupts awaiting service. Conversely, if this bit-field is set to "1", then there is at least one
Receive Section related interrupt, awaiting service.
Bit 0 - One-Second Interrupt Status
This Reset-upon-Read bit field indicates whether or
not a One-Second interrupt has been requested and
is awaiting service.
NOTE: If this bit-field is set to "1", then the µC/µP must
read the Source-Level Interrupt Status register, in order to
clear this bit-field.
If this bit-field is set to "0", then the One-Second interrupt is not awaiting service. Conversely, if this bit-field
is set to "1", then the One-Second interrupt is awaiting service.
Bit 1 - TxDS3/E3 Interrupt Status Indicator
This Read-Only bit-field indicates whether or not a
Transmit-Section related interrupt has been requested and is awaiting service.
NOTE: This bit-field will be cleared immediately after the
µC/µP has read this register.
If this bit-field is set to "0", then there are no TransmitSection related interrupts awaiting service. Converse-
2.4.2.7
Test Register
TEST REGISTER (ADDRESS = 0X0C)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
TxOH
Source
Select
Rx
Payload
Clock
Enable
Tx
Payload
Clock
Enable
Rx
PRBS
Lock
Rx
PRBS
Enable
Tx
PRBS
Enable
R/W
R/W
R/W
RO
R/W
R/W
RO
RUR
0
0
0
0
0
0
0
0
74
BIT 1
BIT 0
Reserved
XRT72L53
THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
áç
PRELIMINARY
REV. P1.1.7
Bit 7 - TxOH Source Select
If the TxOHInd[n] output pin is configured to function
as the Transmit Payload Data Clock output signal,
then the Transmit Payload Data Output interface
block will generate a clock edge via the TxOHInd[n]
output pin. The Local Terminal equipment is expected
to output outbound payload data to the Transmit Payload Data Input Interface block (via the TxSer[n] input
pin) upon the falling edge of this clock signal.
This Read/Write bit-field is used to configure the
Transmit Section of the channel to accept overhead
bits/bytes via the TxSer[n] or TxNib[3:0][n] input pins.
Setting this bit-field to “1” configures the Transmit
Section of the channel to accept overhead bits/bytes
via either the TxSer[n] or TxNib[3:0][n]input pins.
Setting this bit-field to “0” configures the Transmit
Section of the channel to either internally generate or
accept the overhead bits/bytes via the TxOH[n] input
pin.
NOTE: In this mode, the TxOHInd[n] output pin will not generate a clock edge, whenever the Transmit Section of the
XRT72L53 is about to process an overhead bit.
Setting this bit-field to “0” configures the TxOHInd[n]
output pin to function as the Transmit Overhead Data
Output signal. Setting this bit-field to “1” configures
the TxOHInd[n] output pin to function as the Transmit
Payload Data Clock output signal.
Bit 6 - Rx Payload Clock Enable
This Read/Write bit-field is used to configure the Receive Payload Data Output Interface block to output
the receive data in a gapped-clock manner. If the user
chooses this option, then the Receive Payload Data
Output Interface will only generate a clock edge (via
the RxClk[n] output pin) whenever a payload bit is being output via the RxSer[n] output pin. The Receive
Payload Data Output Interface will not generate a
clock edge (via the RxClk[n] output pin) whenever an
overhead bit is being output via the RxSer[n] output
pin.
Bit 4 - Rx PRBS Lock
This Read-Only bit-field indicates whether or not the
PRBS Receiver has acquired PRBS Lock (or Pattern
Sync) with the data generated by the PRBS Generator.
If this bit-field is set to “1”, then the PRBS Receiver
has acquired PRBS lock with the data generated by
the PRBS Generator. If this bit-field is set to “0”, then
the PRBS Receiver has NOT acquired PRBS Lock
with the data generated by the PRBS Generator.
If the user does not select this option then the Receive Payload Data Output Interface block will generate a clock edge for all bits (payload and overhead);
as they are output via the RxSer[n] output pin. However, the Receive Payload Data Output Interface will
also pulse the RxOHInd[n] output pin “High” each
time an overhead bit is being output via the RxSer[n]
output pin.
NOTE: This bit-field is only valid if both the RxPRBS Enable
and Tx PRBS Enable bit-fields are both set to “1”.
Bit 3 - Rx PRBS Enable
This Read/Write bit-field is used to enable the PRBS
Receiver within the channel.
Setting this bit-field to “1” enables the PRBS Receiver
within the channel. Setting this bit-field to “0” disables
the PRBS Receiver.
Setting this bit-field to “1” enables this feature. Setting
this bit-field to “0” disables this feature.
Bit 5 - Tx Payload Clock Enable
Bit 2 - Tx PRBS Enable
This Read/Write bit-field is used to configure the TxOHInd[n] output pin to function as either of the following
roles.
This Read/Write bit-field is used to enable the PRBS
Generator within the channel.
Setting this bit-field to “1” enables the PRBS Generator within the channel. Setting this bit-field to “0” disables the PRBS Generator.
1. The Transmit Overhead Data Output Indicator
2. The Transmit Payload Data Clock Output signal.
If the TxOHInd[n] output pin is configured to function
as the Transmit Overhead Data Output signal, then
this output pin will pulse “High” one bit-period prior to
the instant that the Transmit Section of the channel
(within the XRT72L53) is processing an overhead bit.
Receive DS3 Framer Configuration Registers
2.4.2.8 Receive DS3 Configuration & Status
Register
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REV. P1.1.7
RXDS3 CONFIGURATION & STATUS REGISTER (ADDRESS = 0X10)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
RxAIS
RxLOS
RxIdle
RxOOF
Reserved
Framing On
Parity
FSync
Algo
MSync
Algo
RO
RO
RO
RO
RO
R/W
R/W
R/W
0
0
0
0
0
0
0
0
Bit 7 - RxAIS (Receive AIS Pattern) Indicator
This Read-Only bit-field indicates whether or not the
Receive Section of the channel (within the Framer) is
currently declaring an OOF (Out of Frame) condition.
This Read-Only bit-field indicates whether or not the
Receive Section of the channel, within the XRT72L53
is currently receiving an AIS pattern or not.
If this bit-field is set to "0", then the Receive Section
(of the channel) is currently not declaring the OOF
condition.
The channel will set this bit-field to "0" if it is not currently detecting an AIS pattern in the incoming data
stream. Conversely, the channel will set this bit-field
to "1" if it is currently receiving an AIS pattern in the
incoming data stream.
If this bit-field is set to "1", then the Receive Section
(of the chip) is currently declaring the OOF condition.
NOTE: For more information on the OOF Declaration criteria, for DS3 applications, please see Section 3.3.2.2.
NOTE: For a more detailed discussion on the AIS pattern
for DS3 applications, please see Section 3.3.2.5.2
Bit 3 - Reserved.
Bit 6 - RxLOS (Receive LOS Condition) Indicator
Bit 2 - Framing On Parity ON/OFF Select
This Read-Only bit-field indicates whether or not the
Receive Section of the channel (within the Framer) is
currently declaring an LOS (Loss of Signal) condition
of the incoming DS3 or E3 data stream.
This Read/Write bit field allows the user to require
that the Receive DS3/E3 Framer block (within the
channel) include Parity (P-bit) verification as a condition for declaring itself In-Frame, during Frame Acquisition. This requirement will be imposed in addition to
those criteria selected via Bits 0 and 1 of this register.
If this bit-field is set to "0", then the Receive Section
(of the channel) is currently not declaring an LOS
condition.
This feature also imposes an additional Frame Maintenance requirement on the Receive DS3/E3 Framer
block, in addition to the requirements specified in the
user's selection of Bits 0 and 1 of this register. In particular, if this additional requirement is implemented,
the Receive DS3/E3 Framer block will perform a
frame search if it detects P-bit errors in at least 2 out
of 5 DS3 Frames. Writing a "1" to this bit-field imposes these additional requirements. Whereas, writing a
'0' causes the Receive DS3/E3 Framer block to waive
this requirement.
If this bit-field is set to "1", then the Receive Section
(of the channel) is currently declaring an LOS condition.
NOTE: For more information on the LOS Declaration criteria, for DS3 and E3 applications, please see Section
3.3.2.5.2.
Bit 5 - RxIdle (Receive Idle Pattern) Indicator
This Read-Only bit-field indicates whether or not the
Receive Section of the channel (within the Framer) is
currently detecting the Idle-pattern in the incoming
DS3 data stream.
NOTE: For more information on Framing with Parity please
see Section 3.3.2.2.
If this bit-field is set to "0" then the Receive Section
(of the channel) is currently not detecting the Idle-pattern in the incoming DS3 data stream.
Bit 1 - F Sync Algo(rithim Select)
This 'Read/Write' bit-field, in conjunction with Bits 0
and 2 of this register, allows the user to completely
define the Frame Maintenance Criteria of the Receive
DS3/E3 Framer block. This particular bit-field allows
the user to define the Frame Maintenance Criteria as
it applies to F-bits.
If this bit-field is set to "1" then the Receive Section
(of the channel) is currently detecting the Idle pattern
in the incoming DS3 data stream.
NOTES:
1. This bit-field is only relevant for DS3 applications.
2. For more information on the Idle Pattern, please
see Section 3.3.2.5.3
If the user writes a "1" to this bit-field, then the Receive DS3/E3 Framer block will declare an Out of
Frame (OOF) condition if 3 out of 16 F-Bits are in Error. If the user writes a "0" to this bit-field, then the
Bit 4 - RxOOF (Receive Out-of-Frame) Indicator
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THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
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If the user writes a "1" to this bit-field, then the Receive DS3/E3 Framer block will declare an Out of
Frame (OOF) condition if 3 out of 4 M-bits are in error.
If the user writes a "0" to this bit-field, then the Receive DS3/E3 Framer block will ignore the occurrence
of M-bit errors while operating in the Frame Maintenance mode.
Receive DS3/E3 Framer block will declare an Out of
Frame (OOF) condition is 6 out of 16 F-bits are in error.
NOTE: For more information on the use of this bit, and the
Framing Maintenance operation of the Receive DS3/E3
Framer block, please see Section 3.3.2.2.
Bit 0 - M Sync Algo(rithm Select)
NOTE: For more information on the use of this bit-field, and
the Framing Maintenance operation of the Receive DS3/E3
Framer block, please see Section 3.3.2.2.
This 'Read/Write' bit-field in conjunction with Bits 1
and 2 of this register, allows the user to completely
define the Frame Maintenance Criteria of the Receive
DS3/E3 Framer block. This particular bit-field allows
the user to define the Frame Maintenance criteria, as
it applies to M-bits.
2.4.2.9
Receive DS3 Status Register
RXDS3 STATUS REGISTER (ADDRESS = 0X11)
BIT 7
BIT 6
BIT 5
Reserved
BIT 4
BIT 3
RxFERF
RxAIC
BIT 2
BIT 1
BIT 0
RxFEBE[2:0]
RO
RO
RO
RO
RO
RO
RO
RO
0
0
0
0
0
0
0
0
Bit 4 - RxFERF Indicator
(AIC bit = 1) for at least 63 consecutive frames. This
bit-field is set to "0" if two (2) or more M-frames, out of
the last 15 M-frames, contain a "0" in the AIC bit position.
This Read Only bit-field indicates whether or not the
Receive Section of the channel is declaring a FERF
(Far-End-Receive Failure) condition.
If this bit-field is set to "0", then the Receive Section
(of the channel) is currently not declaring an FERF
condition.
Bits 2:0 - RxFEBE[2:0]
If this bit-field is set to "1", then the Receive Section
(of the chip) is currently declaring an FERF condition.
If these bit-fields are set to "111", then it indicates that
the Remote Receiving Terminal is receiving DS3
frames in an un-erred manner.
These Read-Only bit-fields reflect the FEBE value,
within the most recently received DS3 frame.
NOTE: For more information on how the Receive Section of
the channel declares the FERF condition, please see Section 3.3.2.5.4.
If these bit-fields are set to "011", then it indicates that
the Remote Receiving Terminal has detected Framing or Parity bit errors in the DS3 frames that it is receiving.
Bit 3 - RxAIC
This Read Only bit-field reflect the value of the AIC
bit-field, within the incoming DS3 Frames, as detected by the Receive DS3/E3 Framer block (within the
channel). This bit-field is set to "1" if the incoming
frame is determined to be in the C-bit Parity Format
NOTE: For more information on FEBE (Far-End-Block
Error) please see Section 3.3.2.5.5.
2.4.2.10 Receive DS3 Interrupt Enable Register
RXDS3 INTERRUPT ENABLE REGISTER (ADDRESS = 0X12)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
CP Bit Error
Interrupt
Enable
LOS
Interrupt
Enable
AIS
Interrupt
Enable
Idle Interrupt
Enable
FERF
Interrupt
Enable
AIC
Interrupt
Enable
OOF
Interrupt
Enable
P-Bit Error
Interrupt
Enable
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
0
0
Bit 7 - CP Bit Error Interrupt Enable
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XRT72L53
PRELIMINARY
REV. P1.1.7
Bit 3 - FERF Interrupt Enable
This Read/Write bit-field is used to enable or disable
the Detection of CP-Bit Error Interrupt. Setting this
bit-field to “1’ enables this interrupt. Setting this bitfield to “0” disables this interrupt.
This Read/Write bit-field is used to enable or disable
the Change in FERF (Far End Receive Failure) Status
interrupt. Setting this bit-field to "1" enables this interrupt. Setting this bit-field to "0" disables this interrupt.
NOTES:
1. For more information on the CP-Bit Error Checking/
Detection, please see Section 3.3.2.6.2.
2. This bit-field is only valid if the Channel has been
configured to operate in the DS3, C-Bit Parity
Framing format.
NOTE: For more information on Far-End Receive Failures
(or Yellow Alarms) please see Section 3.3.2.5.4.
Bit 2 - AIC Interrupt Enable
This Read/Write bit field allows the user to enable or
disable the Change in AIC value interrupt. Setting this
bit-field to "1" enables this interrupt. Setting this bitfield to "0" disables this interrupt.
Bit 6 - LOS Interrupt Enable
This Read/Write bit-field is used to enable or disable
the Change in LOS condition interrupt. Setting this
bit-field to "1" enables this interrupt. Setting this bitfield to "0" disables this interrupt.
NOTE: For more information on this interrupt condition,
please see Section 3.3.2.5.6.
Bit 1 - OOF Interrupt Enable
NOTE: For more information on the LOS Condition, please
see Sections 3.3.2.5.1.
This Read/Write bit field is used to enable or disable
the Change in Out-of-Frame (OOF) status interrupt.
Setting this bit-field to "1" enables this interrupt. Setting this bit-field to "0" disables this interrupt.
Bit 5 - AIS Interrupt Enable
This Read/Write bit-field is used to enable or disable
the Change in AIS condition interrupt. Setting this bitfield to "1" enables this interrupt. Setting this bit-field
to "0" disables this interrupt.
NOTE: For more information on the OOF' Condition, please
see Section 3.3.2.2.
Bit 0 - P-Bit Error Interrupt Enable
NOTE: For more information on the AIS Condition, please
see Sections 3.3.2.5.2.
This Read/Write bit-field is used to enable or disable
the Detection of P-Bit Error interrupt. Setting this bitfield to "1" enables this interrupt. Setting this bit-field
to "0" disables this interrupt.
Bit 4 - Idle Interrupt Enable
This Read/Write bit-field is used to enable or disable
the Change in Idle condition interrupt. Setting this bitfield to "1" enables this interrupt. Setting this bit-field
to "0" disables this interrupt.
NOTE: For more information on the P-Bit Error Checking/
Detection, please see Section 3.3.2.6.1.
2.4.2.11 Receive DS3 Interrupt Status Register
NOTE: For more information on the Idle Condition, please
see Section 3.3.2.5.3.
RXDS3 INTERRUPT STATUS REGISTER (ADDRESS = 0X13)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
CP-Bit Error
Interrupt
Status
LOS
Interrupt
Status
AIS
Interrupt
Status
Idle Interrupt
Status
FERF
Interrupt
Status
AIC
Interrupt
Status
OOF
Interrupt
Status
P-Bit Error
Interrupt
Status
RUR
RUR
RUR
RUR
RUR
RUR
RUR
RUR
0
0
0
0
0
0
0
0
Bit 7 - CP Bit Error Interrupt Status
Receive DS3/E3 Framer block detects a CP bit-error
in the incoming DS3 frame.
This Reset-upon-Read bit-field indicates whether or
not the Detection of CP Bit Error Interrupt has occurred since the last read of this register. This bit-field
will be “0” if the Detection of CP-Bit Error Interrupt
has not occurred since the last read of this register.
Conversely, this bit-field will be set to “1” if this interrupt has occurred since the last read of this register.
The Detection of CP Bit Error Interrupt will occur if the
NOTE: This bit-field is only valid if the channel has been
configured to operate in the DS3, C-bit Parity Framing format.
Bit 6 - LOS Interrupt Status
This Reset Upon Read bit will be set to "1", if the Receive DS3/E3 Framer block has detected a Change in
the LOS Status condition, since the last time this reg-
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1. When the Receive DS3/E3 Framer block detects
the onset of the Idle Condition and
2. When the Receive DS3/E3 Framer block detects
the end of the Idle Condition.
The local µP can determine the current state of the
Idle condition by reading bit 5 of the Rx DS3 Configuration and Status Register (Address = 0x10).
ister was read. This bit-field will be asserted under either of the following conditions:
For DS3 Applications
1. When the Receive DS3/E3 Framer block detects
the occurrence of an LOS Condition (e.g., the
occurrence of 180 consecutive spaces in the
incoming DS3 data stream), and
2. When the Receive DS3/E3 Framer block detects
the end of an LOS Condition (e.g., when the
Receive DS3 Framer detects 60 mark pulses in
the last 180 bit periods).
For E3 Applications
NOTE: For more information into the Idle Condition, please
see Section 3.3.2.5.3.
Bit 3 - FERF Interrupt Status
This Reset Upon Read bit will be set to '1' if the Receive DS3/E3 Framer block has detected a Change in
the Rx FERF Condition, since the last time this register was read.
3. When the Receive DS3/E3 Framer block detects
the occurrence of an LOS Condition (e.g., the
occurrence of 32 consecutive spaces in the
incoming E3 data stream).
4. When the Receive DS3/E3 Framer block detects
the end of an LOS Condition (e.g., the occurrence of 32 consecutive bits that does not contain
a string of 4 consecutive “0s”.
The local µP can determine the current state of the
LOS condition by reading bit 6 of the Rx DS3 Configuration and Status Register (Address = 0x10).
This bit-field will be asserted under either of the following two conditions.
1. When the Receive DS3/E3 Framer block first
detects the occurrence of an Rx FERF Condition
(all X-bits are set to '0').
2. When the Receive DS3/E3 Framer block detects
the end of the Rx FERF Condition (all X-bits are
set to '0').
The local microprocessor can determine the current
state of the FERF Condition by reading bit 4, within
the Rx DS3 Status Register (Address = 0x11).
NOTE: For more information in the LOS of Signal (LOS)
Alarm, please see Section 3.3.2.5.1.
Bit 5 - AIS Interrupt Status
NOTE: For more information on the Rx FERF (Yellow
Alarm) condition, please see Section 3.3.2.5.4.
This Reset Upon Read bit field will be set to "1", if the
Receive DS3/E3 Framer block has detected a
Change in the AIS condition, since the last time this
register was read. This bit-field will be asserted under
either of the following two conditions:
Bit 2 - (Change in) AIC Interrupt Status
This Reset Upon Read bit-field is set to "1" if the AIC
bit-field, within the incoming DS3 frames, has
changed state since the last read of this register.
1. When the Receive DS3/E3 Framer block first
detects an AIS Condition in the incoming DS3
data stream, and
2. When the Receive DS3/E3 Framer block has
detected the end of an AIS Condition.
The local µP can determine the current state of the
AIS condition by reading bit 7 of the Rx DS3 Configuration and Status Register (Address = 0x10).
NOTE: For more information on this interrupt condition,
please see Section 3.3.2.5.6.
NOTE: For more information on the AIS Condition please
see Sections 3.3.2.5.2.
1. When the Receive DS3/E3 Framer block has
detected the appropriate conditions to declare an
OOF Condition.
2. When the Receive DS3/E3 Framer block transitions from the OOF Condition (Frame Acquisition
Mode) into the In-Frame Condition (Frame Maintenance mode).
Bit 1 - OOF Interrupt Status
This Reset Upon Read bit-field is set to "1" if the Receive DS3/E3 Framer block has detected a Change in
the Out-of-Frame (OOF) Condition, since the last time
this register was read. Therefore, this bit-field will be
asserted under either of the following two conditions:
Bit 4 - Idle Interrupt Status
This Reset Upon Read bit-field is set to "1" when the
Receive DS3/E3 Framer block detects a Change in
the Idle Condition in the incoming DS3 data stream.
Specifically, the Receive DS3/E3 Framer block will assert this bit-field under either of the following two conditions:
NOTE: For more information of the OOF Condition, please
see Section 3.3.2.2.
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Bit 0 - P-Bit Error Interrupt Status
Framer Block detects a P-bit error in the incoming
DS3 frame.
This Reset Upon Read bit-field indicates whether or
not the Detection of P-bit error interrupt has occurred
since the last read of this register. This bit-field will be
"0" if the Detection of P-bit error interrupt has NOT
occurred since the last read of this register. This bitfield will be set to "1", if this interrupt has occurred
since the last read of this register. The Detection of
P-bit Error interrupt will occur if the Receive DS3/E3
NOTE: For more information into the role of P-bits please
see Section 3.3.2.6.1.
3.3.2.11 Receive DS3 Sync Detect Enable Register
RxDS3 Sync Detect Enable Register (Address =
0x14)
RXDS3 SYNC DETECT ENABLE REGISTER (ADDRESS = 0X14)
BIT 7
BIT 6
BIT 5
Not Used
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
Enable F[4]
Enable F[3]
Enable F[2]
Enable F[1]
Enable F[0]
RO
RO
RO
R/W
R/W
R/W
R/W
R/W
0
0
0
1
1
1
1
1
Bits 4 - 0 Enable5 F(4)- F(0)
Frame Acquisition mode. For proper operation, the
user is highly encouraged to ensure that all of these
bit-fields are set to "1".
These Read/Write bit-fields allows the user to enable
or disable the 5 parallel searches for valid M and Fbit, while the Receive DS3 Framer is operating in the
2.4.2.12 Receive DS3 FEAC Register
RXDS3 FEAC REGISTER (ADDRESS = 0X16)
BIT 7
BIT 6
BIT 5
BIT 4
Not Used
BIT 3
BIT 2
BIT 1
RxFEAC[5:0]
BIT 0
Not Used
RO
RO
RO
RO
R/O
R/O
R/O
R/O
0
1
1
1
1
1
1
0
2. This register is only valid if the Channel has been
configured to operate in the DS3, C-bit Parity Framing format.
This Read/Write register contains the latest 6-bit
FEAC code that has been received and validated by
the Receive FEAC Processor. The contents of this
register will be cleared if the previously validated
code has been removed by the FEAC Processor.
2.4.2.13 Receive DS3 FEAC Interrupt Enable/
Status Register
NOTES:
1. For more information on the operation of the
Receive FEAC Processor, please see Section
3.3.3.1.
RXDS3 FEAC INTERRUPT ENABLE/STATUS REGISTER (ADDRESS = 0X17)
BIT 7
BIT 6
BIT 5
Not Used
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
FEAC Valid
RxFEAC
Remove
Interrupt
Enable
RxFEAC
Remove
Interrupt
Status
RxFEAC
Valid
Interrupt
Enable
RxFEAC
Valid
Interrupt
Status
RO
RO
RO
RO
R/W
RUR
R/W
RUR
0
0
0
0
0
0
0
0
Bit 4 - FEAC Valid
This Read Only bit is set to "1" when an incoming
FEAC Message Code has been validated by the Re-
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THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. P1.1.7
Bit 1 - RxFEAC Valid Interrupt Enable
ceive DS3/E3 Framer block. This bit is cleared to "0"
when the FEAC code is removed.
This Read/Write bit-field is used to enable or disable
the Rx FEAC Valid interrupt. Writing a "1" to this bitfield enables this interrupt. Whereas, writing a "0" disables this interrupt. The value of this bit-field is "0" following power up or reset.
NOTE: For more information on the role of this bit-field and
the Receive FEAC Processor, please see Section 3.3.3.1.
Bit 3 - RxFEAC Remove Interrupt Enable
This Read/Write bit-field is used to enable/disable the
RxFEAC Removal interrupt. Writing a "1" to this bit
enables this interrupt. Likewise, writing a "0" to this
bit-field disables this interrupt.
NOTE: For more information on this bit-field and the
Receive FEAC Processor, please see Section 3.3.3.1.
Bit 0 - RxFEAC Valid Interrupt Status
NOTE: For more information on the role of this bit-field and
the Receive FEAC Processor, please see Section 3.3.3.1.
A "1" in this Read Only bit-field indicates that a newly
received FEAC Message has been validated by the
Receive FEAC Processor.
Bit 2 - RxFEAC Remove Interrupt Status
The Receive FEAC Processor will validate a new
FEAC message, once that message has been received in 8 out of 10 most recently received FEAC
Messages.
A "1" in this Read Only bit-field indicates that the
most recently received and validated FEAC Message
has now been removed by the Receive FEAC Processor. The Receive FEAC Processor will remove a validated FEAC message if 3 out of the last 10 received
FEAC messages differ from the latest valid FEAC
Message.
NOTE: For more information on this bit-field and the
Receive FEAC Processor, please see Section 3.3.3.1.
2.4.2.14 Receive DS3 LAPD Control Register
NOTE: For more information on this bit-field and the
Receive FEAC Processor, please see Section 3.3.3.1.
RXDS3 LAPD CONTROL REGISTER (ADDRESS = 0X18)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
Not Used
BIT 2
BIT 1
BIT 0
RxLAPD
Enable
RxLAPD
Interrupt
Enable
RxLAPD
Interrupt
Status
RO
RO
RO
RO
RO
R/W
R/W
RUR
0
0
0
0
0
0
0
0
Bit 2 RxLAPD Enable
Writing a "0" to this bit-field disables this interrupt (the
default condition). Writing a "1" to this bit-field enables this interrupt.
This Read/Write bit-field is used to enable or disable
the LAPD Receiver. The LAPD Receiver MUST be
enabled before it can begin to receive and process
any LAPD Message frames from the incoming DS3
data stream.
Bit 0 RxLAPD (Message Reception Complete) Interrupt Status
This Read-Only bit field indicates whether or not the
LAPD Message Reception Complete interrupt has
occurred since the last read of this register. The
LAPD Message Reception Complete interrupt will occur once the LAPD Receiver has received the last bit
of a complete LAPD Message frame, extracted the
PMDL message from this LAPD Message frame and
has written this (PMDL) message frame into the Receive LAPD Message buffer. The purpose of this interrupt is to notify the local µP that the Receive LAPD
Message buffer contains a new PMDL message, that
needs to be read and/or processed.
Writing a "0" to this bit-field disables the LAPD Receiver (the default condition). Writing a "1" to this bitfield enables the LAPD Receiver.
Bit 1 RxLAPD (Message Frame Reception Complete) Interrupt Enable
This Read/Write bit-field is used to enable or disable
the LAPD Message Frame Reception Complete interrupt. If this interrupt is enabled, then the channel
(within the Framer IC) will generate this interrupt to
the local µP, once the last bit of a LAPD Message
frame has been received and the PMDL message
has been extracted and written into the Receive
LAPD Message buffer.
A "0" in this bit-field indicates that the LAPD Message
Reception Complete interrupt has NOT occurred
since the last read of this register. A "1" in this bit-field
81
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THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
XRT72L53
PRELIMINARY
REV. P1.1.7
NOTE: For more information on the LAPD Receiver, please
see Section 3.3.3.2.
indicates that the LAPD Message Reception Complete interrupt has occurred since the last read of this
register.
2.4.2.15 Receive DS3 LAPD Status Register
RXDS3 LAPD STATUS REGISTER (ADDRESS = 0X19)
BIT 7
BIT 6
BIT 5
Not Used
RxAbort
RO
RO
RO
0
0
0
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
RxCR Type
RxFCS Error
End of
Message
Flag Present
RO
RO
RO
RO
RO
0
0
0
0
0
RxLAPDType[1:0}
Bit 6 - RxAbort (Receive Abort Sequence)
that the FCS for the latest received LAPD Message
Frame is correct. A "1" in this bit-field indicates that
the FCS for the latest received LAPD Message Frame
is incorrect.
This Read-Only bit-field indicates whether or not the
LAPD Receiver has detected the occurrence of an
Abort Sequence (e.g., a string of seven or more consecutive "1’s") from the remote LAPD Transmitter. A
"0" in this bit-field indicates that no Abort-Sequence
has been detected. A "1" in this bit-field indicates that
the Abort-Sequence has been detected.
NOTE: For more information on the LAPD Receiver, please
see Section 3.3.3.2.
Bit 1 - End Of Message
This Read-Only bit-field indicates whether or not the
LAPD Receiver has completed its reception of the latest incoming LAPD Message frame. The local µP can
poll the progress of the LAPD Receiver by periodically reading this bit-field.
NOTE: For more information on the LAPD Receiver, please
see Section 3.3.3.2.
Bits, 5 and 4 - RxLAPDType[1, 0]
These two Read Only bit-fields combine to indicate
the type of LAPD Message frame that has been received by the LAPD Receiver. The relationship between these two bit-fields and the LAPD Message
Type follows:
BIT 5 BIT 4
MESSAGE TYPE
MESSAGE LENGTH
0
0
CL Path Identification
76 Bytes
0
1
Idle Signal Identification
76 Bytes
1
0
Test Signal Identification
76 Bytes
1
1
ITU-T Path Identification
82 Bytes
A "0" in this bit-field indicates that the LAPD Receiver
is still receiving the latest message from the remote
LAPD Transmitter. A "1" in this bit-field indicates that
the LAPD Receiver has finished receiving the complete LAPD Message Frame.
Bit 0 - Flag Present
This Read-Only bit-field indicates whether or not the
LAPD Receiver has detected the occurrence of the
Flag Sequence byte (0x7E) within the inbound LAPD
channel (e.g., the DL bits in DS3 applications). A "0"
in this bit-field indicates that the LAPD Receiver does
not detect the occurrence of the Flag Sequence byte.
A "1" in this bit-field indicates that the LAPD Receiver
does detect the occurrence of the Flag Sequence
byte.
Bit 3 - RxCR (Command/Response) Type
This Read Only bit field indicates the value of the C/R
(Command/Response) bit-field of the latest received
LAPD Message.
NOTE: For more information on the LAPD Receiver, please
see Section 3.3.3.2.
Bit 2 - Rx FCS (Frame Check Sequence) Error
2.4.3 Receive E3 Framer Configuration Registers (ITU-T G.832)
This Read-Only bit-field indicates whether or not the
LAPD Receiver has detected a Frame Check Sequence (FCS) error in the most recently received
LAPD Message Frame. A "0" in this bit-field indicates
2.4.3.1 Receive E3 Configuration & Status
Register 1 (E3, ITU-T G.832)
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XRT72L53
áç
THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. P1.1.7
RXE3 CONFIGURATION & STATUS REGISTER 1 (ADDRESS = 0X10)
BIT 7
BIT 6
BIT 5
RxPLDType[2:0]
BIT 4
BIT 3
RxFERF
Algo
RxTMark
Algo
BIT 2
BIT 1
BIT 0
RxPLDExp[2:0]
RO
RO
RO
RO
RO
R/W
R/W
R/W
0
0
0
0
0
0
0
0
Bit 7 - 5 - RxPLDType[2:0] (Received Payload
Type[2:0])
tion if the FERF bit-field, within the MA byte is set to
"0" for 5 consecutive incoming E3 Frames.
Bit 3 - RxTMark Algorithm
These three Read-Only bit-fields contain the Payload
Type value within the MA byte of the most recently received E3 frame.
This Read/Write bit-field allows the user to select the
number of consecutive incoming E3 frames, that the
Timing Marker bit-field (within the MA byte-field) must
be of a given logic state, before it is validated by the
Receive DS3/E3 Framer block. Once the Receive
DS3/E3 Framer block has validated the state of the
Timing Marker bit-field, then it will write this logic
state into Bit 1 (RxTMark) within the Rx E3 Configuration & Status Register 2 (Address = 0x11)
NOTES:
1. The Payload Type Mismatch interrupt will be generated if the contents of these bit-fields differ from
that of the Expected Payload Types in Bits 2
through 0 within this Register.
2. These bit-fields are ignored is the channel is configured to support the October 1998 version of the
ITU-T G.832 framing format for E3.
Writing a "0" into this bit-field causes the Receive
DS3/E3 Framer block to validate the Timing Marker
value after receiving 3 consecutive incoming E3
frames, with the Timing Marker bit-field of a given value. Writing a "1" into this bit-field causes the Receive
DS3/E3 Framer block to validate the Timing Marker
value after receiving 5 consecutive incoming E3
frames, with the Timing Marker bit-field of a given value.
Bit 4 - RxFERF Algo
This Read/Write bit-field allows the user to select one
of the two RxFERF Declaration Algorithms:
Writing a "0" to this bit-field selects the following
RxFERF Declaration algorithm:
• The Receive DS3/E3 Framer declares a Far End
Receive Failure (FERF) if the FERF bit-field, within
the MA byte is set to "1" for 3 consecutive incoming
E3 Frames. Likewise, the Receive DS3/E3 Framer
block will negate the Far End Receive Failure condition if the FERF bit-field, within the MA byte is set to
"0" for 3 consecutive incoming E3 Frames.
NOTE: This bit-field is ignored if the channel is configured
to support the October 1998 version of the ITU-T G.832
framing format for E3.
Bits 2 - 0: RxPLDExp[2:0]
This Read/Write bit-field allows the user to specify the
Payload Type that is expected in the MA bytes, of
each incoming E3 frame.
Writing a "1" to this bit-field selects the following
RxFERF Declaration algorithm:
• The Receive DS3/E3 Framer block declares a Far
End Receive Failure (FERF) if the FERF bit-field,
within the MA byte is set to "1" for 5 consecutive E3
Frames. Likewise, the Receive E3/DS3 Framer
block will negate the Far End Receive Failure condi-
If the Receive DS3/E3 Framer detects a Payload Type
that differs from the values within these bit-fields, then
the Framer will generate the Payload Type Mismatch
interrupt.
83
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THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
XRT72L53
PRELIMINARY
REV. P1.1.7
2.4.3.2 Receive E3 Configuration & Status
Register 2 (E3, ITU-T G.832)
RXE3 CONFIGURATION & STATUS REGISTER 2 (ADDRESS = 0X11)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
Rx LOF Algo
RxLOF
RxOOF
RxLOS
RxAIS
RxPld Unstab
RxTMark
RxFERF
R/W
RO
RO
RO
RO
RO
RO
RO
0
1
1
1
1
1
1
1
Bit 7 - RxLOF Algo (Loss of Frame Declaration Algorithm)
E3 Framer block is currently not experiencing an LOS
condition.
This Read/Write bit-field allows the user to select the
LOF (Loss of Frame) Declaration criteria, that will be
used by the Receive DS3/E3 Framer. Writing a "0" to
this bit-field configures the Receive DS3/E3 Framer to
declare an LOF condition, after it has been in the
OOF condition for 24 frame periods (3 ms). Writing a
"1" to this bit-field configures the Receive DS3/E3
Framer to declare an LOF condition, after it has been
in the OOF condition for 8 frame periods (1 ms).
Bit 3 - RxAIS (Alarm Indication Status Declaration)
This Read-Only bit-field indicates whether or not the
Receive DS3/E3 Framer block is currently experiencing an AIS condition. The Receive DS3/E3 Framer
block will declare an AIS condition if it has detected
two consecutive E3 frames, that each contain less
than seven (7) "0’s". If this bit-field is set to "1", then
the Receive DS3/E3 Framer block has declared, and
is continuing to experience an AIS condition. If this
bit-field is set to "0", then the Receive DS3/E3 Framer
block is currently not experiencing an AIS condition.
Bit 6 - RxLOF (Loss of Frame Declaration)
This Read-Only bit-field indicates whether or not the
Receive DS3/E3 Framer block is currently in the Loss
of Frame (LOF) condition. If this bit-field is set to "1",
then the Receive DS3/E3 Framer block is currently in
the LOF condition. Conversely, if this bit-field is set to
"0", then the Receive DS3/E3 Framer block is currently not in the LOF condition.
Bit 2 - RxPLDType UnStab
This Read-Only bit-field indicates whether or not the
Receive DS3/E3 Framer block has been receiving a
consistent Payload Type value (within the MA ByteField) in the last 5 consecutive incoming E3 frames.
Bit 5 - RxOOF (Out of Frame Declaration)
If the Receive DS3/E3 Framer block has detected a
change in the Payload Type value, within the last 5 incoming E3 frames, then it will set this bit-field to "1". If
the Payload Type value has been consistent in the
last 5 E3 frames, then the Receive DS3/E3 Framer
block will set this bit-field to "0".
This Read-Only bit field indicates whether or not the
Receive DS3/E3 Framer block is currently experiencing an Out of Frame (OOF) condition. The Receive
DS3/E3 Framer block will declare an OOF condition if
it has detected errors in the frame alignment bytes
(FA1 and FA2) in four consecutive frames. If this bitfield is set to "1", then the Receive DS3/E3 Framer
block has declared, and is continuing to experience
an OOF condition. If this bit-field is set to "0", then the
Receive DS3/E3 Framer block is currently not experiencing an OOF condition.
Bit 1 - Rx TMark
This Read-Only bit-field reflects the most recently validated Timing Marker value. The Receive DS3/E3
Framer block will validate the Timing Marker state, after it has detected a user-selectable number of consecutive incoming E3 frames with a consistent Timing
Marker value. The user makes this selection by writing the appropriate value to Bit 3 (RxTMarkAlgo) within the Rx E3 Configuration/Status Register (Address
= 0x0E).
Bit 4 - RxLOS (Loss of Signal Declaration)
This Read-Only bit-field indicates whether or not the
Receive DS3/E3 Framer block is currently experiencing a Loss of Signal (LOS) condition. The Receive
DS3/E3 Framer block will declare an LOS condition if
it has detected a string of 32 consecutive "0’s", via the
RxPOS and RxNEG input pins. If this bit-field is set to
"1", then the Receive DS3/E3 Framer block has declared, and is continuing to experience an LOS condition. If this bit-field is set to "0", then the Receive DS3/
Bit 0 - RxFERF (Far End Receive Failure)
This Read-Only bit-field indicates whether or not the
Receive DS3/E3 Framer block is experiencing an
FERF (Far-End-Receive-Failure) condition. The Receive DS3/E3 Framer block will declare a FERF condition, if it has received a user-selectable number of
84
XRT72L53
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THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. P1.1.7
bit-field is set to "0", then the Receive DS3/E3 Framer
block has not declared an FERF condition.
consecutive E3 frames, with the FERF bit-field (within
the MA byte) set to "1". This user-selectable number
is either 3 or 5 E3 frames. Conversely, the Receive E3
Framer will negate the FERF declaration, if it has received this user-selectable number of consecutive E3
frames, with the FERF bit-field set to "0".
NOTE: Please see Section 5.1.1.4, for a more detailed discussion on the meaning of the FERF bit-field, within the E3
frame.
2.4.3.3 3.3.2.17 Receive E3 Interrupt Enable
Register (E3, ITU-T G.832)
If this bit-field is set to "1", then the Receive DS3/E3
Framer block has declared an FERF condition. If this
RXE3 INTERRUPT ENABLE REGISTER - 1 (ADDRESS = 0X12)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
Not Used
SSM MSG
Interrupt
Enable
SSM OOS
Interrupt
Enable
COFA
Interrupt
Enable
OOF
Interrupt
Enable
LOF
Interrupt
Enable
LOS
Interrupt
Enable
AIS
Interrupt
Enable
RO
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
0
0
Bit 6 - SSM Message Interrupt Enable
terrupt. Setting this bit-field to "1" enables this interrupt. Setting this bit-field to "0" disables this interrupt.
This Read/Write bit-field is used to enable or disable
the Change in Synchronous Status Message (SSM)
interrupt. Setting this bit-field to “1” enables this interrupt. Setting this bit-field to “0” disables this interrupt.
NOTE: For more information on the OOF Condition, please
see Section 5.3.2.1.
Bit 2 - LOF (Loss of Frame) Interrupt Enable
NOTE: This bit-field is ignored if the Channel is configured
to support the November 1995 revision of the ITU-T G.832
Framing format for E3.
This Read/Write bit-field allows the user to enable or
disable the Change in Loss-of-Frame (LOF) status interrupt. Setting this bit-field to "1" enables this interrupt. Setting this bit-field to "0" disables this interrupt.
For more information on the LOF Condition, please
see Section 5.3.2.1.
Bit 5 - SSM OOF (Out of Sequence) Interrupt Enable
This Read/Write bit-field is used to enable or disable
the Change in SSM Out of Sequence State interrupt.
Setting this bit-field to “1” enables this interrupt. Setting this bit-field to “0” disables this interrupt.
Bit 1 - LOS (Loss of Signal) Interrupt Enable
This Read/Write bit-field allows the user to enable or
disable the Change in LOS condition interrupt. Setting this bit-field to "1" enables this interrupt. Setting
this bit-field to "0" disables this interrupt.
NOTE: This bit-field is ignored if the Channel is configured
to support the November 1995 revision of the ITU-T G.832
Framing format for E3.
NOTE: For more information on the LOS Condition, please
see Section 5.3.2.6.
Bit 4 - Change of Frame Alignment (COFA) Interrupt Enable
Bit 0 - AIS Interrupt Enable
This Read/Write bit-field allows the user to enable or
disable the Change of Frame Alignment interrupt.
Setting this bit-field to "1" enables this interrupt. Setting this bit-field to "0" disables this interrupt.
This Read/Write bit-field allows the user to enable or
disable the Change in AIS condition interrupt. Setting
this bit-field to "1" enables this interrupt. Setting this
bit-field to "0" disables this interrupt.
Bit 3 - OOF (Out of Frame) Interrupt Enable
NOTE: For more information on the AIS Condition, please
see Section 5.3.2.6.2.
This Read/Write bit field allows the user to enable or
disable the Change in Out-of-Frame (OOF) status in-
85
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THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
XRT72L53
PRELIMINARY
REV. P1.1.7
2.4.3.4 3.3.2.18 Receive E3 Interrupt Enable
Register - 2 (E3, ITU-T G.832)
RXE3 INTERRUPT ENABLE REGISTER - 2 (ADDRESS = 0X13)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
Not Used
TTB
Change
Interrupt
Enable
Not Used
FEBE
Interrupt
Enable
FERF
Interrupt
Enable
BIP-8
Error Interrupt
Enable
Framing
Byte Error
Interrupt
Enable
RxPld
Mis
Interrupt
Enable
RO
R/W
RO
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
0
0
NOTE: For more information on the Change in FERF Condition interrupt, please see Section 5.3.6.1.7.
Bit 6 - TTB Change Interrupt Enable
This Read/Write bit-field allows the user to enable or
disable the Change in Trail Trace Buffer Message interrupt. Setting this bit-field to "1" enables this interrupt. Setting this bit-field to "0" disables this interrupt.
Bit 2 - EM Byte Error Interrupt Enable
This Read/Write bit-field allows the user to enable or
disable the EM Byte Error interrupt. Setting this bitfield to "1" enables this interrupt. Setting this bit-field
to "0" disables this interrupt.
NOTE: For more information on Trail Trace Buffer messages, please see Section 5.3.2.9.
NOTE: For more information on this interrupt, please see
Section 5.3.6.1.9.
Bit 5 - Received LAPD Message Interrupt Enable
This Read/Write bit-field allows the user to enable or
disable the Received LAPD Message frame interrupt.
Setting this bit-field to "1" enables this interrupt. Setting this bit-field to "0" disables this interrupt.
Bit 1 - Framing Byte Error Interrupt Enable
NOTE: For more information on this interrupt, please see
Section 5.3.6.1.12.
This Read/Write bit-field allows the user to enable or
disable the Framing Byte Error interrupt. Setting this
bit-field to "1" enables this interrupt. Setting this bitfield to "0" disables this interrupt.
Bit 4 - FEBE (Far-End Block Error) Interrupt Enable
NOTE: For more information on this interrupt, please see
Section 5.3.6.1.10.
This Read/Write bit-field allows the user to enable or
disable the Far-End-Block Error (FEBE) interrupt.
Setting this bit-field to "1" enables this interrupt. Setting this bit-field to "0" disables this interrupt.
Bit 0 - Receive Payload Type Mismatch Interrupt
Enable
NOTE: For more information on the FEBE Interrupt condition, please see Section 5.3.6.1.8.
This Read/Write bit-field allows the user to enable or
disable the Receive Payload Type Mismatch interrupt.
Setting this bit-field to "1" enables this interrupt. Setting this bit-field to "0" disables this interrupt.
Bit 3 - FERF (Far-End Receive Failure) Interrupt
Enable
NOTE: For more information on this interrupt, please see
Section 5.3.6.1.11.
This Read/Write bit-field allows the user to enable or
disable the Change in FERF Condition interrupt. Setting this bit-field to "1" enables this interrupt. Setting
this bit-field to "0" disables this interrupt.
2.4.3.5 Receive E3 Interrupt Status Register 1 (E3, ITU-T G.832)
RXE3 INTERRUPT STATUS REGISTER - 1 (ADDRESS = 0X14)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
Not Used
SSM MSG
Interrupt
Status
SSM OOS
Interrupt
Status
COFA
Interrupt
Status
OOF
Interrupt
Status
LOF
Interrupt
Status
LOS
Interrupt
Status
AIS
Interrupt
Status
RO
RUR
RUR
RUR
RUR
RUR
RUR
RUR
0
0
0
0
0
0
0
0
86
XRT72L53
THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
áç
PRELIMINARY
REV. P1.1.7
NOTE: For more information of the OOF Condition, please
see Section 5.3.2.1.
Bit 6 - SSM Message Interrupt Status
This Reset-upon-Read bit-field indicates whether or
not a Change of Synchronization Status Message
(SSM) Interrupt has occurred since the last read of
this register. This interrupt will occur whenever a
change in the contents of the SSM (within the inbound E3 data stream) has been detected.
Bit 2 - LOF (Loss of Frame) Interrupt Status
This Reset-upon-Read bit-field will be set to "1" if a
Change in LOF Condition interrupt has occurred
since the last read of this register.
The Receive DS3/E3 Framer block will generate the
Change in LOF Condition interrupt is response to either of the following two occurrences.
If this bit-field has been set to “1”, then the Change of
SSM Interrupt has occurred since the last read of this
register. Conversely, if this bit-field has been set to
“0”, then the Change of SSM Interrupt has not occurred since the last read of this register.
1. Whenever the Receive DS3/E3 Framer block
transitions from the OOF Condition state into the
LOF Condition state, within the E3 Framing
Acquisition/Maintenance algorithm (per
Figure 194).
2. Whenever the Receive DS3/E3 Framer block
transitions from the FA1, FA2 Octet Verification
state to the In-frame state, within the E3 Framing
Acquisition/Maintenance algorithm (per
Figure 194).
Bit 1 - LOS (Loss of Signal) Interrupt Status
NOTE: This bit-field is invalid if the channel has been configured to support the November 1995 revision of the ITU-T
G.832 Framing format for E3.
Bit 5 - SSM Out of Sequence Interrupt Status
This Reset-upon-Read bit-field indicates whether or
not the Change in SSM Out of Sequence State interrupt has occurred since the last read of this register.
This interrupt will occur in response to either of the
following conditions.
This Reset Upon Read bit will be set to "1", if the Receive DS3/E3 Framer block has detected a
1. The Receive Section losses sequence synchronization with the SSM data.
2. The Receive Section re-acquires sequence synchronization with the SSM data.
Change in the LOS Status condition, since the last
time this register was read. This bit-field will be asserted under either of the following two conditions:
NOTE: This bit-field is invalid if the Channel has been configured to support the November 1995 revision of the ITU-T
G.832 Framing format for E3.
1. When the Receive DS3/E3 Framer block detects
the occurrence of an LOS Condition (e.g., the
occurrence of 32 consecutive spaces in the
incoming E3 data stream), and
2. When the Receive DS3/E3 Framer block detects
the end of an LOS Condition (e.g., when the
Receive DS3/E3 Framer block detects a string 32
bits that does not contain a string of four consecutive "0’s").
The local µP can determine the current state of the
LOS condition by reading bit 6 of the Rx E3 Configuration and Status Register (Address = 0x11).
Bit 4 - COFA (Change of Frame Alignment) Interrupt Status
This Reset-upon-Read bit-field will be set to "1" if the
Change of Frame Alignment interrupt has occurred
since the last read of this register.
The Receive DS3/E3 Framer block will generate the
Change of Frame Alignment interrupt if it has detected a change in frame alignment in the incoming E3
frames.
Bit 3 - OOF (Receive E3 Framer) Interrupt Status
NOTE: For more information in the LOS of Signal (LOS)
Alarm, please see Section 5.3.2.6.
This Reset Upon Read bit-field is set to "1" if the Receive DS3/E3 Framer block has detected a Change in
the Out-of-Frame (OOF) Condition, since the last time
this register was read. Therefore, this bit-field will be
asserted under either of the following two conditions:
Bit 0 - AIS Interrupt Status
This Reset Upon Read bit field will be set to "1", if the
Receive DS3/E3 Framer block has detected a
Change in the AIS condition, since the last time this
register was read. This bit-field will be asserted under
either of the following two conditions:
1. When the Receive DS3/E3 Framer block has
detected the appropriate conditions to declare an
OOF Condition.
2. When the Receive DS3/E3 Framer block transitions from the OOF Condition (Frame Acquisition
Mode) into the In-Frame Condition (Frame Maintenance mode).
1. When the Receive DS3/E3 Framer block first
detects an AIS Condition in the incoming E3 data
stream.
2. When the Receive DS3/E3 Framer block has
detected the end of an AIS Condition in the
incoming E3 data stream.
87
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THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
XRT72L53
PRELIMINARY
REV. P1.1.7
2.4.3.6 Receive E3 Interrupt Status Register 2 (E3, ITU-T G.832)
The local µP can determine the current state of the
AIS condition by reading bit 7 of the Rx E3 Configuration and Status Register (Address = 0x11).
NOTE: For more information on the AIS Condition please
see Section 5.3.2.6.2.
RXE3 INTERRUPT STATUS REGISTER - 2 (ADDRESS = 0X15)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
Not Used
TTB
Change
Interrupt
Status
Not Used
FEBE
Interrupt
Status
FERF
Interrupt
Status
BIP-8
Error Interrupt
Status
Framing
Byte Error
Interrupt
Status
RxPld
Mis
Interrupt
Status
RO
RUR
RO
RUR
RUR
RUR
RUR
RUR
0
0
0
0
0
0
0
0
Bit 6 - TTB Change Interrupt Status (Receipt of
New Trail Trace Buffer Message interrupt)
FERF bit, within the last 3 or 5 consecutive E3
frames are set to "0").
This Reset-upon-Read bit-field will be set to "1" if a
Receipt of New Trail Trace Buffer Message interrupt
has occurred since the last read of this register.
NOTE: For more information on the RxFERF (Yellow Alarm)
condition, please see Section 5.3.2.6.3.
The Receive DS3/E3 Framer block will generate the
Receipt of New Trail Trace Buffer Message interrupt,
if it receives an E3 frame in which the value of the TR
byte-field is of the form "1xxxxxxxb". A TR byte-field
value of this form is identified as the frame start marker.
This Reset-upon-Read bit-field will be set to "1" if the
BIP-8 Error interrupt has occurred since the last read
of this register.
Bit 2 - EM (BIP-8) Byte Error Interrupt Status
The Receive DS3/E3 Framer block will generate the
BIP-8 Error interrupt if it has concluded that it has received an errored E3 frame, from the Remote Terminal.
NOTE: Please see Section 5.3.6.1.6 for a more detailed discussion of this interrupt.
NOTE: Please see Section 5.3.6.1.9 for a more detailed discussion of this interrupt.
Bit 4 - FEBE (Far-End Block Error) Interrupt Status
Bit 1 - Framing Byte Error Interrupt Status
This Reset-upon-Read bit-field will be set to "1" if the
FEBE (Far-End-Block Error) interrupt has occurred
since the last read of this register.
This Reset-upon-Read bit-field will be set to "1" if the
Framing Byte Error interrupt has occurred since the
last read of this register.
The Receive DS3/E3 Framer block will generate the
FEBE interrupt anytime it detects a "1" in the FEBE
bit-field within an incoming E3 frame.
The Receive DS3/E3 Framer block will generate the
Framing Byte Error interrupt if it has detected an error
in the FA1 or FA2 bytes, on an incoming E3 frame.
NOTE: Please see Section 5.3.6.1.8 for a more detailed discussion of this interrupt.
NOTE: Please see Section 5.3.6.1.10 for a more detailed
discussion of this interrupt.
Bit 3 - FERF Interrupt Status
This Reset Upon Read bit will be set to '1' if the Receive E3 Framer has detected a Change in the Rx
FERF Condition, since the last time this register was
read.
Bit 0 - Rx Pld Mis Interrupt Status
This bit-field will be asserted under either of the following two conditions.
The Receive DS3/E3 Framer block will generate the
Payload Type Mismatch interrupt when it detects that
the values, within the Payload Type bit-fields of the incoming E3 frame, has changed from that of the previous E3 frame.
This Reset-upon-Read bit-field will be set to "1" if the
Payload Type Mismatch interrupt has occurred since
the last read of this register.
1. When the Receive DS3/E3 Framer block first
detects the occurrence of an RxFERF Condition
(e.g., when the FERF bit, within the last 3 or 5
consecutive E3 frames are set to "1").
2. When the Receive DS3/E3 Framer block detects
the end of the RxFERF Condition (e.g., when the
NOTE: Please see Section 5.3.6.1.11 for a more detailed
discussion on this interrupt.
88
XRT72L53
áç
THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. P1.1.7
2.4.3.7 Receive E3 LAPD Control Register (E3,
ITU-T G.832)
RXE3 LAPD CONTROL REGISTER (ADDRESS = 0X18)
BIT 7
BIT 6
BIT 5
BIT 4
Not Used
BIT 3
BIT 2
BIT 1
BIT 0
DL from NR
RxLAPD
Enable
RxLAPD
Interrupt
Enable
RxLAPD
Interrupt
Status
RO
RO
RO
RO
R/W
R/W
R/W
RUR
0
0
0
0
0
0
0
0
Bit 3 - DL from NR
This Read/Write bit-field allows the user to enable or
disable the Received LAPD Message frame interrupt.
Setting this bit-field to "1" enables this interrupt. Setting this bit-field to "0" disables this interrupt. For
more information on this interrupt, please see Section
5.3.3.
This Read/Write bit-field allows the user to specify
whether the LAPD Receiver should retrieve the bytes,
comprising the incoming LAPD Message frame, from
the NR byte-field, or from the GC byte-field, within
each incoming E3 frame.
Bit 0 - RxLAPD (Received LAPD Message) Interrupt Status
Writing a "1" configures the LAPD Receiver to retrieve the incoming LAPD Message frame octets from
the NR byte-field, within each incoming E3 frame.
Writing a "0" configures the LAPD Receiver to retrieve the incoming LAPD Message frame octets from
the GC byte.
This Reset-upon-Read bit-field will be set to "1" if the
Receipt of New LAPD Message frame interrupt has
occurred since the last read of this register.
The Receive DS3/E3 Framer block will generate this
Receipt of New LAPD Message frame interrupt when
the LAPD Receiver has received a complete LAPD
Message frame from the Remote LAPD Transmitter.
Bit 2 - RxLAPD Enable
This Read/Write bit-field allows the user to enable or
disable the LAPD Receiver, for reception of incoming
LAPD Message frames from the Remote LAPD
Transmitter.
NOTE: Please see section 5.3.6.1.12 for a more detailed
discussion of this interrupt.
2.4.3.8 Receive E3 LAPD Status Register (E3,
ITU-T G.832
Writing a "1" to this bit-field enables the LAPD Receiver. Writing a "0" to this bit-field disables the LAPD
Receiver.
Bit 1 - RxLAPD (Received LAPD Message) Interrupt Enable
RXE3 LAPD STATUS REGISTER (ADDRESS = 0X19)
BIT 7
BIT 6
BIT 5
Not Used
Rx ABORT
RO
RO
RO
0
0
0
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
RxCR
Type
RxFCS
Error
End of
Message
Flag
Present
RO
R/W
R/W
R/W
RUR
0
0
0
0
0
RxLAPDType[1:0]
Bit 6 - Rx Abort
the LAPD Receiver has not detected an abort sequence, since the last read of this register.
This Read-Only bit-field indicates whether or not the
LAPD Receiver is currently detecting an abort sequence (e.g., a string of 7 consecutive "1’s").
Bit 5, 4 - RxLAPD Type[1:0]
These two Read-Only bit-fields combine to indicate
the type and size of LAPD Message frame that has
been received by the LAPD Receiver. The following
This bit-field is set to "1" if the LAPD Receiver is currently detecting an abort sequence in the incoming
LAPD Channel. Conversely, this bit-field is set to "0" if
89
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THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
XRT72L53
PRELIMINARY
REV. P1.1.7
table relates the contents of these bit-fields to the
LAPD Message type/size.
RXLAPDTYPE[1:0]
LAPD MESSAGE FRAME TYPE
PMDL MESSAGE SIZE (INFORMATION
SECTION)
00
CL Path Identification Type
76 Bytes
01
Idle Signal Identification Type
76 Bytes
10
Test Signal Identification Type
76 Bytes
11
ITU-T Path Identification Type
82 Bytes
Bit 3 - Rx CR Type
frame. This bit-field, along with the Receipt of New
LAPD Message frame interrupt, serves to inform the
local µP that the Receive LAPD Message buffer contains a new PMDL message that needs to be read
and processed.
This Read-Only bit-field indicates the state of the C/R
bit-field, within octet # 2 of the most recently received
LAPD Message frame.
Bit 2 - Rx FCS Error
This bit-field is cleared (set to "0") upon reading this
register.
This Read-Only bit-field indicates whether or not the
LAPD Receiver has detected an FCS (Frame Check
Sequence) error, in the most recently received LAPD
Message frame. This bit-field is set to "0" if the LAPD
Receiver does not detect an FCS error in this LAPD
Message frame. Conversely, this bit-field is set to "1"
if the LAPD Receiver does detect an FCS error in this
LAPD Message frame.
Bit 0 - Flag Present
The LAPD Receiver will assert this read-only bit-field
when it is currently detecting the Flag Sequence octet
(7Eh) in the incoming LAPD channel (e.g., either the
GC or the NR byte-field, within each E3 frame). The
LAPD Receiver will negate this bit-field when it is no
longer receiving the Flag Sequence octet in the incoming LAPD channel.
NOTE: For a more detailed discussion on the LAPD
Receiver's handling of the FCS bytes, please see Section
5.3.3.
2.4.3.9
G.832)
Bit 1 - EndOfMessage
Receive E3 NR Byte Register (E3, ITU-T
The LAPD Receiver will assert this read-only bit-field,
when it has received a complete LAPD Message
RXE3 NR BYTE REGISTER (ADDRESS = 0X1A)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
RxNR[7:0]
RO
RO
RO
RO
RO
RO
RO
RO
0
0
0
0
0
0
0
0
2.4.3.10 Receive E3 GC Byte Register (E3, ITUT G.832)
This Read-Only register contains the value of the NR
byte, within the most recently received E3 frame.
Please see Section 5.3.3 for a more detailed discussion on this register.
RXE3 GC BYTE REGISTER (ADDRESS = 0X1B)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
RxGC[7:0]
RO
RO
RO
RO
RO
RO
RO
RO
0
0
0
0
0
0
0
0
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XRT72L53
áç
THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. P1.1.7
2.4.3.11 Receive E3 TTB-0 Register (E3, ITU-T
G.832)
This Read-Only register contains the value of the GC
byte, residing in the most recently received E3 frame.
Please see Section 5.3.3 for a more detailed discussion on this register.
RXE3 TTB-0 REGISTER (ADDRESS = 0X1C)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
RxTTB-0
RO
RO
RO
RO
RO
RO
RO
RO
0
0
0
0
0
0
0
0
CRC-7 value that was calculated over the previous 16
byte Trail Trace Buffer Message.
This Read-Only register contains the frame start
marker byte of the 16 byte Trail Trace Buffer Message
that has been received from the Remote Terminal, via
the TR byte-field within the incoming E3 frames. The
remaining bytes, of this Trail Trace Buffer Message
can be found in the RxTTB-1 through RxTTB-15 registers.
NOTES:
1. The XRT72L53 Framer will not compute or verify
this CRC-7 value. It is up to the user's hardware
and/or software to compute and verify this value.
2. For more information on the use of this register,
please see Section 5.3.2.9.
The data in this register is typically of the form [1, C6,
C5, C4, C3, C2, C1, C0]. The "1" in the MSB position
identifies this byte as being the frame start marker
(e.g., the first byte within the 16 byte Trail Trace Buffer
Message). The remaining bits: C0 - C6 contain the
2.4.3.12 Receive E3 TTB-1 Register (E3, ITU-T
G.832)
RXE3 TTB-1 REGISTER (ADDRESS = 0X1D)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
RxTTB-1
RO
RO
RO
RO
RO
RO
RO
RO
0
0
0
0
0
0
0
0
NOTE: For more information on the use of this register,
please see Section 5.3.2.9.
This Read-Only register contains the second (2nd)
byte within the 16 byte Trail Trace Buffer Message,
that has been received from the Remote Terminal.
This register typical contains an ASCII character that
is required for the E.164 numbering format.
2.4.3.13 Receive E3 TTB-2 Register (E3, ITU-T
G.832)
RXE3 TTB-2 REGISTER (ADDRESS = 0X1E)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
RxTTB-2
RO
RO
RO
RO
RO
RO
RO
RO
0
0
0
0
0
0
0
0
This Read-Only register contains the third (3rd) byte
within the 16 byte Trail Trace Buffer Message, that
has been received from the Remote Terminal. This
register typical contains an ASCII character that is required for the E.164 numbering format.
NOTE: For more information on the use of this register,
please see Section 5.3.2.9.
91
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THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
XRT72L53
PRELIMINARY
REV. P1.1.7
2.4.3.14 Receive E3 TTB-3 Register (E3, ITU-T
G.832)
RXE3 TTB-3 REGISTER (ADDRESS = 0X1F)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
RxTTB-3
RO
RO
RO
RO
RO
RO
RO
RO
0
0
0
0
0
0
0
0
NOTE: For more information on the use of this register,
please see Section 5.3.2.9.
This Read-Only register contains the fourth (4th) byte
within the 16 byte Trail Trace Buffer Message, that
has been received from the Remote Terminal. This
register typical contains an ASCII character that is required for the E.164 numbering format.
2.4.3.15 Receive E3 TTB-4 Register (E3, ITU-T
G.832)
RXE3 TTB-4 REGISTER (ADDRESS = 0X20)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
RxNR[7:0]
RO
RO
RO
RO
RO
RO
RO
RO
0
0
0
0
0
0
0
0
NOTE: For more information on the use of this register,
please see Section 5.3.2.9.
This Read-Only register contains the fifth (5th) byte
within the 16 byte Trail Trace Buffer Message, that
has been received from the Remote Terminal. This
register typical contains an ASCII character that is required for the E.164 numbering format.
2.4.3.16 Receive E3 TTB-5 Register (E3, ITU-T
G.832)
RXE3 TTB-5 REGISTER (ADDRESS = 0X21)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
RxTTB-5
RO
RO
RO
RO
RO
RO
RO
RO
0
0
0
0
0
0
0
0
NOTE: For more information on the use of this register,
please see Section 5.3.2.9.
This Read-Only register contains the sixth (6th) byte
within the 16 byte Trail Trace Buffer Message, that
has been received from the Remote Terminal. This
register typical contains an ASCII character that is required for the E.164 numbering format.
2.4.3.17 Receive E3 TTB-6 Register (E3, ITU-T
G.832)
RXE3 TTB-6 REGISTER (ADDRESS = 0X22)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
RxNR[7:0]
RO
RO
RO
RO
RO
RO
RO
RO
0
0
0
0
0
0
0
0
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XRT72L53
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THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. P1.1.7
NOTE: For more information on the use of this register,
please see Section 5.3.2.9.
This Read-Only register contains the seventh (7th)
byte within the 16 byte Trail Trace Buffer Message,
that has been received from the Remote Terminal.
This register typical contains an ASCII character that
is required for the E.164 numbering format.
2.4.3.18 Receive E3 TTB-7 Register (E3, ITU-T
G.832)
RXE3 TTB-7 REGISTER (ADDRESS = 0X23)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
RxTTB-7
RO
RO
RO
RO
RO
RO
RO
RO
0
0
0
0
0
0
0
0
NOTE: For more information on the use of this register,
please see Section 5.3.2.9.
This Read-Only register contains the eighth (8th) byte
within the 16 byte Trail Trace Buffer Message, that
has been received from the Remote Terminal. This
register typical contains an ASCII character that is required for the E.164 numbering format.
2.4.3.19 Receive E3 TTB-8 Register (E3, ITU-T
G.832)
RXE3 TTB-8 REGISTER (ADDRESS = 0X24)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
RxNR[7:0]
RO
RO
RO
RO
RO
RO
RO
RO
0
0
0
0
0
0
0
0
NOTE: For more information on the use of this register,
please see Section 5.3.2.9.
This Read-Only register contains the ninth (9th) byte
within the 16 byte Trail Trace Buffer Message, that
has been received from the Remote Terminal. This
register typical contains an ASCII character that is required for the E.164 numbering format.
2.4.3.20 Receive E3 TTB-9 Register (E3, ITU-T
G.832)
RXE3 TTB-9 REGISTER (ADDRESS = 0X25)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
RxTTB-9
RO
RO
RO
RO
RO
RO
RO
RO
0
0
0
0
0
0
0
0
This Read-Only register contains the tenth (10th) byte
within the 16 byte Trail Trace Buffer Message, that
has been received from the Remote Terminal. This
register typical contains an ASCII character that is required for the E.164 numbering format.
NOTE: For more information on the use of this register,
please see Section 5.3.2.9.
93
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THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
XRT72L53
PRELIMINARY
REV. P1.1.7
2.4.3.21 Receive E3 TTB-10 Register (E3, ITU-T
G.832)
RXE3 TTB-10 REGISTER (ADDRESS = 0X26)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
RxTTB-10
RO
RO
RO
RO
RO
RO
RO
RO
0
0
0
0
0
0
0
0
NOTE: For more information on the use of this register,
please see Section 5.3.2.9.
This Read-Only register contains the eleventh (11th)
byte within the 16 byte Trail Trace Buffer Message,
that has been received from the Remote Terminal.
This register typical contains an ASCII character that
is required for the E.164 numbering format.
2.4.3.22 Receive E3 TTB-11 Register (E3, ITU-T
G.832)
RXE3 TTB-11 REGISTER (ADDRESS = 0X27)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
RxTTB-11
RO
RO
RO
RO
RO
RO
RO
RO
0
0
0
0
0
0
0
0
NOTE: For more information on the use of this register,
please see Section 5.3.2.9.
This Read-Only register contains the twelfth (12th)
byte within the 16 byte Trail Trace Buffer Message,
that has been received from the Remote Terminal.
This register typical contains an ASCII character that
is required for the E.164 numbering format.
2.4.3.23 Receive E3 TTB-12 Register (E3, ITU-T
G.832)
RXE3 TTB-12 REGISTER (ADDRESS = 0X28)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
RxTTB-12
RO
RO
RO
RO
RO
RO
RO
RO
0
0
0
0
0
0
0
0
NOTE: For more information on the use of this register,
please see Section 5.3.2.9.
This Read-Only register contains the thirteenth (13th)
byte within the 16 byte Trail Trace Buffer Message,
that has been received from the Remote Terminal.
This register typical contains an ASCII character that
is required for the E.164 numbering format.
2.4.3.24 Receive E3 TTB-13 Register (E3, ITU-T
G.832)
RXE3 TTB-13 REGISTER (ADDRESS = 0X29
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
RxTTB-13
RO
RO
RO
RO
RO
RO
RO
RO
0
0
0
0
0
0
0
0
94
XRT72L53
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THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. P1.1.7
NOTE: For more information on the use of this register,
please see Section 5.3.2.9.
This Read-Only register contains the fourteenth
(14th) byte within the 16 byte Trail Trace Buffer Message, that has been received from the Remote Terminal. This register typical contains an ASCII character
that is required for the E.164 numbering format.
2.4.3.25 Receive E3 TTB-14 Register (E3, ITU-T
G.832)
RXE3 TTB-14 REGISTER (ADDRESS = 0X2A)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
RxTTB-14
RO
RO
RO
RO
RO
RO
RO
RO
0
0
0
0
0
0
0
0
NOTE: For more information on the use of this register,
please see Section 5.3.2.9.
This Read-Only register contains the fifteenth (15th)
byte within the 16 byte Trail Trace Buffer Message,
that has been received from the Remote Terminal.
This register typical contains an ASCII character that
is required for the E.164 numbering format.
2.4.3.26 Receive E3 TTB-15 Register (E3, ITU-T
G.832)
RXE3 TTB-15 REGISTER (ADDRESS = 0X2B)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
RxTTB-15
RO
RO
RO
RO
RO
RO
RO
RO
0
0
0
0
0
0
0
0
NOTE: For more information on the use of this register,
please see Section 5.3.2.9.
This Read-Only register contains the sixteenth (16th)
byte within the 16 byte Trail Trace Buffer Message,
that has been received from the Remote Terminal.
This register typical contains an ASCII character that
is required for the E.164 numbering format.
2.4.3.27 Receive E3 Framer SSM Register
RXE3 SSM REGISTER (ADDRESS = 0X2B)
BIT 7
BIT 6
BIT 5
MFI[1:0]
RxSSM
Enable
BIT 4
BIT 3
BIT 2
Reserved
BIT 1
BIT 0
RxSSM[3:0]
R/W
RO
RO
RO
RO
RO
RO
RO
0
0
0
0
0
0
0
0
Bit 7 - RxSSM Enable
the “old” E3, ITU-T G.832 framing standard (November 1995).
This Read/Write bit-field is used to configure the Receive Section of a given channel to support processing of the MA byte via either the “old” or the “new”
ITU-T G.832 Framing format.
Bits 6, 5 - MF[1:0] - SSM Multiframe Indicator Bits
These two bits reflect the states of the SSM Multiframe phase indicators, within the most recently received E3 frame. Stated another ways, these two bitfields reflect Bits 2 and 1 within the MA byte, in the
most recently received E3 frame.
Setting this bit-field to “1” configures the Receive
Section to support the “new” E3, ITU-T G.832 framing
standard (October 1998 Revision). Setting this bitfield to “0” configures the Receive Section to support
NOTE: These two bit-fields are only valid if the Receive
Section of the Channel has been configured to support the
95
áç
THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
XRT72L53
PRELIMINARY
REV. P1.1.7
October 1998 Revision of the ITU-T G.832 Framing format
for E3.
NOTE: These four bit-fields are only valid if the Receive
Section of the Channel has been configured to support the
October 1998 Revision of the ITU-T G.832 Framing format
for E3.
Bits 3-0 - RxSSM[3:0] - Received Synchronization
Status Message
2.4.4 Receive E3 Framer Configuration Registers (ITU-T G.751)
These four Read-Only bits reflect the content of the
SSM, which is currently being received via the inbound E3 data stream.
2.4.4.1 Receive E3 Framer Configuration &
Status Register - 1 (E3, ITU-T G.751)
RXE3 CONFIGURATION & STATUS REGISTER - 1 G.751 (ADDRESS = 0X10)
BIT 7
BIT 6
BIT 5
Reserved
BIT 4
BIT 3
RxFERF
Algo
BIT 2
BIT 1
Reserved
BIT 0
RxBIP4
RO
RO
RO
R/W
RO
RO
RO
R/W
0
0
0
0
0
0
0
0
Bit 4 - RxFERF Algo(rithm) Select
E3 frames, with the A-bit set to "0", have been received.
This Read/Write bit-field is used to select the Received FERF Declaration Algorithm.
Bit 0 - RxBIP4 Enable
This Read/Write bit-field is used to configure the Receive Section of the Channel to verify (or not verify)
the BIP-4 value within each incoming E3 frame.
Setting this bit-field to "0", configures the Receive
Section of the Channel to declare a FERF (Far-EndReceive Failure), after three (3) consecutive E3
frames, with the A-bit set to "1", have been received.
Further, the Receive Section of the Channel will clear
FERF, after three (3) consecutive E3 frames, with the
A-bit set to "0", have been received.
Setting this bit-field to "0", configures the Receive
Section of the Channel to NOT verify the BIP-4 value
within each incoming E3 frame.
Setting this bit-field to "1", configures the Receive
Section of the Channel to verify the BIP-4 value within
each incoming E3 frame.
Setting this bit-field to "1", configures the Receive
Section of the Channel to declare a FERF, after five
(5) consecutive E3 frames, with the A-bit set to "1",
have been received. Further, the Receive Section of
the Channel will clear FERF after five (5) consecutive
2.4.4.2 Receive E3 Framer Configuration &
Status Register -2 (E3, ITU-T G.751)
RXE3 CONFIGURATION & STATUS REGISTER - 2 (ADDRESS = 0X11)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
RxLOF
Algo
RxLOF
RxOOF
RxLOS
RxAIS
R/W
RO
RO
RO
RO
RO
RO
RO
0
1
1
0
0
1
1
1
Not Used
BIT 0
RxFERF
Bit 7 - RxLOF (Receive Loss of Frame) Algo(rithm) Select
clear the Loss of Frame condition, if it resides in the
In-Frame condition for 24 E3 Frame periods.
This Read/Write bit-field is used to select the Receive
Loss of Frame Declaration Algorithm, for the Receive
Section of the Channel.
Setting this bit-field to "1" configures the Receive
Section to declare a Loss of Frame condition, if it resides in the OOF (Out of Frame) condition for 8 E3
Frame periods. Likewise, the Receive Section will
clear the Loss of Frame condition, if it resides in the
In-Frame condition for 8 E3 Frame periods.
Setting this bit-field to "0" configures the Receive
Section to declare a Loss of Frame condition, if it resides in the OOF (Out of Frame) Condition for 24 E3
Frame periods. Likewise, the Receive Section will
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THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. P1.1.7
NOTE: For more information on the LOF and OOF condition, please see Section 4.3.2.2.
if this bit-field is set to "1", then the Receive Section is
declaring the Loss of Signal condition.
Bit 6 - RxLOF (Receive Loss of Frame) Status
NOTE: For more information on the Loss of Signal Condition, please see Section 4.3.2.7.
This Read-Only bit-field indicates whether or not the
Receive Section of the Framer IC is operating in the
Loss of Frame state.
Bit 3 - RxAIS (Receive Alarm Indication Signal)
Status
If this bit-field is set to "0", then the Receive Section is
NOT operating in the Loss of Frame state. Conversely, if this bit-field is set to "1", then the Receive Section is operating in the Loss of Frame state.
This Read-Only bit-field indicates whether or not the
Receive Section of the Channel is currently declaring
an AIS (Alarm Indication Signal) Condition.
If this bit-field is set to "0", then the Receive Section is
NOT declaring a AIS condition. Conversely, if this bitfield is set to "1", then the Receive Section is declaring an AIS condition.
NOTE: For more information on the Loss of Frame State,
please see Section 4.3.2.2.
Bit 5 - RxOOF (Receive Out of Frame) Status
NOTE: For more information on the AIS Condition, please
see Section 4.3.2.8.
This Read-Only bit-field indicates whether or not the
Receive Section of the Channel is operating in the
Out of Frame state.
Bit 0 - RxFERF (Received Far-End-Receive-Failure) Status
If this bit-field is set to "0", then the Receive Section is
NOT operating in the Out of Frame state. Conversely,
if this bit-field is set to "1", then the Receive Section is
operating in the Out of Frame state.
This Read-Only bit-field indicates whether or not the
Receive Section of the Channel is currently declaring
a FERF (Far-End Receive Failure) Condition.
NOTE: For more information on the Out of Frame State,
please see Section 4.3.2.2.
If this bit-field is set to "0", then the Receive Section is
NOT declaring a FERF condition. Conversely, if this
bit-field is set to "1", then the Receive Section is declaring an FERF condition.
Bit 4 - RxLOS (Receive Loss of Signal) Status
This Read-Only bit-field indicates whether or not the
Receive Section of the Channel is currently declaring
an LOS (Loss of Signal) Condition.
NOTE: For more information on the FERF Condition, please
see Section 4.3.2.9.
If this bit-field is set to "0", then the Receive Section is
NOT declaring a Loss of Signal condition. Conversely,
2.4.4.3 Receive E3 Framer Interrupt Enable
Register - 1 (E3, ITU-T G.751)
RXE3 INTERRUPT ENABLE REGISTER - 1 (ADDRESS = 0X12)
BIT 7
BIT 6
BIT 5
Not Used
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
COFA
Interrupt
Enable
OOF
Interrupt
Enable
LOF
Interrupt
Enable
LOS
Interrupt
Enable
AIS
Interrupt
Enable
RO
RO
RO
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
0
0
Bit 4 - COFA (Change of Frame Alignment) Interrupt Enable
NOTE: For more information on the OOF Condition, please
see Section 4.3.2.2.
This Read/Write bit-field allows the user to enable or
disable the Change of Frame Alignment interrupt.
Setting this bit-field to "1" enables this interrupt. Setting this bit-field to "0" disables this interrupt.
Bit 2 - LOF (Change in LOF Condition) Interrupt
Enable
This Read/Write bit-field allows the user to enable or
disable the Change in Loss-of-Frame (LOF) status interrupt. Setting this bit-field to "1" enables this interrupt. Setting this bit-field to "0" disables this interrupt.
Bit 3 - OOF (Change in OOF Condition) Interrupt
Enable
NOTE: For more information on the LOF Condition, please
see Section 4.3.2.2.
This Read/Write bit field allows the user to enable or
disable the Change in Out-of-Frame (OOF) status interrupt. Setting this bit-field to "1" enables this interrupt. Setting this bit-field to "0" disables this interrupt.
Bit 1 - LOS (Change in LOS Condition) Interrupt
Enable
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REV. P1.1.7
This Read/Write bit-field allows the user to enable or
disable the Change in LOS condition interrupt. Setting this bit-field to "1" enables this interrupt. Setting
this bit-field to "0" disables this interrupt.
This Read/Write bit-field allows the user to enable or
disable the Change in AIS condition interrupt. Setting
this bit-field to "1" enables this interrupt. Setting this
bit-field to "0" disables this interrupt.
NOTE: For more information on the LOS Condition, please
see Section 4.3.2.7.
NOTE: For more information on the AIS Condition, please
see Section 4.3.2.8
Bit 0 - AIS (Change in AIS Condition) Interrupt Enable
2.4.4.4 Receive E3 Interrupt Enable Register 2 (E3, ITU-T G.751)
RXE3 INTERRUPT ENABLE REGISTER - 2 (ADDRESS = 0X13)
BIT 7
BIT 6
BIT 5
BIT 4
Not Used
BIT 3
BIT 2
BIT 1
BIT 0
FERF
Interrupt
Enable
BIP-4 Error
Interrupt
Enable
Framing Error
Interrupt
Enable
Not Used
R/W
RO
RO
RO
R/W
R/W
R/W
RO
0
0
0
0
0
0
0
0
Bit 3 - FERF (Far-End Receive Failure) Interrupt
Enable
NOTE: For more information on this interrupt, please see
Section 4.3.6.1.7.
This Read/Write bit-field allows the user to enable or
disable the Change in FERF Condition interrupt. Setting this bit-field to "1" enables this interrupt. Setting
this bit-field to "0" disables this interrupt.
Bit 1 - Framing Error Interrupt Enable
This Read/Write bit-field allows the user to enable or
disable the Framing Error interrupt. Setting this bitfield to "1" enables this interrupt. Setting this bit-field
to "0" disables this interrupt.
NOTE: For more information on the Change in FERF Condition interrupt, please see Section 4.3.6.1.6.
NOTE: For more information on this interrupt, please see
Section 4.3.6.1.8.
Bit 2 - BIP-4 Error Interrupt Enable
2.4.4.5 Receive E3 Interrupt Status Register 1 (E3, ITU-T G.751)
This Read/Write bit-field allows the user to enable or
disable the BIP-4 Error interrupt. Setting this bit-field
to "1" enables this interrupt. Setting this bit-field to "0"
disables this interrupt.
RXE3 INTERRUPT STATUS REGISTER - 1 (ADDRESS = 0X14)
BIT 7
BIT 6
BIT 5
Not Used
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
COFA
Interrupt
Status
OOF
Interrupt
Status
LOF
Interrupt
Status
LOS
Interrupt
Status
AIS
Interrupt
Status
R/W
RO
RO
RUR
RUR
RUR
RUR
RUR
0
0
0
0
0
0
0
0
Bit 4 - COFA (Change of Framing Alignment) Interrupt Status
Bit 3 - OOF (Change in OOF Condition) Interrupt
Status
This Reset-upon-Read bit-field will be set to "1" if the
Change of Frame Alignment interrupt has occurred
since the last read of this register.
This Reset Upon Read bit-field is set to "1" if the Receive DS3/E3 Framer block has detected a Change in
the Out-of-Frame (OOF) Condition, since the last time
this register was read. Therefore, this bit-field will be
asserted under either of the following two conditions:
The Receive E3 Framer will generate the Change of
Frame Alignment interrupt if it has detected a change
in frame alignment in the incoming E3 frames.
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THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
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REV. P1.1.7
1. When the Receive DS3/E3 Framer block detects
the occurrence of an LOS Condition (e.g., the
occurrence of 32 consecutive spaces in the
incoming E3 data stream), and
2. When the Receive DS3/E3 Framer block detects
the end of an LOS Condition (e.g., when the
Receive DS3/E3 Framer block detects a string 32
bits that does not contain a string of four consecutive "0’s").
The local µP can determine the current state of the
LOS condition by reading bit 6 of the Rx E3 Configuration and Status Register (Address = 0x11).
1. When the Receive DS3/E3 Framer block has
detected the appropriate conditions to declare an
OOF Condition.
2. When the Receive DS3/E3 Framer block has
transitioned from the OOF Condition (Frame
Acquisition Mode) into the In-Frame Condition
(Frame Maintenance mode).
NOTE: For more information of the OOF Condition, please
see Section 4.3.2.2.
Bit 2 - LOF (Change in LOF Condition) Interrupt
Status
This Reset-upon-Read bit-field will be set to "1" if a
Change in LOF Condition interrupt has occurred
since the last read of this register.
NOTE: For more information in the LOS of Signal (LOS)
Alarm, please see Section 4.3.2.7.
Bit 0 - AIS (Change in AIS Condition) Interrupt
Status
The Receive DS3/E3 Framer block will generate the
Change in LOF Condition interrupt is response to either of the following two occurrences.
This Reset Upon Read bit field will be set to "1", if the
Receive DS3/E3 Framer block has detected a
Change in the AIS condition, since the last time this
register was read. This bit-field will be asserted under
either of the following two conditions:
1. Whenever the Receive DS3/E3 Framer block
transitions from the OOF Condition state into the
LOF Condition state, within the E3 Framing
Acquisition/Maintenance algorithm (per Figure
114).
2. Whenever the Receive DS3/E3 Framer block
transitions from the FA1, FA2 Octet Verification
state to the In-frame state, within the E3 Framing
Acquisition/Maintenance algorithm (per Figure
114).
Bit 1 - LOS (Change in LOS Condition) Interrupt
Status
1. When the Receive DS3/E3 Framer block first
detects an AIS Condition in the incoming E3 data
stream.
2. When the Receive DS3/E3 Framer block has
detected the end of an AIS Condition in the
incoming E3 data stream.
The local µP can determine the current state of the
AIS condition by reading bit 7 of the Rx E3 Configuration and Status Register (Address = 0x11).
This Reset Upon Read bit will be set to "1", if the Receive DS3/E3 Framer block has detected a Change in
the LOS Status condition, since the last time this register was read. This bit-field will be asserted under either of the following two conditions:
NOTE: For more information on the AIS Condition please
see Section 4.3.2.8.
2.4.4.6 Receive E3 Interrupt Status Register 2 (E3, ITU-T G.751)
RXE3 INTERRUPT STATUS REGISTER - 2 (ADDRESS = 0X15)
BIT 7
BIT 6
BIT 5
BIT 4
Not Used
BIT 3
BIT 2
BIT 1
BIT 0
FERF
Interrupt
Status
BIP-4
Error
Interrupt
Status
Framing
Error
Interrupt
Status
Not Used
RO
RO
RO
RO
RUR
RUR
RUR
RUR
0
0
0
0
0
0
0
0
Bit 3 - FERF (Change in FERF Condition) Interrupt
Status
This bit-field will be asserted under either of the following two conditions.
This Reset Upon Read bit will be set to '1' if the Receive DS3/E3 Framer block has detected a Change in
the Rx FERF Condition, since the last time this register was read.
1. When the Receive DS3/E3 Framer block first
detects the occurrence of an Rx FERF Condition
(e.g., when the FERF bit, within the last 3 or 5
consecutive E3 frames are set to "1").
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REV. P1.1.7
NOTE: Please see Section 4.3.6.1.7 for a more detailed discussion of this interrupt.
2. When the Receive DS3/E3 Framer block detects
the end of the Rx FERF Condition (e.g., when the
FERF bit, within the last 3 or 5 consecutive E3
frames are set to "0").
Bit 1 - Framing Error Interrupt Status
This Reset-upon-Read bit-field will be set to "1" if the
Framing Byte Error interrupt has occurred since the
last read of this register.
NOTE: For more information on the Rx FERF (Yellow
Alarm) condition, please see Section 4.3.2.9.
Bit 2 - BIP-4 (Detection of BIP-4) Error Interrupt
Status
The Receive DS3/E3 Framer block will generate the
Framing Error interrupt if it has detected an error in
the FAS (or Framing Alignment), in an incoming E3
frame.
This Reset-upon-Read bit-field will be set to "1" if the
BIP-4 Error interrupt has occurred since the last read
of this register.
NOTE: Please see Section 4.3.6.1.8 for a more detailed discussion of this interrupt.
The Receive DS3/E3 Framer block will generate the
BIP-4 Error interrupt if it has concluded that it has received an errored E3 frame, from the Remote Terminal.
2.4.4.7 Receive E3 LAPD Control Register (E3,
ITU-T G.751)
RXE3 LAPD CONTROL REGISTER (ADDRESS = 0X18)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
Not Used
BIT 2
BIT 1
BIT 0
RxLAPD
Enable
RxLAPD
Interrupt
Enable
RxLAPD
Interrupt
Enable
RO
RO
RO
RO
RO
R/W
R/W
RUR
0
0
0
0
0
0
0
0
NOTE: For more information on this interrupt, please see
Section 4.3.6.1.9.
Bit 2 - RxLAPD Enable
This Read/Write bit-field allows the user to enable or
disable the LAPD Receiver, for reception of incoming
LAPD Message frames from the Remote LAPD
Transmitter.
Bit 0 - RxLAPD (Received LAPD Message) Interrupt Status
This Reset-upon-Read bit-field will be set to "1" if the
Receipt of New LAPD Message frame interrupt has
occurred since the last read of this register.
Writing a "1" to this bit-field enables the LAPD Receiver. Writing a "0" to this bit-field disables the LAPD
Receiver.
The Receive DS3/E3 Framer block will generate this
Receipt of New LAPD Message frame interrupt when
the LAPD Receiver has received a complete LAPD
Message frame from the Remote LAPD Transmitter.
Bit 1 - RxLAPD (Received LAPD Message) Interrupt Enable
This Read/Write bit-field allows the user to enable or
disable the Received LAPD Message frame interrupt.
Setting this bit-field to "1" enables this interrupt. Setting this bit-field to "0" disables this interrupt.
NOTE: Please see section 4.3.6.1.9 for a more detailed discussion of this interrupt.
2.4.4.8 Receive E3 LAPD Status Register (E3,
ITU-T G.751)
RXE3 LAPD STATUS REGISTER (ADDRESS = 0X19)
BIT 7
BIT 6
BIT 5
Not Used
RxAbort
RO
RO
RO
0
0
0
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
RxCR Type
RxFCS Error
End of
Message
Flag Present
RO
RO
RO
RO
RO
0
0
0
0
0
RxLAPDType[1:0]
Bit 6 - RxAbort
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THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. P1.1.7
Bit 5, 4 - RxLAPD Type[1:0]
This Read-Only bit-field indicates whether or not the
LAPD Receiver is currently detecting an abort sequence (e.g., a string of 7 consecutive "1’s").
These two Read-Only bit-fields combine to indicate
the type and size of LAPD Message frame that has
been received by the LAPD Receiver. The following
table relates the contents of these bit-fields to the
LAPD Message type/size.
This bit-field is set to "1" if the LAPD Receiver is currently detecting an abort sequence in the incoming
LAPD Channel. Conversely, this bit-field is set to "0" if
the LAPD Receiver has not detected an abort sequence, since the last read of this register.
RXLAPDTYPE[1:0]
LAPD MESSAGE FRAME TYPE
PMDL MESSAGE SIZE (INFORMATION
SECTION)
00
CL Path Identification Type
76 Bytes
01
Idle Signal Identification Type
76 Bytes
10
Test Signal Identification Type
76 Bytes
11
ITU-T Path Identification Type
82 Bytes
Bit 3 - RxCR Type
frame. This bit-field, along with the Receipt of New
LAPD Message frame interrupt, serves to inform the
local µP that the Receive LAPD Message buffer contains a new PMDL message that needs to be read
and processed.
This Read-Only bit-field indicates the state of the C/R
bit-field, within octet # 2 of the most recently received
LAPD Message frame.
Bit 2 - RxFCS Error
This bit-field is cleared (set to "0") upon reading this
register.
This Read-Only bit-field indicates whether or not the
LAPD Receiver has detected an FCS (Frame Check
Sequence) error, in the most recently received LAPD
Message frame. This bit-field is set to "0" if the LAPD
Receiver does not detect an FCS error in this LAPD
Message frame. Conversely, this bit-field is set to "1"
if the LAPD Receiver does detect an FCS error in this
LAPD Message frame.
Bit 0 - Flag Present
The LAPD Receiver will assert this read-only bit-field
when it is currently detecting the Flag Sequence octet
(0x7E) in the incoming LAPD channel (e.g., either the
GC or the NR byte-field, within each E3 frame). The
LAPD Receiver will negate this bit-field when it is no
longer receiving the Flag Sequence octet in the incoming LAPD channel.
NOTE: For a more detailed discussion on the LAPD
Receiver's handling of the FCS bytes, please see Section
4.3.3.
2.4.4.9 Receive E3 Service Bits Register (E3,
ITU-T G.751)
Bit 1 - EndOfMessage
The LAPD Receiver will assert this read-only bit-field,
when it has received a complete LAPD Message
RXE3 SERVICE BIT REGISTER (ADDRESS = 0X1A)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
Not Used
BIT 1
BIT 0
RxA
RxN
RO
RO
RO
RO
RO
RO
RO
RO
0
0
0
0
0
0
0
0
Bit 1 - RxA (A-Bit)
This Read-Only bit-field reflects the state of the “A”
bit-field, within the most recently received E3 frame.
This Read-Only bit-field reflects the state of the “N”
bit-field, within the most recently received E3 frame.
2.4.5
Bit 0 - RxN (N-Bit)
Transmit DS3 Configuration Registers
2.4.5.1 Transmit DS3 Configuration Register
(DS3 Applications)
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THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
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PRELIMINARY
REV. P1.1.7
TRANSMIT DS3 CONFIGURATION REGISTER (ADDRESS = 0X30)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
Tx Yellow
Alarm
Tx X Bits
Tx Idle
Tx AIS
Tx LOS
FERF on
LOS
FERF on
OOF
FERF on
AIS
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
1
1
1
Bit 7 - Tx Yellow Alarm
• The X-bits are set to "1"
This Read/Write bit-field is used to command the
Transmit DS3/E3 Framer block to transmit a Yellow
Alarm (e.g., X bits are all "0") in the outbound DS3
data stream.
• A repeating "1100..." pattern in written into the payload portion of the DS3 Frames.
Writing a "1" to this bit-field invokes this command.
Writing a "0" allows the Transmit DS3/E3 Framer
block to function normally (e.g., the Transmit DS3/E3
Framer block will transmit its payload and internally
generated overhead bits).
Writing a "0" to this bit-field disables this feature (the
default condition). In this condition, the X-bits in the
out-bound DS3 frame, are internally generated
(based upon receiver conditions).
NOTE: For more information on this feature, please see
Section 3.2.4.2.1.3.
NOTE: This bit-setting is ignored if Bits 3 or 4 (within this
register) are set to "1".
Writing a "1" to this bit-field invokes this command. In
this condition, the Transmit DS3/E3 Framer block will
override the internally-generated X-bits and force all
of the X-bits of each outbound DS3 frame to "0".
Bit 4 - Tx AIS (Pattern)
NOTE: For more information in this feature, please see Section 3.2.4.2.1.1.
NOTE: This bit-setting is ignored if Bits 3, 4 or 5 (within this
register) are set to "1".
Bit 6 - Tx X-Bit (Force X bits to "1")
This "Read/Write" bit-field is used to command the
Transmit DS3/E3 Framer block to force all of the Xbits, in the outbound DS3 Frames, to "1".
Writing a "0" to this bit-field disables this feature (the
default condition). In this case, the Transmit DS3/E3
Framer block will generate X-bits based upon the receive conditions.
Writing a "1" to this bit-field invokes this command. In
this case, the Transmit DS3/E3 Framer block will
overwrite the internally-generated X-bits and set them
all to "1".
NOTE: For more information on this feature, please see
Section 3.2.4.2.1.2.
NOTE: This bit-setting is ignored if Bits 3, 4, 5, or 7 (within
this register) are set to "1".
Bit 5 - Tx Idle (Pattern)
This Read/Write bit-field is used to command the
Transmit DS3/E3 Framer block to transmit the Idle
Condition pattern. If the user invokes this command,
then the Transmit DS3/E3 Framer block will force the
outbound DS3 Frames to have the following patterns.
• Valid M-bits, F-bits and P-bits
This Read/Write bit-field is used to command the
Transmit DS3/E3 Framer block to transmit an AIS pattern. If the user invokes this command, then the
Transmit DS3/E3 Framer block will force the outbound
DS3 frames to have the following patterns.
• Valid M-bits, F-bits, and P-bits
• All C-bits are set to '0'
• All X-bits are set to '1'
• A repeating '1010...' pattern is written into the payload of the DS3 Frames.
Writing a "1' to this bit-field invokes this command.
Writing a "0" allows the Transmit DS3/E3 Framer
block to function normally (e.g., the Transmit DS3/E3
Framer block will transmit its payload and internally
generated overhead bits).
NOTE: For more information on this feature, please see
Section 3.2.4.2.1.4.
Bit 3 - Tx LOS (Loss of Signal)
This Read/Write bit-field is used to command the
Transmit DS3/E3 Framer block to simulate an LOS
Condition. If the user invokes this command, then the
Transmit DS3/E3 Framer block will stop sending mark
pulses out on the line and will transmit an all-zero pattern.
Writing a '0' to this bit-field disables (or shuts off) this
feature, thereby allowing internally generated DS3
Frames to be generated and transmitted over the line.
• The three CP-Bits (F-frame #3) are "0"
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THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
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REV. P1.1.7
block (within the same channel) detects an OOF
(Out-of-Frame) Condition.
Writing a '1' to this bit-field invokes this command,
causing the Transmit DS3/E3 Framer block to generate an all '0' pattern.
Writing a "1" to this bit-field enables this feature. Writing a "0" to this bit-field disables this feature.
NOTE: For more information on this feature, please see
Section 3.2.4.2.1.5.
NOTE: For more information on this feature, please see
Section 3.2.4.2.1.7.
Bit 2 - FERF on LOS
Bit 0 - FERF on AIS
This Read/Write bit-field allows the user to configure
the Transmit DS3/E3 Framer block to generate a Yellow Alarm if the Near-End Receive DS3/E3 Framer
block (within the same channel) detects a LOS (Loss
of Signal) Condition.
Writing a "1" to this bit-field enables this feature. Writing a "0" to this bit-field disables this feature.
NOTE: For more information on this feature, please see
Section 3.2.4.2.1.6.
This Read/Write bit-field allows the user to configure
the Transmit DS3/E3 Framer block to generate a Yellow Alarm if the Near-End Receive DS3/E3 Framer
block (within the same channel) detects an AIS
(Alarm Indication Signal) Condition.
Writing a "1" to this bit-field enables this feature. Writing a "0" to this bit-field disables this feature.
NOTE: For more information on this feature, please see
Section 3.2.4.2.1.8.
Bit 1 - FERF on OOF
This Read/Write bit-field allows the user to configure
the Transmit DS3/E3 Framer block to generate a Yellow Alarm if the Near-End Receive DS3/E3 Framer
2.4.5.2 Transmit DS3 FEAC Configuration &
Status Register (DS3 Applications)
TRANSMIT DS3 FEAC CONFIGURATION & STATUS REGISTER (ADDRESS = 0X31)
BIT 7
BIT 6
BIT 5
Not Used
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
Tx FEAC
Interrupt
Enable
TxFEAC
Interrupt
Status
TxFEAC
Enable
TxFEAC
GO
TxFEAC
Busy
RO
RO
RO
R/W
RUR
R/W
R/W
RO
0
0
0
0
0
0
0
0
Bit 4 - Tx FEAC Interrupt Enable
If this bit-field is “1”, then the FEAC Message Transmission Complete interrupt has occurred since the
last read of this register.
This Read-Write bit-field is used to enable or disable
the Transmit FEAC Interrupt.
NOTE: For more information on the Transmit FEAC Processor, please see Section 3.2.3.1.
Setting this bit-field to “0” disables this interrupt.
Conversely, setting this bit-field to “1” enables this interrupt.
Bit 2 - TxFEAC Enable
Bit 3 - TxFEAC Interrupt Status
This Read-Only bit-field indicates whether or not the
FEAC Message Transmission Complete interrupt has
occurred since the last read of this register. This interrupt will occur once the Transmit FEAC Processor
has finished its 10th transmission of the 16 bit FEAC
Message (6 bit FEAC Code word + 10 framing bits).
The purpose of this interrupt is to let the local µP
know that the Transmit FEAC Processor has completed its transmission of its latest FEAC Message and is
now ready to transmit another FEAC Message.
If this bit-field is "0", then the FEAC Message Transmission Complete interrupt has NOT occurred since
the last read of this register.
This Read/Write bit-field allows the user to enable or
disable the Transmit FEAC Processor. The Transmit
FEAC Processor will NOT function until it has been
enabled.
Writing a "0" to this bit-field disables the Transmit
FEAC Processor. Writing a "1" to this bit-field enables
the Transmit FEAC Processor.
Bit 1 - TxFEAC Go
This bit-field allows the user to invoke the Transmit
FEAC Message command. Once this command has
been invoked, the Transmit FEAC Processor will do
the following:
• Encapsulate the 6 bit FEAC code word, from the Tx
DS3 FEAC Register (Address = 0x32) into a 16 bit
FEAC Message
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• Serially transmit this 16-bit FEAC Message to the
far-end receiver via the outbound DS3 data-stream,
10 consecutive times.
NOTE: For more information on the Transmit FEAC Processor, please see Section 3.2.3.1.
Bit 0 - TxFEAC Busy
This Read-Only bit-field allows the local µP to poll
and determine if the Transmit FEAC Processor has
completed its 10th transmission of the 16-bit FEAC
Message. This bit-field will contain a "1", if the Transmit FEAC Processor is still transmitting the FEAC
Message. This bit-field will toggle to "0", once the
Transmit FEAC Processor has completed its 10th
transmission of the FEAC Message.
NOTE: For more information on the Transmit FEAC Processor, please see Section 3.2.3.1.
2.4.5.3 Transmit DS3 FEAC Register (DS3
Applications)
TXDS3 FEAC REGISTER (ADDRESS = 0X32)
BIT 7
BIT 6
BIT 5
BIT 4
Not Used
BIT 3
BIT 2
BIT 1
TxFEAC[5:0]
BIT 0
Not Used
RO
R/W
R/W
R/W
R/W
R/W
R/W
RO
0
1
1
1
1
1
1
0
This register contains a six (6) bit read/write field that
allows the user to write in the six-bit FEAC code word,
that is desired to be transmitted to the Far End Receive FEAC Processor, via the outgoing DS3 data
stream. The Transmit FEAC Processor will encapsulate this six-bit code into a 16-bit FEAC message, and
will proceed to transmit this message to the Remote
Receiver via the FEAC bit-field within each out-going
DS3 frame.
NOTE: For more information on the operation of the Transmit FEAC Processor, please see Section 3.2.3.1.
2.4.5.4 Transmit DS3 LAPD Configuration
Register (DS3 Applications)
TXDS3 LAPD CONFIGURATION REGISTER (ADDRESS = 0X33)
BIT 7
BIT 6
BIT 5
BIT 4
Not Used
BIT 3
BIT 2
BIT 1
BIT 0
Auto
Retransmit
Not Used
TxLAPD Msg
Length
TxLAPD
Enable
RO
R/W
R/W
R/W
R/W
R/W
R/W
RO
0
0
0
0
1
0
0
0
Bit 3 - Auto Retransmit
This Read/Write bit-field allows the user to configure
the LAPD Transmitter to either transmit the LAPD
Message frame only once or, repeatedly at one-second intervals.
Writing a "0" to this bit-field configures the LAPD
Transmitter to transmit the LAPD Message frame
once. Afterwards, the LAPD Transmitter will halt
transmission, until it has commanded to transmit another LAPD Message frame.
Writing a "1" to this bit-field configures the LAPD
Transmitter to transmit the LAPD Message frame repeatedly at One-Second intervals. In this configuration, the LAPD Transmitter will repeat its transmission
of the LAPD Message frame until it has been disabled.
This Read/Write bit-field is used to select the length
of the outbound LAPD Message frame.
Setting this bit-field to "0" configures the outbound
LAPD Message frame to be 76 bytes in length. Setting this bit-field to “1” configures the outbound LAPD
Message frame to be 82 bytes in length.
Bit 0 - TxLAPD Enable
This Read/Write bit-field allows the user to enable or
disable the LAPD Transmitter. The LAPD Transmitter
must be enabled before it can be commanded to
transmit a LAPD Message frame (containing a PMDL
message) via the outbound DS3 frames, to the FarEnd Terminal.
Writing a “0" disables the LAPD Transmitter (default
condition). Writing a "1" enables the LAPD Transmitter.
Bit 1 - TxLAPD Message Length Select
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THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
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NOTE: For information on the LAPD Transmitter, please see
Section 3.2.3.2.
2.4.5.5 Transmit DS3 LAPD Status and Interrupt Register (DS3 Applications)
TXDS3 LAPD STATUS AND INTERRUPT REGISTER (ADDRESS = 0X34)
BIT 7
BIT 6
BIT 5
BIT 4
Not Used
BIT 3
BIT 2
BIT 1
BIT 0
TxDL Start
TxDL Busy
TxLAPD
Interrupt
Enable
TxLAPD
Interrupt
Status
RO
RO
RO
RO
R/W
RO
R/W
RUR
0
0
0
0
0
0
0
0
Bit 3 - TxDL Start
LAPD Transmitter has completed its transmission of
the LAPD Message frame.
This Read/Write bit-field allows the user to invoke the
Transmit LAPD Message command. Once the user
invokes this command, the LAPD Transmitter will do
the following:
NOTE: For more information on the LAPD Transmitter,
please see Section 3.2.3.2.
Bit 1 - TxLAPD Interrupt Enable
• Read in the PMDL Message from the Transmit
LAPD Message Buffer.
This Read/Write bit-field allows the user to enable or
disable the LAPD Message Frame Transmission
Complete interrupt.
• Encapsulate the PMDL Message into a complete
LAPD Message frame by including the necessary
header and trailer bytes (e.g., flag sequence bytes,
SAPI, CR, EA values, etc.).
Writing a "0" to this bit-field disables this interrupt.
Writing a "1" to this bit-field enables this interrupt.
Bit 0 - TxLAPD Interrupt Status
• Compute the frame check sequence word (16 bit
value)
• Insert the Frame Check Sequence value into the 2
octet slot after the payload section of the Message.
• Proceed to transmit the LAPD Message Frame to
the far end terminal via the outgoing DS3 frames.
Writing a "1" to this bit-field start the transmission of
the LAPD Message Frame, via the LAPD Transmitter.
NOTE: For more information on the LAPD Transmitter,
please see Section 3.2.3.2.
Bit 2 - TxDL Busy
This Read-Only bit-field allows the local µP to poll
and determine if the LAPD Transmitter has completed
its transmission of the LAPD Message frame. This bitfield will contain a "1", if the LAPD Transmitter is still
transmitting the LAPD Message frame to the far-end
terminal. This bit-field will toggle to "0", once the
This Reset Upon Read bit-field indicates whether or
not the LAPD Message frame Transmission Complete
interrupt has occurred since the last read of this register. The purpose of this interrupt is to let the local µP
know that the LAPD Transmitter has completed its
transmission of the LAPD Message frame (containing
the latest PMDL message) and is now ready to transmit another LAPD Message frame.
A "0" in this bit-field indicates that the LAPD Message
frame Transmission Complete interrupt has not occurred since the read of this register. A "1" in this bitfield indicates that this interrupt has occurred since
the last read of this register.
NOTE: For more information on the TxLAPD Interrupt,
please see Section 3.2.6.
2.4.5.6 Transmit DS3 M-Bit Mask Register
(DS3 Applications)
TXDS3 M-BIT MASK REGISTER (ADDRESS = 0X35)
BIT 7
BIT 6
BIT 5
TxFEBEDat[2:0]
BIT 4
BIT 3
FEBE Reg
Enable
Tx Error
P-Bit
BIT 2
BIT 1
BIT 0
MBit Mask[2] MBit Mask[1] MBit Mask[0]
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
0
0
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Bit 7 - 5: TxFEBEDat[2:0]
These three (3) read/write bit-fields, along with Bit 4
of this register, allows the user to configure and transmit his/her choice for the three (3) FEBE (Far-End
Block Error) bits in each outgoing DS3 Frame. The
user will write his/her value for the FEBE bits into
these bit-fields. The Transmit DS3 Framer block will
insert these values into the FEBE bit-fields of each
outgoing DS3 Frame, once the user has written a "1"
to Bit 4 (FEBE Register Enable).
NOTE: For more information on this feature, please see
Section 3.2.4.2.1.9.
Bit 4 - FEBE Register Enable
This Read/Write bit-field is used to configure the
Transmit DS3 Framer to insert the contents of
TxFEBEDat[2:0] into the FEBE bit-fields each outbound DS3 Frame.
Writing a "0" to this bit-field disables this feature (e.g.,
the Transmit DS3 Framer block will transmit the internally generated FEBE bits). Writing a "1" to this bitfield enables this features (e.g., the internally generated FEBE bits are overwritten by the contents of the
TxFEBEDat[2:0] bit-field).
NOTE: For more information on this feature, please see
Section 3.2.4.2.1.9.
Transmit DS3/E3 Framer block). If the user enables
this feature, then the Transmit DS3/E3 Framer block
will proceed to invert each and every P-bit, from its
computed value, prior to transmission to the Remote
Terminal.
Writing a "0" to this bit-field (the default condition) disables this feature (e.g., the correct P-bits are sent).
Writing a "1" to this bit-field enables this feature (e.g.,
the incorrect P-bits are sent).
NOTE: For more information on this feature, please see
Section 3.2.4.2.2.
Bit 2 - 0 M-Bit Mask[2:0]
These Read/Write bit-fields permit the user to insert
errors in the M-bits for Test and Diagnostic purposes.
The Transmit DS3/E3 Framer block automatically performs an XOR operation on the actual contents of the
M-bit fields to these register bit-fields. Therefore, for
every '1' that exists in these bit-fields, will result in a
change of state of the corresponding M-bit, prior to
being transmitted to the Remote Terminal Equipment.
If the Transmit DS3/E3 Framer block is to be operated
in the normal mode (e.g., when no errors are being
injected into the M-bit fields of the outbound DS3
Frame), then these bit-fields must be all “0’s”.
2.4.5.7 Transmit DS3 F-Bit Mask Register - 1
(DS3 Applications)
Bit 3 - Transmit Erred P-Bit
This Read/Write bit-field is used to insert errors into
the P-bits within the outbound DS3 frames (via the
TXDS3 F-BIT MASK REGISTER - 1 (ADDRESS = 0X36)
BIT 7
BIT 6
BIT 5
BIT 4
Not Used
BIT 3
BIT 2
BIT 1
BIT 0
FBit Mask[27] FBit Mask[26] FBit Mask[25] FBit Mask[24]
RO
RO
RO
RO
R/W
R/W
R/W
R/W
0
0
0
0
0
0
0
0
Bits 3 - 0 F-Bit Mask[27:24]
These Read/Write bit-fields permit the user to insert
errors into the first four F-bits of a DS3 M-frame, for
test and diagnostic purposes. The Transmit DS3/E3
Framer block automatically performs an XOR operation on the actual contents of these F-bit fields to
these register bit-fields. Therefore, for every "1" that
exists in these bit-fields, this will result in a change of
state for the corresponding F-bit, prior to being transmitted to the Remote Receive DS3/E3 Framer.
If the Transmit DS3/E3 Framer block is to be operated
in the normal mode (e.g., when no errors are being
injected into these F-bit fields of the outbound DS3
frames), then all of these bit-fields must be "0’s".
2.4.5.8 Transmit DS3 F-Bit Mask Register - 2
(DS3 Applications)
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THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
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TXDS3 F-BIT MASK REGISTER - 2 (ADDRESS = 0X37)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
FBit Mask[23] FBit Mask[22] FBit Mask[21] FBit Mask[20] FBit Mask[19] FBit Mask[18] FBit Mask[17] FBit Mask[16]
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
0
0
Bits 7 - 0 F-Bit Mask[23:16]
change of state for the corresponding F-bit, prior to
being transmitted to the Remote Terminal Equipment.
These Read/Write bit-fields permit the user to insert
errors into the fifth through twelfth F-bits of a DS3 Mframe, for test and diagnostic purposes. The Transmit
DS3/E3 Framer block automatically performs an XOR
operation on the actual contents of these F-bit fields
to these register bit-fields. Therefore, for every "1"
that exists in these bit-fields, this will result in a
If the Transmit DS3/E3 Framer block is to be operated
in the normal mode (e.g., when no errors are being
injected into these F-bit fields of the outbound DS3
frames), then all of these bit-fields must be "0’s".
2.4.5.9 Transmit F-Bit Mask Register - 3 (DS3
Applications)
TXDS3 F-BIT MASK REGISTER - 3 (ADDRESS = 0X38)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
FBit Mask[15] FBit Mask[14] FBit Mask[13] FBit Mask[12] FBit Mask[11] FBit Mask[10] FBit Mask[9]
BIT 0
FBit Mask[8]
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
0
0
Bits 7 - 0 F-Bit Mask[15:8]
F-bit, prior to being transmitted to the Remote Terminal Equipment.
These Read/Write bit-fields permit the user to insert
errors into the thirteenth through twentieth F-bits of a
DS3 M-frame, for test and diagnostic purposes. The
Transmit DS3/E3 Framer block automatically performs an XOR operation on the actual contents of
these F-bit fields to these register bit-fields. Therefore, for every "1" that exists in these bit-fields, this
will result in a change of state for the corresponding
If the Transmit DS3/E3 Framer block is to be operated
in the normal mode (e.g., when no errors are being
injected into these F-bit fields of the outbound DS3
frames), then all of these bit-fields must be "0’s".
2.4.5.10 Transmit F-Bit Mask Register - 4 (DS3
Applications)
TXDS3 F-BIT MASK REGISTER - 4 (ADDRESS = 0X39)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
FBit Mask[7]
FBit Mask[6]
FBit Mask[5]
FBit Mask[4]
FBit Mask[3]
FBit Mask[2]
FBit Mask[1]
FBit Mask[0]
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
0
0
Bits 7 - 0 F-Bit Mask[7:0]
These Read/Write bit-fields allow the user to insert
errors into the last eight F-bits of a DS3 M-frame, for
test and diagnostic purposes. The Transmit DS3/E3
Framer block automatically performs an XOR operation on the actual contents of these F-bit fields to
these register bit-fields. Therefore, for every "1" that
exists in these bit-fields, this will result in a change of
state for the corresponding F-bit, prior to being transmitted to the Remote Terminal Equipment.
If the Transmit DS3/E3 Framer block is to be operated
in the normal mode (e.g., when no errors are being
injected into these F-bit fields of the outbound DS3
frames), then all of these bit-fields must be "0’s".
2.4.6 Transmit E3 (ITU-T G.832) Configuration
Registers
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REV. P1.1.7
2.4.6.1 Transmit E3 Configuration Register
(E3, ITU-T G.832)
TXE3 CONFIGURATION REGISTER (ADDRESS = 0X30)
BIT 7
BIT 6
BIT 5
Not Used
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
TxDL
in NR
Not Used
TxAIS
Enable
TxLOS
Enable
TxMARx
RO
RO
RO
R/W
RO
R/W
R/W
R/W
0
0
0
0
0
0
0
0
mitting any E3 frames. Consequently, the Remote Terminal
will experience an LOS (Loss of Signal) and OOF (Out of
Frame) condition.
Bit 4 - DLinNR
This Read/Write bit-field is used to specify whether
the LAPD Transmitter should insert the outbound
LAPD Message frame octets into the NR byte-field, or
in the GC-byte-field, within each outbound E3 frame.
Bit 0 - MARx (FERF and FEBE bit-field Loopback)
This Read/Write bit-field allows the user to specify
whether the value of the FERF and FEBE bit-fields, in
the outbound E3 frames, should be based upon Receive DS3/E3 Framer conditions or upon the content
of the Tx MA Byte register (Address = 0x2A).
Writing a "1" configures the LAPD Transmitter to insert the octets of the outbound LAPD Message frame
into the NR byte-field, within each outbound E3
frame. Writing in "0" configures the LAPD Transmitter
to insert the octets of the outbound LAPD Message
frame into the GC byte-field, within each outbound E3
frame.
FERF and FEBE values are based upon Receive E3
Framer Conditions
If the user selects Receive DS3/E3 Framer conditions, then the Transmit DS3/E3 Framer block will set
and clear the FERF and FEBE bit-fields in response
to the following conditions.
Bit 2 - TxAIS Enable
This Read/Write bit-field allows the user to command
the Transmit E3 Framer to transmit an AIS pattern,
upon demand.
a. FERF Bit-field
If the Receive DS3/E3 Framer block (in the same
channel) is currently experiencing an LOS, AIS, or
LOF condition, then the Transmit DS3/E3 Framer
block will set the FERF bit-field (in the outbound E3
frame) to "1". Conversely, if the Receive DS3/E3
Framer block is not experiencing any of these conditions, then the Transmit E3 Framer will set the FERF
bit-field (in the outbound E3 frame) to "0".
Writing a "0" to this bit-field allows the Transmit DS3/
E3 Framer block to transmit internally generated data
(e.g., the ITU-T G.832 compatible E3 frames with the
E3 payload data) to the Remote Terminal. Writing a
"1" to this bit-field causes the Transmit DS3/E3 Framer block to transmit an all "1’s" pattern to the Remote
Terminal.
NOTE: If the Transmit DS3/E3 Framer block is transmitting
an AIS pattern to the Remote Terminal, then it is not transmitting any E3 frames. Consequently, if this command is
invoked, the Remote Terminal will experience an OOF (Out
of Frame) condition.
b. FEBE bit-field
If the Receive DS3/E3 Framer block detects a BIP-8
error in the incoming E3 frame, then the Transmit
DS3/E3 Framer block will set the FEBE bit-field (in
the outbound E3 frame) to "1". Conversely, if the Receive DS3/E3 Framer block does not detect a BIP-8
error in the incoming E3 frame, then the Transmit
DS3/E3 Framer block will set the FEBE bit-field (in
the E3 outbound E3 frame) to "0".
Bit 1 - TxLOS Enable
This Read/Write bit-field allows the user to command
the Transmit E3 Framer to transmit an LOS pattern,
upon demand.
Writing a "0" to this bit-field allows the Transmit E3
Framer to transmit internally generated data (e.g., the
ITU-T G.832 compatible E3 frames with ATM cell data) to the Remote Terminal. Writing a "1" to this bitfield causes the Transmit DS3/E3 Framer block to
transmit an "All 0’s" pattern to the Remote Terminal.
FEBE and FERF values are based upon the contents
of the Tx MA Byte register
NOTE: If the Transmit DS3/E3 Framer block is transmitting
an LOS pattern to the Remote Terminal, then it is not trans-
If the user selects the contents of the Tx MA Byte register, then whatever value has been written into bit 7
(FERF), within the Tx MA Byte register (Address =
2Ah), will be the value of the FERF bit-field, in the
outbound E3 frame. Likewise, whatever value has
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THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. P1.1.7
been written into Bit 6 (FEBE) within the Tx MA Byte
register, will be the value of the FEBE bit-field, in the
outbound E3 frame.
Writing a "1" into Bit 0 (MAx) within the Tx E3 Configuration register configures the Transmit DS3/E3
Framer block to set the FERF and FEBE bit-fields (in
the outbound E3 frames) to values based upon Re-
ceive E3 Framer conditions. Writing a "0" into this bitfield configures the Transmit DS3/E3 Framer block to
set the FEBE and FEBE bit-fields (in the outbound E3
frames) to the values written into bit-fields 6 and 7
within the Tx MA Byte register.
2.4.6.2 Transmit E3 LAPD Configuration Register (E3, ITU-T G.832)
TXE3 LAPD CONFIGURATION REGISTER (ADDRESS = 0X33)
BIT 7
BIT 6
BIT 5
BIT 4
Not Used
BIT 3
BIT 2
BIT 1
BIT 0
Auto
Retransmit
Not Used
TxLAPD
Msg Length
TxLAPD
Enable
RO
RO
RO
RO
R/W
RO
R/W
R/W
0
0
0
0
1
0
0
0
Bit 3 - Auto Retransmit
Setting this bit-field to "0" configures the outbound
LAPD Message frame to be 76 bytes in length. Setting this bit-field to "1" configures the outbound LAPD
Message frame to be 82 bytes in length.
This Read/Write bit-field is used to configure the
LAPD Transmitter to either transmit the LAPD Message frame only once, or repeatedly at one-second
intervals.
Bit 0 - TxLAPD Enable
Writing a "0" to this bit-field configures the LAPD
Transmitter to transmit the LAPD Message frame
once. Afterwards, the LAPD Transmitter will halt
transmission, until it has commanded to transmit another LAPD Message frame.
This Read/Write bit-field is used to enable or disable
the LAPD Transmitter. The LAPD Transmitter must be
enabled before it can be commanded to transmit a
LAPD Message frame (containing a PMDL message)
via the outbound E3 frames, to the Remote Terminal.
Writing a "1" to this bit-field configures the LAPD
Transmitter to transmit the LAPD Message frame repeatedly at One-Second intervals. In this configuration, the LAPD Transmitter will repeat its transmission
of the LAPD Message frame until it has been disabled.
Writing a "0" disables the LAPD Transmitter (default
condition). Writing a "1" enables the LAPD Transmitter.
NOTE: For information on the LAPD Transmitter, please see
Section 3.2.3.2.
2.4.6.3 Transmit E3 LAPD Status and Interrupt
Register (E3, ITU-T G.832)
Bit 1 - TxLAPD Message Length Select
This Read/Write bit-field is used to select the length
of the outbound LAPD Message frame.
TXE3 LAPD STATUS AND INTERRUPT REGISTER (ADDRESS = 0X34)
BIT 7
BIT 6
BIT 5
BIT 4
Not Used
BIT 3
BIT 2
BIT 1
BIT 0
TxDL Start
TxDL Busy
TxLAPD
Interrupt
Enable
TxLAPD
Interrupt
Status
RO
RO
RO
RO
R/W
RO
R/W
RUR
0
0
0
0
0
0
0
0
Bit 3 - TxDL Start
This Read/Write bit-field is used to command the
LAPD Transmitter to do the following.
• Scan through the PMDL Message, within the Transmit LAPD Message buffer, and search for a string of
109
five (5) consecutive "1’s". The LAPD Transmitter will
then insert (or stuff) a "0" into the PMDL Message
data, immediately following any string of 5 consecutive "1’s".
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THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
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• Read in this stuffed PMDL Message from the Transmit LAPD Message buffer, and encapsulate it into a
LAPD Message frame.
• Fragment the resulting LAPD Message frame into
octets.
while it is in the process of transmitting the LAPD
Message frame. However, the LAPD Transmitter will
clear this bit-field to "0" once it has completed its
transmission of the LAPD Message frame.
Bit 1 - TxLAPD Interrupt Enable
• Insert these octets into either the GC byte-field or
the NR byte-field (depending upon the user's selection) into each outbound E3 frame.
This Read/Write bit-field is used to enable or disable
the LAPD Message frame Transmission Complete interrupt.
A "0" to "1" transition, in this bit-field commands the
LAPD Transmitter to initiate the above-mentioned
procedure.
Writing a "0" to this bit-field disables this interrupt.
Writing a "1" to this bit-field enables this interrupt.
Bit 0 - TxLAPD Interrupt Status
NOTE: Once the user has commanded the LAPD Transmitter to start transmission, the LAPD Transmitter will repeat
the above-mentioned process once each second and will
insert flag sequence octets into the outbound LAPD channel, during the idle periods between transmissions.
Bit 2 - TxDL Busy
This Read-Only bit-field is used to poll or monitor the
status of the LAPD Transmitter to see if it has completed its transmission of the LAPD Message frame.
The LAPD Transmitter will set this bit-field to "1",
This Reset-upon-Read bit-field is used to determine if
the LAPD Message Frame Transmission Complete interrupt has occurred since the last read of this register. If this bit-field contains a "1" then the LAPD Message Frame Transmission Complete interrupt has occurred since the last read of this register. Conversely,
if this bit-field contains a "0" then it has not.
2.4.6.4 Transmit E3 GC Byte Register (E3, ITUT G.832)
TXE3 GC BYTE REGISTER (ADDRESS = 0X35)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
TxGC[7:0]
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
0
0
This Read/Write byte-field is used to specify the contents of the GC byte-field in each outbound E3 frame.
support the November 1995 or the October 1998 revision of the ITU-T G.832 framing format for E3.
NOTE: The contents of this register is ignored, if the LAPD
Transmitter is enabled and has been configured to insert
the comprising octets of an outbound LAPD Message
frame into the GC byte-field of each outbound E3 frame
(e.g., if DLinNR = "0").
The bit-format of the TxE3 MA Byte register, for each
of these cases is discussed below.
2.4.6.5 Transmit E3 MA Byte Register (E3, ITUT G.832)
The bit-format of the TxE3 MA Byte register depends
upon whether the channel has been configured to
2.4.6.5.1 The November 1995 Revision
If the channel has been configured to support the November 1995 revision of the ITU-T G.832 Framing
Format for E3, then the bit-format of the TxE3 MA
Byte register is as presented below.
TXE3 MA BYTE REGISTER (ADDRESS = 0X36)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
Transmit MA Byte
FERF
FEBE
Payload Type
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
1
0
0
0
0
110
Payload Dependent
Timing
Marker
XRT72L53
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THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. P1.1.7
each outbound E3 frame, to values based upon Receive
DS3/E3 Framer block conditions.
This Read/Write byte-fields is used to specify the
contents of the MA byte-field in each outbound E3
frame.
NOTE: The values written into bit-fields 6 (FEBE) and 7
(FERF) are inserted into outbound E3 frames, only if bitfield 0 (MAx) within the Tx E3 Configuration Register
(Address = 0x28) is set to "0". Otherwise, the Transmit DS3/
E3 Framer block will set the FERF and FEBE values, within
2.4.6.5.2 The October 1998 Revision
If the channel has been configured to support the October 1998 revision of the ITU-T G.832 framing format
for E3; then the bit-format of the TxE3 MA Byte register is as presented below.
TXE3 MA BYTE REGISTER (ADDRESS = 0X36)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
Transmit MA Byte
FERF
FEBE
Payload Type
MFI[1:0]
SSM
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
1
0
0
0
0
This Read/Write byte-fields is used to specify the
contents of the MA byte-field in each outbound E3
frame.
each outbound E3 frame, to values based upon Receive
DS3/E3 Framer block conditions.
NOTE: The values written into bit-fields 6 (FEBE) and 7
(FERF) are inserted into outbound E3 frames, only if bitfield 0 (MAx) within the Tx E3 Configuration Register
(Address = 0x28) is set to "0". Otherwise, the Transmit DS3/
E3 Framer block will set the FERF and FEBE values, within
2.4.6.6 Transmit E3 NR Byte Register (E3, ITUT G.832)
TXE3 NR BYTE REGISTER (ADDRESS = 0X37)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
TxNR[7:0]
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
1
0
0
0
0
This Read/Write byte-field is used to specify the contents of the NR byte-field in each outbound E3 frame.
frame into the NR byte-field of each outbound E3 frame
(e.g., if DLinNR = "1").
NOTE: The contents of this register is ignored, if the LAPD
Transmitter is enabled and has been configured to insert
the comprising octets of an outbound LAPD Message
2.4.6.7
G.832)
Transmit E3 TTB-0 Register (E3, ITU-T
TXE3 TTB-0 REGISTER (ADDRESS = 0X38)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
TxTTB0[7:0]
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
1
0
0
1
0
0
0
0
This Read/Write byte-field, along with the Tx TTB-1
through Tx TTB-15 registers permit a user to define a
Trail Access Point Identifier sequence of bytes, that
will be transmitted to the Remote Terminal. The Remote Receiving Terminal will use this sequence of
bytes to verify that it is connected to the proper Trans-
111
áç
THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
XRT72L53
PRELIMINARY
REV. P1.1.7
mitting Terminal. The Transmit DS3/E3 Framer block
will take the contents of these 16 registers, and insert
them into the TR byte of the outbound E3 frame. In
the first of a set of 16 E3 Frames, the Transmit DS3/
E3 Framer block will read in the contents of this register, and insert it into the TR byte-field, within the very
next outbound E3 frame.
through C0 are the results of a CRC-7 calculation
over the previous 16-byte frame.
NOTE: The XRT72L53 Framer IC will not compute this
CRC-7 value. It is up to the user's hardware and/or software
to compute this value, prior to writing it into this register.
2.4.6.8
G.832)
Transmit E3 TTB-1 Register (E3, ITU-T
This particular byte-field should contain the pattern
"[1, C6, C5, C4, C3, C2, C1, C0]" where the bits C6
TXE3 TTB-1 REGISTER (ADDRESS = 0X39)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
TxTTB-1[7:0]
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
0
0
This Read/Write byte-field, along with the TxTTB-0
and TxTTB-2 through TxTTB-15 register permit a user to define a Trail Access Point Identifier sequence of
bytes, that will be transmitted to the Remote Terminal.
The Remote Receiving Terminal will use this sequence of bytes to verify that it is connected to the
proper Transmitting Terminal. The Transmit DS3/E3
Framer block will take the contents of these 16 registers, and insert them into the TR byte of the outbound
E3 frame. In the second of a set of 16 E3 Frames, the
Transmit DS3/E3 Framer block will read in the contents of this register, and insert it into the TR bytefield, within the very next outbound E3 frame.
The contents of this register, along with Tx TTB-2
through Tx TTB-15 are used to transmit 15 ASCII
characters required for the E.164 numbering format.
2.4.6.9
G.832)
Transmit E3 TTB-2 Register (E3, ITU-T
TXE3 TTB-2 REGISTER (ADDRESS = 0X3A)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
TxTTB-2[7:0]
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
0
0
This Read/Write byte-field, along with the TxTTB-0,
TxTTB-1 and TxTTB-3 through TxTTB-15 register
permit a user to define a Trail Access Point Identifier
sequence of bytes, that will be transmitted to the Remote Terminal. The Remote Receiving Terminal will
use this sequence of bytes to verify that it is connected to the proper Transmitting Terminal. The Transmit
DS3/E3 Framer block will take the contents of these
16 registers, and insert them into the TR byte of the
outbound E3 frame. In the third of a set of 16 E3
Frames, the Transmit DS3/E3 Framer block will read
in the contents of this register, and insert it into the
TR byte-field, within the very next outbound E3 frame.
The contents of this register, along with Tx TTB-1,
and Tx TTB-3 through Tx TTB-15 are used to transmit 15 ASCII characters required for the E.164 numbering format.
2.4.6.10 Transmit E3 TTB-3 Register (E3, ITU-T
G.832)
112
XRT72L53
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THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. P1.1.7
TXE3 TTB-3 REGISTER (ADDRESS = 0X3B)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
TxTTB-3[7:0]
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
0
0
This Read/Write byte-field, along with the TxTTB-0
through TxTTB-2 and TxTTB-4 through TxTTB-15
registers permit a user to define a Trail Access Point
Identifier sequence of bytes, that will be transmitted to
the Remote Terminal. The Remote Receiving Terminal will use this sequence of bytes to verify that it is
connected to the proper Transmitting Terminal. The
Transmit DS3/E3 Framer block will take the contents
of these 16 registers, and insert them into the TR byte
of the outbound E3 frame. In the fourth of a set of 16
E3 Frames, the Transmit DS3/E3 Framer block will
read in the contents of this register, and insert it into
the TR byte-field, within the very next outbound E3
frame.
The contents of this register, along with Tx TTB-1, Tx
TTB-2 and Tx TTB-4 through Tx TTB-15 are used to
transmit 15 ASCII characters required for the E.164
numbering format.
2.4.6.11 Transmit E3 TTB-4 Register (E3, ITU-T
G.832)
TXE3 TTB-4 REGISTER (ADDRESS = 0X3C)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
TxTTB-4[7:0]
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
0
0
This Read/Write byte-field, along with the TxTTB-0
through TxTTB-3 and TxTTB-5 through TxTTB-15
registers permit a user to define a Trail Access Point
Identifier sequence of bytes, that will be transmitted to
the Remote Terminal. The Remote Receiving Terminal will use this sequence of bytes to verify that it is
connected to the proper Transmitting Terminal. The
Transmit DS3/E3 Framer block will take the contents
of these 16 registers, and insert them into the TR byte
of the outbound E3 frame. In the fifth of a set of 16 E3
Frames, the Transmit DS3/E3 Framer block will read
in the contents of this register, and insert it into the
TR byte-field, within the very next outbound E3 frame.
The contents of this register, along with Tx TTB-1
through Tx TTB-3 and Tx TTB-5 through Tx TTB-15
are used to transmit 15 ASCII characters required for
the E.164 numbering format.
2.4.6.12 Transmit E3 TTB-5 Register (E3, ITU-T
G.832)
TXE3 TTB-5 REGISTER (ADDRESS = 0X3D)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
TxTTB-5[7:0]
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
0
0
This Read/Write byte-field, along with the Tx TTB-0
through Tx TTB-4 and Tx TTB-6 through Tx TTB-15
registers allows a user to define a Trail Access Point
Identifier sequence of bytes, that will be transmitted to
the Remote Terminal. The Remote Receiving Terminal will use this sequence of bytes to verify that it is
connected to the proper Transmitting Terminal. The
Transmit DS3/E3 Framer block will take the contents
of these 16 registers, and insert them into the TR byte
of the outbound E3 frame. In the sixth of a set of 16
E3 Frames, the Transmit DS3/E3 Framer block will
read in the contents of this register, and insert it into
113
áç
THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
XRT72L53
PRELIMINARY
REV. P1.1.7
the TR byte-field, within the very next outbound E3
frame.
are used to transmit 15 ASCII characters required for
the E.164 numbering format.
The contents of this register, along with Tx TTB-1
through Tx TTB-4 and Tx TTB-6 through Tx TTB-15
2.4.6.13 Transmit E3 TTB-6 Register (E3, ITU-T
G.832)
TXE3 TTB-6 REGISTER (ADDRESS = 0X3E)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
TxTTB-6[7:0]
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
0
0
This Read/Write byte-field, along with the Tx TTB-0
through Tx TTB-5 and Tx TTB-7 through Tx TTB-15
registers permit a user to define a Trail Access Point
Identifier sequence of bytes, that will be transmitted to
the Remote Terminal. The Remote Receiving Terminal will use this sequence of bytes to verify that it is
connected to the proper Transmitting Terminal. The
Transmit DS3/E3 Framer block will take the contents
of these 16 registers, and insert them into the TR byte
of the outbound E3 frame. In the seventh of a set of
16 E3 Frames, the Transmit DS3/E3 Framer block will
read in the contents of this register, and insert it into
the TR byte-field, within the very next outbound E3
frame.
The contents of this register, along with Tx TTB-1
through Tx TTB-5 and Tx TTB-7 through Tx TTB-15
are used to transmit 15 ASCII characters required for
the E.164 numbering format.
2.4.6.14 Transmit E3 TTB-7 Register (E3, ITU-T
G.832)
TXE3 TTB-7 REGISTER (ADDRESS = 0X3F)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
TxTTB-7[7:0]
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
0
0
This Read/Write byte-field, along with the Tx TTB-0
through Tx TTB-6 and Tx TTB-8 through Tx TTB-15
registers allows a user to define a Trail Access Point
Identifier sequence of bytes, that will be transmitted to
the Remote Terminal. The Remote Receiving Terminal will use this sequence of bytes to verify that it is
connected to the proper Transmitting Terminal. The
Transmit DS3/E3 Framer block will take the contents
of these 16 registers, and insert them into the TR byte
of the outbound E3 frame. In the eighth of a set of 16
E3 Frames, the Transmit DS3/E3 Framer block will
read in the contents of this register, and insert it into
the TR byte-field, within the very next outbound E3
frame.
The contents of this register, along with Tx TTB-1
through Tx TTB-6 and Tx TTB-8 through Tx TTB-15
are used to transmit 15 ASCII characters required for
the E.164 numbering format.
2.4.6.15 Transmit E3 TTB-8 Register (E3, ITU-T
G.832)
TXE3 TTB-8 REGISTER (ADDRESS = 0X40)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
TxTTB-8[7:0]
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
0
0
114
XRT72L53
áç
THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. P1.1.7
This Read/Write byte-field, along with the Tx TTB-0
through Tx TTB-7 and Tx TTB-9 through Tx TTB-15
registers permit a user to define a Trail Access Point
Identifier sequence of bytes, that will be transmitted to
the Remote Terminal. The Remote Receiving Terminal will use this sequence of bytes to verify that it is
connected to the proper Transmitting Terminal. The
Transmit DS3/E3 Framer block will take the contents
of these 16 registers, and insert them into the TR byte
of the outbound E3 frame. In the ninth of a set of 16
E3 Frames, the Transmit DS3/E3 Framer block will
read in the contents of this register, and insert it into
the TR byte-field, within the very next outbound E3
frame.
The contents of this register, along with Tx TTB-1
through Tx TTB-7 and Tx TTB-9 through Tx TTB-15
are used to transmit 15 ASCII characters required for
the E.164 numbering format.
2.4.6.16 Transmit E3 TTB-9 Register (E3, ITU-T
G.832)
TXE3 TTB-9 REGISTER (ADDRESS = 0X41)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
TxTTB-9[7:0]
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
0
0
This Read/Write byte-field, along with the Tx TTB-0
through Tx TTB-8 and Tx TTB-10 through Tx TTB-15
registers permit a user to define a Trail Access Point
Identifier sequence of bytes, that will be transmitted to
the Remote Terminal. The Remote Receiving Terminal will use this sequence of bytes to verify that it is
connected to the proper Transmitting Terminal. The
Transmit DS3/E3 Framer block will take the contents
of these 16 registers, and insert them into the TR byte
of the outbound E3 frame. In the tenth of a set of 16
E3 Frames, the Transmit DS3/E3 Framer block will
read in the contents of this register, and insert it into
the TR byte-field, within the very next outbound E3
frame.
The contents of this register, along with Tx TTB-1
through Tx TTB-8 and Tx TTB-10 through Tx TTB-15
are used to transmit 15 ASCII characters required for
the E.164 numbering format.
2.4.6.17 Transmit E3 TTB-10 Register (E3, ITU-T
G.832)
TXE3 TTB-10 REGISTER (ADDRESS = 0X42)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
TxTTB-10[7:0]
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
0
0
This Read/Write byte-field, along with the Tx TTB-0
through Tx TTB-9 and Tx TTB-11 through Tx TTB-15
registers permit a user to define a Trail Access Point
Identifier sequence of bytes, that will be transmitted to
the Remote Terminal. The Remote Receiving Terminal will use this sequence of bytes to verify that it is
connected to the proper Transmitting Terminal. The
Transmit DS3/E3 Framer block will take the contents
of these 16 registers, and insert them into the TR byte
of the outbound E3 frame. In the eleventh of a set of
16 E3 Frames, the Transmit DS3/E3 Framer block will
read in the contents of this register, and insert it into
the TR byte-field, within the very next outbound E3
frame.
The contents of this register, along with Tx TTB-1
through Tx TTB-9 and Tx TTB-11 through Tx TTB-15
are used to transmit 15 ASCII characters required for
the E.164 numbering format.
2.4.6.18 Transmit E3 TTB-11 Register (E3, ITU-T
G.832)
115
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THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
XRT72L53
PRELIMINARY
REV. P1.1.7
TXE3 TTB-11 REGISTER (ADDRESS = 0X43)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
TxTTB-11[7:0]
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
0
0
er block will read in the contents of this register, and
insert it into the TR byte-field, within the very next outbound E3 frame.
This Read/Write byte-field, along with the Tx TTB-0
through Tx TTB-10 and Tx TTB-12 through Tx TTB15 registers permit a user to define a Trail Access
Point Identifier sequence of bytes, that will be transmitted to the Remote Terminal. The Remote Receiving Terminal will use this sequence of bytes to verify
that it is connected to the proper Transmitting Terminal. The Transmit DS3/E3 Framer block will take the
contents of these 16 registers, and insert them into
the TR byte of the outbound E3 frame. In the twelfth
of a set of 16 E3 Frames, the Transmit DS3/E3 Fram-
The contents of this register, along with Tx TTB-1
through Tx TTB-10 and Tx TTB-12 through Tx TTB15 are used to transmit 15 ASCII characters required
for the E.164 numbering format.
2.4.6.19 3.3.2.77 Transmit E3 TTB-12 Register
(E3, ITU-T G.832)
TXE3 TTB-12 REGISTER (ADDRESS = 0X44)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
TxTTB-12[7:0]
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
0
0
Framer block will read in the contents of this register,
and insert it into the TR byte-field, within the very next
outbound E3 frame.
This Read/Write byte-field, along with the Tx TTB-0
through Tx TTB-11 and Tx TTB-13 through Tx TTB15 registers permit a user to define a Trail Access
Point Identifier sequence of bytes, that will be transmitted to the Remote Terminal. The Remote Receiving Terminal will use this sequence of bytes to verify
that it is connected to the proper Transmitting Terminal. The Transmit DS3/E3 Framer block will take the
contents of these 16 registers, and insert them into
the TR byte of the outbound E3 frame. In the thirteenth of a set of 16 E3 Frames, the Transmit DS3/E3
The contents of this register, along with Tx TTB-1
through Tx TTB-11 and Tx TTB-13 through Tx TTB15 are used to transmit 15 ASCII characters required
for the E.164 numbering format.
2.4.6.20 Transmit E3 TTB-13 Register (E3, ITU-T
G.832)
TXE3 TTB-13 REGISTER (ADDRESS = 0X45)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
TxTTB-13[7:0]
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
0
0
This Read/Write byte-field, along with the Tx TTB-0
through Tx TTB-12, Tx-TTB-14, and Tx TTB-15 registers permit a user to define a Trail Access Point Identifier sequence of bytes, that will be transmitted to the
Remote Terminal. The Remote Receiving Terminal
will use this sequence of bytes to verify that it is connected to the proper Transmitting Terminal. The
Transmit DS3/E3 Framer block will take the contents
of these 16 registers, and insert them into the TR byte
of the outbound E3 frame. In the fourteenth of a set of
116
XRT72L53
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THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. P1.1.7
used to transmit 15 ASCII characters required for the
E.164 numbering format.
16 E3 Frames, the Transmit DS3/E3 Framer block will
read in the contents of this register, and insert it into
the TR byte-field, within the very next outbound E3
frame.
2.4.6.21 Transmit E3 TTB-14 Register (E3, ITU-T
G.832)
The contents of this register, along with Tx TTB-1
through Tx TTB-12, Tx TTB-14 and Tx TTB-15 are
TXE3 TTB-14 REGISTER (ADDRESS = 0X46)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
TxTTB-14[7:0]
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
0
0
This Read/Write byte-field, along with the Tx TTB-0
through Tx TTB-13 and Tx TTB-15 registers permit a
user to define a Trail Access Point Identifier sequence
of bytes, that will be transmitted to the Remote Terminal. The Remote Receiving Terminal will use this sequence of bytes to verify that it is connected to the
proper Transmitting Terminal. The Transmit DS3/E3
Framer block will take the contents of these 16 registers, and insert them into the TR byte of the outbound
E3 frame. In the fifteenth of a set of 16 E3 Frames,
the Transmit DS3/E3 Framer block will read in the
contents of this register, and insert it into the TR bytefield, within the very next outbound E3 frame.
The contents of this register, along with Tx TTB-1
through Tx TTB-13 and Tx TTB-15 are used to transmit 15 ASCII characters required for the E.164 numbering format.
2.4.6.22 Transmit E3 TTB-15 Register (E3, ITU-T
G.832)
TXE3 TTB-15 REGISTER (ADDRESS = 0X47)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
TxTTB-15[7:0]
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
0
0
This Read/Write byte-field, along with the Tx TTB-0
through Tx TTB-14 registers permit a user to define a
Trail Access Point Identifier sequence of bytes, that
will be transmitted to the Remote Terminal. The Remote Receiving Terminal will use this sequence of
bytes to verify that it is connected to the proper Transmitting Terminal. The Transmit DS3/E3 Framer block
will take the contents of these 16 registers, and insert
them into the TR byte of the outbound E3 frame. In
the sixteenth of a set of 16 E3 Frames, the Transmit
DS3/E3 Framer block will read in the contents of this
register, and insert it into the TR byte-field, within the
very next outbound E3 frame.
The contents of this register, along with Tx TTB-1
through Tx TTB-15 are used to transmit 15 ASCII
characters required for the E.164 numbering format.
2.4.6.23 Transmit E3 FA1 Byte Error Mask Register (E3, ITU-T G.832)
TXE3 FA1 ERROR MASK REGISTER (ADDRESS = 0X48)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
TxFA1_Error_Mask_Byte[7:0]
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
0
0
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THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
XRT72L53
PRELIMINARY
REV. P1.1.7
This Read/Write bit-field is used to insert errors into
the Framing Alignment octet, FA1 of each outbound
E3 frame. The user may wish to do this for equipment
testing purposes. Prior to transmission, the Transmit
DS3/E3 Framer block reads in the FA1 byte, and performs an XOR operation with it and the contents of
this register. The results of this operation are written
back into the FA1 octet position, in each outbound E3
frame. Consequently, to insure errors are not injected
into the FA1 octet of the outbound E3 frames, the
contents of this register must be set to all “0’s” (the
default value).
2.4.6.24 Transmit E3 FA2 Byte Error Mask Register (E3, ITU-T G.832)
TXE3 FA2 ERROR MASK REGISTER (ADDRESS = 0X49)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
TxFA2_Error_Mask_Byte[7:0]
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
0
0
This Read/Write bit-field is used to insert errors into
the Framing Alignment octet, FA2 of each outbound
E3 frame. The user may wish to do this for equipment
testing purposes. Prior to transmission, the Transmit
DS3/E3 Framer block reads in the FA2 byte, and performs an XOR operation with it and the contents of
this register. The results of this operation are written
back into the FA2 octet position, in each outbound E3
frame. Consequently, to insure errors are not injected
into the FA2 octet of the outbound E3 frames, the
contents of this register must be set to all "0’s" (the
default value).
2.4.6.25 Transmit E3 BIP-8 Error Mask Register
(E3, ITU-T G.832)
TXE3 BIP-8 ERROR MASK REGISTER (ADDRESS = 0X4A)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
TxBIP-8_Error_Mask_Byte[7:0]
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
0
0
This Read/Write bit-field is used to insert errors into
EM (Error Monitor) octet of each outbound E3 frame.
The user may wish to do this for equipment testing
purposes. Prior to transmission, the Transmit DS3/E3
Framer block reads in the EM byte, and performs an
XOR operation with it and the contents of this register. The results of this operation are written back into
the EM octet position, in each outbound E3 frame.
Consequently, to insure errors are not injected into
the EM octet of the outbound E3 frames, the contents
of this register must be set to all "0’s" (the default value).
2.4.7 Transmit E3 Framer Configuration Registers (ITU-T G.751)
2.4.7.1 Transmit E3 Configuration Register
(ITU-T G.751)
TXE3 CONFIGURATION REGISTER (ADDRESS = 0X30)
BIT 7
Tx
BIP-4
Enable
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
Tx AIS
Enable
Tx LOS
Enable
Tx FAS
Source
Select
TxASourceSel[1:0]
TxNSourceSel[1:0]
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
0
0
Bit 7 - TxBIP-4 Enable
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THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
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PRELIMINARY
REV. P1.1.7
This Read/Write bit-field is used to configure the
Transmit Section of the Channel, to compute an insert
the BIP-4 value into each outbound E3 frame.
NOTE: For more information on these BIP-4 Calculations,
please see Section 4.2.4.2.2.
Setting this bit-field to "0", configures the Transmit
Section of the Channel to NOT compute and insert
the BIP-4 value into each outbound E3 frame. Instead
these four bits will contain data that has been input
via the Input Interface.
These two Read/Write bit-fields combine to specify
the source of the A-bit, within each outbound E3
frame. The relationship between these two bit-fields
and the resulting source of the A Bit is tabulated below.
Bit 6, 5, TxASourceSel[1:0]
Setting this bit-field to "1", configures the Transmit
Section of the Channel to compute and insert the
BIP-4 value into each outbound E3 frame.
TXASOURCESEL[1:0]
SOURCE OF A BIT
00
TxE3 Service Bits Register (Address = 0x35)
01
Transmit Overhead Data Input Interface
10
Transmit Payload Data Input Interface
11
Functions as a FEBE (Far-End-Block Error) bit-field.
This bit-field is set to "0", if the Near-End Receive Section (within this chip) detects no BIP-4
Errors within the incoming E3 frames.
This bit-field is set to "1", if the Near-End Receive Section (within this chip) detects a BIP-4
Error within the incoming E3 frame.
NOTE: For more information on the A-bit, within the ITU-T
G.751 frame, please see Section 4.1.1.1.
frame. The relationship between these two bit-fields
and the resulting source of the N Bit is tabulated below.
Bits 4, 3, TxNSourceSel[1:0]
These two Read/Write bit-fields combine to specify
the source of the N-bit, within each outbound E3
TXNSOURCESEL[1:0]
SOURCE OF N BIT
00
TxE3 Service Bits Register (Address = 0x35)
01
Transmit Overhead Data Input Interface
10
Transmit LAPD Controller
11
Transmit Payload Data Input Interface.
NOTE: For more information on the N-bit, within the ITU-T
G.751 frame, please see Section 4.1.1.2.
Bit 2 - TxAIS Enable
This Read/Write bit-field is used to configure the
Transmit Section of the Framer IC to transmit an LOS
(e.g., All Zeros) pattern to the remote terminal
This Read/Write bit-field is used to configure the
Transmit Section of the Framer IC to transmit an AIS
pattern to the remote terminal
Setting this bit-field to "0" configures the Transmit
Section (of the chip) to transmit data in a normal manner (e.g., as received via the Input Interface).
Setting this bit-field to "0" configures the Transmit
Section (of the chip) to transmit data in a normal manner (e.g., as received via the Input Interface).
Setting this bit-field to "1" configures the Transmit
Section (of the chip) to transmit an "All Zeros" pattern
(e.g., an LOS pattern) to the remote terminal.
Setting this bit-field to "1" configures the Transmit
Section (of the chip) to transmit an "All Ones" pattern
(e.g., an AIS pattern) to the remote terminal.
NOTE: For more information on the LOS pattern, please
see Section 4.2.4.2.1.2.
NOTE: For more information on the AIS pattern, please see
Section 4.2.4.2.1.1.
This Read/Write bit-field is used to configure the
Transmit Section of the Channel to either:
Bit 0 - TxFAS Source Select
Bit 1 - TxLOS Enable
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THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
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PRELIMINARY
REV. P1.1.7
a. Internally generate the FAS (Framing Alignment
Signal) pattern, within the outbound E3 frames,
or to
Setting this bit-field to "1" configures the Transmit
Section of the Channel to use the Input Interface as
the source for the FAS pattern.
b. use the Input Interface as the source for the FAS
pattern.
NOTE: For more information on the FAS pattern, please see
Section 4.1.
Setting this bit-field to "0" configures the Transmit
Section of the Channel to internally generate the FAS
pattern, for each outbound E3 frame.
2.4.7.2 Transmit E3 LAPD Configuration Register (ITU-T G.751)
TXE3 LAPD CONFIGURATION REGISTER (ADDRESS = 0X33)
BIT 7
BIT 6
BIT 5
BIT 4
Not Used
BIT 3
BIT 2
BIT 1
BIT 0
Auto Retransmit
Not Used
TxLAPD
Msg Length
TxLAPD
Enable
RO
RO
RO
RO
R/W
RO
R/W
R/W
0
0
0
0
1
0
0
0
Bit 3 - Auto Retransmit
This Read/Write bit-field is used to configure the
LAPD Transmitter to either transmit the LAPD Message frame only once, or repeatedly at one-second
intervals.
Setting this bit-field to "0" configures the outbound
LAPD Message frame to be 76 bytes in length. Setting this bit-field to "1" configures the outbound LAPD
Message frame to be 82 bytes in length.
Bit 0 - TxLAPD Enable
Writing a "0" to this bit-field configures the LAPD
Transmitter to transmit the LAPD Message frame
once. Afterwards, the LAPD Transmitter will halt
transmission, until it has commanded to transmit another LAPD Message frame.
This Read/Write bit-field is used to enable or disable
the LAPD Transmitter. The LAPD Transmitter must be
enabled before it can be commanded to transmit a
LAPD Message frame (containing a PMDL message)
via the outbound E3 frames, to the Remote Terminal.
Writing a "1" to this bit-field configures the LAPD
Transmitter to transmit the LAPD Message frame repeatedly at One-Second intervals. In this configuration, the LAPD Transmitter will repeat its transmission
of the LAPD Message frame until it has been disabled.
Writing a "0" disables the LAPD Transmitter (default
condition). Writing a "1" enables the LAPD Transmitter.
NOTE: For information on the LAPD Transmitter, please see
Section 4.2.3.
2.4.7.3 Transmit E3 LAPD Status and Interrupt
Register (ITU-T G.751)
Bit 1 - TxLAPD Message Length Select
This Read/Write bit-field is used to select the length
of the outbound LAPD Message frame.
TXE3 LAPD STATUS AND INTERRUPT REGISTER (ADDRESS = 0X34)
BIT 7
BIT 6
BIT 5
BIT 4
Not Used
BIT 3
BIT 2
BIT 1
BIT 0
TXDL Start
TXDL Busy
TxLAPD
Interrupt
Enable
TxLAPD
Interrupt
Status
RO
RO
RO
RO
R/W
RO
R/W
RUR
0
0
0
0
0
0
0
0
Bit 3 - TxDL Start
This Read/Write bit-field is used to command the
LAPD Transmitter to do the following.
• Scan through the PMDL Message, within the Transmit LAPD Message buffer, and search for a string of
five (5) consecutive "1’s". The LAPD Transmitter will
then insert (or stuff) a "0" into the PMDL Message
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THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. P1.1.7
data, immediately following any string of 5 consecutive "1’s".
• Read in this stuffed PMDL Message from the Transmit LAPD Message buffer, and encapsulate it into a
LAPD Message frame.
The LAPD Transmitter will set this bit-field to "1",
while it is in the process of transmitting the LAPD
Message frame. However, the LAPD Transmitter will
clear this bit-field to "0" once it has completed its
transmission of the LAPD Message frame.
Bit 1 - TxLAPD Interrupt Enable
• Fragment the resulting LAPD Message frame into
octets.
• Insert these octets into either the GC byte-field or
the NR byte-field (depending upon the user's selection) in each outbound E3 frame.
A "0" to "1" transition, in this bit-field commands the
LAPD Transmitter to initiate the above-mentioned
procedure.
This Read/Write bit-field is used to enable or disable
the LAPD Message frame Transmission Complete interrupt.
Writing a "0" to this bit-field disables this interrupt.
Writing a "1" to this bit-field enables this interrupt.
Bit 0 - TxLAPD Interrupt Status
NOTE: Once the user has commanded the LAPD Transmitter to start transmission, the LAPD Transmitter will repeat
the above-mentioned process once each second and will
insert flag sequence octets into the outbound LAPD channel, during the idle periods between transmissions.
Bit 2 - TxDL Busy
This Reset-upon-Read bit-field is used to determine if
the LAPD Message Frame Transmission Complete interrupt has occurred since the last read of this register. If this bit-field contains a "1" then the LAPD Message Frame Transmission Complete interrupt has occurred since the last read of this register. Conversely,
if this bit-field contains a "0" then it has not.
This Read-Only bit-field is used to poll or monitor the
status of the LAPD Transmitter to see if it has completed its transmission of the LAPD Message frame.
2.4.7.4 Transmit E3 Service Bits Register (ITUT G.751)
TXE3 SERVICE BITS REGISTER (ADDRESS = 0X35)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
Not Used
BIT 1
BIT 0
A Bit
N Bit
RO
RO
RO
RO
RO
RO
R/W
R/W
0
0
0
0
0
0
1
0
Bit 1 - A Bit
This Read/Write bit-field is used to define the value of
the A Bit within a given outbound E3 frame. If the user
has configured the source of the A Bit to be the TxE3
Service Bits Register (by setting TxASource[1:0] =
00, within the TxE3 Configuration Register, Address =
0x30), then the value written in this bit-field will specify the value of the A Bit within the outbound E3
Frame.
This Read/Write bit-field is used to define the value of
the N Bit within a given outbound E3 frame. If the user has configured the source of the N Bit to be the
TxE3 Service Bits Register (by setting TxNSource[1:0] = 00, within the TxE3 Configuration Register, Address = 0x30), then the value written in this
bit-field will specify the value of the N Bit within the
outbound E3 Frame.
2.4.7.5 Transmit E3 FAS Mask Register - 0
(ITU-T G.751)
Bit 0 - N Bit
TXE3 FAS ERROR MASK REGISTER - 0 (ADDRESS = 0X48)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
Not Used
BIT 2
BIT 1
BIT 0
TxFAS_Error_Mask_Upper[4:0]
RO
RO
RO
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
0
0
Bits 4 - 0, TxFAS_Error_Mask_Upper[4:0]
This Read/Write bit-field is used to insert errors into
the upper five bits of the Framing Alignment Signal,
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THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
XRT72L53
PRELIMINARY
REV. P1.1.7
FAS of each outbound E3 frame. The user may wish
to do this for equipment testing purposes. Prior to
transmission, the Transmit E3 Framer block reads in
the upper five (5) bits of the FAS value, and performs
an XOR operation with it and the contents of this register. The results of this operation are written back into the upper five (5) bits of the FAS value, in each out-
bound E3 frame. Consequently, to insure errors are
not injected into the FAS of the outbound E3 frames,
the contents of this register must be set to all "0’s"
(the default value).
2.4.7.6 Transmit E3 FAS Error Mask Register 1 (ITU-T G.751)
TXE3 FAS ERROR MASK REGISTER - 1 (ADDRESS = 0X49)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
Not Used
BIT 2
BIT 1
BIT 0
TxFAS_Error_Mask_Lower[4:0]
RO
RO
RO
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
0
0
Bits 4 - 0, TxFAS_Error_Mask_Lower[4:0]
This Read/Write bit-field is used to insert errors into
the lower five bits of the Framing Alignment Signal,
FAS of each outbound E3 frame. The user may wish
to do this for equipment testing purposes. Prior to
transmission, the Transmit E3 Framer block reads in
the lower five (5) bits of the FAS value, and performs
an XOR operation with it and the contents of this reg-
ister. The results of this operation are written back into the lower five (5) bits of the FAS value, in each outbound E3 frame. Consequently, to insure errors are
not injected into the FAS of the outbound E3 frames,
the contents of this register must be set to all "0’s"
(the default value).
2.4.7.7 Transmit E3 BIP-4 Error Mask Register
(ITU-T G.751)
TXE3 BIP-4 ERROR MASK REGISTER (ADDRESS = 0X4A)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
Not Used
BIT 1
BIT 0
TxBIP-4 Mask[3:0]
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
0
0
Bits 3 - 0: TxBIP-4 Mask[3:0]
This Read/Write bit-field is used to insert errors into
the BIP-4 value within each outbound E3 frame. The
user may wish to do this for equipment testing purposes. Prior to transmission, the Transmit DS3/E3
Framer block reads in the BIP-4 value, and performs
an XOR operation with it and the contents of this register. The results of this operation are written back into the BIP-4 nibble position, in each outbound E3
frame. Consequently, to insure errors are not injected
into the BIP-4 value of the outbound E3 frames, the
contents of this register must be set to all "0’s" (the
default value).
NOTE: This register is ignored if Bit 7 (Tx BIP-4 Enable)
within the TxE3 Configuration register (Address = 0x30) is
set to “0”.
2.4.8
Performance Monitor Registers
2.4.8.1 PMON Line Code Violation Count Register - MSB
PMON LCV EVENT COUNT REGISTER - MSB (ADDRESS = 0X50)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
LCV Count - High Byte
RUR
RUR
RUR
RUR
RUR
RUR
RUR
RUR
0
0
0
0
0
0
0
0
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THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. P1.1.7
This Reset-upon-Read register, along with the PMON
LCV Event Count Register - LSB (Address = 0x51)
contains a 16-bit representation of the number of Line
Code Violations that have been detected by the Receive DS3/E3 Framer block, since the last read of
these registers. This register contains the MSB (or
Upper-Byte) value of this 16 bit expression.
2.4.8.2 PMON Line Code Violation Count Register - LSB
PMON LCV EVENT COUNT REGISTER - LSB (ADDRESS = 0X51)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
LCV Count - Low Byte
RUR
RUR
RUR
RUR
RUR
RUR
RUR
RUR
0
0
0
0
0
0
0
0
This Reset-upon-Read register, along with the PMON
LCV Event Count Register - LSB (Address = 0x50)
contains a 16-bit representation of the number of Line
Code Violations that have been detected by the Receive DS3/E3 Framer block, since the last read of
these registers. This register contains the LSB (or
Lower-Byte) value of this 16 bit expression.
2.4.8.3 PMON Framing Bit/Byte Error Count
Register - MSB
PMON FRAMING BIT/BYTE ERROR COUNT REGISTER - MSB (ADDRESS = 0X52)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
Framing Bit/Byte Error Count - High Byte
RUR
RUR
RUR
RUR
RUR
RUR
RUR
RUR
0
0
0
0
0
0
0
0
This Reset-upon-Read register, along with the PMON
Framing Bit/Byte Error Count Register - LSB (Address = 0x53) contains a 16-bit representation of the
number of Framing Bit or Byte Errors that have been
detected by the Receive DS3/E3 Framer block, since
the last read of these registers. This register contains
the MSB (or Upper-Byte) value of this 16 bit expression.
2.4.8.4 PMON Framing Bit/Byte Error Count
Register - LSB
PMON FRAMING BIT/BYTE ERROR COUNT REGISTER - LSB (ADDRESS = 0X53)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
Framing Bit/Byte Error Count - Low Byte
RUR
RUR
RUR
RUR
RUR
RUR
RUR
RUR
0
0
0
0
0
0
0
0
This Reset-upon-Read register, along with the PMON
Framing Bit/Byte Error Count Register - MSB (Address = 0x52) contains a 16-bit representation of the
number of Framing Bit or Byte Errors that have been
detected by the Receive DS3/E3 Framer block, since
the last read of these registers. This register contains
the LSB (or Lower-Byte) value of this 16 bit expression.
2.4.8.5
MSB
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PMON Parity Error Count Register -
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THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
XRT72L53
PRELIMINARY
REV. P1.1.7
PMON PARITY ERROR COUNT REGISTER - MSB (ADDRESS = 0X54)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
Parity Error Count - High Byte
RUR
RUR
RUR
RUR
RUR
RUR
RUR
RUR
0
0
0
0
0
0
0
0
This Reset-upon-Read register, along with the PMON
Parity Error Count Register - LSB (Address = 0x55)
contains a 16-bit representation of the number of Pbit Errors (for DS3 applications), BIP-4 Errors (for E3/
ITU-T G.751 applications) or BIP-8 Errors (for E3/
ITU-T G.832 applications) that have been detected by
the Receive DS3/E3 Framer block, since the last read
of these registers. This register contains the MSB (or
Upper-Byte) value of this 16 bit expression.
2.4.8.6
LSB
PMON Parity Error Count Register -
PMON PARITY ERROR COUNT REGISTER - LSB (ADDRESS = 0X55)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
Parity Error Count - Low Byte
RUR
RUR
RUR
RUR
RUR
RUR
RUR
RUR
0
0
0
0
0
0
0
0
This Reset-upon-Read register, along with the PMON
Parity Error Count Register - MSB (Address = 0x54)
contains a 16-bit representation of the number of Pbit Errors (for DS3 applications), BIP-4 Errors (for E3/
ITU-T G.751 applications) or BIP-8 Errors (for E3/
ITU-T G.832 applications) that have been detected by
the Receive DS3/E3 Framer block, since the last read
of these registers. This register contains the LSB (or
Lower-Byte) value of this 16 bit expression.
2.4.8.7
MSB
PMON FEBE Event Count Register -
PMON FEBE EVENT COUNT REGISTER - MSB (ADDRESS = 0X56)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
FEBE Event Count - High Byte
RUR
RUR
RUR
RUR
RUR
RUR
RUR
RUR
0
0
0
0
0
0
0
0
This Reset-upon-Read register, along with the PMON
FEBE Event Count Register - LSB (Address = 0x57)
contains a 16-bit representation of the number of
FEBE Events that have been detected by the Receive
DS3/E3 Framer block, since the last read of these
registers. This register contains the MSB (or UpperByte) value of this 16 bit expression.
2.4.8.8
LSB
PMON FEBE Event Count Register -
PMON FEBE EVENT COUNT REGISTER - LSB (ADDRESS = 0X57)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
FEBE Event Count - Low Byte
RUR
RUR
RUR
RUR
RUR
RUR
RUR
RUR
0
0
0
0
0
0
0
0
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THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. P1.1.7
registers. This register contains the LSB (or LowerByte) value of this 16 bit expression.
This Reset-upon-Read register, along with the PMON
FEBE Event Count Register - MSB (Address = 0x56)
contains a 16-bit representation of the number of
FEBE Events that have been detected by the Receive
DS3/E3 Framer block, since the last read of these
2.4.8.9 PMON CP-Bit Error Event Count Register - MSB
PMON CP-BIT ERROR COUNT REGISTER - MSB (ADDRESS = 0X58)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
CP-Bit Error Count - High Byte
RUR
RUR
RUR
RUR
RUR
RUR
RUR
RUR
0
0
0
0
0
0
0
0
This Reset-upon-Read register, along with the PMON
CP-Bit Error Count Register - LSB (Address = 0x59)
contains a 16-bit representation of the number of CPbit Errors that have been detected by the Receive
DS3/E3 Framer block (within the channel), since the
last read of these registers. This register contains the
MSB (or Upper-Byte) value of this 16 bit expression.
NOTE: This register is only active if the Channel has been
configured to operate in the DS3, C-bit Parity Framing format.
2.4.8.10 PMON CP-Bit Error Event Count Register - LSB
PMON CP-BIT ERROR COUNT REGISTER - LSB (ADDRESS = 0X59)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
CP-Bit Error Count - Low Byte
RUR
RUR
RUR
RUR
RUR
RUR
RUR
RUR
0
0
0
0
0
0
0
0
This Reset-upon-Read register, along with the PMON
CP-Bit Error Count Register - MSB (Address = 0x58)
contains a 16-bit representation of the number of CPbit Errors that have been detected by the Receive
DS3/E3 Framer block (within the channel), since the
last read of these registers. This register contains the
LSB (or Lower-Byte) value of this 16 bit expression.
NOTE: This register is only active if the Channel has been
configured to operate in the DS3, C-bit Parity Framing format.
2.4.8.11 PMON Holding Register
PMON HOLDING REGISTER (ADDRESS = 0X6C)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
PMON Holding Value
RUR
RUR
RUR
RUR
RUR
RUR
RUR
RUR
0
0
0
0
0
0
0
0
Each of the above-defined PMON registers are 16 bit
Reset-upon-Read registers. However, the bi-drectional data bus (of the Framer IC) is only 8-bits wide. As a
consequence, whenever the Microprocessor intends
to read a PMON register, there are two things to bear
in mind.
125
1. This Microprocessor is going to require two read
accesses in order read out the full 16-bit expression of these PMON registers.
2. The entire 16-bit expression (of a given PMON
register) is going to be reset to 0x0000, immediately after the Microprocessor has completed its
first read access to the PMON register.
áç
THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
XRT72L53
PRELIMINARY
REV. P1.1.7
2.4.8.12 One-Second Error Status Register
Hence, the contents of the other byte (of the partially
read PMON register) will reside within the PMON
Holding register.
ONE-SECOND ERROR STATUS REGISTER (ADDRESS = 0X6D)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
Errored
Second
Severely
Errored
Second
RO
RO
RO
RO
RO
RO
RO
RO
0
0
0
0
0
0
0
0
Bit 1 - Errored Second
Bit 0 - Severely Errored Second
This bit field indicates whether or not an error has occurred within the last One-Second accumulation interval. This bit-field will be set to “1” if at least one error has occurred during the last One-Second accumulation interval. Conversely, this bit-field will be set
to "0" if no errors has occurred during the last onesecond accumulation interval.
This bit-field indicates whether or not the error rate in
the last one-second interval was greater than 1 in
1000. A "0" indicates that the error rate did not exceed 1 in 1000 in the last One-Second interval.
2.4.8.13 One-Second Line Code Violation Accumulator Register - MSB
LCV - ONE-SECOND ACCUMULATOR REGISTER - MSB (ADDRESS = 0X6E)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
LCV - One-Second Count - High Byte
RO
RO
RO
RO
RO
RO
RO
RO
0
0
0
0
0
0
0
0
This Read-Only register, along with the LCV - OneSecond Accumulator Register - LSB (Address =
0x6F) contains a 16-bit representation of the number
of LCV (Line Code Violation) Events that have been
detected by the Receive DS3/E3 Framer block, within
the last one-second sampling period. This register
contains the MSB (or Upper-Byte) value of this 16 bit
expression.
2.4.8.14 One-Second Line Code Violation Accumulator Register - LSB
LCV - ONE-SECOND ACCUMULATOR REGISTER - LSB (ADDRESS = 0X6F)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
LCV - One-Second Count - Low Byte
RO
RO
RO
RO
RO
RO
RO
RO
0
0
0
0
0
0
0
0
This Read-Only register, along with the LCV - OneSecond Accumulator Register - MSB (Address =
0x6E) contains a 16-bit representation of the number
of LCV (Line Code Violation) Events that have been
detected by the Receive DS3/E3 Framer block, within
the last One-Second sampling period. This register
contains the LSB (or Lower-Byte) value of this 16 bit
expression.
2.4.8.15 One-Second Frame Parity Error Accumulator Register - MSB
126
XRT72L53
áç
THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. P1.1.7
FRAME PARITY ERRORS - ONE-SECOND ACCUMULATOR REGISTER - MSB (ADDRESS = 0X70)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
Frame Parity Error Count - High Byte
RO
RO
RO
RO
RO
RO
RO
RO
0
0
0
0
0
0
0
0
This Read-Only register, along with the Frame Parity
Errors - One-Second Accumulator Register - LSB
(Address = 0x71) contains a 16-bit representation of
the number of Frame Parity Errors that have been detected by the Receive DS3/E3 Framer block, within
the last One-Second sampling period. This register
contains the MSB (or Upper-Byte) value of this 16 bit
expression.
NOTES:
1. For DS3 applications, the Frame-Parity Errors One Second Accumulator register contains the
number of P-bit errors that have been detected in
the last one-second sampling period.
2. For E3, ITU-T G.751 applications, the Frame-Parity
Error - One Second Accumulator register contains
the number of BIP-4 errors that have been detected
in the last one-second sampling period.
3. For E3, ITU-T G.832 applications, the Frame-Parity
Error - One Second Accumulator register contains
the number of BIP-8 errors that have been detected
in the last one-second sampling period.
2.4.8.16 One-Second Frame Parity Error Accumulator Register - LSB
FRAME PARITY ERRORS - ONE-SECOND ACCUMULATOR REGISTER - LSB (ADDRESS = 0X71)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
Frame Parity Error Count - Low Byte
RO
RO
RO
RO
RO
RO
RO
RO
0
0
0
0
0
0
0
0
This Read-Only register, along with the Frame Parity
Errors - One-Second Accumulator Register - MSB
(Address = 0x70) contains a 16-bit representation of
the number of Frame Parity Errors that have been detected by the Receive DS3/E3 Framer block, within
the last one-second sampling period. This register
contains the LSB (or Lower-Byte) value of this 16 bit
expression.
NOTES:
1. For DS3 applications, the Frame-Parity Errors One Second Accumulator register contains the
number of P-bit errors that have been detected in
the last one-second sampling period.
2. For E3, ITU-T G.751 applications, the Frame-Parity
Error - One Second Accumulator register contains
the number of BIP-4 errors that have been detected
in the last one-second sampling period.
3. For E3, ITU-T G.832 applications, the Frame-Parity
Error - One Second Accumulator register contains
the number of BIP-8 errors that have been detected
in the last one-second sampling period.
2.4.8.17 One-Second Frame CP-Bit Error Accumulator Register - MSB
FRAME CP-BIT ERRORS - ONE-SECOND ACCUMULATOR REGISTER - MSB (ADDRESS = 0X72)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
CP Bit Error Count - High Byte
RO
RO
RO
RO
RO
RO
RO
RO
0
0
0
0
0
0
0
0
127
áç
THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
XRT72L53
PRELIMINARY
REV. P1.1.7
This Read-Only register, along with the Frame CP-Bit
Error - One-Second Accumulator Register - LSB (Address = 0x73) contains a 16-bit representation of the
number of CP Bit Errors that have been detected by
the Receive DS3/E3 Framer block, within the last
one-second sampling period. This register contains
the MSB (or Upper Byte) value of this 16-bit expression.
NOTE: This register is only active if the Channel has been
configured to operate in the DS3, C-bit Parity framing format.
2.4.8.18 One-Second Frame CP-Bit Error Accumulator Register - LSB
FRAME PARITY ERRORS - ONE-SECOND ACCUMULATOR REGISTER - LSB (ADDRESS = 0X73)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
CP Bit Error Count - Low Byte
RO
RO
RO
RO
RO
RO
RO
RO
0
0
0
0
0
0
0
0
This Read-Only register, along with the Frame CP-Bit
Error - One-Second Accumulator Register - MSB (Address = 0x72) contains a 16-bit representation of the
number of CP Bit Errors that have been detected by
the Receive DS3/E3 Framer block, within the last
one-second sampling period. This register contains
the LSB (or Lower Byte) value of this 16-bit expression.
NOTE: This register is only active if the Channel has been
configured to operate in the DS3, C-bit Parity framing format.
2.4.8.19 Line Interface Drive Register
LINE INTERFACE DRIVE REGISTER (ADDRESS = 0X80)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
REQ
TAOS
ENCODIS
TxLEV
RLOOP
LLOOP
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
0
1
0
0
0
Bit 5 - REQ - (Receive Equalization Bypass Control)
This Read/Write bit-field is used to control the state of
the REQ output pin of the Framer. This output pin is
intended to be connected to either the REQ or the
REQEN input pin of the DS3/E3 LIU IC.
If the user connects the REQ output pin of the Framer
to either the REQDIS or the REQEN input pin of the
DS3/E3 LIU IC, then the user will have Microprocessor Control over the state of the Receive Equalizer
within the DS3/E3 LIU IC.
Writing a "1" to this bit-field causes the Channel to
toggle the REQ output pin "High". Writing a "0" to this
bit-field causes the Channel to toggle the REQ output
pin "Low".
NOTE: If the customer is not using an Exar XRT73L0X
DS3/E3/STS-1 LIU IC, then this bit-field and the REQ output pin can be used for other purposes.
Bit 4 - TAOS - (Transmit All Ones Signal)
This Read/Write bit-field is used to control the state of
the TAOS output pin of the Framer. This output pin is
intended to be connected to the TAOS input pin of the
DS3/E3 LIU IC. If the user forces this signal to toggle
"High", then the LIU will transmit an "All Ones" pattern
onto the line. Conversely, if the user commands this
output signal to toggle "Low" then the LIU IC will proceed to transmit data based upon the pattern that it
receives via the TxPOS[n] and TxNEG[n] output pins
(of the Framer IC).
Writing a "1" to this bit-field will cause the TAOS[n]
output pin to toggle "High". Writing a "0" to this bitfield will cause this output pin to toggle "Low".
NOTE: If the customer is not using an Exar XRT73L0X
DS3/E3/STS-1 LIU IC, then this bit-field, and the TAOS output pin can be used for other purposes.
Bit 3 - Encodis - (B3ZS Encoder Disable)
This Read/Write bit-field allows the user to control the
state of the Encodis output pin of the Framer. This
output pin is intended to be connected to either the
128
XRT72L53
THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
áç
PRELIMINARY
REV. P1.1.7
In order to insure that the transmit output pulses of
the LIU meet the DSX-3 Isolated Pulse Template Requirements (per Bellcore GR-499-CORE), the user is
advised to set this bit-field to "0", if the length of cable
(between the LIU transmit output and the DSX-3
Cross Connect System) is greater than 225 feet.
ENCODIS or the ENDECDIS input pin of the DS3/E3
LIU IC. If the user forces this signal to toggle "High",
then the internal B3ZS/HDB3 encoder (within the
LIU) will be disabled. Conversely, if the user command this output signal to toggle "Low", then the internal B3ZS/HDB3 encoder (within the LIU) will be
enabled.
Conversely, the user is advised to set this bit-field to
"1", if the length of cable (between the LIU transmit
output and the DSX-3 Cross Connect system) is less
than 225 feet.
Writing a "1" to this bit-field causes the Channel to
toggle the Encodis[n] output pin "High". Writing a "0"
to this bit-field will cause the Channel to toggle this
output pin "Low".
Writing a "1" to this bit-field commands the Framer to
toggle the TxLev output "High". Writing a "0" to this
bit-field commands the Framer to toggle this output
signal "Low".
NOTES:
1. The B3ZS/HDB3 encoder, within the DS3/E3 LIU,
is not to be confused with the B3ZS/HDB3 encoding capable that exists within the Transmit Section
of the Framer IC.
2. The user is advised to disabled the B3ZS/HDB3
encoder (within the LIU IC) if the channel is configured to operate in the B3ZS/HDB3 line code.
3. If the customer is not using an Exar XRT73L0X
DS3/E3/STS-1 LIU IC, then this bit-field and the
Encodis[n] output pin can be used for other purposes.
NOTES:
1. The TxLEV function is only applicable to DS3 applications. E3 LIU’s do not support this kind of Line
Build out feature.
2. If the customer is not using an Exar XRT73L0X
DS3/E3 LIU IC, then this bit-field and the TxLev
output pin can be used for other purposes.
Bit 1 - RLOOP - (Remote Loopback)
Bit 2 - TxLev - (Transmit Output Line Build-Out
Select Output)
This Read/Write bit-field is used to control the state of
the TxLev[n] output pin of the Framer. This output pin
is intended to be connected to the TxLev input pin of
the DS3/E3 LIU IC. If the user commands this signal
to toggle High, then the DS3/E3 LIU IC will disable
the Transmit Line Build-Out circuitry, and will transmit
unshaped (square-wave) pulses onto the line. If the
user commands this signal to toggle "Low", then the
DS3/E3 LIU IC will enable the Transmit Line Build-Out
circuitry, and will transmit shaped pulses onto the line.
This Read/Write bit-field is used to control the state of
the RLOOP[n] output pin of the Framer. This output
pin is intended to be connected to the RLOOP input
pin of the DS3/E3 LIU IC.
When using Exar’s family of XRT73L0X DS3/E3
LIU’s, the state of the RLOOP and the LLOOP pins
are used to dictate which loop-back mode the LIU will
operate in. The following table presents the relationship between the state of these two input pins (or bitfields) and the resulting loop-back modes.
RLOOP
LLOOP
RESULTING LOOP-BACK MODE OF THE DS3/E3 LIU
0
0
Normal Operation (No Loop-back Mode)
0
1
Analog Local Loop-back Mode
1
0
Remote Loop-back Mode
1
1
Digital Local Loop-back Mode
Currently the following XRT73L0X Family of DS3/E3/
STS-1 LIU IC Data Sheets are now available:
Writing a "1" into this bit-field commands the Framer
IC to toggle the RLOOP[n] output signal "High". Writing a "0" into this bit-field commands the Framer IC to
toggle this output signal "Low".
• XRT7300 1-Channel DS3/E3/STS-1 LIU IC (5V)
For a detailed description on the operation of a particular Exar XRT73L0X DS3/E3 LIU, while configured
into each of these above-mentioned loop-back
modes, please consult the appropriate LIU Data
Sheet.
• XRT73L00 1-Channel DS3/E3/STS-1 LIU IC (3.3V)
• XRT7302 2-Channel DS3/E3/STS-1 LIU IC (5V)
• XRT73L03 3-Channel DS3/E3/STS-1 LIU IC (3.3V)
• XRT73L04 4-Channel DS3/E3/STS-1 LIU IC (3.3V)
129
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THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
XRT72L53
PRELIMINARY
REV. P1.1.7
NOTE: If the customer is not using an Exar XRT73L0X
DS3/E3/STS-1 LIU IC, then this bit-field and the RLOOP[n]
output pin can be used for other purposes.
Bit 0 - LLOOP - (Local Loop-back)
This Read/Write bit-field is used to control the state of
the LLOOP[n] output pin of the Framer. This output
pin is intended to be connected to the LLOOP input
pin of the DS3/E3 LIU IC.
When using Exar’s family of XRT73L0X DS3/E3
LIU’s, the state of the RLOOP and the LLOOP pins
are used to dictate which loop-back mode the LIU will
operate in. The following table presents the relationship between the state of these two input pins (or bitfields) and the resulting loop-back modes.
RLOOP
LLOOP
RESULTING LOOP-BACK MODE OF THE DS3/E3 LIU
0
0
Normal Operation (No Loop-back Mode)
0
1
Analog Local Loop-back Mode
1
0
Remote Loop-back Mode
1
1
Digital Local Loop-back Mode
Writing a "1" into this bit-field commands the Framer
to toggle the LLOOP[n] output signal "High". Writing a
"0" into this bit-field commands the Framer to toggle
this output signal "Low".
For a detailed description of the operation of a particular Exar XRT73L0X DS3/E3 LIU, while configured
into each of these above-mentioned loop-back
modes, please consult the appropriate LIU IC Data
Sheet.
• XRT7300 1-Channel DS3/E3/STS-1 LIU IC (5V)
• XRT73L00 1-Channel DS3/E3/STS-1 LIU IC (3.3V)
• XRT7302 2-Channel DS3/E3/STS-1 LIU IC (5V)
• XRT73L03 3-Channel DS3/E3/STS-1 LIU IC (3.3V)
• XRT73L04 4-Channel DS3/E3/STS-1 LIU IC (3.3V)
NOTE: If the customer is not using an Exar XRT73L0X
DS3/E3/STS-1 LIU IC, then this bit-field and the LLOOP[n]
output pin can be used for other purposes.
2.4.8.20 Line Interface Scan Register
Currently the following XRT73L0X Family of DS3/E3/
STS-1 LIU IC Data Sheets are now available:
LINE INTERFACE SCAN REGISTER (ADDRESS = 0X81)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
DMO
RLOL
RLOS
RO
RO
RO
RO
RO
RO
RO
RO
0
0
0
0
0
0
0
0
Bit 2 - DMO - (Drive Monitor Output)
This Read-Only bit-field indicates the logic state of
the DMO[n] input pin of the Framer. This input pin is
intended to be connected to the DMO output pin of an
Exar XRT73L0X-type of DS3/E3 LIU IC. If this bit-field
contains a logic "1", then the DMO input pin is "High".
An Exar XRT73L0X-type of DS3/E3 LIU IC will set
this pin "High" if the drive monitor circuitry (within the
LIU) has not detected any bipolar signals at the MTIP
and MRING inputs (of the LIU) within the last 128 +
32 bit periods.
Conversely, if this bit-field contains a logic "0", then
the DMO input pin is "High". The DS3/E3 LIU IC will
set this pin "Low" if bipolar signals are being detected
at the MTIP and MRING input pins.
As a consequence, the DMO output pin can be
thought of as a Transmit Driver Failure indicator.
NOTE: If this customer is not using an Exar XRT73L0X-type
of DS3/E3 LIU IC, then this input pin and bit-field can be
used for a variety of other purposes.
Bit 1 - RLOL - (Receive Loss of Lock)
This Read-Only bit-field indicates the logic state of
the RLOL[n] input pin of the Framer. This input pin is
intended to be connected to the RLOL output pin of
an Exar XRT73L0X-type of DS3/E3 LIU IC. If this bitfield contains a logic "1", then the RLOL[n] input pin is
"High". An Exar XRT73L0X-type of DS3/E3 LIU IC
will set this pin "High" if the clock recovery phaselocked-loop circuitry (within the LIU) has lost lock with
the incoming DS3/E3 data-stream and is not properly
recovering clock and data.
130
XRT72L53
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THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. P1.1.7
Conversely, if this bit-field contains a logic “0”, then
the RLOL input pin is "Low". The DS3/E3 LIU IC will
hold this pin "Low" as long as this clock recovery
phase-locked-loop circuitry (within the LIU) is properly locked onto the incoming DS3 or E3 data-stream,
and is properly recovering clock and data from this
data-stream.
then the RLOS[n] input pin is "High". The LIU will toggle this signal "High" if it (the LIU IC) is currently declaring an LOS (Loss of Signal) condition.
For more information on the operation of these Exar
XRT73L0X-type of DS3/E3/STS-1 LIU IC’s, please
consult any of the following data sheets.
• XRT7300 1-Channel DS3/E3/STS-1 LIU IC (5V)
For more information on the LOS Declaration and
Clearance criteria within the Exar XRT73L0X type of
DS3/E3/STS-1 LIU IC, please consult any of the following data sheets.
• XRT73L00 1-Channel DS3/E3/STS-1 LIU IC (3.3V)
• XRT7300 1-Channel DS3/E3/STS-1 LIU IC (5V)
• XRT7302 2-Channel DS3/E3/STS-1 LIU IC (5V)
• XRT73L00 1-Channel DS3/E3/STS-1 LIU IC (3.3V)
• XRT73L03 3-Channel DS3/E3/STS-1 LIU IC (3.3V)
• XRT7302 2-Channel DS3/E3/STS-1 LIU IC (5V)
• XRT73L04 4-Channel DS3/E3/STS-1 LIU IC (3.3V)
• XRT73L03 3-Channel DS3/E3/STS-1 LIU IC (3.3V)
Conversely, if this bit-field contains a logic "0", then
the RLOS input pin is "Low". The LIU will hold this
signal "Low" if it is NOT currently declaring an LOS
(Loss of Signal) condition.
• XRT73L04 4-Channel DS3/E3/STS-1 LIU IC (3.3V)
NOTE: If the customer is not using an Exar XRT73L0Xtype of DS3/E3/STS-1 IC, then this bit-field, and the
RLOL[n] input pin can be used for other purposes.
Bit 0 - RLOS - (Receive Loss of Signal)
This Read-Only bit-field indicates the logic state of
the RLOS[n] input pin of the Framer. This input pin is
intended to be connected to the RLOS output pin of
the DS3/E3 LIU IC. If this bit-field contains a logic "1",
NOTE: Asserting the RLOS input pin will cause the
XRT72L53 Framer IC to generate the Change in LOS Condition interrupt and declare an LOS (Loss of Signal) condition. Therefore, this input pin should not be used as a general purpose input.
2.4.8.21 HDLC Control Register
HDLC CONTROL REGISTER (ADDRESS = 0X82)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
Framer
By-Pass
HDLC
ON
CRC-32
Select
Reserved
HDLC
Loop-Back
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
0
0
Bit 7 - Framer By-Pass
This Read/Write bit-field is used to enable or disable
(by-pass) the DS3/E3 Framer circuitry, within a given
channel in the XRT72L53.
This feature is used to operate a given Channel in the
Un-framed Mode. Further, this feature also is used to
transmit and receive HDLC frames at the DS3 or E3
line rate of 44.736Mbps or 34.368Mbps, without sacrificing any bandwidth to support the overhead bits/
bytes/
BIT 2
BIT 1
BIT 0
Reserved
ler Mode. If the user invokes this feature, then a
Transmit and Receive byte-wide interface will be enabled, and the channel will be configured to transmit
and receive HDLC Frames via the DS3 or E3 payload
bits.
Setting this bit-field to “1” configures the channel to
operate in the High-Speed HDLC Controller Mode.
Bit 5 - CRC-32
This Read/Write bit-field is used to configure a given
channel to do the following.
Setting this bit-field to “1” disables the Transmit and
Receive DS3/E3 Framer blocks within the channel.
Setting this bit-field to “0” enables the Transmit and
Receive DS3/E3 Framer blocks.
1. To configure the Transmit HDLC Controller block
to compute and append either a CRC-16 or a
CRC-32 value as a trailer to the outbound HDLC
frame.
2. To configure the Receive HDLC Controller block
to compute and verify either CRC-16 or the CRC32 value within each inbound HDLC frame.
Bit 6 - HDLC ON
This Read/Write bit-field is used to configure a given
channel to operate in the High-Speed HDLC Control131
áç
THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
XRT72L53
PRELIMINARY
REV. P1.1.7
TxInClk[n] or the RxLineClk[n] signals. However, if the
Framer experiences a Loss of Clock signal event
such that neither the TxInClk[n] nor the RxLineClk[n]
signal are present, then the Framer Microprocessor
Interface section cease to function.
Setting this bit-field to “0” configures the Transmit
HDLC Controller block to compute and append the
CRC-16 value to the end of the outbound HDLC
frame. Further, this setting also configures the Receive HDLC Controller block compute and verify the
CRC-32 value, which has been appended to the end
of the inbound HDLC frame.
The Framer offers a Loss of Clock (LOC) protection
feature that allows the Microprocessor Interface section to at least complete or terminate an in-process
Read or Write cycle (with the local µP) should this
Loss of Clock event occur. The LOC circuitry consists
of a ring oscillator that continuously checks for signal
transitions at the TxInClk[n] and RxLineClk[n] input
pins. If a Loss of Clock Signal event occur such that
no transitions are occurring on these pins, then the
LOC circuitry will automatically assert the
RDY_DTCK signal in order to complete (or terminate)
the current Read or Write cycle with the Framer Microprocessor Interface section.
Setting this bit-field to “1” configures the Transmit
HDLC Controller block to compute and append the
CRC-32 value to the end of the outbound HDLC
frame. Further, this same setting also configures the
Receive HDLC Controller block to compute and verify
the CRC-32 value, which has been appended to the
end of the inbound HDLC frame.
NOTE: This bit-field is only active if the channel has been
configured to operate in the High-Speed HDLC Controller
Mode.
Bit 3 - HDLC Loop-Back
This LOC Protection may be enabled or disabled feature by writing to Bit 7 (LOC Enable) within the Framer I/O Register, as depicted below.
2.5 THE LOSS OF CLOCK ENABLE FEATURE
The timing for the Microprocessor Interface section,
originates from a line rate (e.g., either a 34.368MHz
or 44.736 MHz) signal that is provided by either the
ADDRESS = 0X01, FRAMER I/O CONTROL REGISTER
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
LOC Enable
Test PMON
Interrupt
Enable
Reset
AMI/B3ZS*
Unipolar/
Bipolar*
TxLine
Clk Inv
RxLine
Clk Inv
Reframe
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
1
0
1
0
0
0
0
0
registers (of the READ PMON register) are reset to
zero upon the first of these two read cycles.
Writing a "1" to this bit-field enables this LOC Protection feature. Writing a "0" to this bit-field disables this
feature.
NOTE: The Ring Oscillator can be a source of noise, within
the Framer chip. Hence, there may be situations where the
user will wish to disable the LOC Protection feature.
2.6 USING THE PMON HOLDING REGISTER
The Microprocessor Interface section consists of an
8-bit bi-directional data bus. As a consequence, the
local µP will be able to read from and write to the
Framer on-chip registers, 8 bit per (read or write) cycle. Since most of the Framer on-chip registers contain 8-bits, communicating with the local µP, over an
8-bit data bus, is not much of an inconvenience. However, all of the PMON registers, within the Framer IC,
contain 16 bits. Consequently, any reads of the
PMON registers, will require two read cycles. To
make matters potentially more complicated, these
PMON registers are Reset-upon-Read registers.
Therefore, the contents of both the MSB and LSB
Fortunately, the XRT72L53 Framer IC includes a feature that will make reading a PMON register a slightly
less complicated task. The Framer chip address
space contains a read-only register known as the
PMON Holding register, which is located at 0x6C.
Whenever the local µP reads in an 8-bit value of a
given PMON registers (e.g., either the upper-byte or
the lower byte value of the PMON register), the other
8-bit value of that PMON register will automatically be
loaded into the PMON Holding register. As a consequence, the other 8-bit value of the PMON register is
accessible by reading the PMON Holding register.
Hence, anytime the local µP is trying to read in the
contents of a PMON register, the first read access
must be made directly to one of the 8-bit values of the
PMON registers (e.g., for example: the PMON LCV
Event Count Register - MSB, Address = 0x50). However, the second read must always be made to a con-
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stant location in system memory, the PMON Holding
Register.
Registers/bits and Interrupt Enable Registers/bits, as
will be discussed below.
2.7 THE INTERRUPT STRUCTURE WITHIN THE FRAMER
MICROPROCESSOR INTERFACE SECTION
The XRT72L53 Framer is equipped with a sophisticated Interrupt Servicing Structure. This Interrupt
Structure includes an Interrupt Request output, INT,
numerous Interrupt Enable Registers and numerous
Interrupt Status Registers. The Interrupt Servicing
Structure, within each of the three channels contains
two levels of hierarchy. The top level is at the functional block level (e.g., the Receive Section, the Transmit
Section, etc.). The lower hierarchical level is at the individual interrupt or source level. Each hierarchical
level consists of a complete set of Interrupt Status
Both of the functional sections, within each channel,
are capable of generating Interrupt Requests to the
local µP/µC. The Framer Interrupt Structure has been
carefully designed to allow the user to quickly determine the exact source of the interrupt (with minimal
latency) which will aid the local µP/µC in determining
which interrupt service routine to call up in order to
respond to or eliminate the condition(s) causing the
interrupt.
Table 6 lists all of the possible conditions that can
generate interrupts, with each functional section of a
given channel.
TABLE 6: LIST OF ALL OF THE POSSIBLE CONDITIONS THAT CAN GENERATE INTERRUPTS WITHIN EACH CHANNEL OF
THE XRT72L53 FRAMER
FUNCTION SECTION
INTERRUPTING CONDITION
Transmit Section
FEAC Message Transfer Complete (DS3, C-Bit Parity Only)
LAPD Message frame Transfer Complete (DS3, C-Bit Parity, All E3)
Receive Section
Change of Status on Receive LOS, OOF, AIS Idle Detection
Validation and removal of received FEAC Code (DS3, C-Bit Parity Only)
New PMDL Message in Receive LAPD Message Buffer.
Detection of Parity Errors (e.g., P-Bit, CP-Bit, BIP-4 and BIP-8 Errors)
Detection of Framing Bit/Byte Errors.
Framer Chip Level
One-Second Interrupt
Each of the three channels, within the XRT72L53
Framer contains an Interrupt Block that comes
equipped with the following registers to support the
servicing of these potential interrupt request sources.
Table 7, 8 , and 9 lists these registers, and their addresses, within the Framer IC for DS3, E3 (ITU-T
G.832) and E3 (ITU-T G.751) framing formats.
TABLE 7: A LISTING OF THE XRT72L53 FRAMER INTERRUPT BLOCK REGISTERS (FOR DS3 APPLICATIONS)
ADDRESS LOCATION
REGISTER NAME
0 x 04
Block Interrupt Enable Register
0 x 05
Block Interrupt Status Register
0 x 12
RxDS3 Interrupt Enable Register
0 x 13
RxDS3 Interrupt Status Register
0 x 17
RxDS3 FEAC Interrupt Enable/Status Register
0 x 18
RxDS3 LAPD Control Register
0 x 31
TxDS3 FEAC Configuration and Status Register
0 x 34
TxDS3 LAPD Status/Interrupt Register
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TABLE 8: A LISTING OF THE XRT72L53 FRAMER INTERRUPT BLOCK REGISTERS (FOR E3, ITU-T G.832
APPLICATIONS)
ADDRESS LOCATION
REGISTER NAME
0 x 04
Block Interrupt Enable Register
0 x 05
Block Interrupt Status Register
0 x 12
RxE3 Interrupt Enable Register -1
0 x 13
RxE3 Interrupt Enable Register -2
0 x 14
RxE3 Interrupt Status Register - 1
0 x 15
RxE3 Interrupt Status Register - 2
0 x 18
RxE3 LAPD Control Register
0 x 34
TxE3 LAPD Status/Interrupt Status
TABLE 9: A LISTING OF THE XRT72L53 FRAMER INTERRUPT BLOCK REGISTER (FOR E3, ITU-T G.751
APPLICATIONS)
ADDRESS LOCATION
REGISTER NAME
0 x 04
Block Interrupt Enable Register
0 x 05
Block Interrupt Status Register
0 x 12
RxE3 Interrupt Enable Register -1
0 x 13
RxE3 Interrupt Enable Register -2
0 x 14
RxE3 Interrupt Status Register - 1
0 x 15
RxE3 Interrupt Status Register - 2
0 x 18
RxE3 LAPD Control Register
0 x 34
TxE3 LAPD Status/Interrupt Status
General Flow of Framer Chip Interrupt Servicing
Determine the Channel Requesting the Interrupt
When any of the conditions, presented in Table 6 occurs, (if their Interrupts is enabled), then the Framer
will generate an interrupt request to the local µP/µC
by asserting the active-low interrupt request output
pin, INT. Shortly after the local µP/µC has detected
the activated INT signal, it will enter into the appropriate user-supplied interrupt service routine. The first
task for the local µP/µC, while running this interrupt
service routine, may be to isolate the source of the interrupt request down to the device level (e.g., the
XRT72L53 Framer), if multiple peripheral devices exist in the user's system. However, once the interrupting peripheral device has been identified, the next
task for the local µP/µC is to determine exactly what
feature or functional section within the device requested the interrupt.
If the interrupting device turns out to be the
XRT72L53 3-Channel DS3/E3 Framer IC;
Determine the Functional Block(s) Requesting the
Interrupt
If the interrupt device turns out to be the XRT72L53
DS3/E3 Framer IC, then the local µC/µP must determine which functional block requested the interrupt.
Hence, upon reaching this state, one of the very first
things that the local µC/µP must do within the user
supplied Framer Interrupt Service routine, is to perform a read of the Block Interrupt Status Register
(Address = 0x05) within the XRT72L53 Framer device. The bit format of the Block Interrupt Status register is presented below.
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BLOCK INTERRUPT STATUS REGISTER (ADDRESS = 0X05)
BIT 7
BIT 6
BIT 5
RxDS3/E3
Interrupt
Status
BIT 4
BIT 3
BIT 2
Not Used
BIT 1
BIT 0
TxDS3/E3
Interrupt
Status
One-Second
Interrupt
Status
RO
RO
RO
RO
RO
RO
RO
RO
0
0
0
0
0
0
0
0
The Block Interrupt Status Register presents the interrupt request status of each functional block, within
the chip. The purpose of the Block Interrupt Status
Register is to help the local µP/µC identify which functional block(s) has requested the interrupt. Whichever
bit(s) are asserted in this register, identifies which
block(s) have experienced an interrupt-generating
condition as presented in Table 6. Once the local µP/
µC has read this register, it can determine which
branch within the interrupt service routine that it must
follow, in order to properly service this interrupt.
The Framer further supports the Functional Block hierarchy by providing the Block Interrupt Enable Register (Address = 0x04). The bit format of this register
is identical to that for the Block Interrupt Status register, and is presented below for the sake of completeness.
BLOCK INTERRUPT ENABLE REGISTER (ADDRESS = 0X04)
BIT 7
BIT 6
BIT 5
RxDS3/E3
Interrupt
Status
BIT 4
BIT 3
BIT 2
Not Used
BIT 1
BIT 0
TxDS3/E3
Interrupt
Status
One-Second
Interrupt
Status
R/W
RO
RO
RO
RO
RO
R/W
R/W
0
0
0
0
0
0
0
0
The Block Interrupt Enable register allows the user to
individually enable or disable the interrupt requesting
capability of the functional blocks, within the Framer
IC. If a particular bit-field, within this register contains
the value "0", then the corresponding functional block
has been disabled from generating any interrupt requests. Conversely, if that bit-field contains the value
"1", then the corresponding functional block has been
enabled for interrupt generation (e.g., those potential
interrupts, within the enabled functional block that are
enabled at the source level, are now enabled). The
user should be aware of the fact that each functional
block, within the Framer IC contains anywhere from 1
to 12 potential interrupt sources. Each of these lower
level interrupt sources contain their own set of interrupt enable bits and interrupt status bits, existing in
various on-chip registers.
Interrupt Service Routing Branching: after reading the Block Interrupt Status Register.
The contents of the Block Interrupt Status Register
identify which of 3 functional blocks (within the Framer IC) has requested interrupt service. The local µP
should use this information in order to determine
where, within the Interrupt Service Routing, program
control should branch to. Table 10 can be viewed as
an interrupt service routine guide. It lists each of the
Functional Blocks, that contain a bit-field in the Block
Interrupt Status Register. Additionally, this table also
presents a list and addresses of corresponding onchip Registers that the Interrupt Service Routine
should branch to and read, based upon the Interrupting Functional Block.
Table 10, Table 11, and Table 12 presents the Interrupt Service Routine guide for DS3, E3/ITU-T G.832
and E3/ITU-T G.751 applications, respectively.
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TABLE 10: INTERRUPT SERVICE ROUTINE GUIDE (FOR DS3 APPLICATIONS)
INTERRUPTING
FUNCTIONAL BLOCK
Receive Section
Transmit Section
THE NEXT REGISTERS TO BE READ DURING THE INTERRUPT SERVICE
ROUTINE
RxDS3 Interrupt Status Register
REGISTER ADDRESS
0 x 013
RxDS3 FEAC Interrupt Enable/Status Register
0 x 17
RxDS3 LAPD Control Register
0 x 18
TxDS3 FEAC Configuration and Status Register
0 x 31
TxDS3 LAPD Status/Interrupt Register
0 x 34
TABLE 11: INTERRUPT SERVICE ROUTINE GUIDE (FOR E3, ITU-T G.832 APPLICATIONS)
INTERRUPTING
FUNCTIONAL BLOCK
Receive Section
Transmit Section
THE NEXT REGISTERS TO BE READ DURING THE INTERRUPT SERVICE
ROUTINE
REGISTER ADDRESS
RxE3 Interrupt Status Register - 1
0 x 014
RxE3 Interrupt Status Register - 2
0 x 15
RxE3 LAPD Control Register
0 x 18
TxE3 LAPD Status and Interrupt Register
0 x 34
TABLE 12: INTERRUPT SERVICE ROUTINE GUIDE (FOR E3, ITU-T G.751 APPLICATIONS)
INTERRUPTING
FUNCTIONAL BLOCK
Receive Section
Transmit Section
THE NEXT REGISTERS TO BE READ DURING THE INTERRUPT SERVICE
ROUTINE
REGISTER ADDRESS
RxE3 Interrupt Status Register - 1
0 x 014
RxE3 Interrupt Status Register - 2
0 x 15
RxE3 LAPD Control Register
0 x 18
TxE3 LAPD Status and Interrupt Register
0 x 34
Once the Microprocessor/Microcontroller has read
the register that corresponds to the interrupting
source within the Framer, the following things will
happen.
1. The Asserted Interrupt Status bit-fields within this
register will be reset upon read.
2. The Asserted bit-field, within the Block Interrupt
Status register will be reset.
3. The Framer device will negate the INT (Interrupt
Request) output pin, by driving this output pin
"High”.
2.7.1 Automatic Reset of Interrupt Enable Bits
Occasionally, the user’s system (which includes the
Framer) may experience a fault condition, such that a
Framer Interrupt Condition will continuously exist. If
this particular interrupt condition has been enabled
(within the Framer IC) then the Framer will generate
an interrupt request to the MIcroprocessor/Microcontroller. Afterwards, the Microprocessor/Microcontroller
will attempt to service this interrupt by reading the
Block Interrupt Status register and the subsequent
source level interrupt status registers. Additionally,
the Microprocessor/Microcontroller will attempt to
perform some system-related tasks in order to try to
resolve those conditions causing the interrupt. After
the Microprocessor/Microcontroller has attempted all
of these things, the Framer IC will negate the INT output pin. However, because the system fault still remains, the conditions causing the Framer to issue this
interrupt request, also still exists. Consequently, the
Framer will generate another interrupt request, which
forces the Microprocessor/Microcontroller to once
again attempt to service this interrupt. This phenome136
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THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
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In order to prevent this phenomenon from ever occurring, the Framer IC allows the user to automatically
reset the interrupt enable bits, following their activation. The user can implement this feature by writing
the appropriate value into Bit 3 (Interrupt Enable Reset) within the Framer Operating Mode register, as illustrated below.
non quickly results in the local Microprocessor/Microcontroller being tied up in a continuous cycle of executing this one interrupt service routine. Consequently, the local Microprocessor/Microcontroller (along
with portions of the overall system) now becomes
non-functional.
FRAMER OPERATING MODE REGISTER (ADDRESS = 0X00)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
Local
Loop-Back
DS3/E3
Internal
LOS Enable
RESET
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
0
0
Interrupt
Frame Format
Enable Reset
BIT 1
BIT 0
TimRefSel[1:0]
• Reading various other Performance Monitor registers.
Writing a “1” to this bit-field configures the Framer to
automatically disable a given interrupt, following its
activation. Writing a “0” to this bit-field configures the
Framer to leave the Interrupt Enable bit as is, following interrupt activation.
• Writing a new PMDL Message into the Transmit
LAPD Message buffer. After the LAPD Transmitter
has been enabled and commanded to initiate transmission of the LAPD Message frame (containing
the PMDL Message, residing within the Transmit
LAPD Message buffer), the LAPD Transmitter will
continue to re-transmit this same LAPD Message
frame, repeatedly at One-Second intervals, until it
has been disabled. If a new PMDL message is written into the Transmit LAPD Message buffer immediately following the occurrence of a One-Second
Interrupt, then this will ensure that this Write activity
will not interfere with this periodic transmission of
the LAPD Message frames.
If the Automatic Reset of Interrupt Enable Bits feature
is implemented, then configure the Microprocessor/
Microcontroller to go back and re-enable these interrupts at a later time.
2.7.2 One-Second Interrupts
The Block Interrupt Status register, and Block Interrupt Enable register each contain a bit-field for the
One-Second Interrupt. If this interrupt is enabled
(within the Block Interrupt Enable register), then the
Framer will automatically generate an interrupt request to the Microprocessor/Microcontroller repeatedly at one-second intervals. At a minimum, the user’s interrupt service routine must service this interrupt by reading the Block Interrupt Status register
(Address = 0x05). Once the Microprocessor/Microcontroller has read this register, then the following
things will happen.
Notes regarding the Block Interrupt Enable and Block
Interrupt Status Registers:
1. The One-Second Interrupt bit-field, within the
Block Interrupt Status register, will be reset to “0”.
2. The Framer will negate the INT (Interrupt
Request) output pin.
The purpose of providing this One-Second interrupt is
to allow the Microprocessor/Microcontroller the opportunity to perform certain tasks at One-Second intervals. This can accomplished by including the necessary code (for these various tasks) as a part of the
interrupt service routine, for the One-Second type interrupt. Some of these tasks could include:
• Reading in the contents of the One-Second Performance Monitor registers.
137
1. The Block Interrupt Enable Register allows for
globally disable all potential interrupts within
either the Transmit or Receive sections, by writing
a “0” into the appropriate bit-field of this register.
However, the Block Interrupt Enable register does
not allow for globally enabling all potential interrupts within a given functional block. In other
words, enabling a given functional block does not
automatically enable all of its potential interrupt
sources. Those potential interrupt sources that
have been disabled at the source level will remain
disabled, independent of the status of their associated functional blocks.
2. The Block Interrupt Enable register is set to
“0x00” upon power or reset. Therefore, some “1’s”
must be written into this register, in order to
enable some of the interrupts.
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THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
XRT72L53
PRELIMINARY
REV. P1.1.7
PORT 0 (P0.0 - P0.7)
The remaining registers, listed in Table 10, Table 11
and Table 12 will be presented in the discussion of
the functional blocks, within the XRT72L53 Framer IC.
These discussions will present more details about the
interrupt causes and how to properly service. them.
This port is a dual-purpose port on pins 32-39 of the
8051 IC. In minimal component designs, it is used as
a general purpose I/O port. For larger designs with
external memory, it becomes a multiplexed address
and data bus (AD0 - AD7).
2.8 INTERFACING THE FRAMER TO AN INTEL-TYPE
MICROPROCESSOR
PORT 1 (P1.0 - P1.7)
The Framer can be interfaced to either Intel-type or
Motorola-type Microprocessor/Microcontrollers. The
following sections will provide one example for each
type of processor. This section discusses how to interface the XRT72L53 DS3/E3 Framer IC to the 8051
Microcontroller.
Port 1 is a dedicated port on pins 1 - 8. The pins, designated at P1.0, P1.1, ... P1.7 are available for interfacing as required. No alternative functions are assigned for Port 1 pins, thus they are used solely for interfacing external devices. Exceptions are the 8032
and 8052 IC’s, which use P1.0 and P1.1 as either as
I/O lines or as external inputs to the third timer.
The 8051 Microcontroller
The 8051 family of microcontrollers is manufactured
by Intel and comes with a variety of amenities. Some
of these amenities include:
PORT 2 (P2.0 - P2.7)
• 4k bytes of ROM
Port 2 (pins 21 - 28) is a dual-purpose port that can
function as a general purpose I/O, or as the high-byte
of the address bus for designs with external code
memory of more than 256 bytes of external data
memory (A8 - A15).
• 128 bytes of RAM
PORT 3
The 8051 Microcontroller consists of 4 - 8-bit I/O
Ports. Some of these ports have alternate functions
as will be discussed below.
Port 3 is a dual purpose port on pins 10 - 17. In addition to functioning as general purpose I/O, these pins
have multiple functions. Each of these pins have an
alternate purpose, as listed in Table 13 below.
• On-chip Serial Port
• Four (4) 8-bit I/O ports (P0 - P3)
TABLE 13: ALTERNATE FUNCTIONS OF PORT 3 PINS
BIT
NAME
ALTERNATE FUNCTION
P3.0
RXD
Receive Data for Serial Port
P3.1
TXD
Transmit Data for Serial Port
P3.2
INT0*
External Interrupt 0
P3.3
INT1*
External Interrupt 1
P3.4
T0
Timer/Counter 0 External Input
P3.5
T1
Timer/Counter 1 External Input
P3.6
WR*
External Data/Memory Write Strobe
P3.7
RD*
External Data/Memory Read Strobe
The 8051 also has numerous additional pins which
are relevant to interfacing to the XRT72L53 DS3/E3
UNI or other peripherals. These pins are:
put or output during the second half of the memory
cycle, when the data transfer takes place.
ALE - Address Latch Enable
INT0* and INT1* are external interrupt request inputs
to the 8051 Microcontroller. Each of these interrupt
pins support direct interrupt processing. In this case,
the term direct means that if one of these inputs are
asserted, then program control will automatically
branch to a specific (fixed) location in code memory.
This location is determined by the circuit design of the
INT0* (P3.2) and INT1* (P3.3)
If Port 0 is used in its alternative mode -as the data
bus and the lower byte of the address bus -- ALE is
the signal that latches the address into an external
register during the first half of a memory cycle. Once
this is done, Port 0 lines are then available for data in-
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8051 Microcontroller IC and cannot be changed.
Table 14 presents the location (in code memory)
where the program control will branch to, if either of
these inputs are asserted.
TABLE 14: INTERRUPT SERVICE ROUTINE LOCATION (IN CODE MEMORY) FOR THE INT0* AND INT1* INTERRUPT
INPUT PINS
INTERRUPT PIN
BRANCH TO LOCATION (IN SYSTEM MEMORY)
INT0*
0x0003
INT1*
0x0013
ing the first half of a memory cycle, Port 0 will operate
as the lower address byte. During the second half of
the memory cycle, Port 0 will operate as the bi-directional data bus. Port 2 will be used as the upper address byte. ALE and the use of a 74HC373 transparent latch can be used to de-multiplex the Address and
Data bus signals.
Therefore, if either one of these inputs are used as an
interrupt request input, then the appropriate interrupt
service routine or unconditional branch instruction (to
the interrupt service routine) must be located at one
of these address locations.
If the 8051 Microcontroller IC is required to interface
to external components in the data memory space of
sizes greater than 256 bytes, then both Ports 0 and 2
must be used as the address and data lines. Port 0
will function as a multiplexed address/data bus. Dur-
Figure 37 presents a schematic illustrating how the
XRT72L53 DS3/E3 Framer can be interfaced to the
8051 Microcontroller IC.
FIGURE 37. SCHEMATIC DEPICTING HOW TO INTERFACE THE XRT72L53 DS3/E3 FRAMER IC TO THE 8051 MICROCONTROLLER
U4
U1
WR
RD
AD0
AD1
AD2
AD3
AD4
AD5
AD6
AD7
HW_RESET*
16
17
39
38
37
36
35
34
33
32
L18
L20
K20
K19
K18
K17
J20
J19
ALE
INT0
INT1
12
13
5.0V
XRT72L53_INT*
3
4
7
8
13
14
17
18
A8
A9
A10
A11
A12
A13
A14
A15
8051
30
21
22
23
24
25
26
27
28
R19
RESET
WRB_RW
RDB_DS
D0
D1
D2
D3
D4
D5
D6
D7
ALE_AS
U3
1D
2D
3D
4D
5D
6D
7D
8D
11
1
ALE
T19
P17
V20
5.0V
A8
A9
A10
ALE
1Q
2Q
3Q
4Q
5Q
6Q
7Q
8Q
2
5
6
9
12
15
16
19
A8
A9
A10
LE
OE
20
VCC
R20
P18
P19
P20
N18
N19
N20
M17
M18
M19
M20
J17
A0
A1
A2
A3
A4
A5
A6
A7
A8
A9
A10
Rdy_Dtck
74HC373
XRT72L53_INT*
From Address Decoder
To Address Decoder
H20
R18
T20
INT
CS
MOTO/INTEL
XRT72L53
The circuitry in Figure 37 will function as follows, during a Framer-request interrupt. The Framer would request an interrupt from the CPU by asserting its ac-
tive low INT output pin. This will cause the INT0* input
pin of the CPU to go "Low”. When this happens the
8051 CPU will finish executing its current instruction,
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2.9 INTERFACING THE FRAMER IC TO A MOTOROLATYPE MICROPROCESSOR
This section discusses how to interface the
XRT72L53 DS3/E3 Framer IC to the MC68000 Microprocessor.
and will then branch program control to the Framer interrupt service routine. In the case of Figure 37, the
interrupt service routine will be located in 0x0003 in
code memory. The 8051 CPU does not issue an Interrupt Acknowledge signal back to the Framer IC. It
will just begin processing through the Framer’s interrupt service routine. One the CPU has eliminated the
cause(s) of the interrupt request, the Framer’s INT
output pin will be negated (e.g., go "High”) and the
CPU will return from the Interrupt Service Routine
and resume normal operation.
Figure 38 presents a schematic on how to interface
the XRT72L53 DS3/E3 Framer IC to the MC68000
Microprocessor, over an 8-bit wide bi-directional data
bus.
FIGURE 38. SCHEMATIC DEPICTING HOW TO INTERFACE THE XRT72L53 DS3/E3 FRAMER IC TO THE MC68000
MICROPROCESSOR
U5
U6
VPA
FC0
FC1
FC2
AS
UDS
LDS
A1
A2
A3
A4
A5
A6
A7
A8
D[15:8]
15
14
9
7
6
HPRI/BIN
10 0/Z10
11 1/Z11
12 2/Z12
13 3/Z13
14 4/Z14
15 5/Z15
16 6/Z16
17 7/Z17
10
11
12
13
1
2
3
4
V18
EN
XRT72L53 INTERRUPT REQUEST
V20
R19
DATA_STROBE*
ADDRESS_STROBE*
5
74HC148
25
24
23
U12A
3
21
U10
28
27
26
BIN/OCT
1
2
4
6
7
8
L18
L20
K20
K19
K18
K17
J20
J19
U9
1 18 1
2
4
1
2
3
6
4
5
5V
29
30
31
32
33
34
35
36
&
1
2
&
4
U13B
1
R20
P18
P19
P20
N18
N19
N20
M17
M18
M19
M20
3
74HC04
74AHCT00
0
1
2
3
4
5
6
7
EN
15
14
13
12
11
10
9
7
H20
RESET
WRB_RW
Rdy_Dtck
D0
D1
D2
D3
D4
D5
D6
D7
RDB_DS
ALE_AS
A0
A1
A2
A3
A4
A5
A6
A7
A8
A9
A10
INT
2
IPL0
IPL1
IPL2
5
4
3
2
1
64
63
62
61
60
59
58
57
56
55
54
74ACT138
U13A
ADDRESS_STROBE*
1
D0
D1
D2
D3
D4
D5
D6
D7
D8
D9
D10
D11
D12
D13
D14
D15
T19
P17
J17
74HC04
From Address Decoder
R18
CS
DATA_STROBE*
1
RESET
R/W
DTACK
18
9
10
3.3V
T20
MOTO/INTEL
DECODED FUNCTION CODE
A9
A10
A11
A12
A13
A14
A15
A16
A17
A18
A19
A20
A21
A22
A23
MC68000
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
XRT72L53
U11
5V
1
2
3
6
4
5
BIN/OCT
1
2
4
&
EN
0
1
2
3
4
5
6
7
15
14
13
12
11
10
9
7
74ACT138
To Address Decoder
In general, the approach to interfacing these two devices is straightforward. However, the XRT72L53
DS3/E3 Framer IC does not provide an interrupt vector to the MC68000 during an Interrupt Acknowledge
cycle. Therefore, the design must be configured to
support auto-vectored interrupts. Auto-vectored interrupt processing is a feature offered by the MC68000
Family of Microprocessors, where, if the microprocessor knows (prior to any IACK cycle) the Interrupt Level of this current interrupt, and that the interrupting
peripheral does not support vectored interrupts, then
the Microprocessor will generate its own Interrupt
Vector. The schematic shown in Figure 38, has been
configured to support auto-vectored interrupts.
Functional Description of Circuit illustrated in
Figure 38.
When the XRT72L53 DS3/E3 Framer IC generates
an Interrupt, the INT output will toggle "Low”. This will
force Input 6, of the Interrupt Priority Encoder chip
140
XRT72L53
THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
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PRELIMINARY
REV. P1.1.7
(U4) to also toggle "Low”. In response to this, the Interrupt Priority Encoder chip will set its three outputs
to the following states: A2 = ‘0’, A1 = ‘0’ and A0 = ‘1’
(which is the number 6 in Highinverted binary format).
The state of three output pins will be read by the active-low interrupt request inputs of the Microprocessor (IPL2, IPL1, IPL0). When the MC68000 Microprocessor detects this value at its three interrupt request
inputs, it will know two things.
1. An interrupt request has been issued by one of
the peripheral devices.
2. The interrupt request is a Level 6 interrupt
request (due to the values of the A2 - A0 outputs
from the Interrupt Priority Encoder IC).
Once the MC68000 Microprocessor has determined
these two things it will initiate an Interrupt Acknowledge (IACK) cycle by doing the following:
1. Identify this new bus cycle as an interrupt service
routine by setting all of its Function Code output
pins (FC2 - FC0) to "High”.
2. Placing the interrupt level on the Address output
pins A[3:1].
When the MC68000 Microprocessor has toggled all
of its Function Code output pin "High”, the Function
Code Decoder chip (U3) will read this value from the
FC2 - FC0 pins as being the binary value for 7. As a
result, U3 will assert its active-low Y7 output pin. At
the same time, the address lines A[3:1] are carrying
the current Interrupt Level of this IACK cycle (level =
6, or “110” in this example) and applying this value to
the A, B, and C inputs of the IACK Level Decoder chip
(U5). Initially, all of the outputs of U5 are tri-stated.
Due to the fact that its active-low G2A and G2B inputs
are negated (e.g., at a logic "High”). However, when
the MC68000 Microprocessor begins the IACK cycle,
it will assert its Address Strobe (AS*) signal. This action will result in asserting the G2A input pin of U5.
Additionally, since the Function Code Decoder chip
has also asserted its Y7 output pin this will, in turn,
assert the G2A input pin of U5. At this point, the output of U5 will no longer be tri-stated. U5 will read in
the contents of its A, B, and C inputs, and assert the
active-low VPA* (Valid Peripheral Address) input pin
of the MC68000. Anytime the MC68000 detects its
VPA* pin being asserted during an IACK cycle, it
knows that this is an Auto-Vectored Interrupt cycle.
Further, it also knows that it will not receive an interrupt vector from the peripheral device (e.g., the
XRT72L53 DS3/E3 Framer IC, in this case), and that
it must generate its own vector. In the very next bus
cycle, the MC68000 is going to implement a pseudoread of the data bus. However, in reality, no data will
be read from the XRT72L53. The MC68000 will instead have determined that since this current IACK
cycle is an Auto-Vectored - Level 6 Interrupt cycle,
which corresponds to Vector Number 30, within the
MC68000’s Exception Vector Table. Vector Number
30 corresponds to an Address Space of 0x78, in the
MC68000’s address space. In the case of this example, an unconditional branch statement (to the location of the XRT72L53 Interrupt Service Routine) is required to be placed at 0x78 in system memory.
Table 15 presents the Auto-Vector Table (e.g., the relationship between the Interrupt Level and the corresponding location in memory for this unconditional
branch statement) for the MC68000 Microprocessor.
TABLE 15: AUTO-VECTOR TABLE FOR THE MC68000 MICROPROCESSOR
INTERRUPT
LEVEL
VECTOR NUMBER
ADDRESS LOCATION (OF UNCONDITIONAL BRANCH INSTRUCTION - FOR INTERRUPT
SERVICE ROUTINE)
1
25
0x064
2
26
0x068
3
27
0x06C
4
28
0x070
5
29
0x074
6
30
0x078
7
31
0x07C
3.0 THE LINE INTERFACE AND SCAN SECTION
The Line Interface and Scan Section of the
XRT72L53 DS3/E3 Framer IC consists of 5 output
pins, 3 input pins, a Read/Write register, and a ReadOnly register.
The purpose of the Line Interface Drive and Scan
section is to permit the user to monitor and exercise
141
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THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. P1.1.7
control over many aspects of the XRT7300 DS3/E3/
STS-1 LIU IC without having to develop the necessary off-chip glue-logic.
Figure 39 presents a simple circuit schematic that depicts how the XRT72L53 DS3/E3 Framer IC could be
interfaced to the XRT7300 DS3/E3/STS-1 LIU IC.
FIGURE 39. SCHEMATIC DEPICTING HOW TO INTERFACE THE XRT72L53 DS3/E3 FRAMER IC TO THE XRT73L03
DS3/E3/STS-1 LIU IC (ONE CHANNEL SHOWN)
RxAVDD_0
TxAVDD_0
DVDD_0
C3
C4
0.01uF
C5
0.01uF
0.01uF
C2
0.01uF
U21
C5
B5
A3
C4
Rx_AIS_Ch_0
RxRED_ALARM_0
Rx_OOF_Ch_0
Rx_LOS_Ch_0
F20
D20
F19
T20
RxFRAME_0
RxFRAME_CLK_0
RxDATA_IN_0
48
RxAIS_0
RxRED_0
RxOOF_0
RxLOS_0
RxFrame_0
RxClk_0
RxSer_0
MOTO
R8 4.7K
F2
RxPOS_0
RxNEG_0
67
42
51
R7 100
F3
50
F1
49
B8
D9
57
55
C7
A5
C6
C9
C3
61
62
63
64
96
RxAVDD0
TxAVDD0
RxDVDD0
TxAVDD0
28
37
LOSTHR_0
HOST/HW
RPOS0
J1
72
RTIP0
6
4
RxLineClk_0
D7
D6
D5
D4
D3
D2
D1
D0
RLOL_0
ExtLOS_0
A[10:0]
M20
M19
M18
M17
N20
N19
N18
P20
P19
P18
R20
J17
R19
V20
P17
R18
H20
READY_OUT*
ALE
RD*
WR*
XRT72L53_CS*
XRT72L53_INT*
T19
HW_RESET*
R9
100
T18
A10
A9
A8
A7
A6
A5
A4
A3
A2
A1
A0
Rdy_Dtck
ALE_AS
RDB_DS
WRB_RW
CSB
INT
RESETB
LLOOP_0
REQB_0
TAOS_0
DMO_0
TxLEV_0
B7
RLOOP_0
ENCODIS_0 (TxOFF_0)
TxPOS_0
TxNEG_0
TxLineClk_0
RCLK0
71
RRING0
3
T3001
R2
R1
37.4
37.4
RLOL_0
RLOS_0
CS
SCLK
SDI
SDO
REG_RESET*
C1
0.01uF
XRT71D03_CS* (Optional)
B2
117
C1
33
D1
32
E2
34
47
TxOFF_0
R3
29
TTIP0
TPDATA_0
J2
1
36
T1 6
1
BNC
TNDATA_0
2
J19
J20
K17
K18
K19
K20
L20
L18
BNC
1
RNEG0
D[7:0]
TxFRAME_0
44.736MHz
TxDATA_OUT_0
T2 1
2
70
U19
4
T3001
R5
30
MTIP0
3
R4
27
TRING0
TCLK_0
EXCLK_0
NIBBLEINTF
36
270
E20
G 4 TxFrame_0
E18 TxInClk_0
TxSER_0
54
73
26
TxAGND0
RxAGND0
270
39
TxAGND0
RxDGND0
R6
31
MRING0
XRT72L53_Ch_0
XRT73L03IV_Ch_0
3.1 BIT-FIELDS WITHIN THE LINE INTERFACE DRIVE
REGISTER
As mentioned above, the Line Interface Drive and
Scan section consists of five output pins and three in-
put pins. The logic state of the output pins are controlled by the contents within the Line Interface Drive
register, as depicted below.
LINE INTERFACE DRIVE REGISTER (ADDRESS = 0X80)
BIT 7
BIT 6
ILOOP
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
REQ
TAOS
ENCODIS
TXLEV
RLOOP
LLOOP
R/O
R/O
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
0
1
0
0
0
The role of each of these bit-fields are their corresponding output pins are depicted below.
Bit 7 - ILOOP (Internal Remote Loop-back)
This Read/Write bit-field allows configuring the corresponding channel (within the XRT72L53) to operate
in the Internal Remote Loop-back Mode. Once the
channel is configured to operate in this remote loopback mode, then the RxPOS[n], RxNEG[n] and RxLi142
XRT72L53
THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
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PRELIMINARY
REV. P1.1.7
If this signal is toggled "High”, then the internal B3ZS/
HDB3 encoder (within the XRT7300) will be disabled.
Conversely, if this output signal is forced to toggle
"Low”, then the internal B3ZS/HDB3 encoder (within
the XRT7300) will be enabled.
neClk[n] signals will be routed directly to the TxPOS[n], TxNEG[n] and TxLineClk[n] signals.
Setting this bit-field to “1” configures the channel to
operate in the Remote Loop-Back Mode.
Bit 5 - REQ - (Receive Equalization Enable/Disable
Select)
This Read/Write bit-field allows for control of the state
of the REQ output pin of the Framer. This output pin is
intended to be connected to the REQ input pin of the
XRT7300 DS3/E3/STS-1 LIU IC. If this signal is toggled "High”, then the internal Receive Equalizer (within the XRT7300) will be disabled. Conversely, if the
this signal is toggled "Low”, then the Receive Equalizer (within the XRT7300) will be enabled.
The purpose of the internal Receive Equalizer (within
the XRT7300) is to compensate for the FrequencyDependent attenuation (e.g., cable loss), that a line
signal will experience as it travels through coaxial cable, from the transmitting to the receiving terminal.
Writing a “1” to this bit-field causes the Framer to toggle the REQ output pin "High”. Writing a “0” to this bitfield causes the Framer to toggle the REQ output pin
"Low”.
For information on the criteria that should be used
when deciding whether to enable or disable the Receive Equalizer, please consult the XRT7300 DS3/
E3/STS-1 LIU IC Data Sheet.
NOTE: If the customer is not using the XRT7300 DS3/E3/
STS-1 IC, then this bit-field and the REQ output pin can be
used for other purposes.
Bit 4 - TAOS - (Transmit All Ones Signal)
This Read/Write bit-field allows for controlling the
state of the TAOS output pin of the Framer. This output pin is intended to be connected to the TAOS input
pin of the XRT7300 DS3/E3/STS-1 LIU IC. If this signal is toggled "High”, then the XRT7300 will transmit
an All Ones pattern onto the line. Conversely, if this
output signal toggles "Low” then the XRT7300 DS3/
E3/STS-1 LIU IC will proceed to transmit data based
upon the data that it receives via the TxPOS and TxNEG output pins (of the Framer IC).
Writing a “1” to this bit-field causes the TAOS output
pin to toggle "High”. Writing a “0” to this bit-field will
cause this output pin to toggle "Low”.
NOTE: If the customer is not using the XRT7300 DS3/E3/
STS-1 LIU IC, then this bit-field, and the TAOS output pin
can be used for other purposes.
Bit 3 - ENCODIS - (B3ZS/HDB3 Encoder Disable)
This Read/Write bit-field is used for controlling the
state of the ENCODIS output pin of the Framer. This
output pin is intended to be connected to the ENCODIS input pin of the XRT7300 DS3/E3/STS-1 LIU IC.
Writing a “1” to this bit-field causes the Framer IC to
toggle the Encodis output pin "High”. Writing a “0” to
this bit-field will cause the Framer IC to toggle this
output pin "Low”.
NOTES:
1. The B3ZS/HDB3 encoder, within the XRT7300 is
not to be confused with the B3ZS/HDB3 encoding
capabilities that exists within the Transmit DS3/E3
Framer block of the Framer IC.
2. It is advisable to disable the B3ZS/HDB3 encoder
(within the XRT7300 IC) if the Transmit and
Receive DS3/E3 Framer (within the XRT72L53) are
configured to operate in the B3ZS/HDB3 line code.
3. If the customer is not using the XRT7300 DS3/E3/
STS-1 LIU IC, then this bit-field and the Encodis
output pin can be used for other purposes.
4. It is permissible to tie both the ENCODIS and
DECODIS input pins (of the XRT7300) to the Encodis output pin of the XRT72L53 DS3/E3 Framer IC.
Bit 2 - TxLEV (Transmit Line Build-Out Enable/
Disable Select)
This Read/Write bit-field allows for the control of the
state of the TxLEV output pin of the Framer. This output pin is intended to be connected to the TxLEV input pin of the XRT7300 DS3/E3/STS-1 LIU IC.
Writing a “1” to this bit-field commands the Framer to
drive the TxLEV output pin "High”.
Writing a “0” to this bit-field commands the Framer to
drive this output signal "Low”.
If this signal is commanded to toggle "High”, then the
Transmit Line Build-Out circuitry, within the XRT7300
will be disabled. In this mode, the XRT7300 LIU IC
will generate unshaped (e.g., square) pulses out onto
the line, via the TTIP and TRING output pins.
Conversely, if this signal is commanded to toggle
"Low”, then the Transmit Line Build-Out circuitry, within the XRT7300 will be enabled. In this mode, the
XRT7300 will generate shaped pulses onto the line,
via the TTIP and TRING output pins.
In order to comply with the Isolated DSX-3 Pulse
Template requirements (per Bellcore GR-499CORE), it is advisable to set this bit-field to “0” if the
cable length (between the transmit output of the
XRT7300 and the DSX-3 Cross Connect System) is
less than 225 feet. Conversely, it is advisable to set
this bit-field to “1” if the cable length (between the
transmit output of the XRT7300 and the DSX-3 Cross
Connect System) is greater than 225 feet.
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THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
XRT72L53
PRELIMINARY
REV. P1.1.7
NOTE: If the customer is not using the XRT7300 DS3/E3/
STS-1 IC, then this bit-field and the TxLEV output pin can
be used for other purposes.
is intended to be connected to the RLOOP input pin
of the XRT73001 LIU IC.
The state of this bit-field (or pin) along with LLOOP
are used to configure the XRT7300 into one of four
(4) loop-back modes. The relationship of the values of
RLOOP, LLOOP and the resulting loop-back mode
(within the XRT7300) is tabulated below.
Bit 1 - RLOOP (Remote Loop-Back Select)
This Read/Write bit-field is used to control the state of
the RLOOP output pin of the Framer. This output pin
TABLE 16: THE RELATIONSHIP BETWEEN THE STATES OF RLOOP, LLOOP AND THE RESULTING LOOP-BACK MODE
WITH THE XRT7300
RLOOP
LLOOP
RESULTING LOOP-BACK MODE (WITHIN THE XRT7300 DS3/E3/STS-1 LIU IC)
0
0
Normal Mode (No Loop-back)
0
1
Analog Local Loop-back Mode
1
0
Remote Loop-back Mode
1
1
Digital Local Loop-back Mode
into this bit-field commands the Framer to toggle this
output signal "Low”.
Writing a “1” into this bit-field commands the Framer
to drive the RLOOP output signal "High”. Writing a “0”
into this bit-field commands the Framer to drive this
output signal "Low”.
For a detailed description of the XRT7300 LIU’s operation during each of these loop-back modes, please
see the XRT7300 DS3/E3/STS-1 LIU IC data sheet.
NOTE: If the customer is not using the XRT7300 DS3/E3/
STS-1 LIU IC, then this bit-field and the RLOOP output pin
can be used for other purposes.
Bit 0 - LLOOP (Local Loop-back Select)
This Read/Write bit-field is used to control the state of
the LLOOP output pin of the Framer. This output pin
is intended to be connected to the LLOOP input pin of
the XRT7300 DS3/E3/STS-1 LIU IC.
The state of this bit-field (or pin) along with RLOOP
are used to configure the XRT7300 into one of four
(4) loop-back modes. The relationship of the values of
RLOOP, LLOOP and the resulting loop-back modes
(within the XRT7300) are presented in Table 16.
Writing a “1” into this bit-field commands the Framer
to toggle the LLOOP output pin "High”. Writing a “0”
For a detailed description of the XRT7300 LIU’s operation during each of these loop-back modes, please
see the XRT7300 DS3/E3/STS-1 LIU IC Data Sheet.
NOTE: If the customer is not using the XRT7300 DS3/E3/
STS-1 LIU IC, then this bit-field and the LLOOP output pin
can be used for other purposes.
3.2 BIT-FIELDS WITHIN THE LINE INTERFACE SCAN
REGISTER
The XRT7300 contains three output pins which can
be made accessible to the Microprocessor Interface,
via the Line Interface Scan register. These three output pins are listed below.
• DMO - Drive Monitor Output
• RLOL - Receive Loss of Lock Indicator
• RLOS - Receive Loss of Signal Indicator.
The logic state of each of these input pins (or output
pins from the LIU) can be monitored by reading the
contents of the Line Interface Scan register, as depicted below.
LINE INTERFACE SCAN REGISTER (ADDRESS = 0X81)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
Not Used
BIT 2
BIT 1
BIT 0
DMO
RLOL
RLOS
R/O
R/O
R/O
R/O
R/O
R/O
R/O
R/O
0
0
0
0
0
0
0
0
The meaning/role of each of these bit-field and their
corresponding input pins are defined below.
Bit 2 - DMO - Drive Monitor Output
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THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
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PRELIMINARY
REV. P1.1.7
This Read-Only bit-field indicates the logic state of
the DMO output pin of the Framer. This input pin is intended to be connected to the DMO output pin of the
XRT7300 DS3/E3/STS-1 LIU IC. If this bit-field contains a logic “1”, then the DMO input pin is "High”.
The XRT7300 DS3/E3/STS-1 LIU IC will set this pin
"High” if the Transmit Driver Monitor circuitry (within
the XRT7300) has not detected any bipolar signals at
the MTIP and MRING inputs (of the XRT7300) within
the last 128 + 32 bit periods.
Conversely, if this bit-field is set to “0”, then the DMO
input pin is "Low”. The XRT7300 DS3/E3/STS-1 LIU
IC will set this pin "Low” if bipolar signals are being
detected at the MTIP and MRING input pins.
For more information on the use/purpose of the Drive
Monitor feature, within the XRT7300 LIU IC, please
see the XRT7300 DS3/E3/STS-1 LIU IC Data Sheet.
NOTE: If this customer is not using the XRT7300 DS3/E3/
STS-1 LIU IC, then this register bit-field and input pin can
be used for a variety of other purposes.
Bit 1 - RLOL - Receive Loss of Lock
This Read-Only bit-field indicates the logic state of
the RLOL input pin of the Framer. This input pin is intended to be connected to the RLOL output pin of the
XRT7300 DS3/E3/STS-1 LIU IC. If this bit-field contains a logic “1”, then the RLOL input pin is "High”.
The XRT7300 LIU IC will drive this pin "High” if the
clock recovery phase locked loop circuitry (within the
XRT7300) has lost lock with the incoming DS3 or E3
data-stream and is not properly recovering clock and
data.
Conversely, if this bit-field contains a logic “0”, then
the RLOL input pin is "Low”. The XRT7300 DS3/E3/
STS-1 LIU IC will hold this pin "Low” for as long as
this clock recovery phase-locked-loop circuit (within
the XRT7300) is properly locked onto the incoming
DS3 or E3 data stream and is properly recovering
clock and data from this data stream.
Bit 0 - RLOS- Receive Loss of Signal
This Read-Only bit-field indicates the logic state of
the RLOS input pin of the Framer. This input pin is intended to be connected to the RLOS output pin of the
XRT7300 DS3/E3/STS-1 LIU IC. If this bit-field contains a logic “1”, then the RLOS input pin is "High”.
The XRT7300 LIU IC will drive this signal "High” if it is
currently declaring an LOS (Loss of Signal) condition.
Conversely, if this bit-field contains a logic “0”, then
the RLOS input pin is "Low”. The XRT7300 LIU IC will
drive this signal "Low”, if it is NOT currently declaring
an LOS (Loss of Signal) condition.
For more information on the LOS Declaration/Clearance criteria, used by the XRT7300, please see the
XRT7300 DS3/E3/STS-1 LIU IC Data Sheet.
NOTE: Asserting the RLOS input pin will cause the Framer
to generate a Change in LOS Condition interrupt and
declare an LOS (Loss of Signal) condition to the Microprocessor/Microcontroller. Therefore, tit is not advisable to use
the RLOS input pin as a General Purpose Input pin.
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THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. P1.1.7
• Section 6.0 - E3, ITU-T G.832 Operation of the
XRT72L53
XRT72L53 CONFIGURATION
The XRT72L53 DS3/E3 Framer IC can be configured
to support any of the following four framing formats.
• Section 7.0 - Framer Local Loop-back Mode
Operation
• DS3/C-Bit Parity
• Section 8.0 - High Speed HDLC Controller Mode
of Operation
• DS3/M13
• E3/ITU-T G.832
4.0 DS3 OPERATION OF THE XRT72L53
This section will discuss in detail, the operation of the
XRT72L53 Framer IC, when it has been configured to
operate in the DS3 Mode.
• E3/ITU-T G.751
As a consequence, the discussion of the XRT72L53
Framer IC will be organized as follows:
• Section 4.0 - DS3 Mode Operation of the
XRT72L53
Configuring the XRT72L53 to Operate in the DS3
Mode
• Section 5.0 - E3, ITU-T G.751 Operation of the
XRT72L53
The XRT72L53 can be configured to operate in the
DS3 Mode by writing a "1" into bit-field 6 within the
Framer Operating Mode register, as illustrated below.
FRAMER OPERATING MODE REGISTER (ADDRESS = 0X00)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT2
Local Loopback
DS3/E3*
Internal LOS
Enable
RESET
Interrupt
Enable Reset
Frame Format
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
x
1
x
0
x
x
x
x
Prior to describing the functional blocks within the
Transmit and Receive Sections of the XRT72L53, it is
important to describe the following two framing formats.
BIT 1
BIT 0
TimRefSel[1:0]
56 bits are overhead and the remaining 4704 bits are
payload bits. The payload data is formatted into packets of 84 bits and the overhead (OH) bits are inserted
between these payload packets. The XRT72L53
Framer supports the following two DS3 framing formats:
• M13
• C-Bit Parity
• C-bit Parity
4.1 DESCRIPTION OF THE DS3 FRAMES AND ASSOCIATED OVERHEAD BITS
The role of the various overhead bits are best described by discussing the DS3 Frame Format as a
whole. The DS3 Frame contains 4760 bits, of which
• M13
Figures 40 and 41 present the DS3 Frame Format for
C-bit Parity and M13, respectively.
FIGURE 40. DS3 FRAME FORMAT FOR C-BIT PARITY
X
I
F1
I
AIC
I
F0
I
NA
I
F0
I
FEAC
I
F1
I
NA
I
F0
I
UDL
I
F1
I
I
X
I
F1
I
UDL
I
F0
I
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FIGURE 40. DS3 FRAME FORMAT FOR C-BIT PARITY
P
I
F1
I
CP
I
F0
I
CP
I
F0
I
CP
I
F1
I
P
I
F1
I
FEBE
I
F0
I
FEBE
I
F0
I
FEBE
I
F1
I
M0
I
F1
I
DL
I
F0
I
DL
I
F0
I
DL
I
F1
I
M1
I
F1
I
UDL
I
F0
I
UDL
I
F0
I
UDL
I
F1
I
M0
I
F1
I
UDL
I
F0
I
UDL
I
F0
I
UDL
I
F1
I
X = Signaling bit for network control
NA = reserved for network application
I = Payload Information (84 bit packets)
FEAC = Far End Alarm and Control
Fi = Frame synchronization bit with logic value i
DL = Data Link
P = Parity bit
CP = CP (Path)-bit parity
Mi = Multiframe synchronization bit with logic value i
FEBE = Far End Block Error
AIC = Application Identification Channel
UDL = User Data Link
FIGURE 41. DS3 FRAME FORMAT FOR M13
X
I
F1
I
C11
I
F0
I
C12
I
F0
I
C13
I
F1
I
I
X
I
F1
I
C21
I
F0
I
C22
I
F0
I
C23
I
F1
I
P
I
F1
I
C31
I
F0
I
C32
I
F0
I
C33
I
F1
I
P
I
F1
I
C41
I
F0
I
C42
I
F0
I
C43
I
F1
I
M0
I
F1
I
C51
I
F0
I
C52
I
F0
I
C53
I
F1
I
M1
I
F1
I
C61
I
F0
I
C62
I
F0
I
C63
I
F1
I
M0
I
F1
I
C71
I
F0
I
C72
I
F0
I
C73
I
F1
I
X = Signaling bit for network control
Mi = multiframe synchronization bit with logic values i
I = Payload Information (84 bit packets)
The user can choose between these two frame formats, by writing the appropriate data to bit 2 of the
Framer Operating Mode Register (Address = 0x00),
as depicted below.
Fi = Frame synchronization bit with logic value i
Cij = jth stuff code bit of ith channel
P = Parity bit
FRAMER OPERATING MODE REGISTER (ADDRESS = 0X00)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT2
Local Loopback
DS3/E3*
Internal LOS
Enable
RESET
Interrupt
Enable Reset
Frame Format
R/W
R/W
R/W
R/W
R/W
R/W
147
BIT 1
BIT 0
TimRefSel[1:0]
R/W
R/W
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FRAMER OPERATING MODE REGISTER (ADDRESS = 0X00)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT2
BIT 1
BIT 0
x
1
x
0
x
x
x
x
Table 17 lists the relationship between the value of
the this bit-field and the resulting DS3 Frame Format.
TABLE 17: THE RELATIONSHIP BETWEEN THE CONTENT
OF BIT 2, (C-BIT PARITY*/M13) WITHIN THE FRAMER
OPERATING MODE REGISTER AND THE RESULTING DS3
FRAMING FORMAT
BIT 2
DS3 FRAME FORMAT
0
C-Bit Parity
1
M13
NOTE: This bit setting also configures the frame format for
both the Transmit and Receive Section of the XRT72L53.
Each of the two DS3 Frame Formats, as presented in
Figure 40 and Figure 41, constitute an M-frame (or a
full DS3 Frame). Each M-frame consists of 7 - 680 bit
F-frames (sometimes referred to as, subframes). In
Figure 40 and 41, each F-frame is represented by
the individual rows of payload and overhead bits.
Each F-frame can be further divided into 8 blocks of
85 bits, with 84 of the 85 bits available for payload information and the remaining one bit used for frame
overhead.
Differences Between the M13 and C-Bit Parity
Frame Formats
The frame formats for M13 and C-bit Parity are very
similar. However, the main difference between these
two framing formats is in the use of the C-bits. In the
M13 Format, the C-bits reflect the status of stuff-opportunities that either were or were not used while
multiplexing the 7 DS2 signals into this DS3 signal. If
two of the three stuff bits, within a F-frame, are "1",
then the associated stuff bit, Si (not shown in
Figure 41), is interpreted as being a stuff bit. In the Cbit Parity framing format, the C bits take on different
roles, as presented in Table 18.
TABLE 18: C-BIT FUNCTIONS FOR THE C-BIT PARITY DS3 FRAME FORMAT
C - BIT
FUNCTION OF C-BITS WHILE IN THE C-BIT PARITY FRAMING FORMAT
C11
AIC (C-Bit Parity Mode)
C12
NA (Reserved for Network Application)
C13
FEAC (Far End Alarm & Control)
C21, C22, C23
(UDL) User Data Link (undefined for DS3 Frame)
C31,C32, C33
CP (Path) Parity Bits
C41, C42, C43
FEBE (Far End Block Error) Indicators
C51, C52, C53
(DL) Path Maintenance Data Link
C61, C62, C63, (UDL) User Data Link (undefined for DS3 Frame)
C71, C72, C73
Definition of the DS3 Frame Overhead Bits
In general, the DS3 Frame Overhead Bits serve the
following three purposes:
1. Support Frame Synchronization between the
Local and Remote DS3 Terminals
2. Provide parity bits in order to facilitate performance monitoring and error detection.
3. Support the transmission of Alarms, Status, and
Data Link information to the Remote DS3 Terminal.
The Overhead bits supporting each of these purposes are further defined below.
4.1.1 Frame Synchronization Bits (Applies to
both M13 and C-bit Parity Framing Formats)
Each DS3 Frame (M-frame) contains a total of 31 bits
that support frame synchronization. Each DS3 Mframe contains three M-bits. According to Figure 40
and Figure 41, these M-bits are the first bits in Fframes 5, 6 and 7. These three bits appear in each Mframe with the repeating pattern of "010". This fact is
also presented in Figure 40 and Figure 41, which
contains bit-fields that are designated as: M0, M1,
and M0 (where M0 = "0", and M1 = "1").
Each F-frame contains four F-bits, which also aid in
synchronization between the Local and the remote
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Sink T.E, (where the DS3 Data Stream is terminated.)
DS3 terminals. Therefore, each DS3 M-frame consists of a total of 28 F-bits. These F-bits exhibit a repeating pattern of "1001" within each F-frame. This
fact is also presented in Figure 40 and Figure 41,
which contains bit-fields that are designated as: F1,
F0, F0, and F1 (where F0 = "0", and F1 = "1").
NOTE: This transmission path from Source T.E. to Sink T.E.
may involve numerous T.E.
• P-Bits are verified and recomputed as it passes
through a Mid-Network T.E. (which is neither a
Source nor Sink T.E.)
Each of these bit-fields will be used by the Receive
DS3 Framer block, within the remote terminal equipment, to perform Frame Acquisition and Frame Maintenance functions.
• The values of the CP-Bits (as generated by the
Source T.E.) must be preserved as a DS3 frame
travels to the Sink T.E. (Through any number of
Mid-Network T.E.)
NOTE: For more information on how the Receive DS3
Framer uses these bit-fields, please see Section 3.3.2.
For more information on how CP-Bits are processed,
please see section 3.3.2.6.2
4.1.2 Performance Monitoring/Error Detection
Bits (Parity)
The DS3 Frame uses numerous bit fields to support
performance monitoring of the transmission link between the Local Transmitting Terminal and the Remote Receiving Terminal. The DS3 frame can contain
two types of parity bits, depending upon the framing
format chosen. P-bits are available in both the M13
and C-bit Parity Formats. However, the C-bit Parity
format also includes additional CP-Parity bits.
4.1.3 Alarm and Signaling-Related Overhead
Bits
The DS3 frame consists of mumerous bit-fields which
are used to support the handling of alarm and signaling information. Each of these bit-fields are defined
below.
The Alarm Indication Signal (AIS) Pattern (C-Bit
Parity Framing Format only)
P-Bits (Applies to M13 and C-Bit Parity Frame Formats)
Each DS3 M-frame consists of two (2) P-bits. These
two P-bits carry the parity information of the previous
DS3 frame for performance monitoring. These two Pbits must be identical, within a given DS3 frame. The
Transmit Section will compute the even parity over all
4704 payload bits within a given DS3 frame, and insert the resulting parity information in the P-bit fields
of the very next DS3 frame. The two P-bits are set to
"1" if the payload of the previous DS3 frame consists
of an odd number of "ones" in the frame. Conversely,
the two P-bits are set to zero if an even number of
"ones" is found in the payload of the previous DS3
frame. For information on how the Receive DS3
Framer handles P-bits, please see Section 3.3.2.6.1.
CP-(Path) Parity Bits (Applies to only the C-Bit
Parity Framing Format)
Each DS3 M-Frame consists of tw0 (2) CP-Bits.
These two bits have a very similar role to those of PBits. Further, the XRT72L53 Framer IC processes
CP-Bits in an identical manner that it handles P-Bits.
The Alarm Indication Signal (AIS) pattern is an alarm
signal that is inserted into the outbound DS3 stream
when a failure is detected by the Local Terminal. The
Transmit DS3 Framer will generate the AIS pattern as
defined in ANSI.T1.107a-1990, which is described as
follows.
VALID M-BITS, F-BITS, AND P-BITS
• All C-bits are zeros
• All X-bits are set to "1"
• A repeating "1010..." pattern is written into the payload of the DS3 frames.
Consequently, no user (or payload) data will be transmitted while the Transmit Section of the chip is transmitting the AIS pattern.
The IDLE Condition Signal
The IDLE Condition signal is used to indicate that the
DS3 channel is functionally sound, but has not yet
been assigned any traffic. The Transmit Section will
transmit the IDLE Condition signal as defined in ANSI
T1.107a-1990, which is described as follows.
• Valid M-bits, F-bits, and P-bits
However for some DS3 applications, there is a difference between P and CP-bits, that should be noted.
• The three CP-bits (F-frame #3) are zeros
• P-Bits are used to support error detection of a DS3
data stream as it travels from one T.E. to the next.
(e.g., a single DS3 link between two T.E.)
• A repeating "1100.." pattern is written into the payload of the DS3 frames.
• CP-Bits are used to support error detection of DS3
data stream as it travels from the Source T.E.
(where the DS3 Data Stream originated), to the
• The X-bits are set to "1"
FEAC - Far End Alarm & Control (Only available
for the C-bit Parity Frame Format)
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The third C-bit (C13 or FEAC) in the first F-frame is
used as the Far End Alarm and Control (FEAC) channel between the Near-End DS3 terminal and the Remote DS3 terminal. The FEAC channel carries:
• Alarm and Status Information
• Loopback commands to initiate and deactivate DS3
and DS1 loopbacks at the distant terminals.
0
d5
d4
d3
d2
d1
d0
The FEAC message consists of a six (6) bit code
word of the form [d5, d4, d3, d2, d1 d0]. This message is encapsulated with 10 framing bits to form a
16 bit FEAC Message, as illustrated below. The
FEAC signals are encoded into repeating 16 bit message of the form:
0
1
Since each DS3 frame carries only one FEAC bit, 16
DS3 frames are required to deliver 1 complete FEAC
message. The six bits labeled "dx" can represent upto 64 distinct messages, of which 43 have been defined in the standards. For a more detailed discussion on the transmission of FEAC Messages, please
see Section 3.2.3.1.
FEBE - Far End Block Error (Only available for the
C-bit Parity Frame Format)
F-Frame # 4 consists of 3 bit fields for the FEBE (FarEnd Block Error) channel. If the (Local) Receive Section (within the Framer IC) detects P-bit parity errors,
CP-bit errors or a framing error on the incoming (received) DS3 stream it will inform the Transmit Section
of this fact. The Transmit Section will, in turn, set the
three FEBE bits (within an outgoing DS3 Frame) to
any pattern other than "111" to indicate an error. The
Transmit Section will then transmit this information
out to the Remote Terminal (e.g., the source of the errored-data). The FEBE bits, in the outbound DS3
frames, are set to "111" only if both of the following
conditions are true:
• The Receive DS3 Framer has detected no M-bit or
F-bit framing errors, and
1
1
1
1
1
1
1
figured such that the Transmit Section will send a Yellow Alarm or a FERF (Far-End Receive Failure) indication to the Remote Terminal by setting both of the
X-bits to zero in the outbound (returning) DS3 path.
The X-bits are set to "1" during non-alarm conditions.
4.1.4 The Data Link Related Overhead Bits
UDL: User Data Link (C-bit Parity Frame Format
Only)
These bit-fields are not used by the framer and are
set to "1" by default. However, these bits may be
used for the transmission of data via a proprietary data link. The user can access these bit-fields via the
Transmit Overhead Data Input Interface and the Receive Overhead Data Output Interface blocks.
DL: Path Maintenance Data Link (C-bit Parity
Frame Format Only)
The LAPD transceiver block uses these bit-fields for
the transmission and reception of path maintenance
data link (PMDL) messages via ITU-T Q.921 (LAP-D)
Message frames. Please see Sections 3.2.3.2 and
3.3.3.2 for more information on the operation and
function of the LAPD Transmitter.
4.2 THE TRANSMIT SECTION OF THE XRT72L53
(DS3 MODE OPERATION)
When the XRT72L53 has been configured to operate
in the DS3 Mode, the Transmit Section of the
XRT72L53 consists of the following functional blocks.
• No P-Bit parity errors have been detected.
• No CP-Bit errors have been detected.
NOTE: A more detailed discussion on the Transmit Section's handling of the FEBE bit-fields can be found in Section 3.2.4.2.1.9.
• Transmit Payload Data Input Interface block
The Yellow Alarm or FERF (Far-End Receive Failure) Indicator
• Transmit Overhead Data Input Interface block
The X-bits are used for sending Yellow Alarms or the
FERF (Far-End Receive Failure) indication. When
the Receive Section (of the XRT72L53), within the
Remote Receiving terminal equipment, cannot identify valid framing, or detects an AIS pattern in the incoming DS3 data-stream, the Framer IC can be con-
• Transmit DS3 HDLC Controller block
• Transmit DS3 Framer block
• Transmit LIU Interface block
Figure 42 presents a simple illustration of the Transmit Section of the XRT72L53 Framer IC.
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FIGURE 42. A SIMPLE ILLUSTRATION OF THE TRANSMIT SECTION, WITHIN THE XRT72L53, WHEN IT HAS BEEN CONDS3 MODE
FIGURED TO OPERATE IN THE
TxOHFrame
TxOHEnable
TxOH
TxOHClk
TxOHIns
TxOHInd
TxSer
TxNib[3:0]
TxInClk
TxNibClk
TxFrame
Transmit Overhead
Input
Interface Block
Transmit
Payload Data
Input
Interface Block
TxPOS
Transmit DS3/E3
Framer Block
Transmit LIU
Interface
Block
TxNEG
TxLineClk
From Microprocessor
Interface Block
Each of these functional blocks will be discussed in
detail in this document.
Tx DS3 HDLC
Tx DS3 HDLC
Controller/Buffer
Controller/Buffer
4.2.1 The Transmit Payload Data Input Interface
Block
Figure 43 presents a simple illustration of the Transmit Payload Data Input Interface block.
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FIGURE 43. A SIMPLE ILLUSTRATION OF THE TRANSMIT PAYLOAD DATA INPUT INTERFACE BLOCK
TxOH_Ind
TxSer
TxNib[3:0]
TxInClk
Transmit
TransmitPayload
Payload
Data
DataInput
Input
Interface
InterfaceBlock
Block
To Transmit DS3 Framer Block
TxNibClk
TxFrame
TxFrameRef
Each of the input and output pins of the Transmit Payload Data Input Interface are listed in Table 19 and
described below. The exact role that each of these
inputs and output pins assume, for a variety of operating scenarios, are described throughout this section.
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TABLE 19: LISTING AND DESCRIPTION OF THE PINS ASSOCIATED WITH THE TRANSMIT PAYLOAD DATA INPUT
INTERFACE
SIGNAL NAME
TYPE
DESCRIPTION
TxSer
Input
Transmit Serial Payload Data Input Pin:
If the user opts to operate the XRT72L53 in the serial mode, then the Terminal Equipment is
expected to apply the payload data (that is to be transported via the outbound DS3 data
stream) to this input pin. The XRT72L53 will sample the data that is at this input pin upon the
rising edge either the RxOutClk or the TxInClk signal (whichever is appropriate).
NOTE: This signal is only active if the NibInt input pin is pulled "Low".
TxNib[3:0]
Input
Transmit Nibble-Parallel Payload Data Input pins:
If the user opts to operate the XRT72L53 in the Nibble-Parallel mode, then the Terminal Equipment is expected to apply the payload data (that is to be transported via the outbound DS3
data stream) to these input pins. The XRT72L53 will sample the data that is at these input
pins upon the rising edge of the TxNibClk signal.
NOTE: These pins are only active if the NibInt input pin is pulled "High".
TxNibFrame
TxInClk
Output Transmit End of Frame Output Indicator - Nibble Mode
The Transmit Section of the XRT72L53 will pulse this output pin "High" (for one nibble-period),
when the Transmit Payload Data Input Interface is processing the last nibble of a given DS3
frame.
The purpose of this output pin is to alert the Terminal Equipment that it needs to begin transmission of a new DS3 frame to the XRT72L53.
Input
Transmit Section Timing Reference Clock Input pin:
The Transmit Section of the XRT72L53 can be configured to use this clock signal as the Timing Reference. If the user has made this configuration selection, then the XRT72L53 will use
this clock signal to sample the data on the TxSer input pin.
NOTE: If this configuration has been selected, then a 44.736 MHz clock signal must be applied
to this input pin.
TxNibClk
Output Transmit Nibble Mode Output
If the user opts to operate the XRT72L53 in the Nibble-Parallel mode, then the XRT72L53 will
derive this clock signal from the selected Timing Reference for the Transmit Section of the chip
(e.g., either the TxInClk or the RxLineClk signals).
The user is advised to configure the Terminal Equipment to output the outbound payload data
(to the XRT72L53 Framer IC) onto the TxNib[3:0] input pins, upon the rising edge of this clock
signal.
NOTE: For DS3 Applications, the XRT72L53 Framer IC will output 1176 clock edges (to the
Terminal Equipment) for each outbound DS3 frame.
TxOHInd
Output Transmit Overhead Bit Indicator Output:
This output pin will pulse "High" one-bit period prior to the time that the Transmit Section of the
XRT72L53 will be processing an Overhead bit. The purpose of this output pin is to warn the
Terminal Equipment that, during the very next bit-period, the XRT72L53 is going to be processing an Overhead bit and will be ignoring any data that is applied to the TxSer input pin.
For DS3 applications, this output pin is only active if the XRT72L53 is operating in the Serial
Mode. This output pin will be pulled "Low" if the device is operating in the Nibble-Parallel
Mode.
TxFrame
Output Transmit End of Frame Output Indicator:
The Transmit Section of the XRT72L53 will pulse this output pin "High" (for one bit-period),
when the Transmit Payload Data Input Interface is processing the last bit of a given DS3 frame.
The purpose of this output pin is to alert the Terminal Equipment that it needs to begin transmission of a new DS3 frame to the XRT72L53 (e.g., to permit the XRT72L53 to maintain
Transmit DS3 framing alignment control over the Terminal Equipment).
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TABLE 19: LISTING AND DESCRIPTION OF THE PINS ASSOCIATED WITH THE TRANSMIT PAYLOAD DATA INPUT
INTERFACE
SIGNAL NAME
TYPE
DESCRIPTION
TxFrameRef
Input
Transmit Frame Reference Input:
The XRT72L53 permits the user to configure the Transmit Section to use this input pin as a
frame reference. If the user makes this configuration selection, then the Transmit Section will
initiate its transmission of a new DS3 frame, upon the rising edge of this signal.
The purpose of this input pin is to permit the Terminal Equipment to maintain Transmit DS3
Framing alignment control over the XRT72L53.
RxOutClk
Output Loop-Timed Timing Reference Clock Output pin:
The Transmit Section of the XRT72L53 can be configured to use the RxLineClk signal as the
Timing Reference (e.g., loop-timing). If the user has made this configuration selection, then
the XRT72L53 will:
• Output a 44.736 MHz clock signal via this pin, to the Terminal Equipment.
• Sample the data on the TxSer input pin, upon the rising edge of this clock signal.
Operation of the Transmit Payload Data Input Interface
A. Loop-Timing (Uses the RxLineClk signal as the
Timing Reference)
The Transmit Payload Data Input Interface is extremely flexible, in that it permits the user to make the
following configuration options.
Since the XRT72L53 is configured to operate in the
loop-timed mode, the Transmit Section (of the
XRT72L53) will use the RxLineClk input clock signal
(e.g., the Recovered Clock signal, from the LIU) as its
timing source. When the XRT72L53 is operating in
this mode it will do the following.
• The Serial or the Nibble-Parallel Interface Mode
• The Loop-Timing or the TxInClk (Local Timing)
Mode
1. It will ignore any signal at the TxInClk input pin.
2. The XRT72L53 will output a 44.736MHz clock
signal via the RxOutClk output pin. This clock
signal functions as the Transmit Payload Data
Input Interface block clock signal.
3. The XRT72L53 will use the rising edge of the
RxOutClk signal to latch in the data residing on
the TxSer input pin.
B. Serial Mode
Further, if the XRT72L53 has been configured to operate in the TxInClk (Local Timing) mode, then the
user has two additional options.
• The XRT72L53 functions as the Frame Master
(e.g., it dictates when the Terminal Equipment will
initiate the transmission of data within a new DS3
frame).
• The XRT72L53 functions as the Frame Slave (e.g.,
the Terminal Equipment will dictate when the
XRT72L53 initiates the transmission of a new DS3
frame).
The XRT72L53 will accept the DS3 payload data from
the Terminal Equipment, in a serial-manner, via the
TxSer input pin The Transmit Payload Data Input Interface block will latch this data into its circuitry, on the
rising edge of the RxOutClk output clock signal.
Given these three set of options, the Transmit Terminal Input Interface can be configured to operate in
one of the six (6) following modes.
C. Delineation of outbound DS3 frames
• Mode 1 - Serial/Loop-Timed Mode
The XRT72L53 will pulse the TxFrame output pin
"High" for one bit-period coincident with the
XRT72L53 processing the last bit of a given DS3
frame.
• Mode 2 - Serial/Local-Timed/Frame Slave Mode
• Mode 3 - Serial/Local-Timed/Frame Master Mode
• Mode 4 - Nibble/Loop-Timed Mode
• Mode 5 - Nibble/Local-Timed/Frame Slave Mode
D. Sampling of Payload Data, from the Terminal
Equipment
• Mode 6 - Nibble/Local-Timed/Frame Master Mode
In Mode 1, the XRT72L53 will sample the data at the
TxSer input, on the rising edge of RxOutClk.
Each of these modes are described, in detail, below.
4.2.1.1 Mode 1 - The Serial/Loop-Timing Mode
The Behavior of the XRT72L53
If the XRT72L53 has been configured to operate in
this mode, then the XRT72L53 will behave as follows.
Interfacing the Transmit Payload Data Input Interface block (of the XRT72L53) to the Terminal
Equipment for Mode 1 Operation
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THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
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PRELIMINARY
REV. P1.1.7
Figure 44 presents an illustration of the Transmit Payload Data Input Interface block (within the XRT72L53)
being interfaced to the Terminal Equipment, for Mode
1 operation.
FIGURE 44. ILLUSTRATION OF THE TERMINAL EQUIPMENT BEING INTERFACED TO THE TRANSMIT PAYLOAD DATA
INPUT INTERFACE BLOCK (OF THE XRT72L53) FOR MODE 1(SERIAL/LOOP-TIMING) OPERATION
DS3_Clock_In
44.736 MHz
DS3_Data_Out
RxOutClk
TxSer
Tx_Start_of_Frame
TxFrame
DS3_Overhead_Ind
TxOH_Ind
NibInt
Terminal Equipment
Mode 1, Operation of the Terminal Equipment
When the XRT72L53 is operating in this mode, it will
function as the source of the 44.736MHz clock signal
(via the RxOutClk signal). This clock signal will be
used as the Terminal Equipment Interface clock by
both the XRT72L53 IC and the Terminal Equipment.
The Terminal Equipment will serially output the payload data of the outbound DS3 data stream via its
DS3_Data_Out pin. The Terminal Equipment will update the data on the DS3_Data_Out pin upon the rising edge of the 44.736 MHz clock signal, at its
DS3_Clock_In input pin (as depicted in Figure 44 and
Figure 45).
The XRT72L53 will latch the outbound DS3 data
stream (from the Terminal Equipment) on the rising
edge of the RxOutClk signal.
The XRT72L53 will indicate that it is processing the
last bit, within a given outbound DS3 frame, by pulsing its TxFrame output pin "High" for one bit-period.
XRT72L5x DS3 Framer
When the Terminal Equipment detects this pulse at its
Tx_Start_of_Frame input, it is expected to begin
transmission of the very next outbound DS3 frame to
the XRT72L53 via the DS3_Data_Out (or TxSer pin).
Finally, the XRT72L53 will indicate that it is about to
process an overhead bit by pulsing the TxOH_Ind
output pin "High" one bit period prior to its processing
of an OH (Overhead) bit. In Figure 44, the TxOH_Ind
output pin is connected to the DS3_Overhead_Ind input pin of the Terminal Equipment. Whenever the
DS3_Overhead_Ind pin is pulsed "High" the Terminal
Equipment is expected to not transmit a DS3 payload
bit upon the very next clock edge. Instead, the Terminal Equipment is expected to delay its transmission of
the very next payload bit, by one clock cycle.
The behavior of the signals, between the XRT72L53
and the Terminal Equipment, for DS3 Mode 1 operation is illustrated in Figure 45.
155
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THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
XRT72L53
PRELIMINARY
REV. P1.1.7
.
FIGURE 45. BEHAVIOR OF THE TERMINAL INTERFACE SIGNALS BETWEEN THE TRANSMIT PAYLOAD DATA INPUT
INTERFACE BLOCK OF THE XRT72L53 AND THE TERMINAL EQUIPMENT (FOR MODE 1 OPERATION)
Terminal Equipment Signals
DS3_Clock_In
Payload[4702]
DS3_Data_Out
Payload[4703]
X-Bit
Payload[0]
X-Bit
Payload[0]
Tx_Start_of_Frame
DS3_Overhead_Ind
XRT72L5x Transmit Payload Data I/F Signals
RxOutClk
Payload[4702]
TxSer
Payload[4703]
TxFrame
TxOH_Ind
DS3 Frame Number N
DS3 Frame Number N + 1
Note: TxFrame pulses high to denote
DS3 Frame Boundary.
Note: X-Bit will not be processed by the
Transmit Payload Data Input Interface.
Note: TxOH_Ind pulses high to
denote Overhead Data
(e.g., the X-bit).
How to configure the XRT72L53 into the Serial/
Loop-Timed/Non-Overhead Interface Mode
2. Set the TimRefSel[1:0] bit fields (within the
Framer Operating Mode Register) to "00", as
illustrated below.
1. Set the NibIntf input pin "Low".
FRAMER OPERATING MODE REGISTER (ADDRESS = 0X00)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT2
BIT 1
BIT 0
Local Loopback
DS3/E3*
Internal
LOS Enable
RESET
Interrupt
Enable Reset
Frame Format
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
1
0
1
0
0
0
TimRefSel[1:0]
3. Interface the XRT72L53, to the Terminal Equipment, as illustrated in Figure 44.
• Mode 6 - Nibble-Parallel/Local-Timed/Frame-Master Mode.
NOTE: The XRT72L53 Framer IC cannot support the
Framer Local Loop-back Mode of operation, when operating in the Loop-Timing Mode. The user must configure the
XRT72L53 Framer IC into any of the following modes, prior
to configuring the Framer Local Loop-back Mode.
For more detailed information on Framer Local Loopback Mode of operation, please see Section 6.0.
• Mode 2 - Serial/Local-Timed/Frame-Slave Mode.
• Mode 3 - Serial/Local-Timed/Frame-Master Mode.
• Mode 5 - Nibble-Parallel/Local-Timed/Frame-Slave
Mode.
4.2.1.2 Mode 2 - The Serial/Local-Timed/
Frame-Slave Mode Behavior of the XRT72L53
If the XRT72L53 has been configured to operate in
this mode, then the XRT72L53 will function as follows.
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THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
áç
PRELIMINARY
REV. P1.1.7
A. Local-Timing - Uses the TxInClk signal as the
Timing Reference
other words, the Transmit Section of the XRT72L53
will initiate frame generation upon the rising edge of
the TxFrameRef input signal).
In this mode, the Transmit Section of the XRT72L53
will use the TxInClk signal as its timing reference.
D. Sampling of payload data, from the Terminal
Equipment
B. Serial Mode
The XRT72L53 will receive the DS3 payload data, in
a serial manner, via the TxSer input pin. The Transmit Payload Data Input Interface (within the
XRT72L53) will latch this data into its circuitry, on the
rising edge of the TxInClk input clock signal.
In Mode 2, the XRT72L53 will sample the data, at the
TxSer input pin, on the rising edge of TxInClk.
C. Delineation of outbound DS3 frames (Frame
Slave Mode)
Figure 46 presents an illustration of the Transmit Payload Data Input Interface block (within the XRT72L53)
being interfaced to the Terminal Equipment, for Mode
2 operation.
Interfacing the Transmit Payload Data Input Interface block (of the XRT72L53) to the Terminal
Equipment for Mode 2 Operation
The Transmit Section (of the XRT72L53) will use the
TxInClk input as its timing reference, and will use the
TxFrameRef input signal as its framing reference. In
FIGURE 46. ILLUSTRATION OF THE TERMINAL EQUIPMENT BEING INTERFACED TO THE TRANSMIT PAYLOAD DATA
INPUT INTERFACE BLOCK OF THE XRT72L53 FOR MODE 2 (SERIAL/LOCAL-TIMED/FRAME-SLAVE) OPERATION
44.736 MHz Clock
Source
DS3_Clock_In
TxInClk
DS3_Data_Out
TxSer
Tx_Start_of_Frame
TxFrameRef
DS3_Overhead_Ind
TxOH_Ind
NibInt
Terminal Equipment
XRT72L5x DS3 Framer
Mode 2, Operation of the Terminal Equipment
As shown in Figure 46, both the Terminal Equipment
and the XRT72L53 will be driven by an external
44.736MHz clock signal. The Terminal Equipment
will receive the 44.736MHz clock signal via its
DS3_Clock_In input pin, and the XRT72L53 Framer
IC will receive the 44.736MHz clock signal via the TxInClk input pin.
The Terminal Equipment will serially output the payload data of the outbound DS3 data stream, via the
DS3_Data_Out output pin, upon the rising edge of
the signal at the DS3_Clock_In input pin.
NOTE: The DS3_Data_Out output pin of the Terminal
Equipment is electrically connected to the TxSer input pin.
The XRT72L53 Framer IC will latch the data, residing
on the TxSer input line, on the rising edge of the TxInClk signal.
In this case, the Terminal Equipment has the responsibility of providing the framing reference signal by
pulsing its Tx_Start_of_Frame output signal (and in
turn, the TxFrameRef input pin of the XRT72L53),
"High" for one-bit period, coincident with the first bit of
a new DS3 frame. Once the XRT72L53 detects the
rising edge of the input at its TxFrameRef input pin, it
will begin generation of a new DS3 frame.
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THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
XRT72L53
PRELIMINARY
REV. P1.1.7
NOTES:
1. In this case, the Terminal Equipment is controlling
the start of Frame Generation, and is therefore
referred to as the Frame Master. Conversely, since
the XRT72L53 does not control the generation of a
new DS3 frame, but is rather driven by the Terminal
Equipment. Hence, the XRT72L53 is referred to as
the Frame Slave.
2. If the user opts to configure the XRT72L53 to operate in Mode 2, it is imperative that the
Tx_Start_of_Frame (or TxFrameRef) signal is synchronized to the TxInClk input clock signal.
Finally, the XRT72L53 will pulse its TxOH_Ind output
pin, one bit-period prior to it processing a given over-
head bit, within the outbound DS3 frame. Since the
TxOH_Ind output pin of the XRT72L53 is electrically
connected to the DS3_Overhead_Ind, whenever the
XRT72L53 pulses the TxOH_Ind output pin "High", it
will also be driving the DS3_Overhead_Ind input pin
(of the Terminal Equipment) "High". Whenever the
Terminal Equipment detects this pin toggling "High", it
should delay transmission of the very next DS3 frame
payload bit by one clock cycle.
The behavior of the signals between the XRT72L53
and the Terminal Equipment for DS3 Mode 2 Operation is illustrated in Figure 47.
FIGURE 47. BEHAVIOR OF THE TERMINAL INTERFACE SIGNALS BETWEEN THE XRT72L53 AND THE TERMINAL
EQUIPMENT (MODE 2 OPERATION)
Terminal Equipment Signals
DS3_Clock_In
Payload[4702]
DS3_Data_Out
Payload[4703]
X-Bit
Payload[1]
X-Bit
Payload[1]
Tx_Start_of_Frame
DS3_Overhead_Ind
XRT72L5x Transmit Payload Data I/F Signals
TxInClk
Payload[4702]
TxSer
Payload[4703]
TxFrameRef
TxOH_Ind
DS3 Frame Number N
DS3 Frame Number N + 1
Note: X-Bit will not be processed by the
Note: TxOH_Ind pulses high to
Transmit Payload Data Input Interface.
denote Overhead Data
(e.g., the X-bit).
Note: TxFrame pulses high to denote
DS3 Frame Boundary.
How to configure the XRT72L53 to operate in this
mode.
2. Set the TimRefSel[1:0] bit-fields (within the
Framer Operating Mode Register) to "01" as
depicted below.
1. Set the NibIntf input pin "Low".
FRAMER OPERATING MODE REGISTER (ADDRESS = 0X00)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT2
Local Loopback
DS3/E3*
Internal LOS
Enable
RESET
Interrupt
Enable Reset
Frame Format
R/W
R/W
R/W
R/W
R/W
R/W
158
BIT 1
BIT 0
TimRefSel[1:0]
R/W
R/W
XRT72L53
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THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. P1.1.7
FRAMER OPERATING MODE REGISTER (ADDRESS = 0X00)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT2
BIT 1
BIT 0
0
0
1
0
1
0
0
1
3. Interface the XRT72L53, to the Terminal Equipment, as illustrated in Figure 46.
4.2.1.3 Mode 3 - The Serial/Local-Timed/
Frame-Master Mode Behavior of the XRT72L53
If the XRT72L53 has been configured to operate in
this mode, then the XRT72L53 will function as follows.
A. Local Timing - (Uses the TxInClk signal as the
Timing Reference)
The Transmit Section of the XRT72L53 will use the
TxInClk signal as its timing reference, and will initiate
DS3 frame generation, asynchronously with respect
to any externally applied signal. The XRT72L53 will
pulse its TxFrame output pin "High" whenever its it
processing the very last bit-field within a given DS3
frame.
D. Sampling of payload data, from the Terminal
Equipment
In this mode, the Transmit Section of the XRT72L53
will use the TxInClk signal as its timing reference.
In Mode 3, the XRT72L53 will sample the data, at the
TxSer input pin, on the rising edge of TxInClk.
B. Serial Mode
Interfacing the Transmit Payload Data Input Interface block of the XRT72L53 to the Terminal Equipment for Mode 3 Operation
The XRT72L53 will receive the DS3 payload data, in
a serial manner, via the TxSer input pin. The Transmit Payload Data Input Interface (within the
XRT72L53) will latch this data into its circuitry, on the
rising edge of the TxInClk input clock signal.
C. Delineation of outbound DS3 frames (Frame
Master Mode)
Figure 48 presents an illustration of the Transmit Payload Data Input Interface block (within the XRT72L53)
being interfaced to the Terminal Equipment, for Mode
3 operation.
FIGURE 48. ILLUSTRATION OF THE TERMINAL EQUIPMENT BEING INTERFACED TO THE TRANSMIT PAYLOAD DATA
INPUT INTERFACE BLOCK OF THE XRT72L53 FOR MODE 3 (SERIAL/LOCAL-TIMED/FRAME-MASTER) OPERATION
44.736 MHz Clock
Source
DS3_Clock_In
TxInClk
DS3_Data_Out
TxSer
Tx_Start_of_Frame
TxFrame
DS3_Overhead_Ind
TxOH_Ind
NibInt
Terminal Equipment
Mode 3 Operation of the Terminal Equipment
In Figure 48, both the Terminal Equipment and the
XRT72L53 are driven by an external 44.736MHz
clock signal. This clock signal is connected to the
XRT72L5x DS3 Framer
DS3_Clock_In input of the Terminal Equipment and
the TxInClk input pin of the XRT72L53.
The Terminal Equipment will serially output the payload data on its DS3_Data_Out output pin, upon the
159
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THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
XRT72L53
PRELIMINARY
REV. P1.1.7
rising edge of the signal at the DS3_Clock_In input
pin. Similarly, the XRT72L53 will latch the data, residing on the TxSer input pin, on the rising edge of TxInClk.
The XRT72L53 will pulse the TxFrame output pin
"High" for one bit-period, coincident while it is processing the last bit-field within a given outbound DS3
frame. The Terminal Equipment is expected to monitor the TxFrame signal (from the XRT72L53) and to
place the first bit, within the very next outbound DS3
frame on the TxSer input pin.
NOTE: In this case, the XRT72L53 dictates exactly when
the very next DS3 frame will be generated.
Master and the Terminal Equipment is referred to as
the Frame Slave.
Finally, the XRT72L53 will pulse its TxOH_Ind output
pin, one bit-period prior to it processing a given overhead bit, within the outbound DS3 frame. Since the
TxOH_Ind output pin (of the XRT72L53) is electrically
connected to the DS3_Overhead_Ind whenever the
XRT72L53 pulses the TxOH_Ind output pin "High", it
will also be driving the DS3_Overhead_Ind input pin
(of the Terminal Equipment) "High". Whenever the
Terminal Equipment detects this pin toggling "High", it
should delay transmission of the very next DS3 frame
payload bit by one clock cycle.
The behavior of the signal between the XRT72L53
and the Terminal Equipment for DS3 Mode 3 Operation is illustrated in Figure 49.
The Terminal Equipment is expected to respond appropriately by providing the XRT72L53 with the first
bit of the new DS3 frame, upon demand. Hence, in
this mode, the XRT72L53 is referred to as the Frame
FIGURE 49. BEHAVIOR OF THE TERMINAL INTERFACE SIGNALS BETWEEN THE XRT72L53 AND THE TERMINAL
EQUIPMENT (DS3 MODE 3 OPERATION)
Terminal Equipment Signals
DS3_Clock_In
DS3_Data_Out
Payload[4702]
Payload[4703]
X-Bit
Payload[1]
X-Bit
Payload[1]
Tx_Start_of_Frame
DS3_Overhead_Ind
XRT72L5x Transmit Payload Data I/F Signals
TxInClk
Payload[4702]
TxSer
Payload[4703]
TxFrame
TxOH_Ind
DS3 Frame Number N
Note: TxFrame pulses high to denote
DS3 Frame Boundary.
DS3 Frame Number N + 1
Note: X-Bit will not be processed by the
Transmit Payload Data Input Interface.
Note: TxOH_Ind pulses high to
denote Overhead Data
(e.g., the X-bit).
How to configure the XRT72L53 to operate in this
mode.
2. Set the TimRefSel[1:0] bit-fields (within the
Framer Operating Mode Register) to "10” or “11"
as depicted below.
1. Set the NibIntf input pin "Low".
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XRT72L53
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THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. P1.1.7
FRAMER OPERATING MODE REGISTER (ADDRESS = 0X00)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT2
BIT 1
BIT 0
Local Loopback
DS3/E3*
Internal LOS
Enable
RESET
Interrupt
Enable Reset
Frame Format
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
1
0
1
0
1
X
TimRefSel[1:0]
3. Interface the XRT72L53, to the Terminal Equipment, as illustrated in Figure 48.
RxOutClk clock signal, following a pulse in the TxNibClk signal (see Figure 51).
4.2.1.4 Mode 4 - The Nibble-Parallel/LoopTimed Mode Behavior of the XRT72L53
If the XRT72L53 has been configured to operate in
this mode, then the XRT72L53 will behave as follows.
NOTE: The TxNibClk signal, from the XRT72L53 operates
nominally at 11.184 MHz (e.g., 44.736 MHz divided by 4).
However, for reasons described below, TxNibClk effectively
operates at a "Low"er clock frequency. The Transmit Payload Data Input Interface is only used to accept the payload
data, which is intended to be carried by outbound DS3
frames. The Transmit Payload Data Input Interface is not
designed to accommodate the entire DS3 data stream.
A. Looped Timing (Uses the RxLineClk as the
Timing Reference)
In this mode, the Transmit Section of the XRT72L53
will use the RxLineClk signal as its timing reference.
When the XRT72L53 is operating in the Nibble-Mode,
it will internally divide the RxLineClk signal, by a factor of four (4) and will output this signal via the TxNibClk output pin.
B. Nibble-Parallel Mode
The XRT72L53 will accept the DS3 payload data,
from the Terminal Equipment in a nibble-parallel manner, via the TxNib[3:0] input pins. The Transmit Terminal Equipment Input Interface block will latch this
data into its circuitry, on the rising edge of the TxNibClk output signal.
C. Delineation of the outbound DS3 frames
The XRT72L53 will pulse the TxNibFrame output pin
"High" for one bit-period coincident with the
XRT72L53 processing the last nibble of a given DS3
frame.
D. Sampling of payload data, from the Terminal
Equipment
In Mode 4, the XRT72L53 will sample the data, at the
TxNib[3:0] input pins, on the third rising edge of the
The DS3 Frame consists of 4704 payload bits or 1176
nibbles. Therefore, the XRT72L53 will supply 1176
TxNibClk pulses between the rising edges of two consecutive TxNibFrame pulses. The DS3 Frame repetition rate is 9.398kHz. Hence, 1176 TxNibClk pulses
for each DS3 frame period amounts to TxNibClk running at approximately 11.052 MHz. The method by
which the 1176 TxNibClk pulses are distributed
throughout the DS3 frame period is presented below.
Nominally, the Transmit Section within the XRT72L53
will generate a TxNibClk pulse for every 4 RxOutClk
(or TxInClk) periods. However, in 14 cases (within a
DS3 frame period), the Transmit Payload Data Input
Interface will allow 5 TxInClk periods to occur between two consecutive TxNibClk pulses.
Interfacing the Transmit Payload Data Input Interface block of the XRT72L53 to the Terminal Equipment for Mode 4 Operation
Figure 50 presents an illustration of the Transmit Payload Data Input Interface block (within the XRT72L53)
being interfaced to the Terminal Equipment, for Mode
4 Operation.
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THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
XRT72L53
PRELIMINARY
REV. P1.1.7
FIGURE 50. ILLUSTRATION OF THE TERMINAL EQUIPMENT BEING INTERFACED TO THE TRANSMIT PAYLOAD DATA
INPUT INTERFACE BLOCK OF THE XRT72L53 FOR MODE 4 (NIBBLE-PARALLEL/LOOP-TIMED) OPERATION
DS3_Nib_Clock_In
11.184MHz
TxNibClk
4
DS3_Data_Out[3:0
]
Tx_Start_of_Fram
TxNib[3:0]
TxNibFrame
VCC
44.736MHz
RxLineClk
NibInt
Terminal
Mode 4 Operation of the Terminal Equipment
When the XRT72L53 is operating in this mode, it will
function as the source of the 11.184MHz (e.g., the
44.736MHz clock signal divided by "4") clock signal,
that will be used as the Terminal Equipment Interface
clock by both the XRT72L53 and the Terminal Equipment.
The Terminal Equipment will output the payload data
of the outbound DS3 data stream via its
DS3_Data_Out[3:0] pins on the rising edge of the
11.184MHz clock signal at the DS3_Nib_Clock_In input pin.
The XRT72L53 will latch the outbound DS3 data
stream (from the Terminal Equipment) on the rising
edge of the TxNibClk output clock signal. The
XRT72L5x DS3
XRT72L53 will indicate that it is processing the last
nibble, within a given DS3 frame, by pulsing its TxNibFrame output pin "High" for one TxNibClk clock period. When the Terminal Equipment detects a pulse at
its Tx_Start_of_Frame input pin, it is expected to
transmit the first nibble, of the very next outbound
DS3 frame to the XRT72L53 via the
DS3_Data_Out[3:0] (or TxNib[3:0] pins).
Finally, for the Nibble-Parallel Mode operation, the
XRT72L53 will continuously pull the TxOHInd output
pin "Low".
The behavior of the signals between the XRT72L53
and the Terminal Equipment for DS3 Mode 4 Operation is illustrated in Figure 51.
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THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. P1.1.7
FIGURE 51. BEHAVIOR OF THE TERMINAL INTERFACE SIGNALS BETWEEN THE XRT72L53 AND THE TERMINAL
EQUIPMENT (MODE 4 OPERATION)
Terminal Equipment Signals
RxOutClk
DS3_Nib_Clock_In
Nibble [1175]
DS3_Data_Out[3:0]
Nibble [0]
Tx_Start_of_Frame
XRT72L5x Transmit Payload Data I/F Signals
RxOutClk
TxNibClk
Nibble [1175]
TxNib[3:0]
Nibble [0]
TxNibFrame
DS3 Frame Number N
DS3 Frame Number N + 1
Note: TxNibFrame pulses high to denote
DS3 Frame Boundary.
Sampling Edge of XRT72L5x Device
How to configure the XRT72L53 into Mode 4
2. Set the TimRefSel[1:0] bit-fields (within the
Framer Operating Mode Register) to “00" as illustrated below.
1. Set the NibIntf input pin "High".
FRAMER OPERATING MODE REGISTER (ADDRESS = 0X00)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT2
Local Loopback
DS3/E3*
Internal LOS
Enable
RESET
Interrupt
Enable Reset
Frame Format
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
1
0
1
0
0
0
3. Interface the XRT72L53, to the Terminal Equipment, as illustrated in Figure 50.
NOTE: The XRT72L53 Framer IC cannot support the
Framer Local Loop-back Mode of operation. The user must
configure the XRT72L53 Framer IC into any of the following
modes, prior to configuring the Framer Local-Loop-back
Mode operation.
• Mode 2 - Serial/Local-Timed/Frame-Slave Mode.
BIT 1
BIT 0
TimRefSel[1:0]
• Mode 3 - Serial/Local-Timed/Frame-Master Mode.
• Mode 5 - Nibble-Parallel/Local-Timed/Frame-Slave
Mode.
• Mode 6 - Nibble-Parallel/Local-Timed/Frame-Master Mode.
For more detailed information on the Framer Local
Loop-back Mode Operation, please see Section 6.0.
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THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
XRT72L53
PRELIMINARY
REV. P1.1.7
4.2.1.5 Mode 5 - The Nibble-Parallel/LocalTimed/Frame-Slave Interface Mode Behavior of
the XRT72L53
If the XRT72L53 has been configured to operate in
this mode, then the XRT72L53 will function as follows:
D. Sampling of payload data, from the Terminal
Equipment
A. Local-Timed (Uses the TxInClk signal as the
Timing Reference)
NOTE: The TxNibClk signal, from the XRT72L53 operates
nominally at 11.184 MHz (e.g., 44.736 MHz divided by 4).
However, for reasons described below, TxNibClk effectively
operates at a "Low"er clock frequency. The Transmit Payload Data Input Interface is only used to accept the payload
data, which is intended to be carried by outbound DS3
frames. The Transmit Payload Data Input Interface is not
designed to accommodate the entire DS3 data stream.
In Mode 5, the XRT72L53 will sample the data, at the
TxNib[3:0] input pins, on the third rising edge of the
TxInClk clock signal, following a pulse in the TxNibClk
signal (see Figure 53).
In this mode, the Transmit Section of the XRT72L53
will use the TxInClk signal at its timing reference.
Further, the chip will internally divide the TxInClk
clock signal by a factor of 4 and will output this divided clock signal via the TxNibClk output pin. The
Transmit Terminal Equipment Input Interface block
(within the XRT72L53) will use the rising edge of the
TxNibClk signal, to latch the data, residing on the TxNib[3:0] into its circuitry.
The DS3 Frame consists of 4704 payload bits or 1176
nibbles. Therefore, the XRT72L53 will supply 1176
TxNibClk pulses between the rising edges of two consecutive TxNibFrame pulses. The DS3 Frame repetition rate is 9.398kHz. Hence, 1176 TxNibClk pulses
for each DS3 frame period amounts to TxNibClk running at approximately 11.052 MHz. The method by
which the 1176 TxNibClk pulses are distributed
throughout the DS3 frame period is presented below.
B. Nibble-Parallel Mode
The XRT72L53 will accept the DS3 payload data,
from the Terminal Equipment, in a parallel manner,
via the TxNib[3:0] input pins. The Transmit Terminal
Equipment Input Interface will latch this data into its
circuitry, on the rising edge of the TxNibClk output
signal.
C. Delineation of outbound DS3 Frames
The Transmit Section will use the TxInClk input signal
as its timing reference and will use the TxFrameRef
input signal as its Framing Reference (e.g., the Transmit Section of the XRT72L53 initiates frame generation upon the rising edge of the TxFrameRef signal).
NOTE: In this case, the Terminal Equipment should pulse
the TxFrameRef input signal (of the XRT72L53 Framer IC)
coincident with it applying the first payload nibble, within a
given outbound DS3 frame. Hence, the duration of this
pulse should be one nibble-period of the DS3 signal (see
Figure 53).
Nominally, the Transmit Section within the XRT72L53
will generate a TxNibClk pulse for every 4 RxOutClk
(or TxInClk) periods. However, in 14 cases (within a
DS3 frame period), the Transmit Payload Data Input
Interface will allow 5 TxInClk periods to occur between two consecutive TxNibClk pulses.
Interfacing the Transmit Payload Data Input Interface block of the XRT72L53 to the Terminal Equipment for Mode 5 Operation
Figure 52 presents an illustration of the Transmit Payload Data Input Interface block (within the XRT72L53)
being interfaced to the Terminal Equipment, for Mode
5 Operation.
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THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
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PRELIMINARY
REV. P1.1.7
FIGURE 52. ILLUSTRATION OF THE TERMINAL EQUIPMENT BEING INTERFACED TO THE TRANSMIT PAYLOAD DATA
INPUT INTERFACE BLOCK OF THE XRT72L53 FOR MODE 5 (NIBBLE-PARALLEL/LOCAL-TIMED/FRAME-SLAVE) OPERATION
44.736MHz Clock Source
TxInClk
DS3_Nib_Clock_In
11.184MHz
TxNibClk
4
DS3_Data_Out[3:0]
TxNib[3:0]
Tx_Start_of_Frame
TxFrameRef
VCC
NibInt
Terminal Equipment
XRT72L5x DS3 Framer
Mode 5 Operation of the Terminal Equipment
In this case, the Terminal Equipment has the responsibility of providing the framing reference signal by
pulsing the Tx_Start_of_Frame output pin (and in
turn, the TxFrameRef input pin of the XRT72L53)
"High" for one bit-period, coincident with the first nibble of a new DS3 frame. Once the XRT72L53 detects
the rising edge of the input at its TxFrameRef input
pin, it will begin generation of a new DS3 frame.
In Figure 52 both the Terminal Equipment and the
XRT72L53 will be driven by an external 11.184MHz
clock signal. The Terminal Equipment will receive the
11.184MHz clock signal via the DS3_Nib_Clock_In
input pin. The XRT72L53 will output the 11.184MHz
clock signal via the TxNibClk output pin.
The Terminal Equipment will serially output the data
on the DS3_Data_Out[3:0] pins, upon the rising edge
of the signal at the DS3_Clock_In input pin.
Finally, the XRT72L53 will always internally generate
the Overhead bits, when it is operating in both the
DS3 and Nibble-parallel modes. The XRT72L53 will
pull the TxOHInd input pin "Low".
NOTE: The DS3_Data_Out[3:0] output pins of the Terminal
Equipment is electrically connected to the TxNib[3:0] input
pins.
The XRT72L53 will latch the data, residing on the TxNib[3:0] input pins, on the rising edge of the TxNibClk
signal.
The behavior of the signals between the XRT72L53
and the Terminal Equipment for DS3 Mode 5 Operation is illustrated in Figure 53.
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THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
XRT72L53
PRELIMINARY
REV. P1.1.7
FIGURE 53. BEHAVIOR OF THE TERMINAL INTERFACE SIGNALS BETWEEN THE XRT72L53 AND THE TERMINAL
EQUIPMENT (DS3 MODE 5 OPERATION)
Terminal Equipment Signals
TxInClk
DS3_Nib_Clock_In
Nibble [1175]
DS3_Data_Out[3:0]
Nibble [0]
Nibble [1]
Tx_Start_of_Frame
XRT72L5x Transmit Payload Data I/F Signals
TxInClk
TxNibClk
Nibble [0]
Nibble [1175]
TxNib[3:0]
Nibble [1]
TxFrameRef
DS3 Frame Number N
DS3 Frame Number N + 1
Sampling edge of the XRT72L5x
Device
Note: TxFrameRef is pulsed high to denote
first nibble within a new DS3 frame
How to configure the XRT72L53 into Mode 5
2. Set the TimRefSel[1:0] bit-fields (within the
Framer Operating Mode Register) to "01" as illustrated below.
1. Set the NibIntf input pin "High".
FRAMER OPERATING MODE REGISTER (ADDRESS = 0X00)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT2
BIT 1
BIT 0
Local Loopback
DS3/E3*
Internal LOS
Enable
RESET
Interrupt
Enable Reset
Frame Format
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
1
0
1
0
0
1
TimRefSel[1:0]
3. Interface the XRT72L53, to the Terminal Equipment, as illustrated in Figure 52.
A. Local-Timed (Uses the TxInClk signal as the
Timing Reference)
4.2.1.6 Mode 6 - The Nibble-Parallel/TxInClk/
Frame-Master Interface Mode Behavior of the
XRT72L53
If the XRT72L53 has been configured to operate in
this mode, then the XRT72L53 will function as follows:
In this mode, the Transmit Section of the XRT72L53
will use the TxInClk signal at its timing reference.
Further, the chip will internally divide the TxInClk
clock signal by a factor of 4 and will output this divided clock signal via the TxNibClk output pin. The
Transmit Terminal Equipment Input Interface block
(within the XRT72L53) will use the rising edge of the
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THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
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PRELIMINARY
REV. P1.1.7
TxNibClk signal, to latch the data, residing on the TxNib[3:0] into its circuitry.
B. Nibble-Parallel Mode
The XRT72L53 will accept the DS3 payload data,
from the Terminal Equipment, in a parallel manner,
via the TxNib[3:0] input pins. The Transmit Terminal
Equipment Input Interface will latch this data into its
circuitry, on the rising edge of the TxNibClk output
signal.
C. Delineation of outbound DS3 Frames
The Transmit Section will use the TxInClk input signal
as its timing reference and will initiate the generation
of DS3 frames, asynchronous with respect to any external signal. The XRT72L53 will pulse the TxFrame
output pin "High" whenever it is processing the last
nibble, within a given outbound DS3 frame.
D. Sampling of payload data, from the Terminal
Equipment
In Mode 6, the XRT72L53 will sample the data, at the
TxNib[3:0] input pins, on the third rising edge of the
TxInClk clock signal, following a pulse in the TxNibClk
signal (see Figure 55).
NOTE: The TxNibClk signal from the XRT72L53, operates
nominally at 11.184 MHz (e.g., 44.736 MHz divided by 4).
However, for reasons described below, TxNibClk effectively
operates at a "Low"er clock frequency. The Transmit Pay-
load Data Input Interface is only used to accept the payload
data, which is intended to be carried by outbound DS3
frames. The Transmit Payload Data Input Interface is not
designed to accommodate the entire DS3 data stream.
The DS3 Frame consists of 4704 payload bits or 1176
nibbles. Therefore, the XRT72L53 will supply 1176
TxNibClk pulses between the rising edges of two consecutive TxNibFrame pulses. The DS3 Frame repetition rate is 9.398kHz. Hence, 1176 TxNibClk pulses
for each DS3 frame period amounts to TxNibClk running at approximately 11.052 MHz. The method by
which the 1176 TxNibClk pulses are distributed
throughout the DS3 frame period is presented below.
Nominally, the Transmit Section within the XRT72L53
will generate a TxNibClk pulse for every 4 RxOutClk
(or TxInClk) periods. However, in 14 cases (within a
DS3 frame period), the Transmit Payload Data Input
Interface will allow 5 TxInClk periods to occur between two consecutive TxNibClk pulses.
Interfacing the Transmit Payload Data Input Interface block of the XRT72L53 to the Terminal Equipment for Mode 6 Operation
Figure 54 presents an illustration of the Transmit Payload Data Input Interface block (within the XRT72L53)
being interfaced to the Terminal Equipment, for Mode
6 Operation.
FIGURE 54. ILLUSTRATION OF THE TERMINAL EQUIPMENT BEING INTERFACED TO THE TRANSMIT PAYLOAD DATA
INPUT INTERFACE BLOCK OF THE XRT72L53 FOR MODE 6 (NIBBLE-PARALLEL/LOCAL-TIMED/FRAME-MASTER)
OPERATION
44.736MHz Clock Source
TxInClk
DS3_Nib_Clock_In
11.184MHz
TxNibClk
4
DS3_Data_Out[3:0]
TxNib[3:0]
Tx_Start_of_Frame
TxNibFrame
VCC
NibInt
Terminal Equipment
Mode 6 Operation of the Terminal Equipment
XRT72L5x DS3 Framer
In Figure 54 both the Terminal Equipment and the
XRT72L53 will be driven by an external 11.184MHz
clock signal. The Teriminal Equipment will receive
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THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
XRT72L53
PRELIMINARY
REV. P1.1.7
the 11.184MHz clock signal via the
DS3_Nib_Clock_In input pin. The XRT72L53 will output the 11.184MHz clock signal via the TxNibClk output pin.
TxFrame output pin (and in turn the
Tx_Start_of_Frame input pin of the Terminal Equipment) "High" for one bit-period, coincident with the
last bit within a given DS3 frame.
The Terminal Equipment will serially output the data
on the DS3_Data_Out[3:0] pins upon the rising edge
of the signal at the DS3_Clock_In input pin. The
XRT72L53 will latch the data, residing on the TxNib[3:0] input pins, on the rising edge of the TxNibClk
signal.
Finally, the XRT72L53 will always internally generate
the Overhead bits, when it is operating in both the
DS3 and Nibble-parallel modes. The XRT72L53 will
pull the TxOHInd input pin "Low".
In this case the XRT72L53 has the responsibility of
providing the framing reference signal by pulsing the
The behavior of the signals between the XRT72L53
and the Terminal Equipment for DS3 Mode 6 Operation is illustrated in Figure 55.
FIGURE 55. BEHAVIOR OF THE TERMINAL INTERFACE SIGNALS BETWEEN THE XRT72L53 AND THE TERMINAL
EQUIPMENT (DS3 MODE 6 OPERATION)
Terminal Equipment Signals
TxInClk
DS3_Nib_Clock_In
Nibble [1175]
DS3_Data_Out[3:0]
Nibble [0]
Tx_Start_of_Frame
XRT72L5x Transmit Payload Data I/F Signals
TxInClk
TxNibClk
Nibble [1175]
TxNib[3:0]
Nibble [0]
TxNibFrame
DS3 Frame Number N
DS3 Frame Number N + 1
Sampling Edge of the XRT72L5x Device
Note: TxNibFrame pulses high to denote
DS3 Frame Boundary.
How to configure the XRT72L53 into Mode 6
2. Set the TimRefSel[1:0] bit-fields (within the
Framer Operating Mode Register) to 1X as illustrated below.
1. Set the NibInt input pin "High".
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XRT72L53
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THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. P1.1.7
FRAMER OPERATING MODE REGISTER (ADDRESS = 0X00)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT2
Local Loopback
DS3/E3*
Internal LOS
Enable
RESET
Interrupt
Enable Reset
Frame Format
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
1
0
1
0
1
x
3. Interface the XRT72L53, to the Terminal Equipment, as illustrated in Figure 54.
4.2.2
face
BIT 1
BIT 0
TimRefSel[1:0]
Figure 56 presents a simple illustration of the Transmit Overhead Data Input Interface block within the
XRT72L53.
The Transmit Overhead Data Input Inter-
FIGURE 56. SIMPLE ILLUSTRATION OF THE TRANSMIT OVERHEAD DATA INPUT INTERFACE BLOCK
TxOHFrame
TxOHEnable
TxOH
Transmit
Transmit
Overhead
Overhead
Data
DataInput
Input
Interface
InterfaceBlock
Block
To Transmit DS3 Framer Block
TxOHClk
TxOHIns
The DS3 Frame consists of 4760 bits. Of these bits,
4704 bits are payload bits and the remaining 56 bits
are overhead bits. The XRT72L53 has been designed to handle and process both the payload type
and overhead type bits for each DS3 frame. Within
the Transmit Section within the XRT72L53, the Transmit Payload Data Input Interface has been designed
to handle the payload data. Likewise, the Transmit
Overhead Data Input Interface has been designed to
handle and process the overhead bits.
The Transmit Section of the XRT72L53 generates or
processes the various overhead bits within the DS3
frame, in the following manner.
The Frame Synchronization Overhead Bits (e.g.,
the F and M bits)
The F and M bits are always internally generated by
the Transmit Section of the XRT72L53. These overhead bits are used (by the Remote Terminal Equipment) for Frame Synchronization purposes. Hence,
the user cannot insert his/her value for the F and M
bits into the outbound DS3 data stream, via the
Transmit Overhead Data Input Interface. Any attempt
to externally insert values for the “F” and “M” bits, will
be ignored by the Transmit Overhead Data Input Interface"High" block.
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THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
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PRELIMINARY
REV. P1.1.7
The Performance Monitoring Overhead Bits (P
and CP Bits)
The Alarm and signaling related Overhead bits
Bits that are used to transport the alarm conditions
can be either internally generated by the Transmit
Section within the XRT72L53, or can be externally
generated and inserted into the outbound DS3 data
stream, via the Transmit Overhead Data Input Interface. The DS3 frame overhead bits that fall into this
category are:
The P-bits are always internally generated by the
Transmit Section of the XRT72L53. The “P” bits are
used by the Remote Terminal Equipment to perform
error-checking/detection of a DS3 data stream, as it
is transmitted from one Terminal Equipment to adjacent Terminal Equipment (e.g., point-to-point checking). Hence, the user cannot insert his/her value for
the P-bits into the outbound DS3 data stream, via the
Transmit Overhead Data Input Interface.
• The X bits
• The FEAC bits
In contrast to “P” bits, “CP” bits are used perform error-checking/detection of a DS3 data stream from the
Source Terminal Equipment to the Sink Terminal
Equipment. In applications where a given DS3 data
stream is received via one port, and is output via another port, it is necessary that the “CP” bit-values remain constant. The only way to insure this to (1) extract out the “CP” bit values, via the Receiving Line
Card and (2) insert these CP-bit values into the outbound DS3 data stream, via the Transmit Overhead
Data Input Interface block. Hence, the Transmit Overhead Data Input Interface block will permit the user to
externally insert the “CP” bits into the outbound DS3
data stream.
• The FEBE bits.
The Data Link Related Overhead Bits
The DS3 frame structure also contains bits which can
be used to transport User Data Link information and
Path Maintenance Data Link information. The UDL
(User Data Link) bits are only accessible via the
Transmit Overhead Data Input Interface. The Path
Maintenance Data Link (PMDL) bits can either be
sourced from the Transmit LAPD Controller/Buffer or
via the Transmit Overhead Data Input Interface.
Table 20 lists the Overhead Bits within the DS3
frame. Additionally, this table also indicates whether
or not these overhead bits can be sourced by the
Transmit Overhead Data Input Interface or not.
TABLE 20: A LISTING OF THE OVERHEAD BITS WITHIN THE DS3 FRAME, AND THEIR POTENTIAL SOURCES, WITHIN THE
XRT72L53 IC
OVERHEAD BIT
INTERNALLY GENERATED
ACCESSIBLE VIA THE TRANSMIT OVERHEAD
DATA INPUT INTERFACE
BUFFER/REGISTER
ACCESSIBLE
P
Yes
No
Yes*
X
Yes
Yes
Yes
F
Yes
No
Yes*
M
Yes
No
Yes*
FEAC
No
Yes
Yes
FEBE
Yes
Yes
Yes
DL
No
Yes
Yes+
UDL
No
Yes
No
CP
No
Yes
No
NOTES:
* The XRT72L53 contains mask register bits that permit the user to alter the state of the internally generated value for these bits.
+ The Transmit LAPD Controller/Buffer can be configured to be the source of the DL bits, within the outbound DS3 data stream.
In all, the Transmit Overhead Data Input Interface
permits the user to insert overhead data into the out-
bound DS3 frames via the following two different
methods.
• Method 1 - Using the TxOHClk clock signal
• Method 2 - Using the TxInClk and the TxOHEnable
signals.
Each of these methods are described below.
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4.2.2.1 4.2.2.1 Method 1 - Using the TxOHClk
Clock Signal
XRT72L53
THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
áç
PRELIMINARY
REV. P1.1.7
The Transmit Overhead Data Input Interface consists
of the five signals. Of these five (5) signals, the following four (4) signals are to be used when implementing Method 1.
• TxOH
• TxOHFrame
• TxOHIns
Each of these signals are listed and described below.
Table 21.
• TxOHClk
TABLE 21: DESCRIPTION OF METHOD 1 TRANSMIT OVERHEAD INPUT INTERFACE SIGNALS
NAME
TYPE
TxOHIns
Input
DESCRIPTION
Transmit Overhead Data Insert Enable input pin.
Asserting this input signal (e.g., setting it "High") enables the Transmit Overhead Data Input Interface to accept overhead data from the Terminal Equipment. In other words, while this input pin is
"High", the Transmit Overhead Data Input Interface will sample the data at the TxOH input pin, on
the falling edge of the TxOHClk output signal.
Conversely, setting this pin "Low" configures the Transmit Overhead Data Input Interface to NOT
sample (e.g., ignore) the data at the TxOH input pin, on the falling edge of the TxOHClk output
signal.
NOTE: If the Terminal Equipment attempts to insert an overhead bit that cannot be accepted by
the Transmit Overhead Data Input Interface (e.g., if the Terminal Equipment asserts the TxOHIns
signal, at a time when one of these non-insertable overhead bits are being processed), that particular insertion effort will be ignored.
TxOH
Input
Transmit Overhead Data Input pin:
The Transmit Overhead Data Input Interface accepts the overhead data via this input
pin, and inserts into the overhead bit position within the very next outbound DS3 frame.
If the TxOHIns pin is pulled "High", the Transmit Overhead Data Input Interface will sample the data at this input pin (TxOH), on the falling edge of the TxOHClk output pin.
Conversely, if the TxOHIns pin is pulled "Low", then the Transmit Overhead Data Input
Interface will NOT sample the data at this input pin (TxOH). Consequently, this data will
be ignored.
TxOHClk
Output
Transmit Overhead Input Interface Clock Output signal:
This output signal serves two purposes:
1. The Transmit Overhead Data Input Interface will provide a rising clock edge on this signal, one
bit-period prior to the instant that the Transmit Overhead Data Input Interface is processing an
overhead bit.
2. The Transmit Overhead Data Input Interface will sample the data at the TxOH input, on the falling edge of this clock signal (provided that the TxOHIns input pin is "High").
NOTE: The Transmit Overhead Data Input Interface will supply a clock edge for all overhead bits
within the DS3 frame (via the TxOHClk output signal). This includes those overhead bits that the
Transmit Overhead Data Input Interface will not accept from the Terminal Equipment.
TxOHFrame
Output
Transmit Overhead Input Interface Frame Boundary Indicator Output:
This output signal pulses "High" when the XRT72L53 is processing the last bit within a
given DS3 frame.
The purpose of this output signal is to alert the Terminal Equipment that the Transmit
Overhead Data Input Interface block is about to begin processing the overhead bits for a
new DS3 frame.
Interfacing the Transmit Overhead Data Input Interface to the Terminal Equipment.
Figure 57 illustrates how one should interface the
Transmit Overhead Data Input Interface to the Terminal Equipment, when using Method 1.
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THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
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PRELIMINARY
REV. P1.1.7
FIGURE 57. ILLUSTRATION OF THE TERMINAL EQUIPMENT BEING INTERFACED TO THE TRANSMIT OVERHEAD DATA
INPUT INTERFACE (METHOD 1)
44.736 MHz Clock Source
TxInClk
DS3_OH_Clock_In
44.736 MHz
Clock Source
TxOHClk
TxOH
DS3_OH_Out]
RxLineClk
Tx_Start_of_Frame
TxOHFrame
Insert_OH
TxOHIns
Terminal Equipment
Method 1 Operation of the Terminal Equipment
If the Terminal Equipment intends to insert any overhead data into the outbound DS3 data stream, (via
the Transmit Overhead Data Input Interface), then it is
expected to do the following.
1. To sample the state of the TxOHFrame signal
(e.g., the Tx_Start_of_Frame input signal) on the
rising edge of the TxOHClk (e.g., the
DS3_OH_Clock_In signal).
2. To keep track of the number of rising clock edges
that have occurred, via the TxOHClk (e.g., the
DS3_OH_Clock_In signal) since the last time the
TxOHFrame signal was sampled "High". By
doing this the Terminal Equipment will be able to
keep track of which overhead bit is being pro-
XRT72L5x DS3 Framer
cessed by the Transmit Overhead Data Input
Interface block at any given time. When the Terminal Equipment knows which overhead bit is
being processed, at a given TxOHClk period, it
will know when to insert a desired overhead bit
value into the outbound DS3 data stream. From
this, the Terminal Equipment will know when it
should assert the TxOHIns input pin and place
the appropriate value on the TxOH input pin (of
the XRT72L53).
Table 22relates the number of rising clock edges (in
the TxOHClk signal, since TxOHFrame was sampled
"High") to the DS3 Overhead Bit, that is being processed.
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THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
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PRELIMINARY
REV. P1.1.7
TABLE 22: THE RELATIONSHIP BETWEEN THE NUMBER OF RISING CLOCK EDGES IN TXOHCLK, (SINCE TXOHFRAME
WAS LAST SAMPLED "HIGH") TO THE DS3 OVERHEAD BIT, THAT IS BEING PROCESSED
NUMBER OF RISING CLOCK EDGES IN
TXOHCLK
THE OVERHEAD BIT EXPECTED BY THE CAN THIS OVERHEAD BIT BE ACCEPTED BY
THE XRT72L53?
XRT72L53
0 (Clock edge is coincident with TxOHFrame being detected "High")
X
Yes
1
F1
No
2
AIC
Yes
3
F0
No
4
NA
Yes
5
F0
No
6
FEAC
Yes
7
F1
No
8
X
Yes
9
F1
No
10
UDL
Yes
11
F0
No
12
UDL
Yes
13
F0
No
14
UDL
Yes
15
F1
No
16
P
No
17
F1
No
18
CP
Yes
19
F0
No
20
CP
Yes
21
F0
No
22
CP
Yes
23
F1
No
24
P
No
25
F1
No
26
FEBE
Yes
27
F0
No
28
FEBE
Yes
29
F0
No
30
FEBE
Yes
31
F1
No
32
M0
No
33
F1
No
34
DL
Yes
35
F0
No
36
DL
Yes
37
F0
No
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THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
XRT72L53
PRELIMINARY
REV. P1.1.7
TABLE 22: THE RELATIONSHIP BETWEEN THE NUMBER OF RISING CLOCK EDGES IN TXOHCLK, (SINCE TXOHFRAME
WAS LAST SAMPLED "HIGH") TO THE DS3 OVERHEAD BIT, THAT IS BEING PROCESSED
NUMBER OF RISING CLOCK EDGES IN
TXOHCLK
THE OVERHEAD BIT EXPECTED BY THE CAN THIS OVERHEAD BIT BE ACCEPTED BY
THE XRT72L53?
XRT72L53
38
DL
Yes
39
F1
No
40
M1
No
41
F1
No
42
UDL
Yes
43
FO
No
44
UDL
Yes
45
FO
No
46
UDL
Yes
47
F1
No
48
M0
No
49
F1
No
50
UDL
Yes
51
F0
No
52
UDL
Yes
53
F0
No
54
UDL
Yes
55
F1
No
3. After the Terminal Equipment has waited the
appropriate number of clock edges (from the
TxOHFrame signal being sampled "High"), it
should assert the TxOHIns input signal. Concurrently, the Terminal Equipment should also place
the appropriate value (of the inserted overhead
bit) onto the TxOH signal.
4. The Terminal Equipment should hold both the
TxOHIns input pin "High" and the value of the
TxOH signal, stable until the next rising edge of
TxOHClk is detected.
Case Study: The Terminal Equipment intends to
insert the appropriate overhead bits into the
Transmit Overhead Data Input Interface (using
Method 1) in order to transmit a Yellow Alarm to
the remote terminal equipment.
In this example, the Terminal Equipment intends to insert the appropriate overhead bits, into the Transmit
Overhead Data Input Interface, such that the
XRT72L53 will transmit a Yellow Alarm to the remote
terminal equipment. Recall that, for DS3 Applications, a Yellow Alarm is transmitted by setting both of
the X bits (within each outbound DS3 frame) to 0.
If one assumes that the connection between the Terminal Equipment and the XRT72L53 are as illustrated
in Figure 57 then Figure 58 presents an illustration of
the signaling that must go on between the Terminal
Equipment and the XRT72L53.
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FIGURE 58. ILLUSTRATION OF THE SIGNAL THAT MUST OCCUR BETWEEN THE TERMINAL EQUIPMENT AND THE
XRT72L53, IN ORDER TO CONFIGURE THE XRT72L53 TO TRANSMIT A YELLOW ALARM TO THE REMOTE TERMINAL
EQUIPMENT
Terminal Equipment/XRT72L5x Interface Signals
0
0-
1
2
3
4
5
6
7
8
8-
TxOHClk
TxOHFrame
TxOHIns
X bit = 0
TxOH
Remaining Overhead Bits with DS3 Frame
TxOHFrame is sample “high”
Terminal Equipment asserts
“TxOHIns” and data on “TxOH” line
X bit = 0
TxOHFrame is sample “high”
Terminal Equipment asserts
“TxOHIns” and data on “TxOH” line
XRT72L5x device samples the TxOHIns and
TxOH signals.
XRT72L5x device samples the TxOHIns and
TxOH signals.
In Figure 58 the Terminal Equipment samples the TxOHFrame signal being "High" at the rising clock edge
# 0. At this point, the Terminal Equipment knows that
the XRT72L53 is just about to process the very first
overhead bit within a given outbound DS3 frame. Additionally, according to Table 22, the very first overhead bit to be processed is the first X bit. In order to
facilitate the transmission of the Yellow Alarm, the
Terminal Equipment must set this X bit to 0. Hence,
the Terminal Equipment starts this process by implementing the following steps concurrently.
Figure 58), the Terminal Equipment will negate the
TxOHIns signal (e.g., toggles it "Low") and will cease
inserting data into the Transmit Overhead Data Input
Interface, until rising clock edge # 8 (of the TxOHClk
signal). According to Table 22, rising clock edge # 8
indicates that the XRT72L53 is just about ready to
process the second X bit within the outbound DS3
frame. Once again, in order to facilitate the transmission of the Yellow Alarm this X-Bit must also be set to
0. Hence, the Terminal Equipment will (once again)
implement the following steps, concurrently.
a. Assert the TxOHIns input pin by setting it "High".
a. Assert the TxOHIns input pin by setting it "High".
b. Set the TxOH input pin to 0.
b. Set the TxOH input to 0.
After the Terminal Equipment has applied these signals, the XRT72L53 will sample the data on both the
TxOHIns and TxOH signals upon the very next falling
edge of TxOHClk (designated at 0- in Figure 58.
Once the XRT72L53 has sampled this data, it will
then insert a "0" into the first X bit position, in the outbound DS3 frame.
Once again, after the Terminal Equipment has applied these signals, the XRT72L53 will sample the data on both the TxOHIns and TxOH signal upon the
very next falling edge of TxOHClk (designated as 8in Figure 58). Once the XRT72L53 has sampled this
data, it will then insert a "0" into the second X bit position, in the outbound DS3 frame.
Upon detection of the very next rising edge of the TxOHClk clock signal (designated as clock edge 1 in
4.2.2.2 Method 2 - Using the TxInClk and TxOHEnable Signals
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Method 1 requires the use of an additional clock signal, TxOHClk. However, there may be a situation in
which the user does not wish to accommodate and
process this extra clock signal to their design, in order
to use the Transmit Overhead Data Input Interface.
Hence, Method 2 is available. When using Method 2,
either the TxInClk or RxOutClk signal is used to sample the overhead bits and signals which are input to
the Transmit Overhead Data Input Interface. Method
2 involves the use of the following signals:
• TxOH
• TxInClk
• TxOHFrame
• TxOHEnable
Each of these signals are listed and described in
Table 23.
TABLE 23: DESCRIPTION OF METHOD 2 TRANSMIT OVERHEAD INPUT INTERFACE SIGNALS
NAME
TYPE
TxOHEnable
Output
DESCRIPTION
Transmit Overhead Data Enable Output pin
The XRT72L53 will assert this signal, for one TxInClk period, just prior to the instant that
the Transmit Overhead Data Input Interface is processing an overhead bit.
TxOHFrame
Output
Transmit Overhead Input Interface Frame Boundary Indicator Output:
This output signal pulses "High" when the XRT72L53 is processing the last bit within a
given DS3 frame.
TxOHIns
Input
Transmit Overhead Data Insert Enable input pin.
Asserting this input signal (e.g., setting it "High") enables the Transmit Overhead Data Input Interface to accept overhead data from the Terminal Equipment. In other words, while this input pin is
"High", the Transmit Overhead Data Input Interface will sample the data at the TxOH input pin, on
the falling edge of the TxInClk output signal.
Conversely, setting this pin "Low" configures the Transmit Overhead Data Input Interface to NOT
sample (e.g., ignore) the data at the TxOH input pin, on the falling edge of the TxOHClk output
signal.
NOTE: If the Terminal Equipment attempts to insert an overhead bit that cannot be accepted by
the Transmit Overhead Data Input Interface (e.g., if the Terminal Equipment asserts the TxOHIns
signal, at a time when one of these non-insertable overhead bits are being processed), that particular insertion effort will be ignored.
TxOH
Input
Transmit Overhead Data Input pin:
The Transmit Overhead Data Input Interface accepts the overhead data via this input
pin, and inserts into the overhead bit position within the very next outbound DS3 frame.
If the TxOHIns pin is pulled "High", the Transmit Overhead Data Input Interface will sample the data at this input pin (TxOH), on the falling edge of the TxOHClk output pin.
Conversely, if the TxOHIns pin is pulled "Low", then the Transmit Overhead Data Input
Interface will NOT sample the data at this input pin (TxOH). Consequently, this data will
be ignored.
Interfacing the Transmit Overhead Data Input Interface
to the Terminal Equipment
Figure 59 illustrates how one should interface the
Transmit Overhead Data Input Interface to the Terminal Equipment when using Method 2.
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FIGURE 59. ILLUSTRATION OF THE TERMINAL EQUIPMENT BEING INTERFACED TO THE TRANSMIT OVERHEAD DATA
INPUT INTERFACE (METHOD 2)
44.736 MHz Clock Source
TxInClk
DS3_Clock_In
44.736 MHz
Clock Source
TxOHEnable
DS3_OH_Enable
TxOH
DS3_OH_Out
RxLineClk
TxOHFrame
Tx_Start_of_Frame
TxOHIns
Insert_OH
Terminal Equipment
XRT72L5x DS3 Framer
Method 2 Operation of the Terminal Equipment
If the Terminal Equipment intends to insert any overhead data into the outbound DS3 data stream (via the
Transmit Overhead Data Input Interface), then it is expected to do the following.
1. To sample the state of both the TxOHFrame and
the TxOHEnable input signals, via the
DS3_Clock_In (e.g., either the TxInClk or the
RxOutClk signal of the XRT72L53) signal. If the
Terminal Equipment samples the TxOHEnable
signal "High", then it knows that the XRT72L53 is
about to process an overhead bit. Further, if the
Terminal Equipment samples both the TxOHFrame and the TxOHEnable pins "High" (at the
same time) then the Terminal Equipment knows
that the XRT72L53 is about to process the first
overhead bit, within a new DS3 frame.
2. To keep track of the number of times that the
TxOHEnable signal has been sampled "High"
since the last time both the TxOHFrame and the
TxOHEnable signals were sampled "High". By
doing this, the Terminal Equipment will be able to
keep track of which overhead bit the Transmit
Overhead Data Input Interface is about ready to
process. From this, the Terminal Equipment will
know when it should assert the TxOHIns input pin
and place the appropriate value on the TxOH
input pins (of the XRT72L53).
Table 24 also relates the number of TxOHEnable output pulses (that have occurred since both the TxOHFrame and TxOHEnable pins were sampled "High")
to the DS3 overhead bit, that is being processed.
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TABLE 24: THE RELATIONSHIP BETWEEN THE NUMBER OF TXOHENABLE PULSES (SINCE THE LAST OCCURRENCE OF
THE TXOHFRAME PULSE) TO THE DS3 OVERHEAD BIT, THAT IS BEING PROCESSED BY THE XRT72L53
NUMBER OF TXOHENABLE PULSES
THE OVERHEAD BIT EXPECTED BY THE CAN THIS OVERHEAD BIT BE ACCEPTED BY
THE XRT72L53?
XRT72L53
0 (The TxOHEnable and TxOHFrame
signals are both sampled "High")
X
Yes
1
F1
No
2
AIC
Yes
3
F0
No
4
NA
Yes
5
F0
No
6
FEAC
Yes
7
F1
No
8
X
Yes
9
F1
No
10
UDL
Yes
11
F0
No
12
UDL
Yes
13
F0
No
14
UDL
Yes
15
F1
No
16
P
No
17
F1
No
18
CP
Yes
19
F0
No
20
CP
Yes
21
F0
No
22
CP
Yes
23
F1
No
24
P
No
25
F1
No
26
FEBE
Yes
27
F0
No
28
FEBE
Yes
29
F0
No
30
FEBE
Yes
31
F1
No
32
M0
No
33
F1
No
34
DL
Yes
35
F0
No
36
DL
Yes
37
F0
No
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TABLE 24: THE RELATIONSHIP BETWEEN THE NUMBER OF TXOHENABLE PULSES (SINCE THE LAST OCCURRENCE OF
THE TXOHFRAME PULSE) TO THE DS3 OVERHEAD BIT, THAT IS BEING PROCESSED BY THE XRT72L53
NUMBER OF TXOHENABLE PULSES
THE OVERHEAD BIT EXPECTED BY THE CAN THIS OVERHEAD BIT BE ACCEPTED BY
THE XRT72L53?
XRT72L53
38
DL
Yes
39
F1
No
40
M1
No
41
F1
No
42
UDL
Yes
43
FO
No
44
UDL
Yes
45
FO
No
46
UDL
Yes
47
F1
No
48
M0
No
49
F1
No
50
UDL
Yes
51
F0
No
52
UDL
Yes
53
F0
No
54
UDL
Yes
55
F1
No
3. After the Terminal Equipment has waited through
the appropriate number of pulses via the TxOHEnable pin, it should then assert the TxOHIns
input signal. Concurrently, the Terminal Equipment should also place the appropriate value (of
the inserted overhead bit) onto the TxOH signal.
4. The Terminal Equipment should hold both the
TxOHIns input pin "High" and the value of the
TxOH signal stable, until the next TxOHEnable
pulse is detected.
Case Study: The Terminal Equipment intends to
insert the appropriate overhead bits into the
Transmit Overhead Data Input Interface (using
Method 2) in order to transmit a Yellow Alarm to
the remote terminal equipment.
In this case, the Terminal Equipment intends to insert
the appropriate overhead bits, into the Transmit Overhead Data Input Interface such that the XRT72L53
will transmit a Yellow Alarm to the remote terminal
equipment. Recall that, for DS3 applications, a Yellow Alarm is transmitted by setting all of the X bits to
0.
If one assumes that the connection between the Terminal Equipment and the XRT72L53 is as illustrated
in Figure 59 then, Figure 60 presents an illustration of
the signaling that must go on between the Terminal
Equipment and the XRT72L53.
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FIGURE 60. BEHAVIOR OF TRANSMIT OVERHEAD DATA INPUT INTERFACE SIGNALS BETWEEN THE XRT72L53 AND
TERMINAL EQUIPMENT (FOR METHOD 2)
THE
TxInClk
TxOHEnable Pulse # 8
TxOHFrame
TxOHEnable
TxOHIns
TxOH
X bit = 0
X bit = 0
Terminal Equipment
samples “TxOHFrame” and
“TxOHEnable” being “HIGH”
XRT72L5x samples TxOH
here.
Terminal Equipment
responds by asserting
TxOHIns and placing desired
data on TxOH.
4.2.3 The Transmit DS3 HDLC Controller
The Transmit DS3 HDLC Controller block can be
used to transport either Bit-Oriented Signaling (BOS)
or Message-Oriented Signaling (MOS) type messages or both types of messages to the remote terminal
equipment. Both BOS and MOS types of HDLC message processing are discussed in detail below.
4.2.3.1 Bit-Oriented Signaling (or FEAC Message) processing via the Transmit DS3 HDLC
Controller.
The Transmit DS3 HDLC Controller block consists of
two major blocks:
0
d5
d4
d3
d2
d1
d0
• The Transmit FEAC Processor.
• The LAPD Transmitter.
This section describes how to operate the Transmit
FEAC Processor. If the Transmit DS3 Framer is operating in the C-bit Parity Framing Format then the
FEAC (Far-End Alarm & Control) bit-field of the DS3
Frame can be used to transmit the FEAC messages
(See Figure 42). The FEAC code word is a 6-bit value which is encapsulated by 10 framing bits, forming
a 16-bit FEAC message of the form:
0
1
1
1
1
1
1
1
1
where '[d5, d4, d3, d2, d1, d0]' is the FEAC code
word. The rightmost bit (e.g., a 1) of the FEAC Message, is transmitted first. Since each DS3 frame contains only 1 FEAC bit, 16 DS3 Frames are required to
transmit the 16 bit FEAC Code Message.
• Tx DS3 FEAC Register (Address = 0x32)
The XRT72L53 contains the following two registers
that support FEAC Message Transmission.
In order to transmit a FEAC message to the remote
terminal, the user must execute the following steps.
• Tx DS3 FEAC Configuration and Status Register
(Address = 0x33)
Operating the Transmit FEAC Processor
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1. Write the 6-bit FEAC code (to be sent) into the Tx
DS3 FEAC Register.
2. Enable the Transmit FEAC Processor.
3. Initiate the Transmission of the FEAC Message.
Each of these steps will be described in detail below.
STEP 1 - Writing in the six bit FEAC Codeword (to
be sent)
In this step, the µP/µC writes the six bit FEAC code
word into the Tx DS3 FEAC Register. The bit format
of this register is presented below.
TX DS3 FEAC REGISTER (ADDRESS = 0X32)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT2
BIT 1
BIT 0
Not Used
TxFEAC[5]
TxFEAC[4]
TxFEAC[3]
TxFEAC[2]
TxFEAC[1]
TxFEAC[0]
Not Used
RO
R/W
R/W
R/W
R/W
R/W
R/W
R0
0
d5
d4
d3
d2
d1
d0
0
STEP 2 - Enabling the Transmit FEAC Processor
In order to enable the Transmit FEAC Processor
(within the Transmit DS3 HDLC Controller block) the
user must write a 1 into bit 2 (Tx FEAC Enable) within
the Tx DS3 FEAC Configuration and Status Register,
as depicted below.
TRANSMIT DS3 FEAC CONFIGURATION AND STATUS REGISTER (ADDRESS = 0X31)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT2
BIT 1
BIT 0
Not Used
Not Used
Not Used
TxFEAC
Interrupt
Enable
TxFEAC
Interrupt
Status
TxFEAC
Enable
TxFEAC
Go
TxFEAC
Busy
RO
RO
RO
R/W
RO
R/W
R/W
R0
x
x
x
x
x
1
X
X
At this point, the Transmit FEAC Processor can be
commanded to begin transmission (See STEP 3).
STEP 3 - Initiate the Transmission of the FEAC
Message
The user can initiate the transmission of the FEAC
code word (residing in the Tx DS3 FEAC register) by
writing a 1 to bit 1 (Tx FEAC Go) within the Tx DS3
FEAC Configuration and Status register, as depicted
below.
TRANSMIT DS3 FEAC CONFIGURATION AND STATUS REGISTER (ADDRESS = 0X31)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT2
BIT 1
BIT 0
Not Used
Not Used
Not Used
TxFEAC
Interrupt
Enable
TxFEAC
Interrupt
Status
TxFEAC
Enable
TxFEAC
Go
TxFEAC
Busy
RO
RO
RO
R/W
RO
R/W
R/W
R0
x
x
x
x
x
1
1
X
NOTE: While executing this particular write operation, the
user should write the binary value 000xx110b into the Tx
DS3 FEAC Configuration and Status Register. By doing
this the user insures that a 1 is also being written to Bit 2
(Tx FEAC Enable) of the register, in order to keep the
Transmit FEAC Processor enabled.
Once this step has been completed, the Transmit
FEAC Processor will proceed to transmit the 16 bit
FEAC code via the outbound DS3 frames. This 16 bit
FEAC message will be transmitted repeatedly 10
consecutive times. Hence, this process will require a
total of 160 DS3 Frames. During this process the Tx
FEAC Busy bit (Bit 0, within the Transmit DS3 FEAC
Configuration and Status register) will be asserted,
indicating that the Tx FEAC Processor is currently
transmitting the FEAC Message to the remote Terminal. This bit-field will toggle to "0" upon completion of
the 10th transmission of the FEAC Code Message.
The Transmit FEAC Processor will generate an interrupt (if enabled) to the local µP/µC, upon completion
of the 10th transmission of the FEAC Message. The
purpose of having the Framer IC generating this interrupt is to let the local µP/µC know that the Transmit
FEAC Processor is now available and ready to transmit a new FEAC message. Finally, once the Transmit
FEAC Processor has completed its 10th transmission
of a FEAC Code Message it will then begin sending
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all 1s in the FEAC bit-field of each DS3 Frame. The
Receive FEAC Processor (at the remote terminal
equipment) will interpret this all 1s message as an
Idle FEAC Message. The Transmit FEAC Processor
will continue sending all 1s in the FEAC bit field, for
an indefinite period of time, until the local µP/µC commands it to transmit a new FEAC message.
Figure 61 presents a flow chart depicting how to use
the Transmit FEAC Processor.
FIGURE 61. A FLOW CHART DEPICTING HOW TO TRANSMIT A FEAC MESSAGE VIA THE FEAC TRANSMITTER
START
START
TRANSMIT FEAC PROCESSOR PROCEEDS TO
TRANSMIT FEAC PROCESSOR PROCEEDS TO
INSERT THE 16-BIT MESSAGE (IN A BIT-BY-BIT
INSERT THE 16-BIT MESSAGE (IN A BIT-BY-BIT
MANNER) INTO THE “FEAC” BIT-FIELDS OF
MANNER) INTO THE “FEAC” BIT-FIELDS OF
EACH OUTBOUND DS3 FRAME.
EACH OUTBOUND DS3 FRAME.
11
WRITE SIX-BIT “OUTBOUND” FEAC VALUE
WRITE SIX-BIT “OUTBOUND” FEAC VALUE
INTO THE TxDS3 FEAC Register
INTO THE TxDS3 FEAC Register
This register is located at Address 0x32.
This register is located at Address 0x32.
NO
ENABLE THE TRANSMIT FEAC PROCESSOR.
ENABLE THE TRANSMIT FEAC PROCESSOR.
This is accomplished by writing “xxxx x1xx”
This is accomplished by writing “xxxx x1xx”
into the TxDS3 FEAC Configuration & Status Register
into the TxDS3 FEAC Configuration & Status Register
Has
Has
the 16-bit
the 16-bit
FEAC Message been
FEAC Message been
transmitted to the
transmitted to the
Remote Terminal
Remote Terminal
10 times
10 times
?
?
Is
Is
Transmission
Transmission
of the 16 Bit FEAC
of the 16 Bit FEAC
Message
Message
Complete
Complete
?
?
YES
YES
INITIATE TRANSMISSION OF THE “OUTBOUND”
INITIATE TRANSMISSION OF THE “OUTBOUND”
FEAC MESSAGE.
FEAC MESSAGE.
This is accomplished by writing “xxxx xx1x” into the
This is accomplished by writing “xxxx xx1x” into the
TxDS3 FEAC Configuration & Status Register.
TxDS3 FEAC Configuration & Status Register.
NO
GENERATE THE TRANSMIT FEAC
GENERATE THE TRANSMIT FEAC
INTERRUPT
INTERRUPT
TRANSMIT FEAC PROCESSOR ENCAPSULATES
TRANSMIT FEAC PROCESSOR ENCAPSULATES
THE “OUTBOUND” FEAC VALUE INTO A 16 BIT
THE “OUTBOUND” FEAC VALUE INTO A 16 BIT
FRAMING STRUCTURE.
FRAMING STRUCTURE.
INVOKE THE “TRANSMIT FEAC INTERRUPT
INVOKE THE “TRANSMIT FEAC INTERRUPT
SERVICE ROUTINE.
SERVICE ROUTINE.
1
1
For a detailed description of the Receive FEAC Processor (within the Receive DS3 HDLC Controller
block), please see Section 3.3.3.1.
4.2.3.2 Message-Oriented Signaling (e.g.,
LAP-D) processing via the Transmit DS3 HDLC
Controller
The LAPD Transmitter (within the Transmit DS3
HDLC Controller Block) allows the user to transmit
path maintenance data link (PMDL) messages to the
remote terminal via the outbound DS3 Frames. In
this case the message bits are inserted into and carried by the 3 DL bit fields of F-Frame #5 within each
DS3 M-frame. The on-chip LAPD transmitter supports both the 76 byte and 82 byte length message
formats, and the Framer IC allocates 88 bytes of onchip RAM (e.g., the Transmit LAPD Message buffer)
to store the message to be transmitted. The message format complies with ITU-T Q.921 (LAP-D) protocol with different addresses and is presented below
in Figure 62.
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FIGURE 62. LAPD MESSAGE FRAME FORMAT
Flag Sequence (8 bits)
SAPI (6-bits)
C/R
EA
EA
TEI (7 bits)
Control (8-bits)
76 or 82 Bytes of Information (Payload)
FCS - MSB
FCS - LSB
Flag Sequence (8-bits)
Control
Where: Flag Sequence = 0x7E
SAPI + CR + EA = 0x3C or 0x3E
The following sections defines each of these bit/bytefields within the LAPD Message Frame Format.
The Control identifies the type of frame being transmitted. There are three general types of frame formats: Information, Supervisory, and Unnumbered.
The Framer assigned the Control byte the value 0x03.
Hence, the Framer will be transmitting and receiving
Unnumbered LAPD Message frames.
Flag Sequence Byte
Information Payload
The Flag Sequence byte is of the value 0x7E, and is
used to for two purposes
The Information Payload is the 76 bytes or 82 bytes of
data (e.g., the PMDL Message) that the user has written into the on-chip Transmit LAPD Message buffer
(which is located at addresses 0x86 through 0xDD).
TEI + EA = 0x01
Control = 0x03
1. To denote the boundaries of the LAPD Message
Frame, and
2. To function as the Idle Pattern (e.g., Transmit
HDLC Controller block transmits a continuous
stream of flag sequence octets, whenever no
LAPD Message is being transmitted).
SAPI - Service Access Point Identifier
The SAPI bit-fields are assigned the value of
001111b or 15 (decimal).
TEI - Terminal Endpoint Identifier
The TEI bit-fields are assigned the value of 0x00.
The TEI field is used in N-ISDN systems to identify a
terminal out of multiple possible terminal. However,
since the Framer IC transmits data in a point-to-point
manner, the TEI value is unimportant.
It is important to note that the user must write in a
specific octet value into the first byte position within
the Transmit LAPD Message buffer (located at Address = 0x86, within the Framer). The value of this
octet depends upon the type of LAPD Message
frame/PMDL Message that the user wishes to transmit. Table 25 presents a list of the various types of
LAPD Message frames/PMDL Messages that are
supported by the XRT72L53 Framer and the corresponding octet value that the user must write into the
first octet position within the Transmit LAPD Message
buffer.
TABLE 25: THE LAPD MESSAGE TYPE AND THE CORRESPONDING VALUE OF THE FIRST BYTE, WITHIN THE
INFORMATION PAYLOAD
LAPD MESSAGE TYPE
VALUE OF FIRST BYTE, WITHIN
INFORMATION PAYLOAD OF MESSAGE
MESSAGE SIZE
CL Path Identification
0x38
76 bytes
IDLE Signal Identification
0x34
76 bytes
Test Signal Identification
0x32
76 bytes
ITU-T Path Identification
0x3F
82 bytes
Frame Check Sequence Bytes
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1. Specify the length of LAPD message to be transmitted.
2. Enable the LAPD Transmitter.
3. Initiate the Transmission of the PMDL Message.
Each of these steps will be discussed in detail.
The 16 bit FCS (Frame Check Sequence) is calculated over the LAPD Message Header and Information
Payload bytes, by using the CRC-16 polynomial, x16
+ x12 + x5 + 1.
Operation of the LAPD Transmitter
If a message is to be transmitted via the LAPD Transmitter, the information portion (or the body) of the
message must be written into the Transmit LAPD
Message Buffer, which is located at 0x86 through
0xDD in on-chip RAM via the Microprocessor Interface. Afterwards, the user must do three things:
STEP 1 - Specifying the Length of the LAPD Message
One of two different sizes of LAPD Messages can be
transmitted. This is accomplish by writing the appropriate data to bit 1 within the Tx DS3 LAPD Configuration Register. The bit-format of this register is presented below.
TRANSMIT DS3 LAPD CONFIGURATION REGISTER (ADDRESS = 0X33)
BIT 7
BIT 6
BIT 5
BIT 4
Not Used
BIT 3
BIT2
BIT 1
BIT 0
Auto
Retransmit
Not Used
TxLAPD
Msg Length
TxLAPD
Enable
R/O
R/O
R/O
R/O
R/W
R/O
R/W
R/W
0
0
0
0
X
0
X
X
The relationship between the contents of bit-fields 1
and the LAPD Message size is given in Table 26.
TABLE 26: RELATIONSHIP BETWEEN TXLAPD MSG
LENGTH AND THE LAPD MESSAGE SIZE
TXLAPD MSG LENGTH
LAPD MESSAGE LENGTH
0
LAPD Message size is 76 bytes
1
LAPD Message size is 82 bytes
NOTE: The Message Type selected must correspond with
the contents of the first byte of the Information (Payload)
portion, as presented in Table 25.
STEP 2 - Enabling the LAPD Transmitter
Prior to the transmission of any data via the LAPD
Transmitter the LAPD Transmitter must be enabled.
This is accomplish this by writing a 1 to bit 0 of the Tx
DS3 LAPD Configuration Register, as depicted below.
TRANSMIT DS3 LAPD CONFIGURATION REGISTER (ADDRESS = 0X33)
BIT 7
BIT 6
BIT 5
BIT 4
Not Used
BIT 3
BIT2
BIT 1
BIT 0
Auto
Retransmit
Not Used
TxLAPD
Msg Length
TxLAPD
Enable
R/O
R/O
R/O
R/O
R/W
R/O
R/W
R/W
0
0
0
0
X
0
X
1
Bit 0 - TxLAPD Enable
This bit-field allow the user to enable or disable the
LAPD Transmitter in accordance with Table 27.
TABLE 27: RELATIONSHIP BETWEEN TXLAPD MSG LENGTH AND THE LAPD MESSAGE SIZE
TXLAPD ENABLE
RESULTING ACTION OF THE LAPD TRANSMITTER
0
The LAPD Transmitter is disabled and the DL bits, in the DS3 frame,
are transmitted as all 1s.
1
The LAPD Transmitter is enabled and is transmitting a continuous
stream of Flag Sequence octets (0x7E).
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Prior to executing step 2 (Enabling the LAPD Transmitter), the LAPD Transmitter will be disabled and the
Transmit DS3 Framer block will be setting each of the
DL bits (within the outbound DS3 data stream) to 1.
After the user executes this step, the LAPD Transmitter will begin transmitting the flag sequence octet
(0x7E) via the DL bits.
At this point, the LAPD Transmitter is ready to begin
transmission. The user has written the information
portion of the PMDL message into the on-chip Transmit LAPD Message buffer. Further, the user has
specified the type of LAPD message that he/she
wishes to transmit, and has enabled the LAPD Transmitter. The only thing remaining to do is to initiate the
transmission of this message. The user initiates this
process by writing a "1" to Bit 3 of the Tx DS3 LAPD
Status/Interrupt Register (TxDL Start). The bit format
of this register is presented below.
NOTE: Upon power up or reset, the LAPD Transmitter is
disabled. Therefore, the user must set this bit to "1" in order
to enable the LAPD Transmitter.
STEP 3 - Initiate the Transmission
TRANSMIT DS3 LAPD STATUS/INTERRUPT REGISTER (ADDRESS = 0X34)
BIT 7
BIT 6
BIT 5
BIT 4
Not Used
BIT 3
BIT2
BIT 1
BIT 0
Tx DL
Start
Tx DL
Busy
TxLAPD
Interrupt
Enable
TxLAPD
Interrupt
Status
R/O
R/O
R/O
R/O
R/W
RO
R/W
RUR
0
0
0
0
1
X
X
X
• Append a trailer Flag Sequence octet to the end of
the message LAPD (following the 16 bit FCS
value).
A "0" to "1" transition of Bit 3 (TxDL Start) in this register, initiates the transmission of the data link message. While the LAPD transmitter is transmitting the
message, the 'TxDL Busy' (bit 2) bit will be set to 1.
This bit-field allows the user to poll the status of the
LAPD Transmitter. Once the message transfer is
completed, this bit-field will toggle back to '0'.
• Serialize the composite LAPD message and begin
inserting the LAPD message into the DL bit fields of
each outgoing DS3 Frame.
The user can configure the LAPD Transmitter to interrupt the µC/µP upon completion of transmission of
the LAPD Message, by setting bit-field "1" (TxLAPD
Interrupt Enable) of the Tx DS3 LAPD Status/Interrupt register to 1. The purpose of this interrupt is to let
the local µC/µP know that the LAPD Transmitter is
available and ready to transmit a new message. Bit 0
will reflect the interrupt status for the LAPD Transmitter.
NOTE: This bit-field will be reset on reading this register.
Details Associated with the Transmission of a
PMDL Message
Once the user has invoked the TxDL Start command,
the LAPD Transmitter will do the following.
• Generate the four octets of LAPD frame header
(e.g., Flag Sequence, SAPI, TEI, Control, etc.) and
insert it into the LAPD Message, prior to the user's
information (see the LAPD Message Frame Format
in Figure 62).
• Compute the 16 bit Frame Check Sum (FCS) of the
LAPD Message Frame (e.g., of the LAPD Message
header and information payload) and append this
value to the LAPD Message.
• Complete the transmission of the frame overhead,
payload, FCS value, and trailer Flag Sequence
octet via the Transmit DS3 Framer.
Once the LAPD Transmitter has completed its transmission of the LAPD Message, the Framer will generate an interrupt to the local µC/µP (if enabled). Afterwards, the LAPD Transmitter will proceed to retransmit the LAPD Message, repeatedly at one second intervals. During Idle periods (e.g., in between these
transmission of the LAPD Message), the LAPD
Transmitter will be sending a continuous stream of
Flag Sequence Bytes. The LAPD Transmitter will
continue this behavior until the user has disabled the
LAPD Transmitter by writing a "0" to bit 0 (TxLAPD
Enable) within the Tx DS3 LAPD Configuration Register. If the LAPD Transmitter is idle, then it will continuously send the Flag Sequence octets (via the DL
bits of each outbound DS3 Frame) to the remote terminal equipment.
NOTE: In order to prevent the user's data (e.g., the payload
portion of the LAPD Message Frame) from mimicking the
Flag Sequence byte, the LAPD Transmitter will insert a "0"
into the LAPD data stream immediately following the detection of five (5) consecutive 1s (this stuffing occurs only while
the information payload is being transmitted). The 'remote'
LAPD Receiver (see Section 4.3.3.2) will have the responsibility of detecting the 5 consecutive 1s and removing the
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subsequent "0" from the payload portion of the incoming
LAPD message.
Figure 63 presents a flow chart depicting the procedure (in 'white boxes') that the user should use in or-
der to transmit a LAPD message. This figure also indicates (via the shaded boxes) what the LAPD Transmitter circuitry will do before and during message
transmission.
FIGURE 63. FLOW CHART DEPICT HOW TO USE THE LAPD TRANSMITTER
LAPD Transmitter inserts Frame Header
octets in front of the user payload.
START
START
WRITE IN DATA LINK INFORMATION
LAPD Transmitter computes the 16 bit FCS
(a CRC-16 value) and inserts it into the LAPD
Message, following the user payload
The user accomplishes this by writing the
information that he/she wishes to transmit
(via the LAPD Transmitter) to locations 0x86
through 0xDD, within the Framer Address Space.
LAPD Transmitter appends a Flag Sequence
Trailer octet to the end of the LAPD Message
(after the 16 bit FCS).
ENABLE THE LAPD
TRANSMITTER FOR TRANSMISSION
This is accomplished by writing 00000xx1b
to the Tx DS3 LAPD Configuration Register.
(where xx dictates LAPD Message Length)
Is
5 consecutive
“1s” detected
?
No
INITIATE TRANSMISSION OF LAPD
MESSAGE
No
This is accomplished by writing 000010x0b
to the Tx DS3 LAPD Status/Interrupt
Register. (where x indicates the user’s choice
to enable/disable “LAPD Message Transfer
Complete” Interrupt
The Mechanics of Transmitting a New LAPD Message
As mentioned above, after the LAPD Transmitter has
been enabled, and commanded to transmit the message, residing in the Transmit LAPD Message buffer,
it will continue to transmit this message at one-second intervals. If another (e.g., different) PMDL message is to be transmitted to the Remote LAPD Receiver, the new message will have to be written into
the Transmit LAPD Message buffer, via the Microprocessor Interface section of the Framer. However,
care must be taken when writing in this new message. If this message is written into the Transmit
Is
Message
Transmission
Complete
?
Yes
Insert a “0” after the
string of 5 consecutive
“1s”
Yes
END
Generate Interrupt
LAPD Transmitter will
continue to transmit
Flag Sequence octets.
LAPD Message buffer at the wrong time (with respect
to these one-second transmissions), the user's action
could interfere with these transmissions, thereby
causing the LAPD Transmitter to transmit a corrupted
message to the Remote LAPD Receiver. In order to
avoid this problem, while writing the new message into the Transmit LAPD Message buffer, the user
should do the following:
1. Configure the Framer to automatically reset activated interrupts
This can be done by writing a "1" into Bit 3 of the
Framer Operating Mode Register, as depicted below.
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REV. P1.1.7
FRAMER OPERATING MODE REGISTER (ADDRESS = 0X00)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT2
Local Loopback
DS3/E3*
Internal
LOS
Enable
RESET
Interrupt
Enable
Reset
Frame
Format
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
1
1
0
1
X
X
X
This action will prevent the LAPD Transmitter from
generating its own one-second interrupts.
BIT 1
BIT 0
TimRefSel[1:0]
This can be done by writing a "1" into Bit 0 of the
Block Interrupt Enable Register, as depicted below.
2. Enable the One-Second Interrupt
BLOCK INTERRUPT ENABLE REGISTER (ADDRESS = 0X04)
BIT 7
BIT 6
BIT 5
RxDS3/E3
Interrupt
Enable
BIT 4
BIT 3
BIT2
Not Used
BIT 1
BIT 0
TxDS3/E3
Interrupt
Enable
One Second
Interrupt
Enable
R/W
RO
RO
RO
RO
RO
R/W
R/W
0
0
0
0
0
0
0
X
3. Write the new message into the Transmit LAPD
Message buffer immediately after the occurrence
of the One-Second interrupt.
By timing the writes to the Transmit LAPD Message
buffer to occur immediately after the occurrence of
the One-Second interrupt, the user avoids conflicting
with the one-second transmissions of the LAPD Message, and will transmit the correct messages to the
remote LAPD Receiver.
4.2.4
The Transmit DS3 Framer Block
4.2.4.1 Brief Description of the Transmit DS3
Framer
The Transmit DS3 Framer block accepts data from
any of the following three sources, and uses it to form
the DS3 data stream.
• The Transmit Payload Data Input block
• The Transmit Overhead Data Input block
• The Transmit HDLC Controller block
• The Internal Overhead Data Generator
The manner in how the Transmit DS3 Framer block
handles data from each of these sources is described
below.
Handling of data from the Internal Overhead Bit
Generator
By default, the Transmit DS3 Framer block will internally generate the overhead bits. However, if the Terminal Equipment inserts its own values for the overhead bits (via the Transmit Overhead Data Input Interface) or, if the user enables and employs the Transmit
DS3 HDLC Controller block, then these internally
generated overhead bits will be overwritten.
Handling of data from the Transmit Overhead Data Input Interface
For DS3 applications, the Transmit DS3 Framer block
automatically generates and inserts the framing alignment bits (e.g., the F and M bits) into the outbound
DS3 frames. Further, the Transmit DS3 Framer block
will automatically compute and insert the P-bits into
the outbound DS3 frames. Hence, the Transmit DS3
Framer block will not accept data from the Transmit
OH Data Input Interface block for the F, M and P bits.
However, the Transmit DS3 Framer block will accept
(and insert) data from the Transmit Overhead Data Input Interface for the following bit-fields.
• X-bits
Handling of data from the Transmit Payload Data
Input Interface
• FEBE bits
For DS3 applications, all data that is input to the
Transmit Payload Data Input Interface will be inserted
into the payload bit positions within the outbound DS3
frames.
• DL bits
• FEAC bits
• UDL bits
• CP bits
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“MOS” type message, then data will be inserted into
the FEAC and “DL” bit-fields as described in Section
3.2.3.
If the user's local Data Link Equipment activates the
Transmit Overhead Data Input Interface block and
writes data into this interface for these bits, then the
Transmit DS3 Framer block will insert this data into
the appropriate overhead bit-fields, within the outbound DS3 frames.
4.2.4.2 Detailed Functional Description of the
Transmit DS3 Framer Block
The Transmit DS3 Framer receives data from the following three sources and combines them together to
form a DS3 data stream.
Handling of Data from the Transmit HDLC Controller block
The exact manner in how the Transmit DS3 Framer
handles data from the Transmit HDLC Controller
block depends upon whether the Transmit HDLC
Controller is transmitting BOS (Bit Oriented Signaling) or MOS (Message Oriented Signaling) data.
• The Transmit Payload Data Input Interface block.
• The Transmit Overhead Data Input Interface block
• The Transmit HDLC Controller block.
Afterwards, this DS3 data stream will be routed to the
Transmit DS3 LIU Interface block, for further processing.
If the Transmit DS3 HDLC Controller block is not activated, then the Transmit DS3 Framer block will insert
a “1” into each FEAC and “DL” bit-field, within each
outbound DS3 frame.
Figure 64 presents a simple illustration of the Transmit DS3 Framer block, along with the associated
paths to the other functional blocks within the chip.
If the Transmit DS3 HDLC Controller block is activated, and is configured to transmit either a “BOS” or
FIGURE 64. A SIMPLE ILLUSTRATION OF THE TRANSMIT DS3 FRAMER BLOCK AND THE ASSOCIATED PATHS TO
FUNCTIONAL BLOCKS
OTHER
Transmit HDLC
Controller/Buffer
Transmit Overhead
Data Input Interface
Transmit
Transmit
DS3
DS3Framer
Framer
Block
Block
To Transmit DS3 LIU Interface Block
Transmit Payload Data
Input Interface
In addition to taking data from multiple sources and
multiplexing them, in appropriate manner, to create
the outbound DS3 frames, the Transmit DS3 Framer
block has the following roles.
ters, to override the data that is being written into the
Transmit Payload Data and Overhead Data Input Interfaces and transmit the following alarm conditions.
• Generating Alarm Conditions
• Manipulate the X-bit (set them to 1)
• Generating Errored Frames (for testing purposes)
• Generate the AIS Pattern
• Routing outbound DS3 frames to the Transmit DS3
LIU Interface block
• Generate the IDLE pattern
Each of these additional roles are discussed below.
4.2.4.2.1 Generating Alarm Conditions
The Transmit DS3 Framer block permits the user to,
by writing the appropriate data into the on-chip regis-
• Generate the Yellow Alarms (or FERF indicators)
• Generate the LOS pattern
• Generate FERF (Yellow) Alarms, in response to
detection of a Red Alarm condition (via the Receive
Section of the XRT72L53).
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• Generate and transmit a desired value for FEBE
(Far-End-Block Error).
The procedure and results of generating any of these
alarm conditions is presented below.
The user can exercise each of these options by writing the appropriate data to the Tx DS3 Configuration
Register (Address = 0x30). The bit format of this register is presented below.
TX DS3 CONFIGURATION REGISTER (ADDRESS = 0X30)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT2
BIT 1
BIT 0
Tx
Yellow Alarm
Tx X-Bit
Tx IDLE
Pattern
Tx AIS
Pattern
Tx LOS
Pattern
FERF on
LOS
FERF on
OOF
FERF on
AIS
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
1
0
1
0
1
1
The role/function of each of these bit-fields within the
register, are discussed below.
4.2.4.2.1.1 Transmit Yellow Alarm - Bit 7
This read/write bit field permits the user to force the
transmission of a Yellow Alarm to the remote terminal
equipment via software control. If the user opts to
transmit a Yellow Alarm then both of the X-bits, within
the outbound DS3 frames will be set to '0'. Table 28
relates the content of this bit field to the Transmit DS3
Framer block's action.
TABLE 28: THE RELATIONSHIP BETWEEN THE CONTENTS OF BIT 7 (TX YELLOW ALARM) WITHIN THE TX DS3
CONFIGURATION REGISTER, AND THE RESULTING TRANSMIT DS3 FRAMER BLOCK'S ACTION
BIT 7
TRANSMIT DS3 FRAMER'S ACTION
0
Normal Operation:
The X-bits are generated by the Transmit DS3 Framer block based upon Near End Receiving Conditions (as
detected by the Receive Section of the chip)
1
Transmit Yellow Alarm:
The Transmit DS3 Framer block will overwrite the X-bits by setting them all to 0. The payload information is
not modified and is transmitted as normal.
NOTE: This bit is ignored when either the TxIDLE, TxAIS, or
the TxLOS bit-fields are set.
4.2.4.2.1.2 Transmit X-bit - Bit 6
This bit field functions as the logical complement to
Bit 7 (e.g., Tx Yellow Alarm). This read/write bit field
permits the user to force all of the X-bits, in the outbound DS3 frames, to "1" and transmit them to the remote terminal equipment. Table 29 relates the content of this bit field to the Transmit DS3 Framer
Block's action.
TABLE 29: THE RELATIONSHIP BETWEEN THE CONTENTS OF BIT 6 (TX X-BITS) WITHIN THE TX DS3 CONFIGURATION
REGISTER, AND THE RESULTING TRANSMIT DS3 FRAMER BLOCK'S ACTION
BIT 6
TRANSMIT DS3 FRAMER'S ACTION
0
Normal Operation:
The X-bits are generated by the Transmit DS3 Framer block based upon Receiving Conditions (as detected
by the Receive Section of the Framer chip).
1
Set X-bits to 1:
The Transmit DS3 Framer will overwrite the X-bits by setting them to 1. Payload information is not modified
and is transmitted as normal.
NOTE: This bit is ignored when either the Transmit Yellow
Alarm, Tx AIS, Tx IDLE, or TxLOS bit is set.
4.2.4.2.1.3
Transmit Idle Pattern - Bit 5
This read/write bit field permits the user to transmit an
Idle pattern to the remote terminal equipment upon
software control. Table 30 relates the contents of this
bit field to the Transmit DS3 Framer's action.
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TABLE 30: THE RELATIONSHIP BETWEEN THE CONTENTS OF BIT 5 (TX IDLE) WITHIN THE TX DS3 CONFIGURATION
REGISTER, AND THE RESULTING TRANSMIT DS3 FRAMER ACTION
BIT 5
TRANSMIT DS3 FRAMER'S ACTION
0
Normal Operation:
The Overhead bits are either internally generated, or they are inserted via the Transmit Overhead Data Input
Interface or the Transmit HDLC Controller blocks. The Payload bits are received from the Transmit Payload Data
Input Interface.
1
Transmit Idle Condition Pattern:
When this command is invoked, the Transmit DS3 Framer will do the following:
• Set the X-bits to 1
• Set the CP-Bits (F-Frame #3) to 0
• Generate Valid M, F, and P bits
Overwrite the data in the DS3 payload with a repeating 1100... pattern.
NOTE: This bit is ignored when either the Tx AIS or the Tx
LOS bit is set.
4.2.4.2.1.4
Transmit AIS Pattern - Bit 4
This read/write bit field allows the user to transmit an
AIS pattern to the remote terminal equipment, upon
software control. Table 31 relates the contents of this
bit field to the Transmit DS3 Framer block's action.
TABLE 31: THE RELATIONSHIP BETWEEN THE CONTENTS OF BIT 4 (TX AIS PATTERN) WITHIN THE TX DS3
CONFIGURATION REGISTER, AND THE RESULTING TRANSMIT DS3 FRAMER BLOCK'S ACTION
BIT 4
TRANSMIT DS3 FRAMER'S ACTION
0
Normal Operation:
The Overhead bits are either internally generated, or they are inserted via the Transmit Overhead Data Input
Interface or the Transmit HDLC Controller blocks. The Payload bits are received from the Transmit Payload Data
Input Interface.
1
Transmit AIS Pattern:
When this command is invoked, the Transmit DS3 Framer block will do the following.
• Set the X-bits to 1
• Set all the C-bits to 0
• Generate valid M, F, and P bits
Overwrite the data in the DS3 payload with a repeating 1010... pattern
NOTE: This bit is ignored when the TxLOS bit is set.
4.2.4.2.1.5 Transmit LOS Pattern - Bit 3
This read/write bit field allows the user to transmit an
LOS (Loss of Signal) pattern to the remote terminal,
upon software control. Table 32 relates the contents
of this bit field to the Transmit DS3 Framer block's action.
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TABLE 32: THE RELATIONSHIP BETWEEN THE CONTENTS OF BIT 3 (TX LOS) WITHIN THE TX DS3 CONFIGURATION
REGISTER, AND THE RESULTING TRANSMIT DS3 FRAMER BLOCK'S ACTION
BIT 3
TRANSMIT DS3 FRAMER'S ACTION
0
Normal Operation:
The Overhead bits are either internally generated, or they are inserted via the Transmit Overhead Data Input
Interface or the Transmit HDLC Controller blocks. The Payload bits are received from the Transmit Payload
Data Input Interface.
1
Transmit LOS Pattern:
When this command is invoked the Transmit DS3 Framer will do the following.
• Set all of the overhead bits to "0" (including the M, F, and P bits)
Overwrite the DS3 payload bits with an all zeros pattern.
NOTE: When this bit is set, it overrides all of the other bits in
this register.
Writing a "1" to this bit-field enables this feature. Writing a "0" to this bit-field disables this feature.
4.2.4.2.1.6 FERF (Far-End Receive Failure) on
LOS - Bit 2
This Read/Write bit-field allows the user to configure
the Transmit DS3 Framer block to automatically generate a Yellow Alarm if the Near-End Receive Section
(of the XRT72L53) detects a LOS (Loss of Signal)
Condition.
4.2.4.2.1.9 Transmitting FEBE (Far-End Block
Error) Values
By default, the Transmit DS3 Framer block will set the
three (3) FEBE bit-fields to [1, 1, 1] if all of the following conditions are true.
• The Local Receive DS3 Framer block detects no PBit Errors.
Writing a "1" to this bit-field enables this feature. Writing a "0" to this bit-field disables this feature.
4.2.4.2.1.7 FERF (Far-End Receive Failure) on
OOF - Bit 1
This Read/Write bit-field allows the user to configure
the Transmit DS3 Framer block to automatically generate a Yellow Alarm if the Near-End Receive Section
(of the XRT72L53) detects an OOF (Out-of-Frame)
Condition.
• The Local Receive DS3 Framer block detects no
CP-Bit Errors
Conversely, the Transmit DS3 Framer block will set
the three (3) FEBE bit-fields to a value other than [1,
1, 1] if any one of the following conditions are true.
• The Local Receive DS3 Framer block detects a Pbit Error in the most recently received DS3 frame.
Writing a "1" to this bit-field enables this feature. Writing a "0" to this bit-field disables this feature.
• The Local Receive DS3 Framer block detects a
“CP” bit Error in the most recently received DS3
frame.
4.2.4.2.2 Generating Errored DS3 Frames
The Transmit DS3 Framer block permits the user to
insert errors into the framing and error detection overhead bits (e.g., the P, M and F-bits) of the outbound
DS3 data stream in order to support Far-End Equipment testing. The user can exercise this option by
writing data to any of the numerous Transmit DS3
Mask Registers. These Mask Registers and their
comprising bit-fields are defined below.
4.2.4.2.1.8 FERF (Far-End Receive Failure) on
AIS - Bit 0
This Read/Write bit-field allows the user to configure
the Transmit DS3 Framer block to automatically generate a Yellow Alarm if the Near-End Receive Section
(of the XRT72L53) detects an AIS (Alarm Indication
Signal) pattern.
TX DS3 M-BIT MASK REGISTER, ADDRESS = 0X35
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
TxFEBE
DAT[2]
TxFEBE
DAT[1]
TxFEBE
DAT[0]
FEBE Reg
Enable
TxErr PBit
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
X
X
X
X
X
X
X
X
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BIT 1
BIT 0
MBit Mask(2) MBit Mask(1) MBit Mask(0)
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REV. P1.1.7
Bits 2 - 0: M-Bit Mask[2:0]
The bit-fields of the Tx DS3 M-bit Mask Register, that
are relevant to error-insertion are shaded. The remaining bit-fields pertain to the FEBE bit-fields, and
are discussed in Section 4.2.4.2.1.9.
The Transmit DS3 Framer will automatically perform
an XOR operation with the M-bits (in the DS3 datastream) and the contents of the corresponding bitfield, within this register. The results of this operation
will be written back into the M-bit positions within the
outbound DS3 Frames. Therefore, to insure that no
errors are inserted into the M-bits, make sure that the
contents of the M-Bit Mask[2:0] bit-fields are 0.
The Tx DS3 M-Bit Mask Register serves two purposes
1. It allows the user to transmit his/her own value for
FEBE (3 bits) - please see Section 4.2.4.2.1.9.
2. It allows the user to transmit errored P-bits.
3. It allows the user to insert errors into the M-bit
(framing bits) in order to support equipment testing.
Each of these bit-fields are discussed below.
F-Bit Error Insertion
The remaining mask registers (Tx DS3 F-Bit Mask1
through Mask4 registers) contain bit-fields which correspond to each of the 28 F-bits, within the DS3
frame. Prior to transmission, these bit-fields are automatically XORed with the contents of the corresponding bit fields within these Mask Registers. The result
of this XOR operation is written back into the corresponding bit-field, within the outgoing DS3 frame, and
is transmitted on the line. Therefore, if none of the
bits are to be modified, then these registers must contain all 0s (the default value).
Bit 3 - Tx Err (Transmit Errored) P-Bit
This bit-field allows the user to insert errors into the
P-bits, of each outbound DS3 Frame, for equipment
testing purposes. If this bit-field is 0, then the P-Bits
are transmitted as calculated from the payload of the
previous DS3 frames. However, if this bit-field is 1,
then the P-bits are inverted (from their calculated value) prior to transmission.
TX DS3 F-BIT MASK1 REGISTER, ADDRESS = 0X36
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT2
BIT 1
BIT 0
Unused
Unused
Unused
Unused
RO
RO
RO
RO
R/W
R/W
R/W
R/W
0
0
0
0
0
0
0
0
BIT 3
BIT2
BIT 1
BIT 0
FBit Mask(27) FBit Mask(26) FBit Mask(25) FBit Mask(24)
TX DS3 F-BIT MASK2 REGISTER, ADDRESS = 0X37
BIT 7
BIT 6
BIT 5
BIT 4
FBit Mask(23) FBit Mask(22) FBit Mask(21) FBit Mask(20) FBit Mask(19) FBit Mask(18) FBit Mask(17) FBit Mask(16)
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
0
0
BIT 3
BIT2
BIT 1
BIT 0
TX DS3 F-BIT MASK3 REGISTER, ADDRESS = 0X38
BIT 7
BIT 6
BIT 5
BIT 4
FBit Mask(15) FBit Mask(14) FBit Mask(13) FBit Mask(12) FBit Mask(11) FBit Mask(10) FBit Mask(9)
FBit Mask(8)
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
0
0
TX DS3 F-BIT MASK4 REGISTER, ADDRESS = 0X39
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT2
BIT 1
BIT 0
FBit Mask(7)
FBit Mask(6)
FBit Mask(5)
FBit Mask(4)
FBit Mask(3)
FBit Mask(2)
FBit Mask(1)
FBit Mask(0)
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
0
0
4.2.5
The Transmit DS3 Line Interface Block
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XRT72L53
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THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. P1.1.7
The XRT72L53 Framer IC is a digital device that
takes DS3 payload and overhead bit information from
some terminal equipment, processes this data and ultimately, multiplexes this information into a series of
outbound DS3 frames. However, for DS3 coaxial cable applications, the XRT72L53 Framer IC lacks the
current drive capability to be able to directly transmit
this DS3 data stream through some transformer-coupled coax cable with enough signal strength for it to
comply with the Isolated Pulse Template requirements and be received by the remote receiver.
Therefore, in order to get around this problem, the
Framer IC requires the use of an LIU (Line Interface
Unit) IC. An LIU is a device that has sufficient drive
capability, along with the necessary pulse-shaping
circuitry to be able to transmit a signal through the
transmission medium in a manner that it can (1) comply with the DSX-3 Isolated Pulse Template requirements and (2) be reliably received by the Remote Terminal Equipment. Figure 65 presents a circuit drawing depicting the Framer IC interfacing to an LIU
(XRT7300 DS3/E3/STS-1 Transmit LIU).
FIGURE 65. APPROACH TO INTERFACING THE XRT72L53 FRAMER IC TO THE XRT73L03 DS3/E3/STS-1 TRANSLIU (ONE CHANNEL SHOWN)
MITTER
U1
TxSER
TxInClk
TxFrame
NIBBLEINTF
RESETB
INTB
CSB
RW
DS
AS
INTB
A[8:0]
46
43
61
25
28
13
8
7
10
9
6
15
16
17
18
19
20
21
22
23
U2
TxSER
TxInClk
TxFrame
R1
TxPOS
TPDATA
TxNEG
TNDATA
5V
32
33
34
35
36
37
38
39
86
88
90
TxLineClk
TCLK
DMO
DMO
RESETB
INTB
CSB
WRB_RW
RDB_DS
ALE_AS
Rdy_Dtck
A0
A1
A2
A3
A4
A5
A6
A7
A8
R2
TRING
ExtLOS
RLOS
RLOL
RLOL
LLOOP
LLB
RLOOP
RLB
D0
D1
D2
D3
D4
D5
D6
D7
4
8
TTIP
TRING
1:1
2
44
1
R3
2
270
MRING
1
43
R4
2
270
TAOS
TAOS
TxLEV
TxLEV
ENCODIS
REQB
REQDIS
RTIP
MOTO
RxPOS
RxSer
RxClk
RxFrame
5
RxNEG
33
8
RNEG
31
1 T2
5
4
8
R5
37.5
RPOS
32
RCLK1
RRING
9
RTIP
RRING
1:1
1
95
94
93
87
1
40
1 T1
36
MTIP
RxLineClk
RxLOS
RxOOF
RxRED
RxAIS
2
2
RxSer
RxClk
RxFrame
1
1
27
41
36
NIBBLEINTF
ENCODIS
D[7:0]
TTIP
RxLOS
RxOOF
RxRED
RxAIS
R6
XRT73L0x
37.5
1
XRT72L5x
2
C1
2
0.01uF
The Transmit Section of the XRT72L53 contains a
block which is known as the Transmit DS3 LIU Interface block. The purpose of the Transmit DS3 LIU Interface block is to take the outbound DS3 data
stream, from the Transmit DS3 Framer block, and to
do the following:
1. Encode this data into one of the following line
codes
a. Unipolar (e.g., Single-Rail)
b. AMI (Alternate Mark Inversion)
c. B3ZS (Bipolar 3 Zero Substitution)
2. And to transmit this data to the LIU IC.
Figure 66 presents a simple illustration of the Transmit DS3 LIU Interface block.
193
áç
XRT72L53
THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. P1.1.7
FIGURE 66. A SIMPLE ILLUSTRATION OF THE TRANSMIT DS3 LIU INTERFACE BLOCK
TxPOS
Transmit DS3
LIU Interface
Block
From Transmit DS3
Framer Block
TxNEG
TxLineClk
od, at the start of each new DS3 frame, and will remain "Low" for the remainder of the frame. Figure 67
presents an illustration of the TxPOS and TxNEG signals during data transmission while the Transmit DS3
LIU Interface block is operating in the Unipolar mode.
This mode is sometimes referred to as Single Rail
mode because the data pulses only exist in one polarity: positive.
The Transmit DS3 LIU Interface block can transmit
data to the LIU IC or other external circuitry via two
different output modes: Unipolar or Bipolar. If the Unipolar (or Single Rail) mode is selected, then the contents of the DS3 Frame is output, in a binary (NRZ
manner) data stream via the TxPOS pin to the LIU IC.
The TxNEG pin will only be used to denote the frame
boundaries. TxNEG will pulse "High" for one bit peri-
FIGURE 67. THE BEHAVIOR OF TXPOS AND TXNEG SIGNALS DURING DATA TRANSMISSION WHILE THE TRANSMIT
DS3 LIU INTERFACE IS OPERATING IN THE UNIPOLAR MODE
Data
1
0
1
1
0
0
1
0
0
1
1
1
0
1
0
1
0
0
1
1
1
0
0
1
TxPOS
TxNEG
TxLineClk
Frame Boundary
When the Transmit DS3 LIU Interface block is operating in the Bipolar (or Dual Rail) mode, then the contents of the DS3 Frame is output via both the TxPOS
and TxNEG pins. If the Bipolar mode is chosen, then
the DS3 data to the LIU can be transmitted via one of
two different line codes: Alternate Mark Inversion
(AMI) or Binary - 3 Zero Substitution (B3ZS). Each
one of these line codes will be discussed below. Bipolar mode is sometimes referred to as Dual Rail because the data pulses occur in two polarities: positive
and negative. The role of the TxPOS, TxNEG and
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XRT72L53
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THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. P1.1.7
TxPOS - Transmit Positive Polarity Pulse: The
Transmit DS3 LIU Interface block will assert this output to the LIU IC when it desires for the LIU to generate and transmit a positive polarity pulse to the remote terminal equipment.
TxLineClk - Transmit Line Clock: The LIU IC uses
this signal from the Transmit DS3 LIU Interface block
to sample the state of its TxPOS and TxNEG inputs.
The results of this sampling dictates the type of pulse
(positive polarity, zero, or negative polarity) that it will
generate and transmit to the remote Receive DS3
Framer.
TxNEG - Transmit Negative Polarity Pulse: The
Transmit DS3 LIU Interface block will assert this output to the LIU IC when it desires for the LIU to generate and transmit a negative polarity pulse to the remote terminal equipment.
4.2.5.1 Selecting the various Line Codes
Either the Unipolar Mode or Bipolar Mode can be selected by writing the appropriate value to Bit 3 of the I/
O Control Register (Address = 0x01), as shown below.
TxLineClk output pins, for this mode are discussed
below.
I/O CONTROL REGISTER (ADDRESS = 0X01)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT2
BIT 1
BIT 0
Disable TxLOC
LOC
Disable
RxLOC
AMI/ZeroSup*
Unipolar/
Bipolar*
TxLine CLK
Invert
RxLine CLK
Invert
Reframe
R/W
RO
R/W
R/W
R/W
R/W
R/W
R/W
1
0
1
0
0
0
0
0
Table 33 relates the value of this bit field to the Transmit DS3 LIU Interface Output Mode.
TABLE 33: THE RELATIONSHIP BETWEEN THE CONTENT OF BIT 3 (UNIPOLAR/BIPOLAR*) WITHIN THE UNI I/O
CONTROL REGISTER AND THE TRANSMIT DS3 FRAMER LINE INTERFACE OUTPUT MODE
BIT 3
TRANSMIT DS3 FRAMER LIU INTERFACE OUTPUT MODE
0
Bipolar Mode: AMI or B3ZS Line Codes are Transmitted and Received
1
Unipolar (Single Rail) Mode of transmission and reception of DS3 data is selected.
NOTES:
1. The default condition is the Bipolar Mode.
2. This selection also effects the operation of the
Receive DS3 LIU Interface block
4.2.5.1.1 The Bipolar Mode Line Codes
If framer is to be operated in the Bipolar Mode, then
the DS3 data-stream can be transmitted via the AMI
(Alternate Mark Inversion) or the B3ZS Line Codes.
The definition of AMI and B3ZS line codes follow.
4.2.5.1.1.1 The AMI Line Code
AMI or Alternate Mark Inversion, means that consecutive one's pulses (or marks) will be of opposite polarity with respect to each other. The line code involves
the use of three different amplitude levels: +1, 0, and 1. +1 and -1 amplitude signals are used to represent
one's (or mark) pulses and the "0" amplitude pulses
(or the absence of a pulse) are used to represent zeros (or space) pulses. The general rule for AMI is: if a
given mark pulse is of positive polarity, then the very
next mark pulse will be of negative polarity and vice
versa. This alternating-polarity relationship exists between two consecutive mark pulses, independent of
the number of 'zeros' that may exist between these
two pulses. Figure 68 presents an illustration of the
AMI Line Code as would appear at the TxPOS and
TxNEG pins of the Framer, as well as the output signal on the line.
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THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
XRT72L53
PRELIMINARY
REV. P1.1.7
FIGURE 68. ILLUSTRATION OF AMI LINE CODE
Data 1 0 1 1 0 0 0 1 0 1 1 1 1 0 1 1 0 1 1 0 0 1 1 0 0 0 0 1
TxPOS
TxNEG
Line Signal
NOTE: One of the main reasons that the AMI Line Code
has been chosen for driving transformer-coupled media is
that this line code introduces no dc component, thereby
minimizing dc distortion in the line.
4.2.5.1.1.2 The B3ZS Line Code
The Transmit DS3 Framer and the associated LIU IC
combine the data and timing information (originating
from the TxLineClk signal) into the line signal that is
transmitted to the far-end receiver. The far-end receiver has the task of recovering this data and timing
information from the incoming DS3 data stream.
Many clock and data recovery schemes rely on the
use of Phase Locked Loop technology. PhaseLocked-Loop (PLL) technology for clock recovery relies on transitions in the line signal, in order to maintain lock with the incoming DS3 data stream. However, PLL-based clock recovery scheme, are vulnerable
to the occurrence of a long stream of consecutive zeros (e.g., the absence of transitions). This scenario
can cause the PLL to lose lock with the incoming DS3
data, thereby causing the clock and data recovery
process of the receiver to fail. Therefore, some approach is needed to insure that such a long string of
consecutive zeros can never happen. One such technique is B3ZS encoding. B3ZS (or Bipolar 3 Zero
Substitution) is a form of AMI line coding that implements the following rule.
In general the B3ZS line code behaves just like AMI
with the exception of the case when a long string of
consecutive zeros occur on the line. Any string of 3
consecutive zeros will be replaced with either a 00V
or a B0V where B refers to a Bipolar pulse (e.g., a
pulse with a polarity that is compliant with the AMI
coding rule). And V refers to a Bipolar Violation pulse
(e.g., a pulse with a polarity that violates the alternating polarity scheme of AMI.) The decision between
inserting an 00V or a B0V is made to insure that an
odd number of Bipolar (B) pulses exist between any
two Bipolar Violation (V) pulses. Figure 69 presents
a timing diagram that illustrates examples of B3ZS
encoding.
FIGURE 69. ILLUSTRATION OF TWO EXAMPLES OF B3ZS ENCODING
Data 1 0 1 1 0 0 0 1 0 1 1 1 1 0 1 1 0 1 1 0 0 1 1 1 0 0 0 1
TxPOS
TxNEG
0 0 V
Line Signal
B 0 V
The user chooses between AMI or B3ZS line coding
by writing to bit 4 of the I/O Control Register (Address
= 0x01), as shown below.
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XRT72L53
áç
THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. P1.1.7
I/O CONTROL REGISTER (ADDRESS = 0X01)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT2
BIT 1
BIT 0
Disable TxLOC
LOC
Disable
RxLOC
AMI/ZeroSup*
Unipolar/
Bipolar*
TxLine CLK
Invert
RxLine CLK
Invert
Reframe
R/W
RO
R/W
R/W
R/W
R/W
R/W
R/W
1
0
1
0
0
0
0
0
Table 34 relates the content of this bit-field to the Bipolar Line Code that DS3 Data will be transmitted and
received at.
TABLE 34: THE RELATIONSHIP BETWEEN BIT 4 (AMI/B3ZS*) WITHIN THE I/O CONTROL REGISTER AND THE BIPOLAR
LINE CODE THAT IS OUTPUT BY THE TRANSMIT DS3 LIU INTERFACE BLOCK
BIT 4
BIPOLAR LINE CODE
0
B3ZS
1
AMI
NOTES:
1. This bit is ignored if the Unipolar mode is selected.
2. This selection also effects the operation of the
Receive DS3 LIU Interface block
put pins) is to be updated on the rising or falling edges of the TxLineClk signal. The purpose of this feature is to insure that the Framer will always be able to
output data to the LIU IC, in such a way that the LIU
set-up and hold time requirements can always be
met. This selection is made by writing to bit 2 of the I/
O Control Register, as depicted below.
4.2.5.2 TxLineClk Clock Edge Selection
The Framer also allows the user to specify whether
the DS3 output data (via TxPOS and/or TxNEG outII/O CONTROL REGISTER (ADDRESS = 0X01)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT2
BIT 1
BIT 0
Disable TxLOC
LOC
Disable
RxLOC
AMI/ZeroSup*
Unipolar/
Bipolar*
TxLine CLK
Invert
RxLine CLK
Invert
Reframe
R/W
RO
R/W
R/W
R/W
R/W
R/W
R/W
1
0
1
0
0
X
X
0
Table 35 relates the contents of this bit field to the
clock edge of TxClk that DS3 Data is output on the
TxPOS and/or TxNEG output pins.
TABLE 35: THE RELATIONSHIP BETWEEN THE CONTENTS OF BIT 2 (TXLINECLK INV) WITHIN THE I/O CONTROL
REGISTER AND THE TXLINECLK CLOCK EDGE THAT TXPOS AND TXNEG ARE UPDATED ON
BIT 2
RESULT
0
Rising Edge:
Outputs on TxPOS and/or TxNEG are updated on the rising edge of TxLineClk.
See Figure 70 for timing relationship between TxLineClk, TxPOS and TxNEG signals, for this selection.
1
Falling Edge:
Outputs on TxPOS and/or TxNEG are updated on the falling edge of TxLineClk.
See Figure 71 for timing relationship between TxLineClk, TxPOS and TxNEG signals, for this selection.
NOTE: The user will typically make the selection based
upon the set-up and hold time requirements of the Transmit
LIU IC.
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THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
XRT72L53
PRELIMINARY
REV. P1.1.7
FIGURE 70. WAVEFORM/TIMING RELATIONSHIP BETWEEN TXLINECLK, TXPOS AND TXNEG - TXPOS AND TXNEG
TXLINECLK
ARE CONFIGURED TO BE UPDATED ON THE RISING EDGE OF
t32
TxLineClk
t30
t33
TxPOS
TxNEG
FIGURE 71. WAVEFORM/TIMING RELATIONSHIP BETWEEN TXLINECLK, TXPOS AND TXNEG - TXPOS AND TXNEG
ARE CONFIGURED TO BE UPDATED ON THE FALLING EDGE OF TXLINECLK
t32
TxLineClk
t31
t33
TxPOS
TxNEG
• Source Level
4.2.6 Transmit Section Interrupt Processing
The Transmit Section of the XRT72L53 can generate
an interrupt to the Microcontroller/Microprocessor for
the following two reasons.
The Block Level
The Enable State of the Block Level for the Transmit
Section Interrupts dictates whether or not interrupts
(if enabled at the source level), are actually enabled.
• Completion of Transmission of FEAC Message
• Completion of Transmission of LAPD Message
4.2.6.1 Enabling Transmit Section Interrupts
As mentioned in Section 1.6, the Interrupt Structure,
within the XRT72L53 contains two hierarchical levels:
• Block Level
The user can enable or disable these Transmit Section interrupts, at the Block Level by writing the appropriate data into Bit 1 (Tx DS3/E3 Interrupt Enable)
within the Block Interrupt Enable register (Address =
0x04), as illustrated below.
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XRT72L53
áç
THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. P1.1.7
BLOCK INTERRUPT ENABLE REGISTER (ADDRESS = 0X04)
BIT 7
BIT 6
BIT 5
RxDS3/E3
Interrupt
Enable
BIT 4
BIT 3
BIT 2
Not Used
BIT 1
BIT 0
TxDS3/E3
Interrupt
Enable
One Second
Interrupt
Enable
R/W
RO
RO
RO
RO
RO
R/W
R/W
0
0
0
0
0
0
0
0
As mentioned earlier, the Transmit Section of the
XRT72L53 Framer IC contains the following two interrupts
Setting this bit-field to “1” enables the Transmit Section (at the Block Level) for Interrupt Generation.
Conversely, setting this bit-field to “0” disables the
Transmit Section for interrupt generation.
• Completion of Transmission of FEAC Message
Interrupt.
What does it mean for the Transmit Section Interrupts to be enabled or disabled at the Block Level?
• Completion of Transmission of LAPD Message
Interrupt.
If the Transmit Section is disabled (for interrupt generation) at the Block Level, then ALL Transmit Section
interrupts are disabled, independent of the interrupt
enable/disable state of the source level interrupts.
If the Transmit Section is enabled (for interrupt generation) at the block level, then a given interrupt will be
enabled at the source level. Conversely, if the Transmit Section is enabled (for interrupt generation) at the
Block level, then a given interrupt will still be disabled,
if it is disabled at the source level.
The Enabling/Disabling and Servicing of each of
these interrupts is described below.
4.2.6.1.1 The Completion of Transmission of
FEAC Message Interrupt.
If the Transmit Section interrupts have been enabled
at the Block level, then the user can enable or disable
the Completion of Transmission of a FEAC Message
Interrupt by writing the appropriate value into Bit 4 (Tx
FEAC Interrupt Enable) within the Transmit DS3
FEAC Configuration & Status Register (Address =
0x31) as illustrated below.
TRANSMIT DS3 FEAC CONFIGURATION & STATUS REGISTER (ADDRESS = 0X31)
BIT 7
BIT 6
BIT 5
Not Used
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
Tx FEAC
Interrupt
Enable
TxFEAC
Interrupt
Status
TxFEAC
Enable
TxFEAC
GO
TxFEAC
Busy
RO
RO
RO
R/W
RUR
R/W
R/W
RO
0
0
0
X
0
0
0
0
Setting this bit-field to “1” enables the Completion of
Transmission of a FEAC Message Interrupt. Conversely, setting this bit-field to “0” disables this interrupt.
4.2.6.1.2 Servicing the Completion of Transmission of a FEAC Message Interrupt
As mentioned earlier, once the user commands the
Transmit FEAC Processor to begin its transmission of
a FEAC Message, it will do the following.
1. It will read in the six-bit contents of the Tx DS3
FEAC Register (Address = 0x32) and encapsulate these 6 bits into a 16-bit data structure.
2. The Transmit FEAC Processor will then begin to
transmit this 16-bit data structure (to the Remote
Terminal Equipment) repeatedly for 10 consecutive times.
3. Upon completion of the 10th transmission, the
XRT72L53 Framer IC will generate the Completion of Transmission of a FEAC Message Interrupt to the Microcontroller/Microprocessor. Once
the XRT72L53 Framer IC generates this interrupt,
it will do the following.
• Assert the Interrupt Output pin (INT) by toggling it
"Low".
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THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
XRT72L53
PRELIMINARY
REV. P1.1.7
• Set Bit 3 (Tx FEAC Interrupt Status) within the Tx
DS3 FEAC Configuration & Status Register, as
illustrated below.
TRANSMIT DS3 FEAC CONFIGURATION & STATUS REGISTER (ADDRESS = 0X31)
BIT 7
BIT 6
BIT 5
Not Used
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
Tx FEAC
Interrupt
Enable
TxFEAC
Interrupt
Status
TxFEAC
Enable
TxFEAC
GO
TxFEAC
Busy
RO
RO
RO
R/W
RUR
R/W
R/W
RO
0
0
0
1
1
0
0
0
If the Transmit Section interrupts have been enabled
at the Block level, then the user can enable or disable
the Completion of Transmission of a LAPD Message
Interrupt by writing the appropriate value into Bit 1
(TxLAPD Interrupt Enable) within the Tx DS3 LAPD
Status & Interrupt Register (Address = 0x34), as illustrated below.
The purpose of this interrupt is to alert the Microcontroller/Microprocessor that the Transmit FEAC Processor has completed its transmission of a given
FEAC message and is now ready to transmit the next
FEAC Message, to the Remote Terminal Equipment.
4.2.6.1.3 The Completion of Transmission of
the LAPD Message Interrupt
TXDS3 LAPD STATUS AND INTERRUPT REGISTER (ADDRESS = 0X34)
BIT 7
BIT 6
BIT 5
BIT 4
Not Used
BIT 3
BIT 2
BIT 1
BIT 0
TxDL Start
TxDL Busy
TxLAPD
Interrupt
Enable
TxLAPD
Interrupt
Status
RO
RO
RO
RO
R/W
RO
R/W
RUR
0
0
0
0
0
0
0
0
Setting this bit-field to “1’ enables the Completion of
Transmission of a LAPD Message Interrupt. Conversely, setting this bit-field to “0” disables the Completion of Transmission of a LAPD Message interrupt.
4.2.6.1.4 Servicing the Completion of Transmission of a LAPD Message Interrupt
As mentioned previously, once the user commands
the LAPD Transmitter to begin its transmission of a
LAPD Message, it will do the following.
1. It will parse through the contents of the Transmit
LAPD Message Buffer (located at address locations 0x86 through 0xDD) and search for a string
of five (5) consecutive “1’s”. If the LAPD Transmitter finds a string of five consecutive “1’s”
(within the content of the LAPD Message Buffer,
then it will insert a “0” immediately after this
string.
2. It will compute the FCS (Frame Check Sequence)
value and append this value to the back-end of
the user-message.
3. It will read out of the content of the user (zerostuffed) message and will encapsulate this data
into a LAPD Message frame.
4. Finally, it will begin transmitting the contents of
this LAPD Message frame via the “DL” bits, within
each outbound DS3 frame.
5. Once the LAPD Transmitter has completed its
transmission of this LAPD Message frame (to the
Remote Terminal Equipment), the XRT72L53
Framer IC will generate the Completion of Transmission of a LAPD Message Interrupt to the
Microcontroller/Microprocessor. Once the
XRT72L53 Framer IC generates this interrupt, it
will do the following.
• Assert the Interrupt Output pin (INT) by toggling it
"Low".
• Set Bit 0 (TxLAPD Interrupt Status) within the
TxDS3 LAPD Status and Interrupt Register, as
illustrated below.
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XRT72L53
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THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. P1.1.7
TXDS3 LAPD STATUS AND INTERRUPT REGISTER (ADDRESS = 0X34)
BIT 7
BIT 6
BIT 5
BIT 4
Not Used
BIT 3
BIT 2
BIT 1
BIT 0
TxDL Start
TxDL Busy
TxLAPD
Interrupt
Enable
TxLAPD
Interrupt
Status
RO
RO
RO
RO
R/W
RO
R/W
RUR
0
0
0
0
0
0
0
1
The purpose of this interrupt is to alert the Microcontroller/MIcroprocessor that the LAPD Transmitter has
completed its transmission of a given LAPD (or PMDL) Message, and is now ready to transmit the next
PMDL Message, to the Remote Terminal Equipment.
• Receive LIU Interface block
4.3 THE RECEIVE SECTION OF THE XRT72L53 (DS3
MODE OPERATION)
When the XRT72L53 has been configured to operate
in the DS3 Mode, the Receive Section of the
XRT72L53 consists of the following functional blocks.
• Receive Payload Data Output Interface block
• Receive HDLC Controller block
• Receive DS3 Framer block
• Receive Overhead Data Output Interface block
Figure 72 presents a simple illustration of the Receive
Section of the XRT72L53 Framer IC.
FIGURE 72. A SIMPLE ILLUSTRATION OF THE RECEIVE SECTION OF THE XRT72L53, WHEN IT HAS BEEN CONFIGURED TO OPERATE IN THE DS3 MODE
RxOHFrame
RxOHEnable
RxOH
Receive Overhead
Input
Interface Block
RxOHClk
RxOHInd
RxSer
RxNib[3:0]
Receive Payload
Data Input
Interface Block
RxClk
RxPOS
Receive DS3/E3
Framer Block
RxFrame
Receive LIU
Interface
Block
RxNEG
RxLineClk
From Microprocessor
Interface Block
Rx
RxDS3
DS3HDLC
HDLC
Controller/Buffer
Controller/Buffer
1. To receive encoded digital data from the DS3 LIU
IC.
2. To decode this data, convert it into a binary data
stream and to route this data to the Receive DS3
Framer block.
Each of these functional blocks will be discussed in
detail in this document.
4.3.1 The Receive DS3 LIU Interface Block
The purpose of the Receive DS3 LIU Interface block
is two-fold:
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THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. P1.1.7
Figure 73 presents a simple illustration of the Receive
DS3 LIU Interface block.
FIGURE 73. A SIMPLE ILLUSTRATION OF THE RECEIVE DS3 LIU INTERFACE BLOCK
RxPOS
Receive DS3
LIU Interface
Block
To Receive DS3
Framer Block
RxNEG
RxLineClk
Single Rail NRZ DS3 data pulses via the RxPOS input pin. The Receive DS3 LIU Interface block will also receive its timing signal via the RxLineClk signal.
The Receive Section of the XRT72L53 will via the Receive DS3 LIU Interface Block receive timing and data
information from the incoming DS3 data stream. The
DS3 Timing information will be received via the RxLineClk input pin and the DS3 data information will be
received via the RxPOS and RxNEG input pins. The
Receive DS3 LIU Interface block is capable of receiving DS3 data pulses in unipolar or bipolar format. If
the Receive DS3 framer is operating in the bipolar format, then it can be configured to decode either AMI or
B3ZS line code data. Each of these input formats
and line codes will be discussed in detail, below.
NOTE: The RxLineClk signal will function as the timing
source for the entire Receive Section of the XRT72L53.
No data pulses will be applied to the RxNEG input
pin. The Receive DS3 LIU Interface block receives a
logic "1" when a logic "1" level signal is present at the
RxPOS pin, during the sampling edge of the RxLineClk signal. Likewise, a logic "0" is received when a
logic "0" level signal is applied to the RxPOS pin.
Figure 74 presents an illustration of the behavior of
the RxPOS, RxNEG and RxLineClk input pins when
the Receive DS3 LIU Interface block is operating in
the Unipolar mode.
4.3.1.1 Unipolar Decoding
If the Receive DS3 LIU Interface block is operating in
the Unipolar (single-rail) mode, then it will receive the
FIGURE 74. BEHAVIOR OF THE RXPOS, RXNEG AND RXLINECLK SIGNALS DURING DATA RECEPTION OF UNIPOLAR
DATA
Data
1
0
1
1
0
0
1
0
0
1
1
1
0
1
0
1
0
0
1
1
1
0
0
1
RxPOS
RxNEG
RxLineClk
The user can configure the Receive DS3 LIU Interface block to operate in either the Unipolar or the Bi-
polar Mode by writing the appropriate data to the I/O
Control Register, as depicted below.
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THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. P1.1.7
II/O CONTROL REGISTER (ADDRESS = 0X01)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT2
BIT 1
BIT 0
Disable TxLOC
LOC
Disable
RxLOC
AMI/ZeroSup*
Unipolar/
Bipolar*
TxLine CLK
Invert
RxLine CLK
Invert
Reframe
R/W
RO
R/W
R/W
R/W
R/W
R/W
R/W
1
0
1
0
0
0
0
0
Table 36 relates the value of this bit-field to the Receive DS3 LIU Interface Input Mode.
TABLE 36: THE RELATIONSHIP BETWEEN THE CONTENTS OF BIT 2 (TXLINECLK INV) WITHIN THE I/O CONTROL
REGISTER AND THE TXLINECLK CLOCK EDGE THAT TXPOS AND TXNEG ARE UPDATED ON
BIT 3
RECEIVE DS3 LIU INTERFACE INPUT MODE
0
.Bipolar Mode (Dual Rail): AMI or B3ZS Line Codes are Transmitted and Received.
1
Unipolar Mode (Single Rail) Mode of transmission and reception of DS3 data is selected.
NOTES:
1. The default condition is the Bipolar Mode.
2. This selection also effects the Transmit DS3 Framer
Line Interface Output Mode
neClk input pins. Figure 75 presents a circuit diagram illustrating how the Receive DS3 LIU Interface
block interfaces to the Line Interface Unit while the
Framer is operating in Bipolar mode. The Receive
DS3 LIU Interface block can be configured to decode
the incoming data from either the AMI or B3ZS line
codes.
4.3.1.2 Bipolar Decoding
If the Receive DS3 LIU Interface block is operating in
the Bipolar Mode, then it will receive the DS3 data
pulses via both the RxPOS, RxNEG, and the RxLi-
FIGURE 75. ILLUSTRATION ON HOW THE RECEIVE DS3 FRAMER (WITHIN THE XRT72L53 FRAMER IC) BEING INTERFACE TO THEXRT73L03 LIU, WHILE THE FRAMER IS OPERATING IN BIPOLAR MODE (ONE CHANNEL SHOWN)
U1
TxSER
TxInClk
TxFrame
NIBBLEINTF
RESETB
INTB
CSB
RW
DS
AS
INTB
A[8:0]
46
43
61
25
28
13
8
7
10
9
6
15
16
17
18
19
20
21
22
23
U2
TxSER
TxInClk
TxFrame
R1
TxPOS
TPDATA
TxNEG
TNDATA
5V
32
33
34
35
36
37
38
39
86
88
90
2
TxLineClk
TCLK
RESETB
INTB
CSB
WRB_RW
RDB_DS
ALE_AS
Rdy_Dtck
A0
A1
A2
A3
A4
A5
A6
A7
A8
R2
TRING
DMO
D0
D1
D2
D3
D4
D5
D6
D7
1
40
ExtLOS
RLOS
RLOL
RLOL
MTIP
LLOOP
LLB
RLOOP
RLB
1
44
R3
RxLOS
RxOOF
RxRED
RxAIS
8
TRING
1:1
2
2
MRING
1
43
R4
2
TAOS
TAOS
TxLEV
TxLEV
REQB
ENCODIS
REQDIS
RTIP
8
RxPOS
RPOS
RxNEG
RNEG
RCLK1
RRING
9
4
8
1:1
R6
37.5
1
2
C1
2
0.01uF
203
5
RTIP
37.5
XRT73L0x
XRT72L5x
1 T2
R5
1
95
94
93
87
4
TTIP
270
RxLineClk
RxLOS
RxOOF
RxRED
RxAIS
5
270
MOTO
RxSer
RxClk
RxFrame
1 T1
36
DMO
2
RxSer
RxClk
RxFrame
1
1
27
41
36
NIBBLEINTF
ENCODIS
D[7:0]
TTIP
RRING
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THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
XRT72L53
PRELIMINARY
REV. P1.1.7
4.3.1.2.1 AMI Decoding
AMI or Alternate Mark Inversion, means that consecutive one's pulses (or marks) will be of opposite polarity with respect to each other. This line code involves
the use of three different amplitude levels: +1, 0, and 1. The +1 and -1 amplitude signals are used to represent one's (or mark) pulses and the "0" amplitude
pulses (or the absence of a pulse) are used to represent zeros (or space) pulses. The general rule for the
AMI line code is: if a given mark pulse is of positive
polarity, then the very next mark pulse will be of negative polarity and vice versa. This alternating-polarity
relationship exists between two consecutive mark
pulses, independent of the number of zeros that exist
between these two pulses. Figure 76 presents an illustration of the AMI Line Code as would appear at
the RxPOS and RxNEG input pins of the Framer, as
well as the corresponding output signal on the line.
FIGURE 76. ILLUSTRATION OF AMI LINE CODE
Data 1 0 1 1 0 0 0 1 0 1 1 1 1 0 1 1 0 1 1 0 0 1 1 0 0 0 0 1
Line Signal
RxPOS
RxNEG
NOTE: One of the reasons that the AMI Line Code has
been chosen for driving copper medium, isolated via transformers, is that this line code has no dc component, thereby
eliminating dc distortion in the line.
to insure that such a long string of consecutive zeros
can never happen. One such technique is B3ZS (or
Bipolar 3 Zero Substitution) encoding.
4.3.1.2.2 B3ZS Decoding
The Transmit DS3 LIU Interface block and the associated LIU embed and combine the data and clocking
information into the line signal that is transmitted to
the remote terminal equipment. The remote terminal
equipment has the task of recovering this data and
timing information from the incoming DS3 data
stream. Most clock and data recovery schemes rely
on the use of Phase-Locked-Loop technology. One of
the problems of using Phase-Locked-Loop (PLL)
technology for clock recovery is that it relies on transitions in the line signal, in order to maintain lock with
the incoming DS3 data-stream. Therefore, these
clock recovery scheme, are vulnerable to the occurrence of a long stream of consecutive zeros (e.g., no
transitions in the line). This scenario can cause the
PLL to lose lock with the incoming DS3 data, thereby
causing the clock and data recovery process of the
receiver to fail. Therefore, some approach is needed
In general the B3ZS line code behaves just like AMI
with the exception of the case when a long string of
consecutive zeros occurs on the line. Any 3 consecutive zeros will be replaced with either a 00V or a B0V
where B refers to a Bipolar pulse (e.g., a pulse with a
polarity that is compliant with the alternating polarity
scheme of the AMI coding rule). And V refers to a Bipolar Violation pulse (e.g., a pulse with a polarity that
violates the alternating polarity scheme of AMI.) The
decision between inserting an 00V or a B0V is made
to insure that an odd number of Bipolar (B) pulses exist between any two Bipolar Violation (V) pulses. The
Receive DS3 Framer, when operating with the B3ZS
Line Code is responsible for decoding the B3ZS-encoded data back into a unipolar (binary-format). For
instance, if the Receive DS3 Framer detects a 00V or
a B0V pattern in the incoming pattern, the Receive
DS3 Framer will replace it with three consecutive zeros. Figure 77 presents a timing diagram that illustrates examples of B3ZS decoding.
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THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. P1.1.7
FIGURE 77. ILLUSTRATION OF TWO EXAMPLES OF B3ZS DECODING
Data 1 0 1 1 0 0 0 1 0 1 1 1 1 0 1 1 0 1 1 0 0 1 1 1 0 0 0 1
0 0 V
Line Signal
B 0 V
RxPOS
RxNEG
4.3.1.2.3 Line Code Violations
The Receive DS3 LIU Interface block will also check
the incoming DS3 data stream for line code violations. For example, when the Receive DS3 LIU Interface block detects a valid bipolar violation (e.g., in
B3ZS line code), it will substitute three zeros into the
binary data stream. However, if the bipolar violation
is invalid, then an LCV (Line Code Violation) is
flagged and the PMON LCV Event Count Register
(Address = 0x50 and 0x51) will also be incremented.
Additionally, the LCV-One Second Accumulation Registers (Address = 0x6E and 0x6F) will be incremented. For example: If the incoming DS3 data is B3ZS
encoded, the Receive DS3 LIU Interface block will also increment the LCV One Second Accumulation
Register if three (or more) consecutive zeros are received.
4.3.1.2.4 RxLineClk Clock Edge Selection
The incoming unipolar or bipolar data, applied to the
RxPOS and the RxNEG input pins are clocked into
the Receive DS3 LIU Interface block via the RxLineClk signal. The Framer IC allows the user to specify which edge (e.g, rising or falling) of the RxLineClk
signal will sample and latch the signal at the RxPOS
and RxNEG input signals into the Framer IC. This
feature was included in the XRT72L53 design in order
to insure that the user can always meet the RxPOS
and RxNEG to RxLineClk set-up and hold time requirements. The user can make this selection by
writing the appropriate data to bit 1 of the I/O Control
Register, as depicted below.
II/O CONTROL REGISTER (ADDRESS = 0X01)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT2
BIT 1
BIT 0
Disable
TxLOC
LOC
Disable
RxLOC
AMI/ZeroSup*
Unipolar/
Bipolar*
TxLine CLK
Invert
RxLine CLK
Invert
Reframe
R/W
RO
R/W
R/W
R/W
R/W
R/W
R/W
1
0
1
0
0
0
0
0
Table 37 depicts the relationship between the value of
this bit-field to the sampling clock edge of RxLineClk.
TABLE 37: THE RELATIONSHIP BETWEEN THE CONTENTS OF BIT 1 (RXLINECLK INV) OF THE I/O CONTROL REGISTER,
AND THE SAMPLING EDGE OF THE RXLINECLK SIGNAL
RXCLKINV
(BIT 1)
RESULT
0
Rising Edge:
RxPOS and RxNEG are sampled at the rising edge of RxLineClk. See Figure 78 for timing relationship
between RxLineClk, RxPOS, and RxNEG.
1
Falling Edge:
RxPOS and RxNEG are sampled at the falling edge of RxLineClk. See Figure 79 for timing relationship
between RxLineClk, RxPOS, and RxNEG.
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XRT72L53
PRELIMINARY
REV. P1.1.7
Figure 78 and Figure 79 present the Waveform and
Timing Relationships between RxLineClk, RxPOS
and RxNEG for each of these configurations.
FIGURE 78. WAVEFORM/TIMING RELATIONSHIP BETWEEN RXLINECLK, RXPOS AND RXNEG - WHEN RXPOS AND
RXNEG ARE TO BE SAMPLED ON THE RISING EDGE OF RXLINECLK
t42
RxLineClk
t39
t38
RxPOS
RxNEG
FIGURE 79. WAVEFORM/TIMING RELATIONSHIP BETWEEN RXLINECLK, RXPOS AND RXNEG - WHEN RXPOS AND
RXNEG ARE TO BE SAMPLED ON THE FALLING EDGE OF RXLINECLK
RxLineClk
t40
t41
RxPOS
RxNEG
4.3.2 The Receive DS3 Framer Block
The Receive DS3 Framer block accepts decoded
DS3 data from the Receive DS3 LIU Interface block,
and routes data to the following destinations.
• The Receive Payload Data Output Interface Block
• The Receive Overhead Data Output Interface
Block.
• The Receive DS3 HDLC Controller Block
Figure 80 presents a simple illustration of the Receive
DS3 Framer block along with the associated paths to
the other functional blocks within the Framer chip.
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THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
áç
PRELIMINARY
REV. P1.1.7
FIGURE 80. A SIMPLE ILLUSTRATION OF THE RECEIVE DS3 FRAMER BLOCK AND THE ASSOCIATED PATHS TO THE
OTHER FUNCTIONAL BLOCKS
To Receive DS3 HDLC
Buffer
Receive Overhead Data
Output Interface
Receive
ReceiveDS3
DS3Framer
Framer
Block
Block
From Receive DS3
LIU Interface Block
Receive Payload Data
Output Interface
Once the B3ZS (or AMI) encoded data has been decoded into a binary data-stream, the Receive DS3
Framer block will use portions of this data-stream in
order to synchronize itself to the remote terminal
equipment. At any given time, the Receive DS3
Framer block will be operating in one of two modes.
• The Frame Acquisition Mode: In this mode, the
Receive DS3 Framer block is trying to acquire synchronization with the incoming DS3 frames, or
• The Frame Maintenance Mode: In this mode, the
Receive DS3 Framer block is trying to maintain
frame synchronization with the incoming DS3
Frames.
Figure 81 presents a State Machine diagram that depicts the Receive DS3 Framer block's DS3 Frame Acquisition/Maintenance Algorithm.
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THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
XRT72L53
PRELIMINARY
REV. P1.1.7
FIGURE 81. THE STATE MACHINE DIAGRAM FOR THE RECEIVE DS3 FRAMER BLOCK'S FRAME ACQUISITION/MAINALGORITHM
TENANCE
10 Consecutive F-bits
Correctly Received
M-Bit Search
F-Bit Synch
Achieved
F-Bit Search
M-bits Correctly
Detected for 3
Consecutive M-Frames
(Framing on Parity is
Not Selected)
OOF Criteria
based upon values
for F-Sync Algo
and M-Sync Algo
M-bits Correctly
Detected for 3
Consecutive M-Frames
(Framing on Parity is
Selected)
Parity Error in
2 out of 5 frames
In-Frame
RxOOF pin
is Negated.
Valid Parity
4.3.2.1 Frame Acquisition Mode Operation
The Receive DS3 Framer block will be performing
Frame Acquisition operation while it is operating in
any of the following states (per the DS3 Frame Acquisition/Maintenance algorithm State Machine diagram,
as depicted in Figure 81.)
• The F-bit Search state
• The M-bit Search state
• The P-Bit Check state (optional)
Once the Receive DS3 Framer block enters the InFrame state (per Figure 81), then it will begin Frame
Maintenance operation.
When the Receive DS3 Framer block is in the frameacquisition mode, it will begin to look for valid DS3
frames by first searching for the F-bits in the incoming
DS3 data stream. At this initial point the Receive
DS3 Framer block will be operating in the F-Bit
Search state within the DS3 Frame Acquisition/Maintenance algorithm state machine diagram (see
Parity Check
(Only if Framing
on Parity is
Selected)
Figure 81). Recall from the discussion in Section 4.1,
that each DS3 F-frame consists of four (4) F-bits that
occur in a repeating 1001 pattern. The Receive DS3
Framer block will attempt to locate this F-bit pattern
by performing five (5) different searches in parallel.
The F-bit search has been declared successful if at
least 10 consecutive F-bits are detected. After the Fbit match has been declared, the Receive DS3 Framer block will then transition into the M-Bit Search state
within the DS3 Frame Acquisition/Maintenance algorithm (per Figure 81). When the Receive DS3 Framer
block reaches this state, it will begin searching for valid M-bits. Recall from the discussion in Section 3.1
that each DS3 M-frame consists of three (3) M-bits
that occur in a repeating 010 pattern. The M-bit
search is declared successful if three consecutive Mframes (or 21 F-frames) are detected correctly. Once
this occurs an M-frame lock is declared, and the Receive DS3 Framer block will then transition to the InFrame state. At this point, the Receive DS3 Framer
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THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. P1.1.7
• Negate the RxOOF bit-field (Bit 4) within the
Receive DS3 Configuration and Status Register.
block will declare itself in the In-Frame condition, and
will begin Frame Maintenance operations. The Receive DS3 Framer block will then indicate that it has
transitioned from the OOF condition into the In-Frame
condition by doing the following.
The user can configure the Receive DS3 Framer to
operate such that 'valid parity' (P-bits) must also be
detected before the Receive DS3 Framer can declare
itself In Frame. The user can set this configuration by
writing the appropriate data to the Rx DS3 Configuration and Status Register, as depicted below.
• Generate a Change in OOF Condition interrupt to
the local µP.
• Negate the RxOOF output pin (e.g., toggle it
"Low").
RX DS3 CONFIGURATION AND STATUS REGISTER, (ADDRESS = 0X10)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT2
BIT 1
BIT 0
RxAIS
RxLOS
RxIdle
RxOOF
Int LOS
Disable
Framing on
Parity
F-Sync Algo
M-Sync Algo
RO
RO
RO
RO
R/W
R/W
R/W
R/W
X
X
X
X
X
X
X
X
Table 38 relates the contents of this bit field to the
framing acquisition criteria.
TABLE 38: THE RELATIONSHIP BETWEEN THE CONTENTS OF BIT 2 (FRAMING ON PARITY) WITHIN THE RX DS3
CONFIGURATION AND STATUS REGISTER, AND THE RESULTING FRAMING ACQUISITION CRITERIA
FRAMING
PARITY
(BIT 2)
FRAMING ACQUISITION CRITERIA
ON
0
The In-frame is declared after F-bit synchronization (10 F-bit matches) followed by M-bit synchronization (Mbit matches for 3 DS3 M-frames)
1
The In-frame condition is declared after F-bit synchronization, followed by M-bit synchronization, with valid
parity over the frames. Also, the occurrence of parity errors in 2 or more out of 5 frames starts a frame search
Once the Receive DS3 Framer block is operating in
the In-Frame condition, normal data recovery and
processing of the DS3 data stream begins. The maximum average reframing time is less than 1.5 ms.
4.3.2.2 Frame Maintenance Mode Operation
When the Receive DS3 Framer block is operating in
the In-Frame state (per Figure 81), it will then begin to
perform Frame Maintenance operations, where it will
continue to verify that the F- and M-bits are present,
at their proper locations. While the Receive DS3
Framer block is operating in the Frame Maintenance
mode, it will declare an Out-of-Frame (OOF) condition
if 3 or 6 F-bits (depending upon user selection) out of
16 consecutive F-bits are in error. The user makes
this selection for the OOF Declaration criteria by writing the appropriate value to bit 1 (F-Sync Algo) of the
Rx DS3 Configuration and Status Register, as depicted below.
RX DS3 CONFIGURATION AND STATUS REGISTER, (ADDRESS = 0X10)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT2
BIT 1
BIT 0
RxAIS
RxLOS
RxIdle
RxOOF
Int LOS
Disable
Framing on
Parity
F-Sync Algo
M-Sync Algo
RO
RO
RO
RO
R/W
R/W
R/W
R/W
X
X
X
X
X
X
X
X
Table 39 relates the contents of this bit-field to the
OOF Declaration criteria
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THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
XRT72L53
PRELIMINARY
REV. P1.1.7
TABLE 39: THE RELATIONSHIP BETWEEN THE CONTENTS OF BIT 1 (F-SYNC ALGO) WITHIN THE RX DS3
CONFIGURATION AND STATUS REGISTER, AND THE RESULTING F-BIT OOF DECLARATION CRITERIA USED BY THE
RECEIVE DS3 FRAMER BLOCK
F-SYNC ALGO (BIT 1)
OOF DECLARATION CRITERIA
0
OOF is declared when 6 out of 16 consecutive F-bits are in error.
1
OOF is declared when 3 out of 16 consecutive F-bits are in error.
NOTE: Once the Receive DS3 Framer block has declared
an OOF condition, it will transition back to the F-Bit Search
state within the DS3 Frame Acquisition/Maintenance algorithm (per Figure 81).
1. M-bit errors do not cause a OOF Declaration, or
2. OOF will be declared if 3 out of 4 consecutive Mbits are in error.
The user will select between these two options by
writing the appropriate value to Bit 0 (M-Sync Algo)
within the Receive DS3 Configuration and Status
Register, as depicted below.
In addition to selecting an OOF Declaration criteria
for the F-bits, the user has the following options for
configuring the OOF Declaration criteria based upon
M-bits.
RX DS3 CONFIGURATION AND STATUS REGISTER, (ADDRESS = 0X10)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT2
BIT 1
BIT 0
RxAIS
RxLOS
RxIdle
RxOOF
Int LOS
Disable
Framing on
Parity
F-Sync Algo
M-Sync Algo
RO
RO
RO
RO
R/W
R/W
R/W
R/W
X
X
X
X
X
X
X
X
Table 40 relates the contents of this Bit Field to the MBit Error criteria for Declaration of OOF.
TABLE 40: THE RELATIONSHIP BETWEEN THE CONTENTS OF BIT 0 (M-SYNC ALGO) WITHIN THE RX DS3
CONFIGURATION AND STATUS REGISTER, AND THE RESULTING M-BIT OOF DECLARATION CRITERIA USED BY THE
RECEIVE DS3 FRAMER BLOCK
MSYNC ALGO
OOF DECLARATION CRITERIA
0
M-Bit Errors do not result in the declaration of OOF
1
OOF is declared when 3 out of 4 M-bits are in error.
The Framing on Parity Criteria for OOF Declaration
Finally, the Framer IC offers the Framing on Parity option, which also effects the OOF Declaration criteria.
As was mentioned earlier, the Framer IC allows the
user to configure the Receive DS3 Framer block to
detect 'valid-parity' before declaring itself In-Frame.
This same selection also configures the Receive DS3
Framer block to also declare an OOF Condition if a Pbit error is detected in 2 of the last 5 M-frames.
Whenever the Receive DS3 Framer block declares
OOF after being in the In-Frame State the following
will happen.
• The Receive DS3 Framer will assert the RxOOF
output pin (e.g., toggles it "High").
• Bit 4 (RxOOF) within the Rx DS3 Configuration and
Status Register will be set to "1" as depicted below.
Rx DS3 Configuration and Status Register, (Address
= 0x10)
RX DS3 CONFIGURATION AND STATUS REGISTER, (ADDRESS = 0X10)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT2
BIT 1
BIT 0
RxAIS
RxLOS
RxIdle
RxOOF
Int LOS
Disable
Framing on
Parity
F-Sync Algo
M-Sync Algo
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THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. P1.1.7
RX DS3 CONFIGURATION AND STATUS REGISTER, (ADDRESS = 0X10)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT2
BIT 1
BIT 0
R/O
R/O
R/O
R/O
R/W
R/W
R/W
R/W
X
X
X
X
X
X
X
X
• The Receive DS3 Framer block will also issue a
Change in OOF Status interrupt request, anytime
there is a change in the OOF status.
I/O Control Register, as depicted below, then the Receive DS3 Framer will be forced into the Frame Acquisition Mode, (or more specifically, in the F-Bit Search
State per Figure 81). Afterwards, the Receive DS3
Framer block will begin its search for valid F-Bits. The
Framer IC will also respond to this command by asserting the RxOOF output pin, and generating a
Change in OOF Status interrupt.
4.3.2.3 Forcing a Reframe via Software Command
The Framer IC permits the user to force a reframe
procedure of the Receive DS3 Framer block via software command. If the user writes a "1" into Bit 0 the
I/O CONTROL REGISTER (ADDRESS = 0X01)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT2
BIT 1
BIT 0
Disable
TxLOC
LOC
Disable
RxLOC
AMI/ZeroSup*
Unipolar/
Bipolar*
TxLine CLK
Invert
RxLine CLK
Invert
Reframe
R/W
RO
R/W
R/W
R/W
R/W
R/W
R/W
1
0
1
0
0
0
0
0
4.3.2.4 Performance Monitoring of the Receive
DS3 Framer block
The user can monitor the number of framing bit errors
(M and F bits) that have been detected by the Re-
ceive DS3 Framer block. This is accomplished by periodically reading the PMON Framing Bit Error Count
Registers (Address = 0x52 and 0x53), as depicted
below.
PMON FRAMING BIT ERROR EVENT COUNT REGISTER - MSB (ADDRESS = 0X52)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT2
BIT 1
BIT 0
F-Bit Error Count - High Byte
RO
RO
RO
RO
RO
RO
RO
RO
1
0
1
0
0
0
0
0
BIT2
BIT 1
BIT 0
PMON FRAMING BIT ERROR EVENT COUNT REGISTER - LSB (ADDRESS = 0X53)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
F-Bit Error Count - Low Byte
RO
RO
RO
RO
RO
RO
RO
RO
0
0
0
0
0
0
0
0
When the µP/µC reads these registers, it will read in
the number of framing bit errors that have been detected since the last read of these two registers.
These registers are reset upon read.
4.3.2.5 DS3 Receive Alarms
The Receive DS3 Framer block is capable of detecting any of the following alarm conditions.
• LOS (Loss of Signal)
• AIS (Alarm Indication Signal)
• The Idle Pattern.
• FERF (Far-End Receive Failure) of Yellow Alarm
condition.
• FEBE (Far-End-Block Error)
• Change in AIC State
The methods by which the Receive DS3 Framer block
uses to detect and declare each of these alarm conditions are described below.
4.3.2.5.1 The Loss of Signal (LOS) Alarm
The Receive DS3 Framer block will declare a Loss of
Signal (LOS) state when it detects 180 consecutive
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1. Asserting the RxLOS output pin (e.g., toggles it
"High").
2. Setting Bit 6 (RxLOS) within the Rx DS3 Configuration and Status Register to 1, as depicted
below.
incoming 0s via the RxPOS and RxNEG input pins or
if the RLOS input pin (from the XRT7300 DS3 LIU or
the XRT7295 Line Receiver IC) is asserted (e.g., driven "High"). The Receive DS3 Framer block will indicate the occurrence of an LOS condition by:
RX DS3 CONFIGURATION AND STATUS REGISTER, (ADDRESS = 0X10)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT2
BIT 1
BIT 0
RxAIS
RxLOS
RxIdle
RxOOF
Int LOS
Disable
Framing on
Parity
F-Sync Algo
M-Sync Algo
R/O
R/O
R/O
R/O
R/W
R/W
R/W
R/W
0
1
0
1
x
x
x
x
3. The Receive DS3 Framer block will generate a
Change in LOS Status interrupt request.
NOTE: The Receive DS3 Framer will also declare an OOF
condition and perform all of the notification procedures as
described in Section 3.3.2.2.
4. Force the on-chip Transmit Section to transmit a
FERF (Far-End Receive Failure) indicator back
out to the remote terminal.
The Receive DS3 Framer block will clear the LOS
condition when at least 60 out of 180 consecutive received bits are 1.
NOTE: The Receive DS3 Framer block will also generate
the Change in LOS Condition interrupt, when it clears the
LOS Condition.
The Framer chip allows the user to modify the LOS
Declaration criteria such that an LOS condition is declared only if the RLOS input pin (from the XRT7300
DS3/E3/STS-1 LIU IC) is asserted. In this case, the
internally-generated LOS criteria of 180 consecutive
0s will be disabled. The user can accomplish this by
writing a "1" to bit 3 (Int LOS Disable) of the Rx DS3
Configuration and Status Register, as depicted below.
RX DS3 CONFIGURATION AND STATUS REGISTER, (ADDRESS = 0X10)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT2
BIT 1
BIT 0
RxAIS
RxLOS
RxIdle
RxOOF
Int LOS
Disable
Framing on
Parity
F-Sync Algo
M-Sync Algo
RO
RO
RO
RO
R/W
R/W
R/W
R/W
X
X
X
X
1
X
X
X
NOTE: For more information on the RLOS input pin, please
see Section 2.1.
4.3.2.5.2 The Alarm Indication Signal (AIS)
The Receive DS3 Framer block will identify and declare an AIS condition if it detects all of the following
conditions in the incoming DS3 Data Stream:
detects a non-AIS type M-frame. The Receive DS3
Framer block will declare an AIS Condition if this
counter reaches the value of 63 M-frames or greater.
Explained another way, the AIS condition is declared
if the number of AIS-type M-frames is detected, such
that it meets the following conditions:
• Valid M-bits, F-bits and P-bits
NAIS - NVALID > 63
• All C-bits are zeros.
where:
• X-bits are set to 1
NAIS = the number of M-frames containing the AIS
pattern.
• The Payload portion of the DS3 Frame exhibits a
repeating 1010... pattern.
The Receive DS3 Framer block contains, within its
circuitry, an Up/Down Counter that supports the assertion and negation of the AIS condition. This
counter begins with the value of 0x00 upon power up
or reset. The counter is then incremented anytime
the Receive DS3 Framer block detects an AIS Type
M-frame. This counter is then decremented, or kept
at zero value, when the Receive DS3 Framer block
NVALID = the number of M-frames not containing the
AIS pattern
If at anytime, the contents of this Up/Down counter
exceeds 63 M-frames, then the Receive DS3 Framer
block will:
1. Assert the RxAIS output pin by toggling it "High".
2. Set Bit 7 (RxAIS) within the Rx DS3 Configuration
and Status Register, to "1" as depicted below.
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RX DS3 CONFIGURATION AND STATUS REGISTER, (ADDRESS = 0X10)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT2
BIT 1
BIT 0
RxAIS
RxLOS
RxIdle
RxOOF
Int LOS
Disable
Framing on
Parity
F-Sync Algo
M-Sync Algo
1
X
X
X
X
X
X
X
3. Generate a Change in AIS Status Interrupt
Request to the µP/µC.
4. Force the Transmit Section to transmit a FERF
indication back to the remote terminal.
The Receive DS3 Framer block will clear the AIS condition when the following expression is true.
NAIS - NVALID < 0.
In other words, once the Receive DS3 Framer block
has detected a sufficient number of normal (or NonAIS) M-frames, such that this Up/Down counter
reaches zero, then the Receive DS3 Framer block will
clear the AIS Condition indicators. The Receive DS3
Framer block will inform the µC/µP of this negation of
the AIS Status by generating a Change in AIS Status
interrupt.
4.3.2.5.3 The Idle (Condition) Alarm
The Receive DS3 Framer block will identify and declare an Idle Condition if it receives a sufficient number of M-Frames that meets all of the following conditions.
M-frames that have been identified as exhibiting the
Idle Condition by the Receive DS3 Framer block. The
contents of this counter are set to zero upon reset or
power up. This counter is then incremented whenever the Receive DS3 Framer block detects an Idle-type
M-frame. The counter is decremented, or kept at zero if a non-Idle M-frame is detected. If the Receive
DS3 Framer block detects a sufficient number of Idletype M-frames, such that the counter reaches the
number 63, then the Receive DS3 Framer block will
declare the Idle Condition. Explained another way,
the Receive DS3 Framer block will declare an Idle
Condition if the number of Idle-Pattern M-frames is
detected such that it meets the following conditions.
NIDLE - NVALID > 63,
where:
NIDLE = the number of M-frames containing the Idle
Pattern
NVALID = the number of M-frames not exhibit the Idle
Pattern
Anytime the contents of this Up/Down Counter reaches the number 63, then the Receive DS3 Framer
block will:
• Valid M-bits, F-bits, and P-bits
• The 3 CP-bits (in F-Frame #3) are zeros.
• The X-bits are set to 1
1. Set Bit 5 (RxIdle) within the Rx DS3 Configuration
and Status Register, to "1" as depicted below.
• The payload portion of the DS3 Frame exhibits a
repeating 1100... pattern.
The Receive DS3 Framer block circuitry includes an
Up/Down Counter that is used to track the number of
RX DS3 CONFIGURATION AND STATUS REGISTER, (ADDRESS = 0X10)
RX DS3 CONFIGURATION AND STATUS REGISTER, (ADDRESS = 0X10)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT2
BIT 1
BIT 0
RxAIS
RxLOS
RxIdle
RxOOF
Int LOS
Disable
Framing on
Parity
F-Sync Algo
M-Sync Algo
R/O
R/O
R/O
R/O
R/W
R/W
R/W
R/W
X
X
1
X
X
X
X
X
2. Generate a Change in Idle Status Interrupt
Request to the local µP/µC.
The Receive DS3 Framer block will clear the Idle
Condition if it has detected a sufficient number of
Non-Idle M-frames, such that this Up/Down Counter
reaches the value 0.
4.3.2.5.4 The Detection of (FERF) or Yellow
Alarm Condition
The Receive DS3 Framer block will identify and declare a Yellow Alarm condition or a Far-End Receive
Failure (FERF) condition, if it starts to receive DS3
frames with both of its X-bits set to 0.
When the Receive DS3 Framer block detects a FERF
condition in the incoming DS3 frames, then it will then
do the following.
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REV. P1.1.7
1. It will assert the RxFERF (bit-field 4) within the
Rx DS3 Status Register, as depicted below.
RX DS3 STATUS REGISTER (ADDRESS = 0X11)
BIT 7
BIT 6
BIT 5
Not Used
BIT 4
BIT 3
BIT2
BIT 1
BIT 0
Rx FERF
RxAIC
RxFEBE [2]
RxFEBE [1]
RxFEBE [0]
RO
RO
RO
RO
RO
RO
RO
RO
0
0
0
1
X
X
X
X
This bit-field will remain asserted for the duration that
the Yellow Alarm condition exists.
Consequently, the Receive DS3 Framer block will
also assert the FERF Interrupt Status bit, within
the Rx DS3 Interrupt Status Register, as depicted
below.
2. The Receive DS3 Framer block will also generate
a Change in FERF Status interrupt to the µP/µC.
RX DS3 INTERRUPT STATUS REGISTER (ADDRESS = 0X13)
BIT 7
Cp Bit Error
Interrupt
Status
BIT 6
BIT 5
BIT 4
BIT 3
LOS Interrupt AIS Interrupt IDLE Interrupt
Status
Status
Status
FERF Interrupt Status
BIT2
BIT 1
BIT 0
AIC Interrupt OOF Interrupt P-Bit Interrupt
Status
Status
Status
RO
RUR
RUR
RUR
RUR
RUR
RUR
RUR
0
X
X
X
1
X
X
X
1], during un-erred conditions. Hence, if the Receive
DS3 Framer block (within the XRT72L53 Framer IC)
receives DS3 frames with the FEBE bits set to [1, 1,
1] it will interpret this event as an un-erred event, and
will continue normal operation.
The Receive DS3 Framer block will clear the FERF
condition, when it starts to receive Receive DS3
Frames that have its X bits set to 1.
NOTE: The FERF indicator is frequently referred to as the
Yellow Alarm.
4.3.2.5.5 The Detection of the FEBE Events
As described in Section 3.2.4.2.1.9, a given Terminal
Equipment will set the three FEBE (Far-End Block Error) bit-fields to the value [1, 1, 1] (e.g., all of the
FEBE bits are set to “1”) within the outbound DS3
frames if, all of the following conditions are true about
the incoming DS3 line signal.
• The Receive Circuitry (within the Terminal Equipment) detects no P-Bit Errors.
• The Receive Circuitry (within the Terminal Equipment) detects no CP-Bit Errors.
If the Receive Section of the Terminal Equipment detects any P or CP bit errors, then the Transmit Section
of the Terminal Equipment will set the three FEBE
bits (within the outbound DS3 data stream) to a value
other than [1, 1, 1].
How does the Receive DS3 Framer block (within the
XRT72L53) respond when it receives a DS3 frame
with all three (3) of its FEBE bit-fields set to “1”?
As mentioned above, the Terminal Equipment will
transmit DS3 frames, with the FEBE bits set to [1, 1,
However, if the Receive DS3 Framer block receives a
DS3 frame with the FEBE bits set to a value other
than [1, 1, 1], then it will increment the PMON FEBE
Event Count Registers (which are located at address
locations 0x58 and 0x59 within the Framer Address
space).
4.3.2.5.6 Detection of Change in the AIC State
Section 3.1 indicates that the AIC (Application Identification Channel) bit-field is the third overhead bit,
within F-Frame # 1. This particular bit-field is set to
“1” for the C-Bit Parity Framing Format, and is set to
“0” for the M13 Framing Format.
Hence, a given Terminal Equipment receiving a DS3
data stream can identify the framing format of this
DS3 data stream, by reading the value fo the AIC bitfield. The Receive DS3 Framer block permits the user’s Microcontroller/MIcroprocessor to determine the
state of the AIC bit-field (within the incoming DS3 data stream) by writing the value of the AIC bit-field,
within the most recently received DS3 frame, into bit
3 (RxAIC) within the Rx DS3 Status Register (Address = 0x11), as illustrated below.
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REV. P1.1.7
RXDS3 STATUS REGISTER (ADDRESS = 0X11)
BIT 7
BIT 6
BIT 5
Reserved
BIT 4
BIT 3
RxFERF
RxAIC
BIT 2
BIT 1
BIT 0
RxFEBE[2:0]
RO
RO
RO
RO
RO
RO
RO
RO
0
0
0
0
0
0
0
0
Bit 2 (AIC Interrupt Status) within the Rx DS3 Interrupt Stauts Register (Address = 0x13) to “1” as illustrated below.r
The Receive DS3 Framer block will also generate an
interrupt if it detects a change of state in the AIC bitfield (within the incoming DS3 data stream). If this
occurs, then the Receive DS3 Framer block will set
RXDS3 INTERRUPT STATUS REGISTER (ADDRESS = 0X13)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
CP-Bit Error
Interrupt
Status
LOS
Interrupt
Status
AIS
Interrupt
Status
Idle Interrupt
Status
FERF
Interrupt
Status
AIC
Interrupt
Status
OOF
Interrupt
Status
P-Bit Error
Interrupt
Status
RUR
RUR
RUR
RUR
RUR
RUR
RUR
RUR
0
0
0
0
0
1
0
0
4.3.2.6 Performance Monitoring of the DS3
Transport Medium
The DS3 Frame consists of some overhead bits that
are used to support performance monitoring of the
DS3 Transmission Link. These bits are the P-Bits
and the CP-Bits.
will then compare this locally computed parity value
to that of the P-bit fields within the very next DS3
Frame. If the Receive DS3 Framer block detects a
parity error, then two things will happen:
1. The Receive DS3 Framer block will inform the µP/
µC of this occurrence by generating a Detection
of P-Bit Error interrupt,
2. The Receive DS3 Framer block will alter the
value of the FEBE bits, (to a pattern other than
111) that the Near-End Transmit DS3 Framer will
be transmitting back to the remote Terminal.
3. The XRT72L53 Framer IC will increment the
PMON Parity Error Event Count Registers
(Address = 0x54 and 0x55) for each detected
parity error, in the incoming DS3 data stream.
The bit-format of these two registers follows.
4.3.2.6.1 P-Bit Checking/Options
The remote Transmit DS3 Framer will compute the
even parity of the payload portion of an outbound
DS3 Frame and will place the resulting parity bit value
in the 2 P-bit-fields within the very next outbound DS3
Frame. The value of these two bits fields is expected
to be the identical.
The Receive DS3 Framer block, while receiving each
of these DS3 Frames (from the remote Transmit DS3
Framer), will compute the even-parity of the payload
portion of the frame. The Receive DS3 Framer block
PMON PARITY ERROR EVENT COUNT REGISTER - MSB (ADDRESS = 0X54)
BIT 7
BIT 6
BIT 5
BIT 4
RO
RO
RO
RO
0
0
0
0
BIT 3
BIT2
BIT 1
BIT 0
RO
RO
RO
RO
0
0
0
0
BIT2
BIT 1
BIT 0
RO
RO
RO
Parity Error Count - High Byte
PMON PARITY ERROR EVENT COUNT REGISTER - LSB (ADDRESS = 0X55)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
Parity Error Count - "Low" Byte
RO
RO
RO
RO
RO
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REV. P1.1.7
PMON PARITY ERROR EVENT COUNT REGISTER - LSB (ADDRESS = 0X55)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT2
BIT 1
BIT 0
0
0
0
0
0
0
0
0
terminal) through any number of mid-network terminals to the sink terminal).
2. P-bits are used to permit performance monitoring
of a DS3 data stream, as it is transmitted from
one terminal to an adjacent terminal.
How CP-Bits are Processed
When the µP reads these registers, it will read in the
number of parity-bit errors that have been detected by
the Receive DS3 Framer block, since the last time
these registers were read. These registers are reset
upon read.
NOTE: When the Framing with Parity option is selected, the
Receive DS3 Framer block will declared an OOF condition
if P-bit errors were detected in two out of 5 consecutive DS3
M-frames.
The following section describes how the CP-bits are
processed at three locations.
3.3.2.6.2 CP-Bit Checking/Options
• The Source Terminal Equipment
CP-bits are very similar to P-bits except for the following.
• The Mid-Network Terminal Equipment
1. CP-bits are used to permit performance monitoring over an entire DS3 path (e.g., from the source
Figure_62 presents a simple illustration of the locations of these three types of Terminal Equipment,
within the Wide-Area Network.
• The Sink Terminal Equipment
FIGURE 82. A SIMPLE ILLUSTRATION OF THE LOCATIONS OF THE SOURCE, MID-NETWORK AND SINK TERMINAL
EQUIPMENT (FOR CP-BIT PROCESSING)
Sink
Sink
Terminal
Terminal
Equipment
Equipment
Customer
Customer
Premises
Premises
Equipment
Equipment
Source
Source
Terminal
Terminal
Equipment
Equipment
Customer
Customer
Premises
Premises
Equipment
Equipment
Mid-Network
Mid-Network
Terminal
Terminal
Equipment
Equipment
The Wide Area Network
NOTE: The use of the terms Source and Sink Terminal
Equipment are used to simplify this discussion of CP-Bit
Processing. In reality, the Source Terminal Equipment (in
Figure_62) will also function as the Sink Terminal Equipment (for DS3 traffic traveling in the opposite direction).
Likewise, the Sink Terminal Equipment (in Figure_62) will
also function as the Source Terminal Equipment.
Processing at the Source Terminal Equipment
The Source Terminal Equipment (located at one edge
of the wide-area network) will typically receive its DS3
payload data from some Customer Premise Equipment (CPE). As the Source Terminal Equipment receives this data from the CPE, it will compute the
even-parity value over all bits within a given outbound
DS3 frame. The Terminal Equipment will then insert
this even parity value into both of the P-bit fields and
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THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
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PRELIMINARY
REV. P1.1.7
both of the CP-bits fields, within the very next outbound DS3 frame.
• Receiving a DS3 data stream, via the Receive
WAN Interface Line Card.
Hence, both the P-bit values and CP-bit values will
originate at the Source Terminal Equipment.
• Transmitting this same DS3 data stream (out to
another Remote Terminal Equipment) via the
Transmit WAN Interface Line Card.
Processing at the Mid-Network Terminal Equipment
Figure 83 presents an illustration of the basic architecture of the Mid-Network Terminal Equipment.
The Mid-Network Terminal Equipment has the task of
doing the following.
FIGURE 83. ILLUSTRATION OF THE PRESUMED CONFIGURATION OF THE MID-NETWORK TERMINAL EQUIPMENT
System Back-plane
DS3 Traffic
from “Source”
Terminal
Equipment
The
TheReceiving
Receiving
DS3
DS3Line
LineCard
Card
The
TheTransmitting
Transmitting
DS3
DS3Line
LineCard
Card
DS3 Traffic to
“Sink” Terminal
Equipment
The Mid-Network Terminal Equipment
Operation of the Receive WAN Interface Line Card
The Receive WAN Interface line card receives a DS3
data stream from some remote Terminal Equipment.
As the Receive WAN Interface card does this, it will
also do the following:
1. Compute and verify the “P-Bits” of each inbound
DS3 frame.
2. Compute and verify the “CP-Bits” of each
inbound DS3 frame.
3. Output both the payload and overhead bits to the
system back-plane.
Operation of the Transmit WAN Interface Line
Card
The Transmit WAN Interface Line Card receives the
outbound DS3 data stream from the system back-
plane. As the Transmit WAN Interface Line Card receives this data it will also do the following.
1. Extract out the “CP-bit” values, from the Receive
WAN Interface line card (via the system backplane) and insert these values into the CP-bit
fields, within the outbound DS3 data stream, via
the Transmit Overhead Data Input Interface block
of the XRT72L53 Framer IC.
2. Compute the even-parity over all bits, within a
given outbound DS3 frame, and insert this value
into the “P” bits within the very next outbound
DS3 frame.
3. Transmit this resulting DS3 data stream to the
remote terminal equipment.
Processing at the Sink Terminal
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THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
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REV. P1.1.7
4.3.3.1 Bit-Oriented Signaling (or FEAC) Processing via the Receive DS3 HDLC Controller.
The Receive DS3 HDLC Controller block consists of
two major sub-blocks
The Sink Terminal Equipment (located at the opposite
edge of the wide-area-network, from the Source Terminal Equipment) will receive and terminate this DS3
data stream. As the Sink Terminal Equipment receives this DS3 data stream it will also do the following.
• The Receive FEAC Processor
• The LAPD Receiver
1. Compute and verify the “P”-bits within each
inbound DS3 frame.
2. Compute and verify the “CP” bits within each
inbound DS3 frame.
This section describes how to operate the Receive
FEAC Processor.
If the Receive DS3 Framer block is operating in the Cbit Parity Framing format, then the FEAC bit-field
within the DS3 Frame can be used to receive FEAC
(Far End Alarm and Control) messages (See
Figure 84). Each FEAC code word is actually six bits
in length. However, this six bit FEAC Code word is
encapsulated with 10 framing bits to form a 16 bit
message of the form:
4.3.3 The Receive HDLC Controller Block
The Receive DS3 HDLC Controller block can be used
to receive either bit-oriented signaling (BOS) or message-oriented signaling (MOS) type data link messages. The Receive DS3 HDLC Controller block can
also be configured to receive both types of message
from the remote terminal equipment.
Both BOS and MOS types of HDLC message processing are discussed in detail below.
FEAC CODE WORD
0
d5
d4
d3
d2
FRAMING
d1
d0
0
1
Where, [d5, d4, d3, d2, d1, d0] is the FEAC Code
word. The rightmost bit of the 16-bit data structure
(e.g., a 1) will be received first. Since each DS3
Frame contains only 1 FEAC bit-field, 16 DS3 Frames
are required to transmit the 16 bit FEAC code message. The six bits, labeled “d5” through “d0” can represent 64 distinct messages, of which 43 have been
defined in the standards.
The Receive FEAC Processor frames and validates
the incoming FEAC data from the remote Transmit
FEAC Processor via the received FEAC channel. Additionally, the Receive FEAC Processor will write the
Received FEAC code words into an 8 bit Rx-FEAC
register. Framing is performed by looking for two 0s
spaced 6 bits apart preceded by 8 1s. The Receive
DS3 HDLC Controller contains two registers that support FEAC Message Reception.
• Rx DS3 FEAC Register (Address = 0x16)
• Rx DS3 FEAC Interrupt Enable/Status Register
(Address = 0x17)
The Receive FEAC Processor generates an interrupt
upon validation and removal of the incoming FEAC
Code words.
1
1
1
1
1
1
1
Operation of the Receive DS3 FEAC Processor
The Receive FEAC Processor will validate or remove
FEAC code words that it receives from the remote
Transmit FEAC Processor. The FEAC Code Validation and Removal functions are described below.
FEAC Code Validation
When the remote terminal equipment wishes to send
a FEAC message to the Local Receive FEAC Processor, it (the remote terminal equipment) will transmit
this 16 bit message, repeatedly for a total of 10 times.
The Receive FEAC Processor will frame to this incoming FEAC Code Message, and will attempt to validate this message. Once the Receive FEAC Processor has received the same FEAC code word in at
least 8 out of the last 10 received codes, it will validate this code word by writing this 6 bit code word into the Receive DS3 FEAC Register. The Receive
FEAC Processor will then inform the µC/µP of this
Receive FEAC validation event by generating a Rx
FEAC Valid interrupt and asserting the FEAC Valid
and the RxFEAC Valid Interrupt Status Bits in the Rx
DS3 Interrupt Enable/Status Register, as depicted
below. The Bit Format of the Rx DS3 FEAC Register
is presented below.
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THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
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RX DS3 FEAC INTERRUPT ENABLE/STATUS REGISTER (ADDRESS = 0X17)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT2
BIT 1
BIT 0
Not Used
Not Used
Not Used
FEAC
Valid
RxFEAC
Remove
Interrupt
Enable
RxFEAC
Remove
Interrupt
status
RxFEAC
Valid
Interrupt
Enable
RxFEAC
Valid
Interrupt
Status
RO
RO
RO
RO
R/W
RUR
R/W
RUR
X
X
X
1
X
0
1
1
The bit-format of the Rx DS3 FEAC register is presented below. It is important to note that the last vali-
dated FEAC code word will be written into the shaded
bit-fields below.
RX DS3 FEAC REGISTER (ADDRESS = 0X16)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT2
BIT 1
BIT 0
Not Used
RxFEAC [5]
RxFEAC [4]
RxFEAC [3]
RxFEAC [2]
RxFEAC [1]
RxFEAC [0]
Not Used
RO
RO
RO
RO
RO
RO
RO
RO
0
d5
d4
d3
d2
d1
d0
0
The purpose of generating an interrupt to the µP, upon FEAC Code Word Validation is to inform the local
µP that the Framer has a newly received FEAC message that needs to be read. The local µP would readin this FEAC code word from the Rx DS3 FEAC Register (Address = 0x16).
FEAC Code Removal
After the 10th transmission of a given FEAC code
word, the remote terminal equipment may proceed to
transmit a different FEAC code word. When the Receive FEAC processor detects this occurrence, it
must Remove the FEAC codeword that is presently
residing in the Rx DS3 FEAC Register. The Receive
FEAC Processor will remove the existing FEAC code
word when it detects that 3 (or more) out of the last
10 received FEAC codes are different from the latest
validated FEAC code word. The Receive FEAC Processor will inform the local µP/µC of this removal
event by generating a Rx FEAC Removal interrupt,
and asserting the RxFEAC Remove Interrupt Status
bit in the Rx DS3 Interrupt Enable/Status Register, as
depicted below.
RX DS3 FEAC INTERRUPT ENABLE/STATUS REGISTER (ADDRESS = 0X17)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT2
BIT 1
BIT 0
Not Used
Not Used
Not Used
FEAC
Valid
RxFEAC
Remove
Interrupt
Enable
RxFEAC
Remove
Interrupt
status
RxFEAC
Valid
Interrupt
Enable
RxFEAC
Valid
Interrupt
Status
RO
RO
RO
RO
R/W
RUR
R/W
RUR
X
X
X
0
1
1
X
0
Additionally, the Receive FEAC processor will also
denote the removal event by setting the FEAC Valid
bit-field (Bit 4), within the Rx DS3 FEAC Interrupt Enable/Status Register to 0, as depicted above.
The description of Bits 0 through 3 within this register,
all support Interrupt Processing, and will therefore be
presented in Section 3.3.6. Figure 84 presents a flow
diagram depicting how the Receive FEAC Processor
functions.
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THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
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FIGURE 84. FLOW DIAGRAM DEPICTING HOW THE RECEIVE FEAC PROCESSOR FUNCTIONS
START
START
1
1
Has this
Has this
same FEAC
same FEAC
Code Word been
Code Word been
Received in 8 out of the last
Received in 8 out of the last
10 FEAC Message
10 FEAC Message
Receptions?
Receptions?
ENABLE THE “FEAC REMOVAL AND
ENABLE THE “FEAC REMOVAL AND
“VALIDATION” INTERRUPTS.
“VALIDATION” INTERRUPTS.
This is accomplished by writing “xxxx 1010” into the
This is accomplished by writing “xxxx 1010” into the
“RxDS3
“RxDS3FEAC
FEACInterrupt/Status
Interrupt/StatusRegister
Register(Address
(Address==0x17)
0x17)
GENERATE “FEAC
GENERATE “FEAC
VALIDATION” INTERRUPT
VALIDATION” INTERRUPT
NO
RECEIVE FEAC PROCESSOR BEGINS READING IN
RECEIVE FEAC PROCESSOR BEGINS READING IN
THE FEAC BIT-FIELDS (OF INCOMING DS3 FRAMES)
THE FEAC BIT-FIELDS (OF INCOMING DS3 FRAMES)
The Receive FEAC Processor checks for the “FEAC Framing
The Receive FEAC Processor checks for the “FEAC Framing
Alignment” pattern of “01111110”.
Alignment” pattern of “01111110”.
IsIsthe
the
“FEAC
“FEACFraming
Framing
Alignment”pattern
Alignment”pattern
present
presentininthe
theFEAC
FEAC
Channel
Channel
??
YES
INVOKE “FEAC VALIDATION”
INVOKE “FEAC VALIDATION”
INTERRUPTSERVICE ROUTINE.
INTERRUPTSERVICE ROUTINE.
Has
Hasa aFEAC
FEAC
Code Word (other than
Code Word (other than
the
last
“Validated
the last “ValidatedCode
CodeWord)
Word)
been
Received
in
3
out
been Received in 3 outofofthe
thelast
last
10
10FEAC
FEACMessage
Message
Receptions?
Receptions?
NO
NO
11
YES
GENERATE
GENERATE“FEAC
“FEAC
REMOVAL”
REMOVAL”INTERRUPT
INTERRUPT
YES
READ IN THE “6-BIT FEAC CODE WORD”
READ IN THE “6-BIT FEAC CODE WORD”
The
The6-bit
6-bitFEAC
FEACCode
CodeWord
Wordimmediately
immediatelyfollows
followsthe
the“FEAC
“FEAC
Framing Alignment” Pattern.
Framing Alignment” Pattern.
1
1
INVOKE
INVOKE“FEAC
“FEACREMOVAL”
REMOVAL”
INTERRUPTSERVICE ROUTINE.
INTERRUPTSERVICE ROUTINE.
NOTES:
1. The white (e.g., unshaded) boxes reflect tasks that
the user’s system must perform in order to configure the Receive FEAC Processor to receive FEAC
messages.
2. A brief description of the steps that must exist
within the FEAC Validation and FEAC Removal
Interrupt Service Routines exists in Section 3.6
LAPD frame into the Receive LAPD Message Buffer,
which is located at addresses: 0xDE through 0x135
within the on-chip RAM. The LAPD Receiver has the
following responsibilities.
4.3.3.2 The Message Oriented Signaling (e.g.,
LAP-D) Processing via the Receive DS3 HDLC
Controller block
The LAPD Receiver (within the Receive DS3 HDLC
Controller block) allows the user to receive PMDL
messages from the remote terminal equipment, via
the inbound DS3 frames. In this case, the inbound
message bits will be carried by the 3 DL bit-fields of
F-Frame 5, within each DS3 M-Frame. The remote
LAPD Transmitter will transmit a LAPD Message to
the Near-End Receiver via these three bits within
each DS3 Frame. The LAPD Receiver will receive
and store the information portion of the received
• Storing the Frame Message into the Receive LAPD
Message Buffer
• Framing to the incoming LAPD Messages
• Filtering out stuffed 0s (within the information payload)
• Perform Frame Check Sequence (FCS) Verification
• Provide status indicators for
End of Message (EOM)
Flag Sequence Byte detected
Abort Sequence detected
Message Type
C/R Type
The occurrence of FCS Errors
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The LAPD receiver's actions are facilitated via the following two registers.
• Rx DS3 LAPD Control Register
• Rx DS3 LAPD Status Register
Operation of the LAPD Receiver
The LAPD Receiver, once enabled, will begin searching for the boundaries of the incoming LAPD message. The LAPD Message Frame boundaries are delineated via the Flag Sequence octets (0x7E), as depicted in Figure 85.
FIGURE 85. LAPD MESSAGE FRAME FORMAT
Flag Sequence (8 bits)
C/R
SAPI (6-bits)
TEI (7 bits)
EA
EA
Control (8-bits)
76 or 82 Bytes of Information (Payload)
FCS - MSB
FCS - LSB
Flag Sequence (8-bits)
SAPI + CR + EA = 0x3C or 0x3E
mation field and the corresponding message type/
size follow:
TEI + EA = 0x01
CL Path Identification
Control = 0x03
IDLE Signal Identification = 0x34 (76 bytes)
Where: Flag Sequence = 0x7E
= 0x38 (76 bytes)
The 16 bit FCS is calculated using CRC-16, x16 +
x12 + x5 + 1
Test Signal Identification = 0x32 (76 bytes)
The microprocessor/microcontroller (at the remote
terminal), while assembling the LAPD Message
frame, will insert an additional byte at the beginning of
the information (payload) field. This first byte of the
information field indicates the type and size of the
message being transferred. The value of this infor-
The LAPD Receiver must be enabled before it can
begin receiving any LAPD messages. The LAPD Receiver can be enabled by writing a "1" into Bit 2 (RxLAPD Enable) within the Rx DS3 LAPD Control Register. The bit format of this register is depicted below.
ITU-T Path Identification = 0x3F (82 bytes)
RX DS3 LAPD CONTROL REGISTER (ADDRESS = 0X18)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT2
BIT 1
BIT 0
Not Used
Not Used
Not Used
Not Used
Not Used
RxLAPD
Enable
RxLAPD
Interrupt
Enable
RxLAPD
Interrupt
Status
RO
RO
RO
RO
RO
R/W
R/W
RUR
0
0
0
0
0
1
X
X
Once the LAPD Receiver has been enabled, it will begin searching for the Flag Sequence octets (0x7E), in
the DL bit-fields, within the incoming DS3 frames.
When the LAPD Receiver finds the flag sequence
byte, it will assert the Flag Present bit (Bit 0) within
the Rx DS3 LAPD Status Register, as depicted below.
RX DS3 LAPD STATUS REGISTER (ADDRESS = 0X19)
BIT 7
BIT 6
Not Used
RxAbort
X
X
BIT 5
BIT 4
RxLAPD Type[1, 0]
X
BIT 3
BIT2
BIT 1
BIT 0
RxCR Type
RxFCS Error
End of
Message
Flag
Present
X
X
X
1
X
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PRELIMINARY
REV. P1.1.7
The receipt of the Flag Sequence octet can mean
one of two things.
1. The Flag Sequence byte marks the beginning or
end of an incoming LAPD Message.
2. The received Flag Sequence octet could be just
one of many Flag Sequence octets that are transmitted via the DS3 Transport Medium, during idle
periods between the transmission of LAPD Messages.
The LAPD Receiver will clear the Flag Present bit as
soon as it has received an octet that is something
other than the Flag Sequence octet. At this point, the
LAPD Receiver should be receiving either octet #2 of
the incoming LAPD Message, or an Abort Sequence
(e.g., a string of seven or more consecutive 1s). If
this next set of data is an abort sequence, then the
LAPD Receiver will assert the RxAbort bit (Bit 6) within the Rx DS3 LAPD Status Register. However, if this
next octet is Octet #2 of an incoming LAPD Message,
then the Rx DS3 LAPD Status Register will begin to
present some additional status information on this incoming message. Each of these indicators is presented below in sequential order.
Bit 3 - RxCR Type - C/R (Command/Response)
Type
This bit-field reflects the contents of the C/R bit-field
within octet #2 of the LAPD Frame Header. When
this bit is "0" it means that this message is originating
from a customer installation. When this bit is "1" it
means that this message is originating from a network terminal.
Bit 4,5 - RxLAPD Type[1, 0] - LAPD Message Type
The combination of these two bit fields indicate the
Message Type and the Message Size of the incoming
LAPD Message frame. Table 41 relates the values of
Bits 4 and 5 to the Incoming LAPD Message Type/
Size.
TABLE 41: THE RELATIONSHIP BETWEEN RXLAPDTYPE[1:0] AND THE RESULTING LAPD MESSAGE TYPE AND SIZE
RXLAPD TYPE[1, 0]
MESSAGE TYPE
MESSAGE SIZE
00
Test Signal Identification
76 bytes
01
Idle Signal Identification
76 bytes
10
CL Path Identification
76 bytes
11
TU-T Path Identification
82 bytes
NOTE: The Message Size pertains to the size of the Information portion of the LAPD Message Frame (as presented
in Figure 85).
Bit 3 - Flag Present
The LAPD Receiver should receive another Flag Sequence octet, which marks the End of the Message.
Therefore, this bit field should be asserted once
again.
Bit 1 - EndOfMessage - End of LAPD Message
Frame
Upon receipt of the closing Flag Sequence octet, this
bit-field should be asserted. The assertion of this bitfield indicates that a LAPD Message Frame has been
completely received. Additionally, if this newly received LAPD Message is different from the previous
message, then the LAPD Receiver will inform the µC/
µP of the EndOfMessage event by generating an interrupt.
Bit 2 - RxFCSErr - Frame Check Sequence Error
Indicator
The LAPD Receiver will take the incoming LAPD
Message and compute its own version of the Frame
Check Sequence (FCS) word. Afterwards, the LAPD
Receiver will compare its computed value with that it
has received from the remote LAPD Transmitter. If
these two values match, then the LAPD Receiver will
presume that the LAPD Message has been properly
received and the contents of the Received LAPD
Message (payload portion) will be retained at locations 0xDE through 0x135 in on-chip RAM. The
LAPD Receiver will indicate an error-free reception of
the LAPD Message by keeping this bit field negated
(Bit 2 = 0). However, if these two FCS values do not
match, then the received LAPD Message is corrupted
and the user is advised not to process this erroneous
information. The LAPD Receiver will indicate an erred
receipt of this message by setting this bit-field to 1.
NOTE: The Receive DS3 HDLC Controller block will not
generate an interrupt to the µP due to the detection of an
FCS error. Therefore, the user is advised to validate each
and every received LAPD message by checking this bitfield prior to processing the LAPD message.
Removal of Stuff Bits from the Payload Portion of
the incoming LAPD Message
While the LAPD Receiver is receiving a LAPD Message, it has the responsibility of removing all of the
"0" stuff bits from the Payload Portion of the incoming
LAPD Message Frame. Recall that the text in Section
3.2.3.2 indicated that the LAPD Transmitter (at the re-
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THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
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PRELIMINARY
REV. P1.1.7
The LAPD receiver will obtain the LAPD Message
frame from the incoming DS3 data-stream. In addition to processing the framing overhead octets, performing error checking (via FCS) and removing the
stuffed 0s from the user payload data. The LAPD Receiver will also write the payload portion of the LAPD
Frame into the Receive LAPD Message buffer at locations 0xDE through 0x135 in on-chip RAM.
mote terminal) will insert a "0" immediately following a
string of 5 consecutive 1s within the payload portion
of the LAPD Message frame. The LAPD Transmitter
performs this bit-stuffing procedure in order to prevent
the user data from mimicking the Flag Sequence octet (0x7E) or the ABORT sequence. Therefore, in order to recover the user data to its original content (prior to the bit-stuffing), the LAPD Receiver will remove
the "0" that immediately follows a string of 5 consecutive 1s.
Therefore, the local µP/µC must read this location
when it wishes to process this newly received LAPD
Message.
Writing the Incoming LAPD Message into the Receive LAPD Message Buffer
Figure 86 presents a flow chart depicting how the
LAPD Receiver works.
FIGURE 86. FLOW CHART DEPICTING THE FUNCTIONALITY OF THE LAPD RECEIVER
START
START
ENABLE THE LAPD RECEIVER
This is done by writing the value “0xFC into the
RxLAPD Control Register (Address = 0x18)
LAPD
LAPDReceiver
Receiverisisreading
readinginina aLAPD
LAPD
Message
Frame,
containing
Message Frame, containinga aPMDL
PMDL
Message.
Message.
Does
Does
the
theLAPD
LAPD
Receiver detect 6
Receiver detect 6
consecutive
consecutive
Zeros
Zeros
??
NO
LAPD Receiver begins reading in the DL bits
from each inbound DS3 frame
VERIFY
VERIFYTHE
THEFCS
FCSVALUE
VALUE
Report
Reportresults
resultsininthe
theRxLAPD
RxLAPD
Status Register..
Status Register..
“Un-stuff contents of Received
“Un-stuff contents of Received
Message”
Message”
YES
Does
Does
the LAPD
the LAPD
Receiver detect 6
Receiver detect 6
consecutive
consecutive
Zeros
Zeros
?
?
1
1
YES
Does
Does
the
theLAPD
LAPD
Receiver detect 7
Receiver detect 7
consecutive
consecutive
Zeros
Zeros
??
NO
ABORT Sequence
ABORT Sequence
YES
YES
End
EndofofMessage
Message(EOM)
(EOM)
Generate
Generate“Received
“ReceivedLAPD
LAPD
Interrupt”
Interrupt”
Does
Does
the LAPD
the LAPD
Receiver detect 7
Receiver detect 7
consecutive
consecutive
Zeros
Zeros
?
?
Execute
ExecuteReceive
ReceiveLAPD
LAPD
Interrupt Service Routine
Interrupt Service Routine
NO
11
Write
WriteReceived
ReceivedPMDL
PMDLMessage
Message
into the Receive LAPD Message
into the Receive LAPD Message
Buffer (Addresses 0xDE - 0x135)
Buffer (Addresses 0xDE - 0x135)
NO
Flag Sequence
Flag Sequence
NOTES:
1. The white (e.g., unshaded) boxes reflect tasks that
the user’s system must perform in order to configure the LAPD Receiver to receive LAPD Messages.
2. A brief description of the steps that must exist
within the Receive LAPD Interrupt Service routine
exists in Section 3.3.6.
4.3.4 The Receive Overhead Data Output Interface
Figure 87 presents a simple illustration of the Receive
Overhead Data Output Interface block within the
XRT72L53.
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PRELIMINARY
REV. P1.1.7
FIGURE 87. A SIMPLE ILLUSTRATION OF THE RECEIVE OVERHEAD OUTPUT INTERFACE BLOCK
RxOHFrame
RxOH
RxOHClk
Receive
ReceiveOverhead
Overhead
Output
Interface
Output Interface
Block
Block
From Receive
DS3 Framer Block
RxOHEnable
ta Link Layer equipment to sample and process these
overhead bits, via the following two methods.
The DS3 frame consists of 4760 bits. Of these bits,
4704 bits are payload bits and the remaining 56 bits
are overhead bits. The XRT72L53 has been designed to handle and process both the payload type
and overhead type bits for each DS3 frame.
• Method 1- Using the RxOHClk clock signal.
• Method 2 - Using the RxClk and RxOHEnable output signals.
The Receive Payload Data Output Interface block,
within the Receive Section of the XRT72L53, has
been designed to handle the payload bits. Likewise,
the Receive Overhead Data Output Interface block
has been designed to handle and process the overhead bits.
Each of these methods are described below.
The Receive Overhead Data Output Interface block
unconditionally outputs the contents of all overhead
bits within the incoming DS3 data stream. The
XRT72L53 does not offer the user a means to shut off
this transmission of data. However, the Receive
Overhead Output Interface block does provide the user with the appropriate output signals for external Da-
4.3.4.1 Method 1 - Using the RxOHClk Clock
signal
The Receive Overhead Data Output Interface block
consists of four (4) signals. Of these four signals, the
following three signals are to be used when sampling
the DS3 overhead bits via Method 1.
• RxOH
• RxOHClk
• RxOHFrame
Each of these signals are listed and described below
in Table 42.
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TABLE 42: LISTING AND DESCRIPTION OF THE PIN ASSOCIATED WITH THE RECEIVE OVERHEAD DATA OUTPUT
INTERFACE BLOCK
SIGNAL NAME
TYPE
DESCRIPTION
RxOH
Output
Receive Overhead Data Output pin:
The XRT72L53 will output the overhead bits, within the incoming DS3 frames, via this pin.
The Receive Overhead Data Output Interface block will output a given overhead bit, upon the
falling edge of RxOHClk. Hence, the external data link equipment should sample the data, at
this pin, upon the rising edge of RxOHClk.
The XRT72L53 will always output the DS3 Overhead bits via this output pin. There are no
external input pins or register bit settings available that will disable this output pin.
RxOHClk
Output
Receive Overhead Data Output Interface Clock Signal:
The XRT72L53 will output the Overhead bits (within the incoming DS3 frames), via the RxOH
output pin, upon the falling edge of this clock signal.
As a consequence, the user's data link equipment should use the rising edge of this clock signal to sample the data on both the RxOH and RxOHFrame output pins.
This clock signal is always active.
RxOHFrame
Output
Receive Overhead Data Output Interface - Start of Frame Indicator:
The XRT72L53 will drive this output pin "High" (for one period of the RxOHClk signal), whenever the first overhead bit within a given DS3 frame is being driven onto the RxOH output pin.
Interfacing the Receive Overhead Data Output Interface block to the Terminal Equipment (Method
1)
Terminal Equipment when using Method 1 to sample
and process the overhead bits from the inbound DS3
data stream.
Figure 88 illustrates how one should interface the Receive Overhead Data Output Interface block to the
FIGURE 88. ILLUSTRATION OF HOW TO INTERFACE THE TERMINAL EQUIPMENT TO THE RECEIVE OVERHEAD DATA
OUTPUT INTERFACE BLOCK (FOR METHOD 1).
RxOHClk
DS3_OH_Clock_In
RxOH
DS3_OH_In
RxOHFrame
Rx_Start_of_Frame
Terminal Equipment
Method 1 Operation of the Terminal Equipment
XRT72L5x DS3 Framer IC
If the Terminal Equipment intends to sample any
overhead data from the inbound DS3 data stream (via
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PRELIMINARY
REV. P1.1.7
doing this, the Terminal Equipment will be able to
keep track of which overhead bit is being output
via the RxOH output pin. Based upon this information, the Terminal Equipment will be able to
derive some meaning from these overhead bits.
Table 43 relates the number of rising clock edges (in
the RxOHClk signal, since the RxOHFrame signal
was last sampled "High") to the DS3 Overhead bit
that is being output via the RxOH output pin.
the Receive Overhead Data Output Interface block)
then it is expected to do the following:
1. Sample the state of the RxOHFrame signal (e.g.,
the Rx_Start_of_Frame input signal) on the rising
edge of the RxOHClk (e.g., the
DS3_OH_Clock_In) signal.
2. Keep track of the number of rising clock edges
that have occurred in the RxOHClk (e.g., the
DS3_OH_Clock_In) signal, since the last time the
RxOHFrame signal was sampled "High". By
TABLE 43: THE RELATIONSHIP BETWEEN THE NUMBER OF RISING CLOCK EDGES IN RXOHCLK, (SINCE
RXOHFRAME WAS LAST SAMPLED "HIGH") TO THE DS3 OVERHEAD BIT, THAT IS BEING OUTPUT VIA THE RXOH
OUTPUT PIN
NUMBER OF RISING CLOCK EDGES IN RXOHCLK
THE OVERHEAD BIT BEING OUTPUT BY THE
XRT72L53
0 (Clock edge is coincident with RxOHFrame being detected "High")
X
1
F1
2
AIC
3
F0
4
NA
5
F0
6
FEAC
7
F1
8
X
9
F1
10
UDL
11
F0
12
UDL
13
F0
14
UDL
15
F1
16
P
17
F1
18
CP
19
F0
20
CP
21
F0
22
CP
23
F1
24
P
25
F1
26
FEBE
27
F0
28
FEBE
29
F0
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THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
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TABLE 43: THE RELATIONSHIP BETWEEN THE NUMBER OF RISING CLOCK EDGES IN RXOHCLK, (SINCE
RXOHFRAME WAS LAST SAMPLED "HIGH") TO THE DS3 OVERHEAD BIT, THAT IS BEING OUTPUT VIA THE RXOH
OUTPUT PIN
NUMBER OF RISING CLOCK EDGES IN RXOHCLK
THE OVERHEAD BIT BEING OUTPUT BY THE
XRT72L53
30
FEBE
31
F1
32
M0
33
F1
34
DL
35
F0
36
DL
37
F0
38
DL
39
F1
40
M1
41
F1
42
UDL
43
FO
44
UDL
45
FO
46
UDL
47
F1
48
M0
49
F1
50
UDL
51
F0
52
UDL
53
F0
54
UDL
55
F1
Figure 89 presents the typical behavior of the Receive Overhead Data Output Interface block, when
Method 1 is being used to sample the incoming DS3
overhead bits.
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FIGURE 89. ILLUSTRATION OF THE SIGNALS THAT ARE OUTPUT VIA THE RECEIVE OVERHEAD OUTPUT INTERFACE
(FOR METHOD 1).
RxOHClk
RxOHFrame
RxOH
X
F1
AIC
Terminal Equipment should sample
the “RxOHFrame” and “RxOH” signals
here.
F0
FEAC
Recommended Sampling Edges
Method 2 - Using RxOutClk and the RxOHEnable
signals
face. Hence, Method 2 is available. Method 2 involves the use of the following signals.
Method 1 requires that the Terminal Equipment be
able to handle an additional clock signal, RxOHClk.
However, there may be a situation in which the Terminal Equipment circuitry does not have the means to
accommodate and process this extra clock signal, in
order to use the Receive Overhead Data Output Inter-
• RxOH
• RxOutClk
• RxOHEnable
• RxOHFrame
Each of these signals are listed and described below
in Table 44.
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TABLE 44: LISTING AND DESCRIPTION OF THE PIN ASSOCIATED WITH THE RECEIVE OVERHEAD DATA OUTPUT
INTERFACE BLOCK (METHOD 2)
SIGNAL NAME
TYPE
DESCRIPTION
RxOH
Output
Receive Overhead Data Output pin:
The XRT72L53 will output the overhead bits, within the incoming DS3 frames, via this pin.
The Receive Overhead Output Interface will pulse the RxOHEnable output pin (for one RxOutClk period) at approximately the middle of the RxOH bit period. The user is advised to design
the Terminal Equipment to latch the contents of the RxOH output pin, whenever the RxOHEnable output pin is sampled "High" on the falling edge of RxOutClk.
RxOHEnable
Output
Receive Overhead Data Output Enable - Output pin:
The XRT72L53 will assert this output signal for one RxOutClk period when it is safe for the Terminal Equipment to sample the data on the RxOH output pin.
RxOHFrame
Output
Receive Overhead Data Output Interface - Start of Frame Indicator:
The XRT72L53 will drive this output pin "High" (for one period of the RxOH signal), whenever
the first overhead bit, within a given DS3 frame is being driven onto the RxOH output pin.
RxOutClk
Output
Receive Section Output Clock Signal:
This clock signal is derived from the RxLineClk signal (from the LIU) for loop-timing applications, and the TxInClk signal (from a local oscillator) for local-timing applications. For DS3
applications, this clock signal will operate at 44.736MHz.
The user is advised to design the Terminal Equipment to latch the contents of the RxOH pin,
anytime the RxOHEnable output signal is sampled "High" on the falling edge of this clock signal.
Interfacing the Receive Overhead Data Output Interface block to the Terminal Equipment (Method
2)
Figure 90 illustrates how one should interface the Receive Overhead Data Output Interface block to the
Terminal Equipment, when using Method 2 to sample
and process the overhead bits from the inbound DS3
data stream.
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FIGURE 90. ILLUSTRATION OF HOW TO INTERFACE THE TERMINAL EQUIPMENT TO THE RECEIVE OVERHEAD DATA
OUTPUT INTERFACE BLOCK (FOR METHOD 2).
DS3_OH_In
RxOH
DS3_OH_Enable_In
RxOHEnable
DS3_Clk_In
RxOutClk
Rx_Start_of_Frame
RxOHFrame
Terminal Equipment
XRT72L5x DS3 Framer IC
Method 2 Operation of the Terminal Equipment
"High". By doing this, the Terminal Equipment
will be able to keep track of which overhead bit is
being output via the RxOH output pin. Based
upon this information, the Terminal Equipment
will be able to derive some meaning from these
overhead bits.
3. Table 45 relates the number of RxOHEnable output pulses (that have occurred since both the
RxOHFrame and the RxOHEnable pins were
both sampled "High") to the DS3 overhead bit
that is being output via the RxOH output pin.
If the Terminal Equipment intends to sample any
overhead data from the inbound DS3 data stream (via
the Receive Overhead Data Output Interface), then it
is expected to do the following.
1. Sample the state of the RxOHFrame signal (e.g.,
the Rx_Start_of_Frame input) on the falling edge
of the RxOutClk clock signal, whenever the RxOHEnable output signal is also sampled "High".
2. Keep track of the number of times that the RxOHEnable signal has been sampled "High" since
the last time the RxOHFrame was also sampled
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TABLE 45: THE RELATIONSHIP BETWEEN THE NUMBER OF RXOHENABLE OUTPUT PULSES ((SINCE RXOHFRAME
WAS LAST SAMPLED "HIGH") TO THE DS3 OVERHEAD BIT, THAT IS BEING OUTPUT VIA THE RXOH OUTPUT PIN
NUMBER OF RXOHENABLE OUTPUT PULSES
THE OVERHEAD BIT BEING OUTPUT BY THE
XRT72L53
0 (The RxOHEnable and RxOHFrame signals are both sampled "High")
X
1
F1
2
AIC
3
F0
4
NA
5
F0
6
FEAC
7
F1
8
X
9
F1
10
UDL
11
F0
12
UDL
13
F0
14
UDL
15
F1
16
P
17
F1
18
CP
19
F0
20
CP
21
F0
22
CP
23
F1
24
P
25
F1
26
FEBE
27
F0
28
FEBE
29
F0
30
FEBE
31
F1
32
M0
33
F1
34
DL
35
F0
36
DL
37
F0
38
DL
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TABLE 45: THE RELATIONSHIP BETWEEN THE NUMBER OF RXOHENABLE OUTPUT PULSES ((SINCE RXOHFRAME
WAS LAST SAMPLED "HIGH") TO THE DS3 OVERHEAD BIT, THAT IS BEING OUTPUT VIA THE RXOH OUTPUT PIN
NUMBER OF RXOHENABLE OUTPUT PULSES
THE OVERHEAD BIT BEING OUTPUT BY THE
XRT72L53
39
F1
40
M1
41
F1
42
UDL
43
FO
44
UDL
45
FO
46
UDL
47
F1
48
M0
49
F1
50
UDL
51
F0
52
UDL
53
F0
54
UDL
55
F1
Figure 91 presents the typical behavior of the Receive Overhead Data Output Interface block, when
Method 2 is being used to sample the incoming DS3
overhead bits.
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FIGURE 91. ILLUSTRATION OF THE SIGNALS THAT ARE OUTPUT VIA THE RECEIVE OVERHEAD DATA OUTPUT INTERMETHOD 2).
FACE BLOCK (FOR
RxOutClk
RxOHEnable
Recommended
Sampling
Edges
RxOHFrame
RxOH
4.3.5
face
F1
X
The Receive Payload Data Output Inter-
F1
AIC
F0
Figure 92 presents a simple illustration of the Receive
Payload Data Output Interface block.
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FIGURE 92. A SIMPLE ILLUSTRATION OF THE RECEIVE PAYLOAD DATA OUTPUT INTERFACE BLOCK
RxOHInd
RxSer
RxNib[3:0]
RxClk
Receive
ReceivePayload
Payload
Data
Output
Data Output
Interface
Interface
From Receive DS3
Framer Block
RxOutClk
RxFrame
Each of the output pins of the Receive Payload Data
Output Interface block are listed in Table 46 and described below. The exact role that each of these out-
put pins assume, for a variety of operating scenarios
are described throughout this section.
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TABLE 46: LISTING AND DESCRIPTION OF THE PIN ASSOCIATED WITH THE RECEIVE PAYLOAD DATA OUTPUT
INTERFACE BLOCK
SIGNAL NAME
TYPE
DESCRIPTION
RxSer
Output Receive Serial Payload Data Output pin:
If the user opts to operate the XRT72L53 in the serial mode, then the chip will output the payload
data, of the incoming DS3 frames, via this pin. The XRT72L53 will output this data upon the rising edge of RxClk.
The user is advised to design the Terminal Equipment such that it will sample this data on the
falling edge of RxClk.
This signal is only active if the NibInt input pin is pulled "Low".
RxNib[3:0]
Output Receive Nibble-Parallel Payload Data Output pins:
If the user opts to operate the XRT72L53 in the nibble-parallel mode, then the chip will output the
payload data, of the incoming DS3 frames, via these pins. The XRT72L53 will output data via
these pins, upon the falling edge of the RxClk output pin.
The user is advised to design the Terminal Equipment such that it will sample this data upon the
rising edge of RxClk.
These pins are only active if the NibInt input pin is pulled "High".
RxClk
Output Receive Payload Data Output Clock pin:
The exact behavior of this signal depends upon whether the XRT72L53 is operating in the Serial
or in the Nibble-Parallel-Mode.
Serial Mode Operation
In the serial mode, this signal is a 44.736MHz clock output signal. The Receive Payload Data
Output Interface will update the data via the RxSer output pin, upon the rising edge of this clock
signal.
The user is advised to design (or configure) the Terminal Equipment to sample the data on the
RxSer pin, upon the falling edge of this clock signal.
Nibble-Parallel Mode Operation
In this Nibble-Parallel Mode, the XRT72L53 will derive this clock signal, from the RxLineClk signal. The XRT72L53 will pulse this clock 1176 times for each inbound DS3 frame. The Receive
Payload Data Output Interface will update the data, on the RxNib[3:0] output pins upon the falling
edge of this clock signal.
The user is advised to design (or configure) the Terminal Equipment to sample the data on the
RxNib[3:0] output pins, upon the rising edge of this clock signal
RxOHInd
Output Receive Overhead Bit Indicator Output:
This output pin will pulse "High" whenever the Receive Payload Data Output Interface outputs an
overhead bit via the RxSer output pin. The purpose of this output pin is to alert the Terminal
Equipment that the current bit, (which is now residing on the RxSer output pin), is an overhead
bit and should not be processed by the Terminal Equipment.
The XRT72L53 will update this signal, upon the rising edge of the RxClk signal.
The user is advised to design (or configure) the Terminal Equipment to sample this signal (along
with the data on the RxSer output pin) on the falling edge of the RxClk signal.
For DS3 applications, this output pin is only active if the XRT72L53 is operating in the Serial
Mode. This output pin will be "Low" if the device is operating in the Nibble-Parallel Mode.
RxFrame
Output Receive Start of Frame Output Indicator:
The exact behavior of this pin, depends upon whether the XRT72L53 has been configured to
operate in the Serial Mode or the Nibble-Parallel Mode.
Serial Mode Operation:
The Receive Section of the XRT72L53 will pulse this output pin "High" (for one bit period) when
the Receive Payload Data Output Interface block is driving the very first bit of a given DS3 frame,
onto the RxSer output pin.
Nibble-Parallel Mode Operation:
The Receive Section of the XRT72L53 will pulse this output pin "High" (for one nibble period),
when the Receive Payload Data Output Interface is driving the very first nibble of a given DS3
frame, onto the RxNib[3:0] output pins.
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Operation of the Receive Payload Data Output Interface block
The XRT72L53 will output the payload data, of the incoming DS3 frames via the RxSer output, upon the
rising edge of RxClk.
The Receive Payload Data Output Interface permits
the user to read out the payload data of inbound DS3
frames, via either of the following modes.
Delineation of inbound DS3 Frames
The XRT72L53 will pulse the RxFrame output pin
"High" for one bit-period, coincident with it driving the
first bit within a given DS3 frame, via the RxSer output pin.
• Serial Mode
• Nibble-Parallel Mode
Each of these modes are described in detail, below.
Interfacing the XRT72L53 to the Receive Terminal
Equipment
4.3.5.1 Serial Mode Operation
Behavior of the XRT72L53
Figure 93 presents a simple illustration as how the
user should interface the XRT72L53 to that terminal
equipment which processes Receive Direction payload data.
If the XRT72L53 has been configured to operate in
the Serial mode, then the XRT72L53 will behave as
follows.
Payload Data Output
FIGURE 93. ILLUSTRATION OF THE XRT72L53 DS3/E3 FRAMER IC BEING INTERFACED TO THE RECEIVE TERMINAL
EQUIPMENT (SERIAL MODE OPERATION)
Rx_DS3_Clock_In
44.736 MHz
Clock Source
44.736 MHz Clock Signal
RxClk
DS3_Data_In
RxSer
RxLineClk
Rx_Start_of_Frame
RxFrame
Rx_DS3_OH_Ind
RxOHIns
Terminal Equipment
(Receive Payload Section)
XRT72L5x DS3 Framer
Required Operation of the Terminal Equipment
• RxOHInd
The XRT72L53 will update the data on the RxSer output pin, upon the rising edge of RxClk. However, because the rising edge of RxClk to data delay is between 14ns to 16ns, the Terminal Equipment should
sample the data on the RxSer output pin (or the
DS3_Data_In pin at the Terminal Equipment) upon
the rising edge of RxClk. This will still permit the Terminal Equipment with a RxSer to RxClk set-up time of
approximately 6ns and a hold time of 14 to 16ns. As
the Terminal Equipment samples RxSer with each rising edge of RxClk it should also be sampling the following signals.
The Need for sampling RxFrame
• RxFrame
The XRT72L53 will pulse the RxFrame output pin
"High" coincident with it driving the very first bit of a
given DS3 frame onto the RxSer output pin. If knowledge of the DS3 Frame Boundaries is important for
the operation of the Terminal Equipment, then this is
a very important signal for it to sample.
The Need for sampling RxOHInd
The XRT72L53 will indicate that it is currently driving
an overhead bit onto the RxSer output pin, by pulsing
the RxOHInd output pin "High". If the Terminal Equipment samples this signal "High", then it should know
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REV. P1.1.7
that the bit, that it is currently sampling via the RxSer
pin is an overhead bit and should not be processed.
The Behavior of the Signals between the Receive
Payload Data Output Interface block and the Terminal Equipment
The behavior of the signals between the XRT72L53
and the Terminal Equipment for DS3 Serial Mode Operation is illustrated in Figure 94.
FIGURE 94. AN ILLUSTRATION OF THE BEHAVIOR OF THE SIGNALS BETWEEN THE RECEIVE PAYLOAD DATA OUTPUT
INTERFACE BLOCK OF THE XRT72L53 AND THE TERMINAL EQUIPMENT (SERIAL MODE OPERATION)
Terminal Equipment Signals
DS3_Clock_In
DS3_Data_In
Payload[4702]
Payload[4703]
X-Bit
Payload[0]
X-Bit
Payload[0]
Rx_Start_of_Frame
DS3_Overhead_Ind
XRT72L5x Receive Payload Data I/F Signals
RxClk
Payload[4702]
RxSer
Payload[4703]
RxFrame
RxOH_Ind
DS3 Frame Number N
DS3 Frame Number N + 1
Note: RxFrame pulses high to denote
DS3 Frame Boundary.
Note: X-Bit will not be processed by the
Transmit Payload Data Input Interface.
Note: RxOH_Ind pulses high to
denote Overhead Data
(e.g., the X-bit).
2. Unlike Serial Mode operation, the duty cycle of
RxClk, in Nibble-Parallel Mode operation is approximately 25%.
4.3.5.2 Nibble-Parallel Mode Operation
Behavior of the XRT72L53
If the XRT72L53 has been configured to operate in
the Nibble-Parallel Mode, then the XRT72L53 will behave as follows.
Payload Data Output
The XRT72L53 will output the payload data of the incoming DS3 frames, via the RxNib[3:0] output pins,
upon the falling edge of RxClk.
NOTES:
1. In this case, RxClk will function as the Nibble Clock
signal between the XRT72L53 the Terminal Equipment. The XRT72L53 will pulse the RxClk output
signal "High" 1176 times, for each inbound DS3
frame.
Delineation of Inbound DS3 Frames
The XRT72L53 will pulse the RxFrame output pin
"High" for one nibble-period coincident with it driving
the very first nibble, within a given inbound DS3
frame, via the RxNib[3:0] output pins.
Interfacing the XRT72L53 the Terminal Equipment.
Figure 95 presents a simple illustration as how the
user should interface the XRT72L53 to that terminal
equipment which processes Receive Direction payload data.
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REV. P1.1.7
FIGURE 95. ILLUSTRATION OF THE XRT72L53 DS3/E3 FRAMER IC BEING INTERFACED TO THE RECEIVE SECTION
OF THE TERMINAL EQUIPMENT (NIBBLE-MODE OPERATION)
Rx_DS3_Clock_In
44.736 MHz
Clock Source
11.184 MHz Clock Signal
RxClk
DS3_Data_In[3:0]
RxNib[3:0]
RxLineClk
Rx_Start_of_Frame
RxFrame
Terminal Equipment
(Receive Payload Section)
Required Operation of the Terminal Equipment
The XRT72L53 will update the data on the RxNib[3:0]
line, upon the falling edge of RxClk. Hence, the Terminal Equipment should sample the data on the RxNib[3:0] output pins (or the DS3_Data_In[3:0] input
pins at the Terminal Equipment) upon the rising edge
of RxClk. As the Terminal Equipment samples RxSer
with each rising edge of RxClk it should also be sampling the RxFrame signal.
The Need for Sampling RxFrame
The XRT72L53 will pulse the RxFrame output pin
"High" coincident with it driving the very first nibble of
a given DS3 frame, onto the RxNib[3:0] output pins.
XRT72L5x DS3 Framer
If knowledge of the DS3 Frame Boundaries is important for the operation of the Terminal Equipment, then
this is a very important signal for it to sample.
NOTE: For DS3/Nibble-Parallel Mode Operation, none of
the Overhead bits will be output via the RxNib[3:0] output
pins. Hence, the RxOH_Ind output pin will be in-active in
this mode.
The Behavior of the Signals between the Receive
Payload Data Output Interface block and the Terminal Equipment
The behavior of the signals between the XRT72L53
and the Terminal Equipment for DS3 Nibble-Mode operation is illustrated in Figure 96.
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FIGURE 96. AN ILLUSTRATION OF THE BEHAVIOR OF THE SIGNALS BETWEEN THE RECEIVE PAYLOAD DATA OUTPUT
INTERFACE BLOCK OF THE XRT72L53 AND THE TERMINAL EQUIPMENT (NIBBLE-MODE OPERATION).
Terminal Equipment Signals
RxOutClk
Rx_DS3_Clock_In
DS3_Data_In[3:0]
Nibble [0]
Nibble [1]
Rx_Start_of_Frame
XRT72L5x Receive Payload Data I/F Signals
RxOutClk
RxClk
RxNib[3:0]
Nibble [0]
Nibble [1]
RxFrame
DS3 Frame Number N
DS3 Frame Number N + 1
Note: RxFrame pulses high to denote
DS3 Frame Boundary.
Recommended Sampling Edge of Terminal
Equipment
4.3.6 Receive Section Interrupt Processing
The Receive Section of the XRT72L53 can generate
an interrupt to the Microcontroller/Microprocessor for
the following reasons.
• Change of State of Receive LOS (Loss of Signal)
condition
• Change of State of Receive OOF (Out of Frame)
condition
• Change of State of Receive AIS (Alarm Indicator
Signal) condition
• Change of State of Receive Idle Condition.
• Change of State of Receive FERF (Far-End
Receive Failure) condition.
• Change of State of AIC (Application Identification
Channel) bit.
• Detection of P-Bit Error in a DS3 frame
• Detection of CP-Bit Error in a DS3 frame
• The Receive FEAC Message - Validation Interrupt
• The Receive FEAC Message - Removal Interrupt
• Completion of Reception of a LAPD Message
4.3.6.1 Enabling Receive Section Interrupts
As mentioned in Section 1.6, the Interrupt Structure,
within the XRT72L53 contains two hierarchical levels.
• Block Level
• Source Level
The Block Level
The Enable state of the Block level for the Receive
Section Interrupts dictates whether or not interrupts
(if enabled at the source level), are actually enabled.
The user can enable or disable these Receive Section interrupts, at the Block Level by writing the appropriate data into Bit 7 (Rx DS3/E3 Interrupt Enable)
within the Block Interrupt Enable register (Address =
0x04), as illustrated below.
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BLOCK INTERRUPT ENABLE REGISTER (ADDRESS = 0X04)
BIT 7
BIT 6
BIT 5
RxDS3/E3
Interrupt
Enable
BIT 4
BIT 3
BIT 2
Not Used
BIT 1
BIT 0
TxDS3/E3
Interrupt
Enable
One Second
Interrupt
Enable
R/W
RO
RO
RO
RO
RO
R/W
R/W
X
0
0
0
0
0
0
0
Setting this bit-field to “1” enables the Receive Section (at the Block Level) for interrupt generation. Conversely, setting this bit-field to “0” disables the Receive Section for interrupt generation.
4.3.6.2 Enabling/Disabling and Servicing
Receive Section Interrupts
As mentioned earlier, the Receive Section of the
XRT72L53 Framer IC contains numerous interrupts.
The Enabling/Disabling and Servicing of each of
these interrupts is described below.
Conditions causing the XRT72L53 Framer IC to
declare an LOS condition
• If the XRT7300 LIU IC declares an LOS condition,
and drives the RLOS input pin (of the XRT72L53
Framer IC) "High".
• If the XRT72L53 Framer IC detects a 180 consecutive “0’s”, via the RxPOS and RxNEG input pins.
Conditions causing the XRT72L53 Framer IC to
clear the LOS condition.
• When the XRT7300 LIU IC ceases declaring an
LOS condition and drives the RLOS input pin (of
the XRT72L53 Framer IC) "Low".
4.3.6.2.1 The Change of State on Receive LOS
Interrupt
If the Change of State on Receive LOS (Loss of Signal) Interrupt is enabled, then the XRT72L53 Framer
IC will generate an interrupt in response to either of
the following conditions.
• When the XRT72L53 Framer IC detects at least 60
marks (via the RxPOS and RxNEG input pins) out
of 180 bit-periods.
Enabling and Disabling the Change of State on
Receive LOS Interrupt:
1. When the XRT72L53 Framer IC declares an LOS
(Loss of Signal) condition, and
2. When the XRT72L53 Framer IC clears the LOS
(Loss of Signal) condition.
The user can enable or disable the Change of State
on Receive LOS Interrupt, by writing the appropriate
value into Bit 6 (LOS Interrupt Enable) within the
RxDS3 Interrupt Enable Register, as illustrated below.
RXDS3 INTERRUPT ENABLE REGISTER (ADDRESS = 0X12)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
CP Bit Error
Interrupt
Enable
LOS
Interrupt
Enable
AIS
Interrupt
Enable
Idle Interrupt
Enable
FERF
Interrupt
Enable
AIC
Interrupt
Enable
OOF
Interrupt
Enable
P-Bit Error
Interrupt
Enable
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
0
0
Setting this bit-field to “1” enables this interrupt. Conversely, setting this bit-field to “0” disables this interrupt.
Servicing the Change of State on Receive LOS Interrupt
Whenever the XRT72L53 Framer IC detects this interrupt, it will do all of the following.
• It will assert the Interrupt Request output pin (INT)
by driving this pin "Low".
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• It will set Bit 6 (LOS Interrupt Status) within the
RxDS3 Interrupt Status register to “1”, as illustrated
below.
RXDS3 INTERRUPT STATUS REGISTER (ADDRESS = 0X13)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
CP-Bit Error
Interrupt
Status
LOS
Interrupt
Status
AIS
Interrupt
Status
Idle Interrupt
Status
FERF
Interrupt
Status
AIC
Interrupt
Status
OOF
Interrupt
Status
P-Bit Error
Interrupt
Status
RUR
RUR
RUR
RUR
RUR
RUR
RUR
RUR
0
1
0
0
0
0
0
0
or clears the LOS defects. Hence, the user can
determine the current state of the LOS defect by
reading the state of Bit 6 (RxLOS), within the
RxDS3 Configuration & Status Registers, as illustrated below.
Whenever the user’s system encounters the Change
of LOS on Receive Interrupt, then it should do the following.
1. It should determine the current state of the LOS
condition. Recall, that this interrupt can generated, whenever the XRT72L53 Framer declares
RXDS3 CONFIGURATION & STATUS REGISTER (ADDRESS = 0X10)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
RxAIS
RxLOS
RxIdle
RxOOF
Reserved
Framing On
Parity
FSync
Algo
MSync
Algo
RO
RO
RO
RO
RO
RO
RO
RUR
0
1
0
0
0
0
0
0
If the LOS State is TRUE
1. It should transmit a FERF (Far-End Receive Failure) to the Remote Terminal Equipment. The
XRT72L53 Framer IC automatically supports this
action via the FERF-upon-LOS feature.
2. It should transmit the appropriate FEAC Message
(per Bellcore GR-499-CORE), to the Remote Terminal, indicating that a Loss of Signal condition
has been declared.
If the LOS State is FALSE
1. It should cease transmitting a FERF indicator to
the Remote Terminal Equipment. The XRT72L53
Framer IC automatically supports this action via
the FERF-upon-LOS feature.
2. It should transmit the appropriate FEAC Message
(per Bellcore GR-499-CORE), to the Remote Terminal Equipment, indicating that the Loss of Signal condition has been cleared.
4.3.6.2.2 The Change of State on Receive OOF
Interrupt
If the Change of State on Receive OOF (Out-ofFrame) Interrupt is enabled, then the XRT72L53
Framer IC will generate an interrupt in response to either of the following conditions.
1. When the XRT72L53 Framer IC declares an OOF
(Out of Frame) condition, and
2. When the XRT72L53 Framer IC clears the OOF
(Out of Frame) condition.
Conditions causing the XRT72L53 Framer IC to
declare an OOF condition
• If the Receive DS3 Framer block (within the
XRT72L53 Framer IC) detects at least either 3 or 6
F-bit errors, in the last 16 F-bits.
Conditions causing the XRT72L53 Framer IC to
clear the OOF condition.
• Whenever, the Receive DS3 Framer block transitions from the M-Bit Search into the In-Frame state
(within the Frame Acquisition/Maintenance State
Machine Diagram).
Enabling and Disabling the Change of State on
Receive OOF Interrupt:
The user can enable or disable the Change of State
on Receive OOF Interrupt, by writing the appropriate
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value into Bit 1 (OOF Interrupt Enable) within the
RxDS3 Interrupt Enable Register, as illustrated below.
RXDS3 INTERRUPT ENABLE REGISTER (ADDRESS = 0X12)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
CP Bit Error
Interrupt
Enable
LOS
Interrupt
Enable
AIS
Interrupt
Enable
Idle Interrupt
Enable
FERF
Interrupt
Enable
AIC
Interrupt
Enable
OOF
Interrupt
Enable
P-Bit Error
Interrupt
Enable
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
0
0
Setting this bit-field to “1” enables this interrupt. Conversely, setting this bit-field to “0” disables this interrupt.
Servicing the Change of State on Receive OOF Interrupt
• It will assert the Interrupt Request output pin (INT)
by driving this pin "Low".
• It will set Bit 1 (OOF Interrupt Status), within the
RxDS3 Interrupt Status Register to “1”, as indicated
below.
Whenever the XRT72L53 Framer IC detects this interrupt, it will do all of the following.
RXDS3 INTERRUPT STATUS REGISTER (ADDRESS = 0X13)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
CP-Bit Error
Interrupt
Status
LOS
Interrupt
Status
AIS
Interrupt
Status
Idle Interrupt
Status
FERF
Interrupt
Status
AIC
Interrupt
Status
OOF
Interrupt
Status
P-Bit Error
Interrupt
Status
RUR
RUR
RUR
RUR
RUR
RUR
RUR
RUR
0
0
0
0
0
0
1
0
or clears the OOF defects. Hence, the user can
determine the current state of the OOF defect by
reading the state of Bit 4 (RxOOF), within the
RxDS3 Configuration & Status Registers, as illustrated below.
Whenever the Terminal Equipment encounters a
Change in OOF on Receive Interrupt, then it should
do the following.
1. It should determine the current state of the OOF
condition. Recall, that this interrupt can generated, whenever the XRT72L53 Framer declares
RXDS3 CONFIGURATION & STATUS REGISTER (ADDRESS = 0X10)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
RxAIS
RxLOS
RxIdle
RxOOF
Reserved
Framing On
Parity
FSync
Algo
MSync
Algo
RO
RO
RO
RO
RO
RO
RO
RUR
0
0
0
0
0
0
0
0
If OOF is TRUE.
1. It should transmit a FERF (Far-End Receive Failure) to the Remote Terminal Equipment. The
XRT72L53 Framer IC automatically supports this
action via the FERF-upon-OOF feature.
2. It should transmit the appropriate FEAC Message
(per Bellcore GR-499-CORE), to the Remote Terminal, indicating that a Service Affecting condi-
tion has been detected in the Local Terminal
Equipment.
if OOF is FALSE
242
1. It should cease transmitting a FERF (Far-End
Receive Failure) indicator to the Remote Terminal
Equipment. The XRT72L53 Framer IC automatically supports this action via the FERF-uponOOF feature.
XRT72L53
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THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. P1.1.7
2. It should transmit the appropriate FEAC Message
(per Bellcore GR-499-CORE), to the Remote Terminal Equipment, indicating that the Service
Affecting condition has been cleared.
4.3.6.2.3 The Change of State of Receive AIS
Interrupt
If the Change of State on Receive AIS (Alarm Indication Signal) Interrupt is enabled, then the XRT72L53
Framer IC will generate an interrupt in response to either of the following conditions.
1. When the XRT72L53 Framer IC detects an AIS
pattern, in the incoming DS3 data stream, and
2. When the XRT72L53 Framer IC no longer detects
the AIS pattern in the incoming DS3 data stream.
Conditions causing the XRT72L53 Framer IC to
declare an AIS condition
• If the Receive DS3 Framer block (within the
XRT72L53 Framer IC) detects at least 63 DS3
frames, which contains the AIS pattern.
Conditions causing the XRT72L53 Framer IC to
clear the AIS condition.
• Whenever, the Receive DS3 Framer block detects
63 DS3 frames, which do not contain the AIS pattern.
Enabling and Disabling the Change of State on
Receive AIS Interrupt:
The user can enable or disable the Change of State
on Receive AIS Interrupt, by writing the appropriate
value into Bit 5 (AIS Interrupt Enable) within the
RxDS3 Interrupt Enable Register, as illustrated below.
RXDS3 INTERRUPT ENABLE REGISTER (ADDRESS = 0X12)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
CP Bit Error
Interrupt
Enable
LOS
Interrupt
Enable
AIS
Interrupt
Enable
Idle Interrupt
Enable
FERF
Interrupt
Enable
AIC
Interrupt
Enable
OOF
Interrupt
Enable
P-Bit Error
Interrupt
Enable
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
0
0
Setting this bit-field to “1” enables this interrupt. Conversely, setting this bit-field to “0” disables this interrupt.
Servicing the Change of State on Receive AIS Interrupt
• It will assert the Interrupt Request output pin (INT)
by driving it "Low".
• It will set Bit 5 (AIS Interrupt Status) within the
RxDS3 Interrupt Status Register, to “1”, as indicated below.
Whenever the XRT72L53 Framer IC detects this interrupt, it will do all of the following.
RXDS3 INTERRUPT STATUS REGISTER (ADDRESS = 0X13)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
CP-Bit Error
Interrupt
Status
LOS
Interrupt
Status
AIS
Interrupt
Status
Idle Interrupt
Status
FERF
Interrupt
Status
AIC
Interrupt
Status
OOF
Interrupt
Status
P-Bit Error
Interrupt
Status
RUR
RUR
RUR
RUR
RUR
RUR
RUR
RUR
0
0
1
0
0
0
0
0
or clears the AIS defects. Hence, the user can
determine the current state of the AIS defect by
reading the state of Bit 7 (RxAIS), within the
RxDS3 Configuration & Status Registers, as illustrated below
Whenever the Terminal Equipment encounters a
Change in AIS on Receive interrupt, it should do the
following.
1. It should determine the current state of the AIS
condition. Recall, that this interrupt can generated, whenever the XRT72L53 Framer declares
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THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
XRT72L53
PRELIMINARY
REV. P1.1.7
RXDS3 CONFIGURATION & STATUS REGISTER (ADDRESS = 0X10)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
RxAIS
RxLOS
RxIdle
RxOOF
Reserved
Framing On
Parity
FSync
Algo
MSync
Algo
RO
RO
RO
RO
RO
RO
RO
RUR
0
0
0
0
0
0
0
0
If the AIS Condition is TRUE
1. The Local Terminal Equipment should transmit a
FERF (Far-End Receive Failure) to the Remote
Terminal Equipment. The XRT72L53 Framer IC
automatically supports this action via the FERFupon-AIS feature.
2. It should transmit the appropriate FEAC Message
(per Bellcore GR-499-CORE), to the Remote Terminal, indicating that a Service Affecting condition has been detected in the Local Terminal
Equipment.
If the AIS Condition is FALSE
1. The Local Terminal Equipment should cease
transmitting a FERF (Far-End Receive Failure)
indicator to the Remote Terminal Equipment.
The XRT72L53 Framer IC automatically supports
this action via the FERF-upon-AIS feature.
2. It should transmit the appropriate FEAC Message
(per Bellcore GR-499-CORE) to the Remote Terminal, indicates that the Service Affecting condition no longer exists.
4.3.6.2.4
Interrupt
If the Change of State on Receive Idle Interrupt is enabled, then the XRT72L53 Framer IC will generate an
interrupt in response to either of the following conditions.
1. When the XRT72L53 Framer IC detects an Idle
pattern, in the incoming DS3 data stream, and
2. When the XRT72L53 Framer IC no longer detects
the Idle pattern in the incoming DS3 data stream.
Conditions causing the XRT72L53 Framer IC to
declare an Idle condition
• If the Receive DS3 Framer block (within the
XRT72L53 Framer IC) detects at least 63 DS3
frames, which contains the Idle pattern.
Conditions causing the XRT72L53 Framer IC to
clear the Idle condition.
• Whenever, the Receive DS3 Framer block detects
63 DS3 frames, which do not contain the Idle pattern.
Enabling and Disabling the Change of State on
Receive Idle Interrupt:
The user can enable or disable the Change of State
on Receive Idle Interrupt, by writing the appropriate
value into Bit 4 (Idle Interrupt Enable) within the
RxDS3 Interrupt Enable Register, as illustrated below.
The Change of State of Receive Idle
RXDS3 INTERRUPT ENABLE REGISTER (ADDRESS = 0X12)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
CP Bit Error
Interrupt
Enable
LOS
Interrupt
Enable
AIS
Interrupt
Enable
Idle Interrupt
Enable
FERF
Interrupt
Enable
AIC
Interrupt
Enable
OOF
Interrupt
Enable
P-Bit Error
Interrupt
Enable
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
0
0
Setting this bit-field to “1” enables this interrupt. Conversely, setting this bit-field to “0” disables this interrupt.
Servicing the Change of State on Receive Idle Interrupt
• It will assert the Interrupt Request Output pin (INT)
by driving it "Low".
• It will set Bit 4 (Idle Interrupt Status), within the Rx
DS3 Interrupt Status Register to “1”, as indicated
below.
Whenever the XRT72L53 Framer IC detects this interrupt, it will do all of the following.
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THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. P1.1.7
RXDS3 INTERRUPT STATUS REGISTER (ADDRESS = 0X13)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
CP-Bit Error
Interrupt
Status
LOS
Interrupt
Status
AIS
Interrupt
Status
Idle Interrupt
Status
FERF
Interrupt
Status
AIC
Interrupt
Status
OOF
Interrupt
Status
P-Bit Error
Interrupt
Status
RUR
RUR
RUR
RUR
RUR
RUR
RUR
RUR
0
0
0
1
0
0
0
0
or clears the Idle condition. Hence, the user can
determine the current state of the Idle condition
by reading the state of Bit 5 (RxIdle), within the
RxDS3 Configuration & Status Registers, as illustrated below
Whenever the Terminal Equipment encounters the
Change in Idle Condition Receive Interrupt, it should
do the following.
1. It should determine the current state of the Idle
condition. Recall, that this interrupt can generated, whenever the XRT72L53 Framer declares
RXDS3 CONFIGURATION & STATUS REGISTER (ADDRESS = 0X10)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
RxAIS
RxLOS
RxIdle
RxOOF
Reserved
Framing On
Parity
FSync
Algo
MSync
Algo
RO
RO
RO
RO
RO
RO
RO
RUR
0
0
0
0
0
0
0
0
4.3.6.2.5 The Change of State of Receive FERF
Interrupt
If the Change of State on Receive FERF Interrupt is
enabled, then the XRT72L53 Framer IC will generate
an interrupt in response to either of the following conditions.
1. When the XRT72L53 Framer IC detects the
FERF indicator, in the incoming DS3 data stream,
and
2. When the XRT72L53 Framer IC no longer detects
the FERF indicator, in the incoming DS3 data
stream.
Conditions causing the XRT72L53 Framer IC to
declare an FERF (Far-End-Receive Failure) condition
• If the Receive DS3 Framer block (within the
XRT72L53 Framer IC) detects some incoming DS3
frames with both of the “X” bits set to “0”.
Conditions causing the XRT72L53 Framer IC to
clear the FERF condition.
• Whenever, the Receive DS3 Framer block starts to
detect some incoming DS3 frames, in which the “X”
bits are not set to “0”.
Enabling and Disabling the Change of State on
Receive FERF Interrupt:
The user can enable or disable the Change of State
on Receive FERF Interrupt, by writing the appropriate
value into Bit 3 (FERF Interrupt Enable) within the
RxDS3 Interrupt Enable Register, as illustrated below.
RXDS3 INTERRUPT ENABLE REGISTER (ADDRESS = 0X12)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
CP Bit Error
Interrupt
Enable
LOS
Interrupt
Enable
AIS
Interrupt
Enable
Idle Interrupt
Enable
FERF
Interrupt
Enable
AIC
Interrupt
Enable
OOF
Interrupt
Enable
P-Bit Error
Interrupt
Enable
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
0
0
Setting this bit-field to “1” enables this interrupt. Conversely, setting this bit-field to “0” disables this inter-
rupt.
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PRELIMINARY
REV. P1.1.7
Servicing the Change of State on Receive FERF
Interrupt
• It will assert the Interrupt Request Output pin (INT)
by driving it "High".
Whenever the XRT72L53 Framer IC detects this interrupt, it will do all of the following.
• It will set Bit 3 (FERF Interrupt Status), within the
Rx DS3 Interrupt Status Register, to “1”, as indicated below.
RXDS3 INTERRUPT STATUS REGISTER (ADDRESS = 0X13)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
CP-Bit Error
Interrupt
Status
LOS
Interrupt
Status
AIS
Interrupt
Status
Idle Interrupt
Status
FERF
Interrupt
Status
AIC
Interrupt
Status
OOF
Interrupt
Status
P-Bit Error
Interrupt
Status
RUR
RUR
RUR
RUR
RUR
RUR
RUR
RUR
0
0
0
0
1
0
0
0
or clears the FERF condition. Hence, the user
can determine the current state of the FERF condition by reading the state of Bit 5 (RxIdle), within
the RxDS3 Configuration & Status Registers, as
illustrated below
Whenever the Terminal Equipment encounters a
Change in FERF Condition on Receive Interrupt, it
should do the following.
1. It should determine the current state of the FERF
condition. Recall, that this interrupt can generated, whenever the XRT72L53 Framer declares
RXDS3 STATUS REGISTER (ADDRESS = 0X11)
BIT 7
BIT 6
BIT 5
Reserved
BIT 4
BIT 3
RxFERF
RxAIC
BIT 2
BIT 1
BIT 0
RxFEBE[2:0]
RO
RO
RO
RO
RO
RO
RO
RO
0
0
0
0
0
0
0
0
Enabling and Disabling the Change of State of
Receive AIC Interrupt:
4.3.6.2.6 The Change of State of Receive AIC
Interrupt
If the Change of State of Receive AIC Interrupt is enabled, then the XRT72L53 Framer IC will generate an
interrupt, anytime the Receive DS3 Framer block has
detected a change in the value of the AIC bit, within
the incoming DS3 data stream.
The user can enable or disable the Change of State
on Receive AIC Interrupt, by writing the appropriate
value into Bit 2 (AIC Interrupt Enable) within the
RxDS3 Interrupt Enable Register, as illustrated below.
RXDS3 INTERRUPT ENABLE REGISTER (ADDRESS = 0X12)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
CP Bit Error
Interrupt
Enable
LOS
Interrupt
Enable
AIS
Interrupt
Enable
Idle Interrupt
Enable
FERF
Interrupt
Enable
AIC
Interrupt
Enable
OOF
Interrupt
Enable
P-Bit Error
Interrupt
Enable
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
0
0
Setting this bit-field to “1” enables this interrupt. Conversely, setting this bit-field to “0” disables this interrupt.
Servicing the Change of State on Receive AIC Interrupt
Whenever the XRT72L53 Framer IC detects this interrupt, it will do all of the following.
• It will assert the Interrupt Request Output pin (INT)
by driving it "High".
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THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. P1.1.7
• It will set Bit 3 (AIC Interrupt Status), within the Rx
DS3 Interrupt Status Register, to “1”, as indicated
below.
RXDS3 INTERRUPT STATUS REGISTER (ADDRESS = 0X13)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
CP-Bit Error
Interrupt
Status
LOS
Interrupt
Status
AIS
Interrupt
Status
Idle Interrupt
Status
FERF
Interrupt
Status
AIC
Interrupt
Status
OOF
Interrupt
Status
P-Bit Error
Interrupt
Status
RUR
RUR
RUR
RUR
RUR
RUR
RUR
RUR
0
0
0
0
0
1
0
0
Whenever the Terminal Equipment encounters this interrupt, it should do the following.
• It should continue to check the state of the AIC bit,
in order to see if this change is constant.
• If this change is constant, then the user should configure the XRT72L53 Framer IC to operate in the
M13 framing format, if the AIC bit-field is “0”.
Enabling and Disabling the Detection of P-Bit Error Interrupt:
The user can enable or disable the Detection of P-Bit
Error Interrupt, by writing the appropriate value into
Bit 0 (P-Bit Error Interrupt Enable) within the RxDS3
Interrupt Enable Register, as illustrated below.
• Conversely, if the AIC bit-field is “1”, then the user
should configure the XRT72L53 Framer IC to operate in the C-bit Parity framing format.
4.3.6.2.7
If the Detection of P-Bit Error Interrupt is enabled,
then the XRT72L53 Framer IC will generate an interrupt, anytime the Receive DS3 Framer block has detected a P-bit error, within the incoming DS3 data
stream.
The Detection of P-Bit Error Interrupt
RXDS3 INTERRUPT ENABLE REGISTER (ADDRESS = 0X12)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
CP Bit Error
Interrupt
Enable
LOS
Interrupt
Enable
AIS
Interrupt
Enable
Idle Interrupt
Enable
FERF
Interrupt
Enable
AIC
Interrupt
Enable
OOF
Interrupt
Enable
P-Bit Error
Interrupt
Enable
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
0
0
Setting this bit-field to “1” enables this interrupt. Conversely, setting this bit-field to “0” disables this interrupt.
Servicing the Detection of P-Bit Error Interrupt
Whenever the XRT72L53 Framer IC detects this interrupt, it will do all of the following.
• It will assert the Interrupt Request output pin (INT)
by driving it "High".
• It will set Bit 0 (P-Bit Error Interrupt Status) within
the Rx DS3 Interrupt Status Register, to “1”, as indicated below.
RXDS3 INTERRUPT STATUS REGISTER (ADDRESS = 0X13)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
CP-Bit Error
Interrupt
Status
LOS
Interrupt
Status
AIS
Interrupt
Status
Idle Interrupt
Status
FERF
Interrupt
Status
AIC
Interrupt
Status
OOF
Interrupt
Status
P-Bit Error
Interrupt
Status
RUR
RUR
RUR
RUR
RUR
RUR
RUR
RUR
0
0
0
0
0
0
0
1
Whenever the Terminal Equipment encounters the
Detection of P-bit Error Interrupt, It should read the
contents of PMON Parity Error Count Register (locat-
ed at 0x54 and 0x55), in order to determine the number of P-bit errors recently received.
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PRELIMINARY
REV. P1.1.7
Enabling and Disabling the Detection of CP-Bit
Error Interrupt:
4.3.6.2.8 The Detection of CP-Bit Error Interrupt
If the Detection of CP-Bit Error Interrupt is enabled,
then the XRT72L53 Framer IC will generate an interrupt, anytime the Receive DS3 Framer block has detected a CP-bit error, within the incoming DS3 data
stream.
The user can enable or disable the Detection of CPBit Error Interrupt, by writing the appropriate value into Bit 7 (CP-Bit Error Interrupt Enable) within the
RxDS3 Interrupt Enable Register, as illustrated below.
RXDS3 INTERRUPT ENABLE REGISTER (ADDRESS = 0X12)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
CP Bit Error
Interrupt
Enable
LOS
Interrupt
Enable
AIS
Interrupt
Enable
Idle Interrupt
Enable
FERF
Interrupt
Enable
AIC
Interrupt
Enable
OOF
Interrupt
Enable
P-Bit Error
Interrupt
Enable
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
0
0
Setting this bit-field to “1” enables this interrupt. Conversely, setting this bit-field to “0” disables this interrupt.
Servicing the Detection of CP-Bit Error Interrupt
Whenever the XRT72L53 Framer IC detects this interrupt, it will do all of the following.
• It will assert the Interrupt Request output pin (INT)
by driving it "High".
• It will set Bit 7 (CP-Bit Error Interrupt Status) within
the Rx DS3 Interrupt Status Register, to “1”, as indicated below.
RXDS3 INTERRUPT STATUS REGISTER (ADDRESS = 0X13)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
CP-Bit Error
Interrupt
Status
LOS
Interrupt
Status
AIS
Interrupt
Status
Idle Interrupt
Status
FERF
Interrupt
Status
AIC
Interrupt
Status
OOF
Interrupt
Status
P-Bit Error
Interrupt
Status
RUR
RUR
RUR
RUR
RUR
RUR
RUR
RUR
1
0
0
0
0
0
0
1
Whenever the Terminal Equipment encounters the
Detection of CP-bit Error Interrupt, it should do the
following.
• It should read contents of PMON Frame CP-Bit
Error Count Register (located at 0x72 and 0x73), in
order to determine the number of CP-bit errors
recently received.
4.3.6.2.9 The Receive FEAC Message - Validation Interrupt
If the Receive FEAC Message - Validation Interrupt is
enabled, then the XRT72L53 Framer IC will generate
an interrupt any time the Receive FEAC Processor
validates a new FEAC (Far-End Alarm & Control)
Message.
In particular, the Receive FEAC Processor will validate a FEAC Message, it that same FEAC Message
has been received in 8 of the last 10 FEAC Message
receptions.
Enabling/Disabling the Receive FEAC Message Validation Interrupt
The user can enable or disable the Receive FEAC
Message - Validation Interrupt, by writing the appropriate data into Bit 1 (RxFEAC Valid Interrupt Enable)
within the RxDS3 FEAC Interrupt Enable/Status Register, as indicated below.
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THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. P1.1.7
RXDS3 FEAC INTERRUPT ENABLE/STATUS REGISTER (ADDRESS = 0X17)
BIT 7
BIT 6
BIT 5
Not Used
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
FEAC Valid
RxFEAC
Remove
Interrupt
Enable
RxFEAC
Remove
Interrupt
Status
RxFEAC
Valid
Interrupt
Enable
RxFEAC
Valid
Interrupt
Status
RO
RO
RO
RO
R/W
RUR
R/W
RUR
0
0
0
0
0
0
X
0
Setting this bit-field to “1” enables this interrupt. Conversely, setting this bit-field to “0” disables this interrupt.
Servicing the Receive FEAC Message - Validation
Interrupt.
• It will assert the Interrupt Request output pin (INT)
by driving it "Low".
• It will set Bit 0 (RxFEAC Valid Interrupt Status),
within the RxDS3 FEAC Interrupt Enable/Status
Register to “1”, as indicated below.
Whenever the XRT72L53 Framer IC generates this
interrupt, it will do the following.
RXDS3 FEAC INTERRUPT ENABLE/STATUS REGISTER (ADDRESS = 0X17)
BIT 7
BIT 6
BIT 5
Not Used
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
FEAC Valid
RxFEAC
Remove
Interrupt
Enable
RxFEAC
Remove
Interrupt
Status
RxFEAC
Valid
Interrupt
Enable
RxFEAC
Valid
Interrupt
Status
RO
RO
RO
RO
R/W
RUR
R/W
RUR
0
0
0
0
0
0
1
1
BIT 3
BIT 2
BIT 1
BIT 0
• It will write the contents of this validated FEAC
Message into the Rx DS3 FEAC Register, as indicated below.
RXDS3 FEAC REGISTER (ADDRESS = 0X16)
BIT 7
BIT 6
BIT 5
BIT 4
Not Used
RxFEAC[5:0]
Not Used
RO
RO
RO
RO
R/O
R/O
R/O
R/O
0
0
0
0
0
0
0
0
In particular, the Receive FEAC Processor will remove a FEAC Message, it has received a different
FEAC Message (from the most recently validated
message) in 3 of the last 10 FEAC Message receptions.
Whenever the Terminal Equipment encounters the
Receive FEAC Message - Validation Interrupt, then it
should do the following.
• It should read the contents of the High RxDS3
FEAC Register, and respond accordingly.
4.3.6.2.10 The Receive FEAC Message Removal Interrupt
if the Receive FEAC Message - Removal Interrupt is
enabled, then the XRT72L53 Framer IC will generate
an interrupt any time the High Receive FEAC Processor removes a new FEAC (Far-End Alarm & Control)
Message.
Enabling/Disabling the Receive FEAC Message Removal Interrupt
The user can enable or disable the Receive FEAC
Message - Removal Interrupt, by writing the appropriate data into Bit 1 (RxFEAC Remove Interrupt Enable) within the RxDS3 FEAC Interrupt Enable/Status
Register, as indicated below.
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RXDS3 FEAC INTERRUPT ENABLE/STATUS REGISTER (ADDRESS = 0X17)
BIT 7
BIT 6
BIT 5
Not Used
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
FEAC Valid
RxFEAC
Remove
Interrupt
Enable
RxFEAC
Remove
Interrupt
Status
RxFEAC
Valid
Interrupt
Enable
RxFEAC
Valid
Interrupt
Status
RO
RO
RO
RO
R/W
RUR
R/W
RUR
0
0
0
0
X
0
X
0
Setting this bit-field to “1” enables this interrupt. Conversely, setting this bit-field to “0” disables this interrupt.
Servicing the Receive FEAC Message - Validation
Interrupt.
• It will assert the Interrupt Request output pin (INT)
by driving it "Low".
• It will set Bit 2 (RxFEAC Remove Interrupt Status),
within the RxDS3 FEAC Interrupt Enable/Status
Register to “1”, as indicated below.
Whenever the XRT72L53 Framer IC generates this
interrupt, it will do the following.
RXDS3 FEAC INTERRUPT ENABLE/STATUS REGISTER (ADDRESS = 0X17)
BIT 7
BIT 6
BIT 5
Not Used
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
FEAC Valid
RxFEAC
Remove
Interrupt
Enable
RxFEAC
Remove
Interrupt
Status
RxFEAC
Valid
Interrupt
Enable
RxFEAC
Valid
Interrupt
Status
RO
RO
RO
RO
R/W
RUR
R/W
RUR
0
0
0
0
0
0
1
1
BIT 3
BIT 2
BIT 1
BIT 0
• It will write the delete contents of the most recently
validated FEAC Message from the Rx DS3 FEAC
Register, as indicated below.
RXDS3 FEAC REGISTER (ADDRESS = 0X16)
BIT 7
BIT 6
BIT 5
BIT 4
Not Used
RxFEAC[5:0]
Not Used
RO
RO
RO
RO
R/O
R/O
R/O
R/O
0
X
X
X
X
X
X
0
4.3.6.2.11 The Completion of Reception of a
LAPD Message Interrupt
If the Completion of Reception of a LAPD Message
interrupt is enabled, then the XRT72L53 Framer IC
will generate an interrupt anytime the Receive HDLC
Controller block has received a new LAPD Message
buffer, from the Remote Terminal Equipment, and has
stored the contents of this message in the Receive
LAPD Message Buffer.
Enabling/Disable the Receive LAPD Message Interrupt
The user can enable or disable the Receive LAPD
Message Interrupt by writing the appropriate data into
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Bit 1 (RxLAPD Interrupt Enable) within the RxDS3
LAPD Control Register, as indicated below.
RXDS3 LAPD CONTROL REGISTER (ADDRESS = 0X18)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
Not Used
BIT 2
BIT 1
BIT 0
RxLAPD
Enable
RxLAPD
Interrupt
Enable
RxLAPD
Interrupt
Status
RO
RO
RO
RO
RO
R/W
R/W
RUR
0
0
0
0
0
0
X
0
Writing a “1” into this bit-field enables the Receive
LAPD Message Interrupt. Conversely, writing a “0”
into this bit-field disables the Receive LAPD Message
interrupt.
Servicing the Receive LAPD Message Interrupt
• It will assert the Interrupt Request output pin (INT)
by driving it "Low".
• It will set Bit 0 (RxLAPD Interrupt Status), within the
Rx DS3 LAPD Control Register to “1”, as indicated
below.
Whenever the XRT72L53 Framer IC generates this
interrupt, it will do the following.
RXDS3 LAPD CONTROL REGISTER (ADDRESS = 0X18)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
Not Used
BIT 2
BIT 1
BIT 0
RxLAPD
Enable
RxLAPD
Interrupt
Enable
RxLAPD
Interrupt
Status
RO
RO
RO
RO
RO
R/W
R/W
RUR
0
0
0
0
0
0
1
1
• It will write the contents of this newly Received
LAPD Message into the Receive LAPD Message
buffer (located at 0xDE through 0x135).
Whenever the Terminal Equipment encounters the
Receive LAPD Interrupt, then it should read out the
contents of the Receive LAPD Message buffer, and
respond accordingly.
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5.0 E3/ITU-T G.751 OPERATION OF THE
XRT72L53
Configuring the XRT72L53 to Operate in the E3,
ITU-T G.751 Mode
The XRT72L53 can be configured to operate in the
E3/ITU-T G.751 Mode by writing a “0” into bit-field 6
and a “0” into bit-field 2, within the Framer Operating
Mode register, as illustrated below.
FRAMER OPERATING MODE REGISTER (ADDRESS = 0X00)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT2
BIT 1
BIT 0
Local
Loopback
DS3/E3*
Internal
LOS
Enable
RESET
Interrupt
Enable
Reset
Frame
Format
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
x
0
x
0
x
0
x
x
TimRefSel[1:0]
• A 10 bit FAS (Framing Alignment Signal) pattern.
This pattern is assigned the constant pattern of
“1111010000”, and is used by the Receive E3
Framer block to acquire and maintain Frame Synchronization with the incoming E3 frames.
Prior to describing the functional blocks within the
Transmit and Receive Sections of the XRT72L53, it is
important to describe the E3, ITU-T G.751 framing
format.
5.1 DESCRIPTION OF THE E3, ITU-T G.751 FRAMES
AND ASSOCIATED OVERHEAD BITS
The role of the various overhead bytes are best described by discussing the E3, ITU-T G.751 Frame
Format as a whole. The E3, ITU-T G.751 Frame contains 1536 bits, of which 12 bits are overhead and the
remaining 1524 bits are payload bits.
• The “A” (or Alarm) Bit.
• The “N” (or National) Bit.
• The BIP-4 Bits (if configured).
The frame repetition rate for this type of E3 frame is
22375 times per second, thereby resulting in the
standard E3 bit rate of 34.368 Mbps. Figure 97 presents an illustration of the E3, ITU-T G.751 Frame
Format.
Each E3, ITU-T G.751 Frame consists of the following
12 overhead bits.
FIGURE 97. ILLUSTRATION OF THE E3, ITU-T G.751 FRAMING FORMAT.
1
10
Frame
Alignment
Signal
11
12
A
N
384 385
Data
768 769
Data
1152 1153
Data
1532
Data
1536
BIP-4
if Selected
Framing Alignment Signal Pattern = 1111010000
5.1.1 Definition of the Overhead Bits
Each of these Overhead Bits are further defined below.Frame Alignment Signaling (FAS) Pattern Bits
The first 10 bits, within each E3, ITU-T G.751 frame
are known as the FAS (or Framing Alignment Signaling) bits. The Receive E3 Framer block, while trying
to acquire or maintain framing synchronization with its
incoming E3 frames, will attempt to locate the FAS
bits. The FAS pattern is assigned the value
“1111010000”.
5.1.1.1
The “A” (Alarm) Bit
The “A” bit typically functions as a FERF (Far-End
Receive Failure) indicator bit. However, if the user
configures the XRT72L53 Framer IC to transmit and
receive E3 frames which are carrying the BIP-4 value
(located at the end of a given E3 frame), then this bit
will also function as the FEBE indicator bit. A detailed
discussion on the practical use of the “A” is presented
in Section 4.2.2. Each of these roles of the “A” bit are
briefly discussed below.
The “A” Bit Functioning as the FERF bit-field
If the Receive E3 Framer block (at a Local Terminal)
is experiencing problems receiving E3 frame data
from a Remote Terminal (e.g., an LOS, OOF or AIS
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condition), then it will inform the Remote Terminal
Equipment of this fact by commanding the Local
Transmit E3 Framer block to set the “A” bit-field, within the next outbound E3 frame, to “1”. The Local
Transmit E3 Framer block will continue to set the “A”
bit-field (within the subsequent outbound E3 frames)
to “1” until the Receive E3 Framer block no longer experiences problems in receiving the E3 frame data. If
the Remote Terminal Equipment receives a certain
number of consecutive E3 frames, with the “A” bitfield set to “1”, then the Remote Terminal Equipment
will interpret this signaling as an indication of a FarEnd Receive Failure (e.g., a problem with the Local
Terminal Equipment).
Conversely, if the Receive E3 Framer block (at a Local Terminal Equipment) is not experiencing any
problems receiving E3 frame data from a Remote Terminal Equipment, then it will also inform the Remote
Terminal Equipment of this fact by commanding the
Local Transmit E3 Framer block to set the “A” bit-field
within an outbound E3 frame (which is destined for
the Remote Terminal) to “0”. The Remote Terminal
Equipment will interpret this form of signaling as an
indication of a normal operation.
A detailed discussion into the practical use of the A
bit-field is presented in Section 4.2.2.
5.1.1.2 The “N” Bit
The “N” bit is typically used to transport PMDL (Path
Maintenance Data Link) information, from one terminal to the next. However, the “N” bit-field can also be
used to transport a proprietary data link, if configured
according.
A detailed discussion into the practical use of the Nbit field is presented in Section 4.2.2.
5.2 THE TRANSMIT SECTION OF THE XRT72L53 (E3,
ITU-T G.751 MODE OPERATION)
When the XRT72L53 has been configured to operate
in the E3, ITU-T G.751 Mode, the Transmit Section of
the XRT72L53 consists of the following functional
blocks.
• Transmit Payload Data Input Interface block
• Transmit Overhead Data Input Interface block
• Transmit E3 Framer block
• Transmit HDLC Controller block
• Transmit LIU Interface block
Figure 98 presents a simple illustration of the Transmit Section of the XRT72L53 Framer IC.
FIGURE 98. A SIMPLE ILLUSTRATION OF THE XRT72L53 TRANSMIT SECTION WHEN IT HAS BEEN CONFIGURED TO
OPERATE IN THE E3 MODE
TxOHFrame
TxOHEnable
TxOH
TxOHClk
TxOHIns
TxOHInd
TxSer
TxNib[3:0]
TxInClk
TxNibClk
TxFrame
Transmit Overhead
Input
Interface Block
Transmit
Payload Data
Input
Interface Block
TxPOS
Transmit DS3/E3
Framer Block
Transmit LIU
Interface
Block
TxNEG
TxLineClk
From Microprocessor
Interface Block
Tx E3 HDLC
Tx E3 HDLC
Controller/Buffer
Controller/Buffer
Each of these functional blocks will be discussed in
detail in this document.
5.2.1 The Transmit Payload Data Input Interface
Block
Figure 99 presents a simple illustration of the Transmit Payload Data Input Interface block.
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FIGURE 99. A SIMPLE ILLUSTRATION OF THE TRANSMIT PAYLOAD DATA INPUT INTERFACE BLOCK
TxOH_Ind
TxSer
TxNib[3:0]
TxInClk
Transmit
TransmitPayload
Payload
Data
DataInput
Input
Interface
InterfaceBlock
Block
To Transmit DS3 Framer Block
TxNibClk
TxFrame
TxFrameRef
Each of the input and output pins of the Transmit Payload Data Input Interface are listed in Table 47 and
described below. The exact role that each of these in-
puts and output pins assume, for a variety of operating scenarios are described throughout this section.
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TABLE 47: LISTING AND DESCRIPTION OF THE PINS ASSOCIATED WITH THE TRANSMIT PAYLOAD DATA INPUT
INTERFACE
SIGNAL NAME
TYPE
DESCRIPTION
TxSer
Input
Transmit Serial Payload Data Input Pin:
If the user opts to operate the XRT72L53 in the serial mode, then the Terminal Equipment is
expected to apply the payload data (that is to be transported via the outbound E3 data stream)
to this input pin. The XRT72L53 will sample the data that is at this input pin upon the rising
edge either the RxOutClk or the TxInClk signal (whichever is appropriate).
NOTE: This signal is only active if the NibInt input pin is pulled "Low".
TxNib[3:0]
Input
Transmit Nibble-Parallel Payload Data Input pins:
If the user opts to operate the XRT72L53 in the Nibble-Parallel mode, then the Terminal Equipment is expected to apply the payload data (that is to be transported via the outbound E3 data
stream) to these input pins. The XRT72L53 will sample the data that is at these input pins
upon the rising edge of the TxNibClk signal.
NOTE: These pins are only active if the NibInt input pin is pulled "High".
TxInClk
Input
Transmit Section Timing Reference Clock Input pin:
The Transmit Section of the XRT72L53 can be configured to use this clock signal as the Timing Reference. If the user has made this configuration selection, then the XRT72L53 will use
this clock signal to sample the data on the TxSer input pin.
NOTE: If this configuration is selected, then a 34.368 MHz clock signal must be applied to this
input pin.
TxNibClk
Output Transmit Nibble Mode Output
If the user opts to operate the XRT72L53 in the Nibble-Parallel mode, then the XRT72L53 will
derive this clock signal from the selected Timing Reference for the Transmit Section of the chip
(e.g., either the TxInClk or the RxLineClk signals).
The XRT72L53 will use this signal to sample the data on the TxNib[3:0] input pins.
TxOHInd
Output Transmit Overhead Bit Indicator Output:
This output pin will pulse "High" one-bit period prior to the time that the Transmit Section of the
XRT72L53 will be processing an Overhead bit. The purpose of this output pin is to warn the
Terminal Equipment that, during the very next bit-period, the XRT72L53 is going to be processing an Overhead bit and will be ignoring any data that is applied to the TxSer input pin.
TxFrame
Output Transmit End of Frame Output Indicator:
The Transmit Section of the XRT72L53 will pulse this output pin "High" (for one bit-period),
when the Transmit Payload Data Input Interface is processing the last bit of a given E3 frame.
The purpose of this output pin is to alert the Terminal Equipment that it needs to begin transmission of a new E3 frame to the XRT72L53 (e.g., to permit the XRT72L53 to maintain Transmit E3 framing alignment control over the Terminal Equipment).
TxFrameRef
RxOutClk
Input
Transmit Frame Reference Input:
The XRT72L53 permits the user to configure the Transmit Section to use this input pin as a
frame reference. If the user makes this configuration selection, then the Transmit Section will
initiate its transmission of a new E3 frame, upon the rising edge of this signal.
The purpose of this input pin is to permit the Terminal Equipment to maintain Transmit E3
Framing alignment control over the XRT72L53.
Output Loop-Timed Timing Reference Clock Output pin:
The Transmit Section of the XRT72L53 can be configured to use the RxLineClk signal as the
Timing Reference (e.g., loop-timing). If the user has made this configuration selection, then the
XRT72L53 will:
• Output a 34.368 MHz clock signal via this pin, to the Terminal Equipment.
• Sample the data on the TxSer input pin, upon the rising edge of this clock signal.
Operation of the Transmit Payload Data Input Interface
The Transmit Terminal Input Interface is extremely
flexible, in that it permits the user to make the following configuration options.
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• The Serial or the Nibble-Parallel Interface Mode
timing source. When the XRT72L53 is operating in
this mode it will do the following.
• The Loop-Timing or the TxInClk (Local Timing)
Mode
1. It will ignore any signal at the TxInClk input pin.
2. The XRT72L53 will output a 34.368MHz clock
signal via the RxOutClk output pin. This clock signal functions as the Transmit Payload Data Input
Interface block clock signal.
3. The XRT72L53 will use the rising edge of the
RxOutClk signal to latch in the data residing on
the TxSer input pin.
B. Serial Mode
Further, if the XRT72L53 has been configured to operate in the Local-Timing mode, then the user has
two additional options.
• The XRT72L53 is the Frame Master (e.g., it dictates
when the Terminal Equipment will initiate the transmission of data within a new E3 frame).
• The XRT72L53 is the Frame Slave (e.g., the Terminal Equipment will dictate when the XRT72L53 initiates the transmission of a new E3 frame).
The XRT72L53 will accept the E3 payload data from
the Terminal Equipment, in a serial-manner, via the
TxSer input pin The Transmit Payload Data Input Interface will latch this data into its circuitry, on the rising edge of the RxOutClk output clock signal.
Given these three set of options, the Transmit Terminal Input Interface can be configured to operate in
one of the six (6) following modes.
• Mode 1 - Serial/Loop-Timed Mode
C. Delineation of outbound E3 frames
• Mode 2 - Serial/Local-Timed/Frame Slave Mode
The XRT72L53 will pulse the TxFrame output pin
"High" for one bit-period coincident with the
XRT72L53 processing the last bit of a given E3
frame.
• Mode 3 - Serial/Local-Timed/Frame Master Mode
• Mode 4 - Nibble/Loop-Timed Mode
• Mode 5 - Nibble/Local-Timed/Frame Slave Mode
• Mode 6 - Nibble/Local-Timed/Frame Master Mode
D. Sampling of Payload Data, from the Terminal
Equipment
Each of these modes are described, in detail, below.
5.2.1.1 Mode 1 - The Serial/Loop-Timing Mode
The Behavior of the XRT72L53
If the XRT72L53 has been configured to operate in
this mode, then the XRT72L53 will behave as follows.
A. Loop-Timing (Uses the RxLineClk signal as the
Timing Reference)
Since the XRT72L53 is configured to operate in the
loop-timed mode, the Transmit Section of the
XRT72L53 will use the RxLineClk input clock signal
(e.g., the Recovered Clock signal, from the LIU) as its
In Mode 1, the XRT72L53 will sample the data at the
TxSer input, on the rising edge of RxOutClk.
Interfacing the Transmit Payload Data Input Interface block of the XRT72L53 to the Terminal Equipment for Mode 1 Operation
Figure 100 presents an illustration of the Transmit
Payload Data Input Interface block (within the
XRT72L53) being interfaced to the Terminal Equipment, for Mode 1 operation.
FIGURE 100. ILLUSTRATION OF THE TERMINAL EQUIPMENT BEING INTERFACED TO THE TRANSMIT PAYLOAD DATA
INPUT INTERFACE BLOCK OF THE XRT72L53 FOR MODE 1 (SERIAL/LOOP-TIMED) OPERATION
E3_Clock_In
34.368 MHz
E3_Data_Out
RxOutClk
TxSer
Tx_Start_of_Frame
TxFrame
E3_Overhead_Ind
TxOH_Ind
NibInt
Terminal Equipment
XRT72L5x E3 Framer
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Mode 1 Operation of the Terminal Equipment
When the XRT72L53 is operating in this mode, it will
function as the source of the 34.368MHz clock signal.
This clock signal will be used as the Terminal Equipment Interface clock by both the XRT72L53 IC and
the Terminal Equipment.
The Terminal Equipment will serially output the payload data of the outbound E3 data stream via its
E3_Data_Out pin. The Terminal Equipment will update the data on the E3_Data_Out pin upon the rising
edge of the 34.368 MHz clock signal, at its
E3_Clock_In input pin (as depicted in Figure 100 and
Figure 101).
The XRT72L53 will latch the outbound E3 data
stream (from the Terminal Equipment) on the rising
edge of the RxOutClk signal.
The XRT72L53 will indicate that it is processing the
last bit, within a given outbound E3 frame, by pulsing
its TxFrame output pin "High" for one bit-period.
When the Terminal Equipment detects this pulse at its
Tx_Start_of_Frame input, it is expected to begin
transmission of the very next outbound E3 frame to
the XRT72L53 via the E3_Data_Out (or TxSer pin).
Finally, the XRT72L53 will indicate that it is about to
process an overhead bit by pulsing the TxOH_Ind
output pin "High" one bit period prior to its processing
of an OH (Overhead) bit. In Figure 100, the
TxOH_Ind output pin is connected to the
E3_Overhead_Ind input pin of the Terminal Equipment. Whenever the E3_Overhead_Ind pin is pulsed
"High" the Terminal Equipment is expected to not
transmit a E3 payload bit upon the very next clock
edge. Instead, the Terminal Equipment is expected to
delay its transmission of the very next payload bit, by
one clock cycle.
The behavior of the signals, between the XRT72L53
and the Terminal Equipment, for E3 Mode 1 operation
is illustrated in Figure 101.
Inserting the A and N bits into the outbound E3
frames via the Transmit Payload Data Input Interface block
The XRT72L53 DS3/E3 Framer permits the Terminal
Equipment to insert its own values for the “A” and/or
“N” bits, into the outbound E3 frame, via the Transmit
Payload Data Input Interface block. If the user desires
to do this, the XRT72L53 Framer IC must be configured to accept the Terminal Equipment’s value for the
“A” and “N” bits, by writing to appropriate data into the
TxASourceSel[1:0] and TxNSourceSel[1:0] bit-fields,
within the TxE3 Configuration Register (Address
=0x30), as illustrated below.
TXE3 CONFIGURATION REGISTER (ADDRESS = 0X30)
BIT 7
BIT 6
Tx
BIP-4
Enable
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
Tx AIS
Enable
Tx LOS
Enable
Tx FAS
Source
Select
TxASourceSel[1:0]
TxNSourceSel[1:0]
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
X
X
X
X
0
0
0
Configuring the Transmit Payload Data Input Interface block to accept the “A Bits” from the Terminal Equipment
For completeness, the relationship between the contents of the TxASourceSel[1:0] bits and the resulting
source of the “A” bit is listed below.
If the user wishes to configure the Transmit Payload
Data Input Interface block to accept the “A” bits from
the Terminal Equipment, then the user must write the
value “10” into the TxASourceSel[1:0] bit-fields. Once
the user does this, then any value, which resides on
the TxSer input pin, when the “A” bit is being processed by the Transmit Section will be inserted into
the “A” bit-field within the very next outbound E3
frame.
Bit 6, 5, TxASourceSel[1:0]
These two Read/Write bit-fields combine to specify
the source of the A-bit, within each outbound E3
frame. The relationship between these two bit-fields
and the resulting source of the A Bit is tabulated below.
TXASOURCESEL[1:0]
00
SOURCE OF A BIT
TxE3 Service Bits Register (Address = 0x35)
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TXASOURCESEL[1:0]
SOURCE OF A BIT
01
Transmit Overhead Data Input Interface
10
Transmit Payload Data Input Interface
11
Functions as a FEBE (Far-End-Block Error) bit-field.
This bit-field is set to "0", if the Near-End Receive Section (within this chip) detects no BIP-4
Errors within the incoming E3 frames.
This bit-field is set to "1", if the Near-End Receive Section (within this chip) detects a BIP-4
Error within the incoming E3 frame.
Configuring the Transmit Payload Data Input Interface
block to accept the “N” Bits from the Terminal Equipment, then the user must write the value “11” into the
TxNSourceSel[1:0] bit-fields. Once the user does this,
then any value, which resides on the TxSer input pin,
when the “N” bit is being processed by the Transmit
Section will be inserted into the “N” bit-field within the
very next outbound E3 frame.
For completeness, the relationship between the contents of the TxNSourceSel[1:0] bits and the resulting
source of the “N” bit is listed below.
Bits 4, 3, TxNSourceSel[1:0]
These two Read/Write bit-fields combine to specify
the source of the N-bit, within each outbound E3
frame. The relationship between these two bit-fields
and the resulting source of the N Bit is tabulated below.
TXNSOURCESEL[1:0]
SOURCE OF N BIT
00
TxE3 Service Bits Register (Address = 0x35)
01
Transmit Overhead Data Input Interface
10
Transmit LAPD Controller
11
Transmit Payload Data Input Interface.
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FIGURE 101. BEHAVIOR OF THE TERMINAL INTERFACE SIGNALS BETWEEN THE XRT72L53 TRANSMIT PAYLOAD
DATA INPUT INTERFACE BLOCK AND THE TERMINAL EQUIPMENT (FOR MODE 1 OPERATION)
Terminal Equipment Signals
E3_Clock_In
Payload[1522]
E3_Data_Out
Payload[1523]
FAS, Bit 9
FAS, Bit 8
FAS, Bit 9
FAS, Bit 8
Tx_Start_of_Frame
E3_Overhead_Ind
XRT72L5x Transmit Payload Data I/F Signals
RxOutClk
TxSer
Payload[1522]
Payload[1523]
TxFrame
TxOH_Ind
E3 Frame Number N
E3 Frame Number N + 1
Note: TxFrame pulses high to denote
E3 Frame Boundary.
Note: The FAS pattern will not be processed by the
Transmit Payload Data Input Interface.
Note: TxOH_Ind pulses high for
12 bit periods in order to
denote Overhead Data
(e.g., the FAS pattern and the
A & N bits).
How to configure the XRT72L53 into the Serial/
Loop-Timed/Non-Overhead Interface Mode
2. Set the TimRefSel[1:0] bit fields (within the
Framer Operating Mode Register) to "00", as
illustrated below.
1. Set the NibIntf input pin "Low".
FRAMER OPERATING MODE REGISTER (ADDRESS = 0X00)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT2
BIT 1
BIT 0
Local
Loopback
DS3/E3*
Internal
LOS
Enable
RESET
Interrupt
Enable
Reset
Frame
Format
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
1
0
1
0
0
0
TimRefSel[1:0]
3. Interface the XRT72L53, to the Terminal Equipment, as illustrated in Figure 100.
In this mode, the Transmit Section of the XRT72L53
will use the TxInClk signal as its timing reference.
5.2.1.2 Mode 2 - The Serial/Local-Timed/
Frame-Slave Mode Behavior of the XRT72L53
If the XRT72L53 has been configured to operate in
this mode, then the XRT72L53 will function as follows.
B. Serial Mode
A. Local-Timed - Uses the TxInClk signal as the
Timing Reference
The XRT72L53 will receive the E3 payload data, in a
serial manner, via the TxSer input pin. The Transmit
Payload Data Input Interface (within the XRT72L53)
will latch this data into its circuitry, on the rising edge
of the TxInClk input clock signal.
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THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. P1.1.8
C. Delineation of outbound E3 frames (Frame
Slave Mode)
In Mode 2, the XRT72L53 will sample the data, at the
TxSer input pin, on the rising edge of TxInClk.
The Transmit Section of the XRT72L53 will use the
TxInClk input as its timing reference, and will use the
TxFrameRef input signal as its framing reference. In
other words, the Transmit Section of the XRT72L53
will initiate frame generation upon the rising edge of
the TxFrameRef input signal).
Interfacing the Transmit Payload Data Input Interface block of the XRT72L53 to the Terminal Equipment for Mode 2 Operation
Figure 102 presents an illustration of the Transmit
Payload Data Input Interface block (within the
XRT72L53) being interfaced to the Terminal Equipment, for Mode 2 operation.
D. Sampling of payload data, from the Terminal
Equipment
FIGURE 102. ILLUSTRATION OF THE TERMINAL EQUIPMENT BEING INTERFACED TO THE TRANSMIT PAYLOAD DATA
INPUT INTERFACE BLOCK OF THE XRT72L53 FOR MODE 2 (SERIAL/LOCAL-TIMED/FRAME-SLAVE) OPERATION
34.368 MHz
34.368
MHz
Clock
Source
Clock Source
E3_Clock_In
E3_Clock_In
E3_Data_Out
E3_Data_Out
TxStart_of_Frame
TxStart_of_Frame
E3_Overhead_Ind
E3_Overhead_Ind
TxInClk
TxInClk
TxSer
TxSer
TxFrameRef
TxFrameRef
TxOH_Ind
TxOH_Ind
NibInt
NibInt
Terminal Equipment
XRT72L5X E3 Framer
Mode 2 Operation of the Terminal Equipment
pulsing its Tx_Start_of_Frame output signal (and in
turn, the TxFrameRef input pin of the XRT72L53),
"High" for one-bit period, coincident with the first bit of
a new E3 frame. Once the XRT72L53 detects the rising edge of the input at its TxFrameRef input pin, it
will begin generation of a new E3 frame.
As shown in Figure 102, both the Terminal Equipment
and the XRT72L53 will be driven by an external
34.368MHz clock signal. The Terminal Equipment will
receive the 34.368MHz clock signal via its
E3_Clock_In input pin, and the XRT72L53 Framer IC
will receive the 34.368MHz clock signal via the TxInClk input pin.
The Terminal Equipment will serially output the payload data of the outbound E3 data stream, via the
E3_Data_Out output pin, upon the rising edge of the
signal at the E3_Clock_In input pin.
NOTE: The E3_Data_Out output pin of the Terminal Equipment is electrically connected to the TxSer input pin
The XRT72L53 Framer IC will latch the data, residing
on the TxSer input line, on the rising edge of the TxInClk signal.
In this case, the Terminal Equipment has the responsibility of providing the framing reference signal by
NOTES:
1. In this case, the Terminal Equipment is controlling
the start of Frame Generation, and is therefore
referred to as the Frame Master. Conversely, since
the XRT72L53 does not control the generation of a
new E3 frame, but is rather driven by the Terminal
Equipment, the XRT72L53 is referred to as the
Frame Slave.
2. If the user opts to configure the XRT72L53 to operate in Mode 2, it is imperative that the
Tx_Start_of_Frame (or TxFrameRef) signal is synchronized to the TxInClk input clock signal.
Finally, the XRT72L53 will pulse its TxOH_Ind output
pin, one bit-period prior to it processing a given overhead bit, within the outbound E3 frame. Since the
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XRT72L53
THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. P1.1.8
TxOH_Ind output pin of the XRT72L53 is electrically
connected to the E3_Overhead_Ind whenever the
XRT72L53 pulses the TxOH_Ind output pin "High", it
will also be driving the E3_Overhead_Ind input pin (of
the Terminal Equipment) "High". Whenever the Terminal Equipment detects this pin toggling "High", it
should delay transmission of the very next E3 frame
payload bit by one clock cycle.
The behavior of the signals between the XRT72L53
and the Terminal Equipment for E3 Mode 2 Operation
is illustrated in Figure 103.
FIGURE 103. BEHAVIOR OF THE TERMINAL INTERFACE SIGNALS BETWEEN THE XRT72L53 AND THE TERMINAL
EQUIPMENT (MODE 2 OPERATION)
Terminal Equipment Signals
E3_Clock_In
Payload[1522]
E3_Data_Out
Payload[1523]
FAS, Bit 9
FAS, Bit 8
Tx_Start_of_Frame
E3_Overhead_Ind
XRT72L5x Transmit Payload Data I/F Signals
TxInClk
Payload[1522]
TxSer
Payload[1523]
FAS, Bit 9
FAS, Bit 8
TxFrameRef
TxOH_Ind
E3 Frame Number N
E3 Frame Number N + 1
Note: FAS Pattern bits will not be processed by the
Note: TxOH_Ind pulses high for
Transmit Payload Data Input Interface.
12 bit periods in order to
denote Overhead Data
Note: TxFrame pulses high to denote
(e.g., the FAS pattern
E3 Frame Boundary.
and the A & N bits).
How to configure the XRT72L53 to operate in this
mode.
2. Set the TimRefSel[1:0] bit-fields (within the
Framer Operating Mode Register) to "01" as
depicted below.
1. Set the NibIntf input pin "Low".
FRAMER OPERATING MODE REGISTER (ADDRESS = 0X00)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT2
Local
Loopback
DS3/E3*
Internal
LOS
Enable
RESET
Interrupt
Enable
Reset
Frame
Format
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
1
0
1
0
0
1
3. Interface the XRT72L53, to the Terminal Equipment, as illustrated in Figure 102.
5.2.1.3 Mode 3 - The Serial/Local-Timed/
Frame-Master Mode Behavior of the XRT72L53
BIT 1
BIT 0
TimRefSel[1:0]
If the XRT72L53 has been configured to operate in
this mode, then the XRT72L53 will function as follows.
A. Local-Timed - Uses the TxInClk signal as the
Timing Reference
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XRT72L53
THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. P1.1.8
In this mode, the Transmit Section of the XRT72L53
will use the TxInClk signal as its timing reference.
B. Serial Mode
The XRT72L53 will receive the E3 payload data, in a
serial manner, via the TxSer input pin. The Transmit
Payload Data Input Interface (within the XRT72L53)
will latch this data into its circuitry, on the rising edge
of the TxInClk input clock signal.
pulse its TxFrame output pin "High" whenever its it
processing the very last bit-field within a given E3
frame.
D. Sampling of payload data, from the Terminal
Equipment
In Mode 3, the XRT72L53 will sample the data, at the
TxSer input pin, on the rising edge of TxInClk.
C. Delineation of outbound DS3 frames (Frame
Master Mode)
Interfacing the Transmit Payload Data Input Interface block of the XRT72L53 to the Terminal Equipment for Mode 3 Operation
The Transmit Section of the XRT72L53 will use the
TxInClk signal as its timing reference, and will initiate
E3 frame generation, asynchronously with respect to
any externally applied signal. The XRT72L53 will
Figure 104 presents an illustration of the Transmit
Payload Data Input Interface block (within the
XRT72L53) being interfaced to the Terminal Equipment, for Mode 3 operation.
FIGURE 104. ILLUSTRATION OF THE TERMINAL EQUIPMENT BEING INTERFACED TO THE TRANSMIT PAYLOAD DATA
INPUT INTERFACE BLOCK OF THE XRT72L53 FOR MODE 3 (SERIAL/LOCAL-TIME/FRAME-MASTER) OPERATION
34.368 MHz Clock
Source
TxInClk
E3_Clock_In
TxSer
E3_Data_Out
Tx_Start_of_Frame
TxFrame
E3_Overhead_Ind
TxOH_Ind
NibInt
Terminal Equipment
Mode 3 Operation of the Terminal Equipment
In Figure 104, both the Terminal Equipment and the
XRT72L53 are driven by an external 34.368 MHz
clock signal. This clock signal is connected to the
E3_Clock_In input of the Terminal Equipment and the
TxInClk input pin of the XRT72L53.
The Terminal Equipment will serially output the payload data on its E3_Data_Out output pin, upon the
rising edge of the signal at the E3_Clock_In input pin.
Similarly, the XRT72L53 will latch the data, residing
on the TxSer input pin, on the rising edge of TxInClk.
XRT72L5x E3 Framer
The XRT72L53 will pulse the TxFrame output pin
"High" for one bit-period, coincident while it is processing the last bit-field within a given outbound E3
frame. The Terminal Equipment is expected to monitor the TxFrame signal (from the XRT72L53) and to
place the first bit, within the very next outbound E3
frame on the TxSer input pin.
NOTE: In this case, the XRT72L53 dictates exactly when
the very next E3 frame will be generated. The Terminal
Equipment is expected to respond appropriately by providing the XRT72L53 with the first bit of the new E3 frame,
upon demand. Hence, in this mode, the XRT72L53 is
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THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. P1.1.8
referred to as the Frame Master and the Terminal Equipment is referred to as the Frame Slave.
Finally, the XRT72L53 will pulse its TxOH_Ind output
pin, one bit-period prior to it processing a given overhead bit, within the outbound E3 frame. Since the
TxOH_Ind output pin (of the XRT72L53) is electrically
connected to the E3_Overhead_Ind whenever the
XRT72L53 pulses the TxOH_Ind output pin "High”, it
will also be driving the E3_Overhead_Ind input pin (of
the Terminal Equipment) "High". Whenever the Terminal Equipment detects this pin toggling "High", it
should delay transmission of the very next DS3 frame
payload bit by one clock cycle.
The behavior of the signal between the XRT72L53
and the Terminal Equipment for E3 Mode 3 Operation
is illustrated in Figure 105.
FIGURE 105. BEHAVIOR OF THE TERMINAL INTERFACE SIGNALS BETWEEN THE XRT72L53 AND THE TERMINAL
EQUIPMENT (E3 MODE 3 OPERATION)
Terminal Equipment Signals
E3_Clock_In
Payload[1522]
E3_Data_Out
Payload[1523]
FAS , Bit 9
FAS, Bit 8
FAS, Bit 9
FAS, Bit 8
Tx_Start_of_Frame
E3_Overhead_Ind
XRT72L5x Transmit Payload Data I/F Signals
TxInClk
Payload[1522]
TxSer
Payload[1523]
TxFrame
TxOH_Ind
E3 Frame Number N
E3 Frame Number N + 1
Note: TxFrame pulses high to denote
E3 Frame Boundary.
Note: TxOH_Ind pulses high for 12
bit-periods in order to denote
Overhead Data (e.g., the FAS pattern,
the A and N bits).
How to configure the XRT72L53 to operate in this
mode.
Note: FAS pattern will not be processed by the
Transmit Payload Data Input Interface.
2. Set the TimRefSel[1:0] bit-fields (within the
Framer Operating Mode Register) to "01" as
depicted below.
1. Set the NibIntf input pin "Low".
FRAMER OPERATING MODE REGISTER (ADDRESS = 0X00)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT2
Local
Loopback
DS3/E3*
Internal
LOS
Enable
RESET
Interrupt
Enable
Reset
Frame
Format
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
1
0
1
0
0
0
3. Interface the XRT72L53, to the Terminal Equipment, as illustrated in Figure 104.
BIT 1
BIT 0
TimRefSel[1:0]
5.2.1.4 Mode 4 - The Nibble-Parallel/LoopTimed Mode Behavior of the XRT72L53
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THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. P1.1.8
If the XRT72L53 has been configured to operate in
this mode, then the XRT72L53 will behave as follows.
A. Looped Timing (Uses the RxLineClk as the
Timing Reference)
In this mode, the Transmit Section of the XRT72L53
will use the RxLineClk signal as its timing reference.
When the XRT72L53 is operating in the Nibble-Mode,
it will internally divide the RxLineClk signal, by a factor of four (4) and will output this signal via the TxNibClk output pin.
B. Nibble-Parallel Mode
The XRT72L53 will accept the E3 payload data, from
the Terminal Equipment in a nibble-parallel manner,
via the TxNib[3:0] input pins. The Transmit Terminal
Equipment Input Interface block will latch this data into its circuitry, on the rising edge of the TxNibClk output signal.
C. Delineation of the outbound E3 frames
The XRT72L53 will pulse the TxNibFrame output pin
"High" for one bit-period coincident with the
XRT72L53 processing the last nibble of a given E3
frame.
D. Sampling of payload data, from the Terminal
Equipment
In Mode 4, the XRT72L53 will sample the data, at the
TxNib[3:0] input pins, on the third rising edge of the
RxOutClk clock signal, following a pulse in the TxNibClk signal (see Figure 107).
NOTE: The TxNibClk signal, from the XRT72L53 operates
nominally at 8.592 MHz (e.g., 34.368 MHz divided by 4).
The E3 Frame consists of 1536 bits or 384 nibbles.
Therefore, the XRT72L53 will supply 384 TxNibClk
pulses between the rising edges of two consecutive
TxNibFrame pulses. The E3 Frame repetition rate is
22.375kHz. Hence, 384 TxNibClk pulses for each E3
frame period amounts to TxNibClk running at approximately 8.592 MHz. The method by which the 384 TxNibClk pulses are distributed throughout the E3 frame
period is presented below.
Nominally, the Transmit Section within the XRT72L53
will generate a TxNibClk pulse for every 4 RxOutClk
(or TxInClk) periods.
Interfacing the Transmit Payload Data Input Interface block of the XRT72L53 to the Terminal Equipment for Mode 4 Operation
Figure 106 presents an illustration of the Transmit
Payload Data Input Interface block (within the
XRT72L53) being interfaced to the Terminal Equipment, for Mode 4 Operation.
FIGURE 106. ILLUSTRATION OF THE TERMINAL EQUIPMENT BEING INTERFACED TO THE TRANSMIT PAYLOAD DATA
INPUT INTERFACE BLOCK OF THE XRT72L53 FOR MODE 4 (NIBBLE-PARALLEL/LOOP-TIMED) OPERATION
VCC
8.592 MHz
E3_Nib_Clock_In
E3_Data_Out[3:0]
TxNibClk
NibInt
4
TxNib[3:0]
Tx_Start_of_Frame
TxNibFrame
E3_Overhead_Ind
TxOH_Ind
Terminal Equipment
Mode 4 Operation of the Terminal Equipment
When the XRT72L53 is operating in this mode, it will
function as the source of the 8.592MHz (e.g., the
34.368MHz clock signal divided by 4) clock signal,
that will be used as the Terminal Equipment Interface
clock by both the XRT72L53 and the Terminal Equipment.
34.368MHz
RxLineClk
XRT72L5x E3 Framer
The Terminal Equipment will output the payload data
of the outbound E3 data stream via its
E3_Data_Out[3:0] pins on the rising edge of the
8.592MHz clock signal at the E3_Nib_Clock_In input
pin.
The XRT72L53 will latch the outbound E3 data
stream (from the Terminal Equipment) on the rising
edge of the TxNibClk output clock signal. The
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XRT72L53
THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. P1.1.8
for 3 nibble-periods (e.g., the 3 nibbles consisting of
the 10 bit FAS pattern, the “A” and the “N” bits). The
TxOHInd output pin will remain "Low” for the remainder of the frame period. The TxOHInd output pin will
toggle "High” one-nibble period before the Transmit
Section (of the Framer IC) processes the first four bits
of the FAS pattern.
XRT72L53 will indicate that it is processing the last
nibble, within a given E3 frame, by pulsing its TxNibFrame output pin "High" for one TxNibClk clock period. When the Terminal Equipment detects a pulse at
its Tx_Start_of_Frame input pin, it is expected to
transmit the first nibble, of the very next outbound E3
frame to the XRT72L53 via the E3_Data_Out[3:0] (or
TxNib[3:0] pins).
The behavior of the signals between the XRT72L53
and the Terminal Equipment for E3 Mode 4 Operation
is illustrated in Figure 107.
Finally, for the Nibble-Parallel Mode operation, the
XRT72L53 will pulse the TxOHInd output pin "High”
FIGURE 107. BEHAVIOR OF THE TERMINAL INTERFACE SIGNALS BETWEEN THE XRT72L53 AND THE TERMINAL
EQUIPMENT (MODE 4 OPERATION)
Terminal Equipment Signals
RxOutClk
E3_Nib_Clock_In
Payload Nibble [380]
E3_Data_Out[3:0]
Overhead Nibble [0]
Tx_Start_of_Frame
E3_Overhead_Ind
XRT72L5x Transmit Payload Data I/F Signals
RxOutClk
TxNibClk
Nibble [380]
TxNib[3:0]
Overhead Nibble [0]
TxNibFrame
TxOH_Ind
Note: TxNibFrame pulses high to denote
E3 Frame Boundary.
E3 Frame Number N
E3 Frame Number N + 1
TxOH_Ind pulses high for 3 Nibble periods
How to configure the XRT72L53 into Mode 4
2. Set the TimRefSel[1:0] bit-fields (within the
Framer Operating Mode Register) to "00" as illustrated below.
1. Set the NibIntf input pin "High".
FRAMER OPERATING MODE REGISTER (ADDRESS = 0X00)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT2
Local
Loopback
DS3/E3*
Internal
LOS
Enable
RESET
Interrupt
Enable
Reset
Frame
Format
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
1
0
1
0
0
0
265
BIT 1
BIT 0
TimRefSel[1:0]
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XRT72L53
THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. P1.1.8
3. Interface the XRT72L53, to the Terminal Equipment, as illustrated in Figure 106.
signal, to latch the data, residing on the TxNib[3:0] into its circuitry.
NOTE: The XRT72L53 Framer IC cannot support the
Framer Local Loop-back Mode of operation, while operating
in Mode 4. The user must configure the XRT72L53 Framer
IC into any of the following modes prior to configuring the
Framer Local Loop-back Mode operation.
B. Nibble-Parallel Mode
The XRT72L53 will accept the E3 payload data, from
the Terminal Equipment, in a parallel manner, via the
TxNib[3:0] input pins. The Transmit Terminal Equipment Input Interface will latch this data into its circuitry, on the rising edge of the TxNibClk output signal.
• Mode 2 - Serial/Local-Timed/Frame-Slave Mode
• Mode 3 - Serial/Local-Timed/Frame-Master Mode
C. Delineation of outbound E3 Frames
• Mode 5 - Nibble-Parallel/Local-Timed/Frame-Slave
Mode
The Transmit Section will use the TxInClk input signal
as its timing reference and will use the TxFrameRef
input signal as its Framing Reference (e.g., the Transmit Section of the XRT72L53 initiates frame generation upon the rising edge of the TxFrameRef signal).
• Mode 6 - Nibble-Parallel/Local-Timed/Frame-Master Mode.
For more detailed information on the Framer Local
Loop-back Mode, please see Section 6.0.
D. Sampling of payload data, from the Terminal
Equipment
5.2.1.5 Mode 5 - The Nibble-Parallel/LocalTimed/Frame-Slave Interface Mode Behavior of
the XRT72L53
If the XRT72L53 has been configured to operate in
this mode, then the XRT72L53 will function as follows:
In Mode 5, the XRT72L53 will sample the data, at the
TxNib[3:0] input pins, on the third rising edge of the
TxInClk clock signal, following a pulse in the TxNibClk
signal (see Figure 108).
NOTE: The TxNibClk signal, from the XRT72L53 operates
nominally at 8.592 MHz (e.g., 34.368 MHz divided by 4).
A. Local-Timed - Uses the TxInClk signal as the
Timing Reference
In this mode, the Transmit Section of the XRT72L53
will use the TxInClk signal at its timing reference. Further, the chip will internally divide the TxInClk clock
signal by a factor of 4 and will output this divided
clock signal via the TxNibClk output pin. The Transmit
Terminal Equipment Input Interface block (within the
XRT72L53) will use the rising edge of the TxNibClk
Interfacing the Transmit Payload Data Input Interface block of the XRT72L53 to the Terminal Equipment for Mode 5 Operation
Figure 108 presents an illustration of the Transmit
Payload Data Input Interface block (within the
XRT72L53) being interfaced to the Terminal Equipment, for Mode 5 Operation.
FIGURE 108. ILLUSTRATION OF THE TERMINAL EQUIPMENT BEING INTERFACED TO THE TRANSMIT PAYLOAD DATA
INPUT INTERFACE BLOCK OF THE XRT72L53 FOR MODE 5 (NIBBLE-PARALLEL/LOCAL-TIMED/FRAME-SLAVE) OPERATION
34.368MHz Clock Source
VCC
TxInClk
E3_Nib_Clock_In
8.592MHz
NibInt
TxNibClk
4
E3_Data_Out[3:0]
TxNib[3:0]
Tx_Start_of_Frame
TxFrameRef
E3_Overhead_Ind
TxOH_Ind
Terminal Equipment
XRT72L5x E3 Framer
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THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. P1.1.8
Mode 5 Operation of the Terminal Equipment
In this case, the Terminal Equipment has the responsibility of providing the framing reference signal by
pulsing the Tx_Start_of_Frame output pin (and in
turn, the TxFrameRef input pin of the XRT72L53)
"High" for one bit-period, coincident with the first bit of
a new E3 frame. Once the XRT72L53 detects the rising edge of the input at its TxFrameRef input pin, it
will begin generation of a new E3 frame.
In Figure 108 both the Terminal Equipment and the
XRT72L53 will be driven by an external 8.592MHz
clock signal. The Terminal Equipment will receive the
8.592MHz clock signal via the E3_Nib_Clock_In input
pin. The XRT72L53 will output the 8.592MHz clock
signal via the TxNibClk output pin.
The Terminal Equipment will serially output the data
on the E3_Data_Out[3:0] pins, upon the rising edge
of the signal at the E3_Clock_In input pin.
Finally, the XRT72L53 will always internally generate
the Overhead bits, when it is operating in both the E3
and Nibble-parallel modes. The XRT72L53 will pull
the TxOHInd input pin "Low".
NOTE: The E3_Data_Out[3:0] output pins of the Terminal
Equipment is electrically connected to the TxNib[3:0] input
pins.
The XRT72L53 will latch the data, residing on the TxNib[3:0] input pins, on the rising edge of the TxNibClk
signal.
The behavior of the signals between the XRT72L53
and the Terminal Equipment for E3 Mode 5 Operation
is illustrated in Figure 109.
FIGURE 109. BEHAVIOR OF THE TERMINAL INTERFACE SIGNALS BETWEEN THE XRT72L53 AND THE TERMINAL
EQUIPMENT (E3, MODE 5 OPERATION)
Terminal Equipment Signals
TxInClk
E3_Nib_Clock_In
E3_Data_Out[3:0]
Payload Nibble [380]
Overhead Nibble [0]
Tx_Start_of_Frame
E3_Overhead_Ind
XRT72L5x Transmit Payload Data I/F Signals
TxInClk
TxNibClk
TxNib[3:0]
Nibble [380]
Overhead Nibble [0]
TxFrameRef
TxOH_Ind
Note: Terminal Equipment pulses
“TxFrameRef” in order to denote
the E3 Frame Boundary.
E3 Frame Number N
E3 Frame Number N + 1
TxOH_Ind pulses high for 3 Nibble periods
How to configure the XRT72L53 into Mode 5
2. Set the TimRefSel[1:0] bit-fields (within the
Framer Operating Mode Register) to "01" as illustrated below.
1. Set the NibIntf input pin "High".
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XRT72L53
THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. P1.1.8
FRAMER OPERATING MODE REGISTER (ADDRESS = 0X00)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT2
BIT 1
BIT 0
Local
Loopback
DS3/E3*
Internal
LOS
Enable
RESET
Interrupt
Enable
Reset
Frame
Format
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
1
0
1
0
0
1
TimRefSel[1:0]
3. Interface the XRT72L53, to the Terminal Equipment, as illustrated in Figure 108.
ment Input Interface will latch this data into its circuitry, on the rising edge of the TxNibClk output signal.
5.2.1.6 4.2.1.6 Mode 6 - The Nibble-Parallel/
Local-Timed/Frame-Master Interface Mode
Behavior of the XRT72L53
If the XRT72L53 has been configured to operate in
this mode, then the XRT72L53 will function as follows:
C. Delineation of outbound E3 Frames
The Transmit Section will use the TxInClk input signal
as its timing reference and will initiate the generation
of E3 frames, asynchronous with respect to any external signal. The XRT72L53 will pulse the TxFrame
output pin "High" whenever it is processing the last
bit, within a given outbound E3 frame.
A. Local-Timed - Uses the TxInClk signal as the
Timing Reference
In this mode, the Transmit Section of the XRT72L53
will use the TxInClk signal at its timing reference. Further, the chip will internally divide the TxInClk clock
signal by a factor of 4 and will output this divided
clock signal via the TxNibClk output pin. The Transmit
Terminal Equipment Input Interface block (within the
XRT72L53) will use the rising edge of the TxNibClk
signal, to latch the data, residing on the TxNib[3:0] into its circuitry.
B. Nibble-Parallel Mode
The XRT72L53 will accept the E3 payload data, from
the Terminal Equipment, in a parallel manner, via the
TxNib[3:0] input pins. The Transmit Terminal Equip-
D. Sampling of payload data, from the Terminal
Equipment
In Mode 6, the XRT72L53 will sample the data, at the
TxNib[3:0] input pins, on the third rising edge of the
TxInClk clock signal, following a pulse in the TxNibClk
signal (see Figure 111).
NOTE: The TxNibClk signal, from the XRT72L53 operates
nominally at 8.592 MHz (e.g., 34.368 MHz divided by 4).
Interfacing the Transmit Payload Data Input Interface block of the XRT72L53 to the Terminal Equipment for Mode 6 Operation
Figure 110 presents an illustration of the Transmit
Payload Data Input Interface block (within the
XRT72L53) being interfaced to the Terminal Equipment, for Mode 6 Operation.
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FIGURE 110. ILLUSTRATION OF THE TERMINAL EQUIPMENT BEING INTERFACED TO THE TRANSMIT PAYLOAD DATA
INPUT INTERFACE BLOCK OF THE XRT72L53 FOR MODE 6 (NIBBLE-PARALLEL/LOCAL-TIMED/FRAME-MASTER)
OPERATION
34.368MHz Clock Source
VCC
TxInClk
E3_Nib_Clock_In
NibInt
8.592MHz
TxNibClk
4
E3_Data_Out[3:0]
TxNib[3:0]
Tx_Start_of_Frame
TxNibFrame
E3_Overhead_Ind
TxOH_Ind
Terminal Equipment
Mode 6 Operation of the Terminal Equipment
In Figure 110 both the Terminal Equipment and the
XRT72L53 will be driven by an external 8.592MHz
clock signal. The Terminal Equipment will receive the
8.592MHz clock signal via the E3_Nib_Clock_In input
pin. The XRT72L53 will output the 8.592MHz clock
signal via the TxNibClk output pin.
The Terminal Equipment will serially output the data
on the E3_Data_Out[3:0] pins upon the rising edge of
the signal at the E3_Clock_In input pin. The
XRT72L53 will latch the data, residing on the TxNib[3:0] input pins, on the rising edge of the TxNibClk
signal.
XRT72L5x E3 Framer
In this case the XRT72L53 has the responsibility of
providing the framing reference signal by pulsing the
TxFrame output pin (and in turn the
Tx_Start_of_Frame input pin of the Terminal Equipment) "High" for one bit-period, coincident with the
last bit within a given E3 frame.
Finally, the XRT72L53 will always internally generate
the Overhead bits, when it is operating in both the E3
and Nibble-parallel modes. The XRT72L53 will pull
the TxOHInd input pin "Low".
The behavior of the signals between the XRT72L53
and the Terminal Equipment for E3 Mode 6 Operation
is illustrated in Figure 111.
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FIGURE 111. BEHAVIOR OF THE TERMINAL INTERFACE SIGNALS BETWEEN THE XRT72L53 AND THE TERMINAL
EQUIPMENT (E3 MODE 6 OPERATION)
Terminal Equipment Signals
TxInClk
E3_Nib_Clock_In
Payload Nibble [380]
E3_Data_Out[3:0]
Overhead Nibble [0]
Tx_Start_of_Frame
E3_Overhead_Ind
XRT72L5x Transmit Payload Data I/F Signals
TxInClk
TxNibClk
Nibble [380]
TxNib[3:0]
Overhead Nibble [0]
TxNibFrame
TxOH_Ind
Note: TxNibFrame pulses high to denote
E3 Frame Boundary.
E3 Frame Number N + 1
E3 Frame Number N
TxOH_Ind pulses high for 3 Nibble periods
How to configure the XRT72L53 into Mode 6
2. Set the TimRefSel[1:0] bit-fields (within the
Framer Operating Mode Register) to "1X" as illustrated below.
1. Set the NibInt input pin "High".
FRAMER OPERATING MODE REGISTER (ADDRESS = 0X00)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT2
Local
Loopback
DS3/E3*
Internal
LOS
Enable
RESET
Interrupt
Enable
Reset
Frame
Format
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
1
0
1
0
1
x
3. Interface the XRT72L53, to the Terminal Equipment, as illustrated in Figure 110.
5.2.2
face
The Transmit Overhead Data Input Inter-
BIT 1
BIT 0
TimRefSel[1:0]
Figure 112 presents a simple illustration of the Transmit Overhead Data Input Interface block within the
XRT72L53.
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FIGURE 112. SIMPLE ILLUSTRATION OF THE TRANSMIT OVERHEAD DATA INPUT INTERFACE BLOCK
TxOHFrame
TxOHEnable
TxOH
Transmit
Transmit
Overhead
Overhead
Data
DataInput
Input
Interface
InterfaceBlock
Block
To Transmit DS3 Framer Block
TxOHClk
TxOHIns
The E3, ITU-T G.751 Frame consists of 1536 bits. Of
these bits, 1524 are payload bits and the remaining
12 are overhead bits. The XRT72L53 has been designed to handle and process both the payload type
and overhead type bits for each E3 frame. Within the
Transmit Section within the XRT72L53, the Transmit
Payload Data Input Interface has been designed to
handle the payload data. Likewise, the Transmit Overhead Input Interface has been designed to handle
and process the overhead bits.
The Transmit Section of the XRT72L53 generates or
processes the various overhead bits within the E3
frame, in the following manner.
The Frame Alignment Signaling (FAS) Overhead
Bits
The FAS (Framing Alignment Signaling) bits are always internally generated by the Transmit Section of
the XRT72L53. Hence, the user cannot insert his/her
value for the FAS bits into the outbound E3 data
stream, via the Transmit Overhead Data Input Interface.
The “A” bit is used to transport the FERF (Far-End
Receive Failure) condition. This bit-field can be either
internally generated by the Transmit Section within
the XRT72L53, or can be externally generated and inserted into the outbound E3 data stream, via the
Transmit Overhead Data Input Interface. The Data
Link Related Overhead Bits
The “N” (National) Overhead bit
The E3 frame structure also contains the N bit which
can be used to transport a proprietary User Data Link
information and or Path Maintenance Data Link information. The UDL (User Data Link) bits are only accessible via the Transmit Overhead Data Input Interface. The Path Maintenance Data Link (PMDL) bits
can either be sourced from the Transmit LAPD Controller/Buffer or via the Transmit Overhead Data Input
Interface.
Table 48 lists the Overhead Bits within the E3 frame.
In addition, this table also indicates whether or not
these overhead bits can be sourced by the Transmit
Overhead Data Input Interface.
The “A” (Alarm) Overhead bit
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TABLE 48: A LISTING OF THE OVERHEAD BITS WITHIN THE E3 FRAME, AND THEIR POTENTIAL SOURCES, WITHIN THE
XRT72L53 IC
OVERHEAD BIT
INTERNALLY GENERATED
ACCESSIBLE VIA THE TRANSMIT OVERHEAD
DATA INPUT INTERFACE
BUFFER/REGISTER
ACCESSIBLE
FAS Signal - Bit 9
Yes
Yes
Yes*
FAS Signal - Bit 8
Yes
Yes
Yes
FAS Signal - Bit 7
Yes
Yes
Yes*
FAS Signal - Bit 6
Yes
Yes
Yes*
FAS Signal - Bit 5
Yes
Yes
Yes
FAS Signal - Bit 4
Yes
Yes
Yes
FAS Signal - Bit 3
Yes
Yes
Yes
FAS Signal - Bit 2
Yes
Yes
Yes
FAS Signal - Bit 1
Yes
Yes
Yes
FAS Signal - Bit 0
Yes
Yes
Yes
A Bit
Yes
Yes
Yes
N Bit
Yes
Yes
Yes
NOTES:
1. The XRT72L53 contains mask register bits that
permit the user to alter the state of the internally
generated value for these bits.
2. The Transmit LAPD Controller/Buffer can be configured to be the source of the N bits, within the outbound E3 data stream.
5.2.2.1 Method 1 - Using the TxOHClk Clock
Signal
The Transmit Overhead Data Input Interface consists
of the five signals. Of these five (5) signals, the following four (4) signals are to be used when implementing
Method 1.
The Transmit Overhead Data Input Interface permits
the user to insert overhead data into the outbound E3
frames via the following two different methods.
• TxOHClk
• TxOH
• TxOHFrame
• Method 1 - Using the TxOHClk clock signal
• TxOHIns
• Method 2 - Using the TxInClk and the TxOHEnable
signals.
Each of these signals are listed and described below.
Table 49.
Each of these methods are described below.
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TABLE 49: DESCRIPTION OF METHOD 1 TRANSMIT OVERHEAD INPUT INTERFACE SIGNALS
NAME
TYPE
TxOHIns
Input
DESCRIPTION
Transmit Overhead Data Insert Enable input pin.
Asserting this input signal (e.g., setting it "High”) enables the Transmit Overhead Data Input Interface to accept overhead data from the Terminal Equipment. In other words, while this input pin is
"High", the Transmit Overhead Data Input Interface will sample the data at the TxOH input pin, on
the falling edge of the TxOHClk output signal.
Conversely, setting this pin "Low" configures the Transmit Overhead Data Input Interface to NOT
sample (e.g., ignore) the data at the TxOH input pin, on the falling edge of the TxOHClk output
signal.
NOTE: If the Terminal Equipment attempts to insert an overhead bit that cannot be accepted by
the Transmit Overhead Data Input Interface (e.g., if the Terminal Equipment asserts the TxOHIns
signal, at a time when one of these non-insertable overhead bits are being processed), that particular insertion effort will be ignored.
TxOH
Input
Transmit Overhead Data Input pin:
The Transmit Overhead Data Input Interface accepts the overhead data via this input
pin, and inserts into the overhead bit position within the very next outbound E3 frame. If
the TxOHIns pin is pulled "High", the Transmit Overhead Data Input Interface will sample the data at this input pin (TxOH), on the falling edge of the TxOHClk output pin. Conversely, if the TxOHIns pin is pulled "Low", then the Transmit Overhead Data Input Interface will NOT sample the data at this input pin (TxOH). Consequently, this data will be
ignored.
TxOHClk
Output
Transmit Overhead Input Interface Clock Output signal:
This output signal serves two purposes:
1. The Transmit Overhead Data Input Interface will provide a rising clock edge on this signal, one
bit-period prior to the instant that the Transmit Overhead Data Input Interface is processing an
overhead bit.
2. The Transmit Overhead Data Input Interface will sample the data at the TxOH input, on the falling edge of this clock signal (provided that the TxOHIns input pin is "High").
NOTE: The Transmit Overhead Data Input Interface will supply a clock edge for all overhead bits
within the DS3 frame (via the TxOHClk output signal). This includes those overhead bits that the
Transmit Overhead Data Input Interface will not accept from the Terminal Equipment.
TxOHFrame
Output
Transmit Overhead Input Interface Frame Boundary Indicator Output:
This output signal pulses "High" when the XRT72L53 is processing the last bit within a
given E3 frame.
The purpose of this output signal is to alert the Terminal Equipment that the Transmit
Overhead Data Input Interface block is about to begin processing the overhead bits for a
new E3 frame.
Interfacing the Transmit Overhead Data Input Interface to the Terminal Equipment.
Figure 113 illustrates how one should interface the
Transmit Overhead Data Input Interface to the Terminal Equipment, when using Method 1.
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FIGURE 113. ILLUSTRATION OF THE TERMINAL EQUIPMENT BEING INTERFACED TO THE TRANSMIT OVERHEAD DATA
INPUT INTERFACE (METHOD 1)
34.368 MHz Clock Source
TxInClk
E3_OH_Clock_In
34.368 MHz
Clock Source
TxOHClk
E3_OH_Out]
TxOH
RxLineClk
Tx_Start_of_Frame
TxOHFrame
Insert_OH
TxOHIns
Terminal Equipment
XRT72L5x E3 Framer
Method 1 Operation of the Terminal Equipment
If the Terminal Equipment intends to insert any overhead data into the outbound E3 data stream, (via the
Transmit Overhead Data Input Interface), then it is expected to do the following.
1. To sample the state of the TxOHFrame signal
(e.g., the Tx_Start_of_Frame input signal) on the
rising edge of the TxOHClk (e.g., the
E3_OH_Clock_In signal).
2. To keep track of the number of rising clock edges
that have occurred, via the TxOHClk (e.g., the
E3_OH_Clock_In signal) since the last time the
TxOHFrame signal was sampled "High". By doing
this the Terminal Equipment will be able to keep
track of which overhead bit is being processed by
the Transmit Overhead Data Input Interface block
at any given time. When the Terminal Equipment
knows which overhead bit is being processed, at
a given TxOHClk period, it will know when to
insert a desired overhead bit value into the outbound E3 data stream. From this, the Terminal
Equipment will know when it should assert the
TxOHIns input pin and place the appropriate
value on the TxOH input pin (of the XRT72L53).
Table 50 relates the number of rising clock edges (in
the TxOHClk signal, since TxOHFrame was sampled
"High") to the E3 Overhead Bit, that is being processed.
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TABLE 50: THE RELATIONSHIP BETWEEN THE NUMBER OF RISING CLOCK EDGES IN TXOHCLK, (SINCE TXOHFRAME
WAS LAST SAMPLED "HIGH") TO THE E3 OVERHEAD BIT, THAT IS BEING PROCESSED
NUMBER OF RISING CLOCK EDGES IN
TXOHCLK
THE OVERHEAD BIT EXPECTED BY THE CAN THIS OVERHEAD BIT BE ACCEPTED BY
THE XRT72L53?
XRT72L53
0 (Clock edge is coincident with TxOHFrame being detected "High”)
FAS Signal - Bit 9
Yes
1
FAS Signal - Bit 8
Yes
2
FAS Signal - Bit 7
Yes
3
FAS Signal - Bit 6
Yes
4
FAS Signal - Bit 5
Yes
5
FAS Signal - Bit 4
Yes
6
FAS Signal - Bit 3
Yes
7
FAS Signal - Bit 2
Yes
8
FAS Signal - Bit 1
Yes
9
FAS Signal - Bit 0
Yes
10
A Bit
Yes
11
N Bit
Yes
3. After the Terminal Equipment has waited the
appropriate number of clock edges (from the
TxOHFrame signal being sampled "High"), it
should assert the TxOHIns input signal. Concurrently, the Terminal Equipment should also place
the appropriate value (of the inserted overhead
bit) onto the TxOH signal.
4. The Terminal Equipment should hold both the
TxOHIns input pin "High" and the value of the
TxOH signal, stable until the next rising edge of
TxOHClk is detected.
Case Study: The Terminal Equipment intends to
insert the appropriate overhead bits into the
Transmit Overhead Data Input Interface (using
Method 1) in order to transmit a Yellow Alarm to
the remote terminal equipment.
In this example, the Terminal Equipment intends to insert the appropriate overhead bits, into the Transmit
Overhead Data Input Interface, such that the
XRT72L53 will transmit a Yellow Alarm to the remote
terminal equipment. Recall that, for E3, ITU-T G.751
Applications, a Yellow Alarm is transmitted by setting
the "A" bit to "1".
If one assumes that the connection between the Terminal Equipment and the XRT72L53 are as illustrated
in Figure 113 then Figure 114 presents an illustration
of the signaling that must go on between the Terminal
Equipment and the XRT72L53.
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FIGURE 114. ILLUSTRATION OF THE SIGNAL THAT MUST OCCUR BETWEEN THE TERMINAL EQUIPMENT AND THE
XRT72L53 IN ORDER TO CONFIGURE THE XRT72L53 TO TRANSMIT A YELLOW ALARM TO THE REMOTE TERMINAL
EQUIPMENT
Terminal Equipment/XRT72L5x Interface Signals
0
1
4
5
6
7
8
9
10 10-
TxOHClk
TxOHFrame
TxOHIns
TxOH
Remaining Overhead Bits with E3 Frame
A bit = 1
TxOHFrame is sampled “High”
Terminal Equipment asserts TxOHIns and
Data on TxOH line.
XRT72L5x Framer device samples TxOH and
TxOHIns signals
In Figure 114 the Terminal Equipment samples the
TxOHFrame signal being "High" at rising clock edge #
0. From this point, the Terminal Equipment will wait
until it has detected the 10th rising edge of the TxOHClk signal. At this point, the Terminal Equipment
knows that the XRT72L53 is just about to process the
“A” bit within a given outbound E3 frame. Additionally,
according to Table 50, the 10th overhead bit to be
processed is the "A" bit. In order to facilitate the transmission of the Yellow Alarm, the Terminal Equipment
must set this "A" bit to "1". Hence, the Terminal Equipment starts this process by implementing the following steps concurrently.
a. Assert the TxOHIns input pin by setting it "High".
b. Set the TxOH input pin to "1".
After the Terminal Equipment has applied these signals, the XRT72L53 will sample the data on both the
TxOHIns and TxOH signals upon the very next falling
edge of TxOHClk (designated as "10-" in Figure 114).
Once the XRT72L53 has sampled this data, it will
then insert a "1" into the "A" bit position, in the outbound E3 frame.
Upon detection of the very next rising edge of the TxOHClk clock signal (designated as clock edge 1 in
Figure 114, the Terminal Equipment will negate the
TxOHIns signal (e.g., toggles it "Low") and will cease
inserting data into the Transmit Overhead Data Input
Interface.
After the Terminal Equipment has performed this insertion procedure, it leaves the remaining overhead
bits (within this particular outbound E3 frame) in-tact,
by terminating this Overhead Bit Insertion procedure.
The Terminal Equipment should now terminate this
overhead bit insertion, by doing the following.
a. Assert the TxOHIns input pin by setting it "High".
b. Set the TxOH input to "0".
If the Terminal Equipment wishes to continue its
transmission of the Yellow Alarm condition to the Remote Terminal Equipment, then it should resume the
Overhead Bit Insertion procedure (as described
above), at the beginning of each outbound E3 frame
(or each time TxOHFrame is sampled "High”).
5.2.2.2 Method 2 - Using the TxInClk and TxOHEnable Signals
Method 1 requires the use of an additional clock signal, TxOHClk. However, there may be a situation in
which the user does not wish to add this extra clock
signal to their design, in order to use the Transmit
Overhead Data Input Interface. Hence, Method 2 is
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available. When using Method 2, either the TxInClk or
RxOutClk signal is used to sample the overhead bits
and signals which are input to the Transmit Overhead
Data Input Interface. Method 2 involves the use of the
following signals:
• TxOH
• TxInClk
• TxOHFrame
• TxOHEnable
Each of these signals are listed and described in
Table 51.
TABLE 51: DESCRIPTION OF METHOD 2 TRANSMIT OVERHEAD INPUT INTERFACE SIGNALS
NAME
TYPE
DESCRIPTION
TxOHEnable
Output
Transmit Overhead Data Enable Output pin
The XRT72L53 will assert this signal, for one TxInClk period, just prior to the instant that the
Transmit Overhead Data Input Interface is processing an overhead bit.
TxOHFrame
Output
Transmit Overhead Input Interface Frame Boundary Indicator Output:
This output signal pulses "High" when the XRT72L53 is processing the last bit within a given DS3
frame.
TxOHIns
Input
Transmit Overhead Data Insert Enable input pin.
Asserting this input signal (e.g., setting it "High") enables the Transmit Overhead Data Input Interface to accept overhead data from the Terminal Equipment. In other words, while this input pin is
"High", the Transmit Overhead Data Input Interface will sample the data at the TxOH input pin, on
the falling edge of the TxInClk output signal.
Conversely, setting this pin "Low" configures the Transmit Overhead Data Input Interface to NOT
sample (e.g., ignore) the data at the TxOH input pin, on the falling edge of the TxOHClk output
signal.
NOTE: If the Terminal Equipment attempts to insert an overhead bit that cannot be accepted by
the Transmit Overhead Data Input Interface (e.g., if the Terminal Equipment asserts the TxOHIns
signal, at a time when one of these non-insertable overhead bits are being processed), that particular insertion effort will be ignored.
TxOH
Input
Transmit Overhead Data Input pin:
The Transmit Overhead Data Input Interface accepts the overhead data via this input pin, and
inserts into the overhead bit position within the very next outbound DS3 frame. If the TxOHIns pin
is pulled "High", the Transmit Overhead Data Input Interface will sample the data at this input pin
(TxOH), on the falling edge of the TxOHClk output pin. Conversely, if the TxOHIns pin is pulled
"Low", then the Transmit Overhead Data Input Interface will NOT sample the data at this input pin
(TxOH). Consequently, this data will be ignored.
Interfacing the Transmit Overhead Data Input Interface
to the Terminal Equipment
Figure 115 illustrates how one should interface the
Transmit Overhead Data Input Interface to the Terminal Equipment when using Method 2.
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FIGURE 115. ILLUSTRATION OF THE TERMINAL EQUIPMENT BEING INTERFACED TO THE TRANSMIT OVERHEAD DATA
INPUT INTERFACE (METHOD 2)
34.368 MHz Clock Source
TxInClk
E3_Clock_In
34.368 MHz
Clock Source
E3_OH_Enable
TxOHEnable
TxOH
E3_OH_Out
RxLineClk
TxOHFrame
Tx_Start_of_Frame
TxOHIns
Insert_OH
Terminal Equipment
XRT72L5x E3 Framer
Method 2 Operation of the Terminal Equipment
If the Terminal Equipment intends to insert any overhead data into the outbound E3 data stream (via the
Transmit Overhead Data Input Interface), then it is expected to do the following.
1. To sample the state of both the TxOHFrame and
the TxOHEnable input signals, via the
E3_Clock_In (e.g., either the TxInClk or the
RxOutClk signal of the XRT72L53) signal. If the
Terminal Equipment samples the TxOHEnable
signal "High", then it knows that the XRT72L53 is
about to process an overhead bit. Further, if the
Terminal Equipment samples both the TxOHFrame and the TxOHEnable pins "High" (at the
same time) then the Terminal Equipment knows
that the XRT72L53 is about to process the first
overhead bit, within a new E3 frame.
2. To keep track of the number of times that the
TxOHEnable signal has been sampled "High"
since the last time both the TxOHFrame and the
TxOHEnable signals were sampled "High". By
doing this, the Terminal Equipment will be able to
keep track of which overhead bit the Transmit
Overhead Data Input Interface is about ready to
process. From this, the Terminal Equipment will
know when it should assert the TxOHIns input pin
and place the appropriate value on the TxOH
input pins of the XRT72L53.
Table 52 also relates the number of TxOHEnable output pulses (that have occurred since both the TxOHFrame and TxOHEnable pins were sampled "High")
to the E3 overhead bit, that is being processed.
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TABLE 52: THE RELATIONSHIP BETWEEN THE NUMBER OF TXOHENABLE PULSES (SINCE THE LAST OCCURRENCE OF
THE TXOHFRAME PULSE) TO THE E3 OVERHEAD BIT, THAT IS BEING PROCESSED BY THE XRT72L53
NUMBER OF TXOHENABLE PULSES
THE OVERHEAD BIT EXPECTED BY THE CAN THIS OVERHEAD BIT BE ACCEPTED BY
THE XRT72L53?
XRT72L53
0 (Clock edge is coincident with TxOHFrame being detected "High”)
FAS Signal - Bit 9
Yes
1
FAS Signal - Bit 8
Yes
2
FAS Signal - Bit 7
Yes
3
FAS Signal - Bit 6
Yes
4
FAS Signal - Bit 5
Yes
5
FAS Signal - Bit 4
Yes
6
FAS Signal - Bit 3
Yes
7
FAS Signal - Bit 2
Yes
8
FAS Signal - Bit 1
Yes
9
FAS Signal - Bit 0
Yes
10
A Bit
Yes
11
N Bit
Yes
3. After the Terminal Equipment has waited through
the appropriate number of pulses via the TxOHEnable pin, it should then assert the TxOHIns
input signal. Concurrently, the Terminal Equipment should also place the appropriate value (of
the inserted overhead bit) onto the TxOH signal.
4. The Terminal Equipment should hold both the
TxOHIns input pin "High" and the value of the
TxOH signal stable, until the next TxOHEnable
pulse is detected.
Case Study: The Terminal Equipment intends to
insert the appropriate overhead bits into the
Transmit Overhead Data Input Interface (using
Method 2) in order to transmit a Yellow Alarm to
the remote terminal equipment.
In this case, the Terminal Equipment intends to insert
the appropriate overhead bits, into the Transmit Overhead Data Input Interface such that the XRT72L53
will transmit a Yellow Alarm to the remote terminal
equipment. Recall that, for E3, ITU-T G.751 applications, a Yellow Alarm is transmitted by setting the “A”
bit to “1".
If one assumes that the connection between the Terminal Equipment and the XRT72L53 is as illustrated
in Figure 115 then, Figure 116 presents an illustration
of the signaling that must go on between the Terminal
Equipment and the XRT72L53.
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FIGURE 116. BEHAVIOR OF TRANSMIT OVERHEAD DATA INPUT INTERFACE SIGNALS BETWEEN THE XRT72L53 AND
TERMINAL EQUIPMENT (FOR METHOD 2)
THE
TxInClk
TxOHFrame
TxOHEnable Pulse # 10
TxOHEnable Pulse # 0
TxOHEnable
TxOHIns
A bit = 1
TxOH
Terminal Equipment
samples “TxOHFrame” and
“TxOHEnable” being “HIGH”
Terminal Equipment counts the number of
TxOHEnable pulses. At “pulse # 10” the Terminal
Equipment asserts the “TxOHIns” signal and places the
desired data on TxOH.
5.2.3 The Transmit E3 HDLC Controller
The Transmit E3 HDLC Controller block can be used
to transport Message-Oriented Signaling (MOS) type
messages to the remote terminal equipment as discussed in detail below.
5.2.3.1 Message-Oriented Signaling (e.g.,
LAP-D) processing via the Transmit DS3 HDLC
Controller
The LAPD Transmitter (within the Transmit E3 HDLC
Controller Block) allows the user to transmit path
maintenance data link (PMDL) messages to the re-
XRT72L5x samples TxOH
here.
mote terminal via the outbound E3 Frames. In this
case the message bits are inserted into and carried
by the “N” bit, within the outbound E3 frames. The onchip LAPD transmitter supports both the 76 byte and
82 byte length message formats, and the Framer IC
allocates 88 bytes of on-chip RAM (e.g., the Transmit
LAPD Message buffer) to store the message to be
transmitted. The message format complies with ITUT Q.921 (LAP-D) protocol with different addresses
and is presented below in Figure 117.
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PRELIMINARY
REV. P1.1.8
FIGURE 117. LAPD MESSAGE FRAME FORMAT
Flag Sequence (8 bits)
C/R
SAPI (6-bits)
EA
EA
TEI (7 bits)
Control (8-bits)
76 or 82 Bytes of Information (Payload)
FCS - MSB
FCS - LSB
Flag Sequence (8-bits)
Where: Flag Sequence = 0x7E
SAPI + CR + EA = 0x3C or 0x3E
TEI + EA = 0x01
Control = 0x03
The following sections defines each of these bit/bytefields within the LAPD Message Frame Format.
Flag Sequence Byte
The Flag Sequence byte is of the value 0x7E, and is
used to denote the boundaries of the LAPD Message
Frame.
SAPI - Service Access Point Identifier
The SAPI bit-fields are assigned the value of
"001111b" or 15 (decimal).
TEI - Terminal Endpoint Identifier
The TEI bit-fields are assigned the value of 0x00. The
TEI field is used in N-ISDN systems to identify a terminal out of multiple possible terminal. However,
since the Framer IC transmits data in a point-to-point
manner, the TEI value is unimportant.
Control
The Control identifies the type of frame being transmitted. There are three general types of frame formats: Information, Supervisory, and Unnumbered.
The Framer assigned the Control byte the value 03h.
Hence, the Framer will be transmitting and receiving
Unnumbered LAPD Message frames.
Information Payload
The Information Payload is the 76 bytes or 82 bytes of
data (e.g., the PMDL Message) that the user has written into the on-chip Transmit LAPD Message buffer
(which is located at addresses 0x86 through 0xDD).
It is important to note that the user must write in a
specific octet value into the first byte position within
the Transmit LAPD Message buffer (located at Address = 0x86, within the Framer). The value of this octet depends upon the type of LAPD Message frame/
PMDL Message that the user wishes to transmit.
Table 53 presents a list of the various types of LAPD
Message frames/PMDL Messages that are supported
by the XRT72L53 Framer device and the corresponding octet value that the user must write into the first
octet position within the Transmit LAPD Message
buffer.
TABLE 53: THE LAPD MESSAGE TYPE AND THE CORRESPONDING VALUE OF THE FIRST BYTE, WITHIN THE
INFORMATION PAYLOAD
LAPD MESSAGE TYPE
VALUE OF FIRST BYTE, WITHIN INFORMATION
PAYLOAD OF MESSAGE
MESSAGE SIZE
CL Path Identification
0x38
76 bytes
IDLE Signal Identification
0x34
76 bytes
Test Signal Identification
0x32
76 bytes
ITU-T Path Identification
0x3F
82 bytes
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2. Specify the length of LAPD message to be transmitted.
3. Specify whether the LAPD Transmitter should
transmit this LAPD Message frame only once, or
an indefinite number of times at One-Second
intervals.
4. Enable the LAPD Transmitter.
5. Initiate the Transmission of the PMDL Message.
Each of these steps will be discussed in detail.
Frame Check Sequence Bytes
The 16 bit FCS (Frame Check Sequence) is calculated over the LAPD Message Header and Information
Payload bytes, by using the CRC-16 polynomial, x16
+ x12 + x5 + 1.
Operation of the LAPD Transmitter
If the user wishes to transmit a message via the
LAPD Transmitter, the information portion (or the
body) of the message must be written into the Transmit LAPD Message Buffer, which is located at 0x86
through 0xDD in on-chip RAM via the Microprocessor
Interface. Afterwards, the user must do five things:
STEP 1 - Configure the source of the “N” bit (within each outbound E3 frame, to be the LAPD Transmitter.
This is accomplished by writing the appropriate data
into the TxNSourceSel[1:0] bit-fields, within the TxE3
Configuration Register, as illustrated below.
1. Configure the source of the “N” bit (within each
outbound E3 frame, to be the LAPD Transmitter.
TXE3 CONFIGURATION REGISTER (ADDRESS = 0X30)
BIT 7
Tx
BIP-4
Enable
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
Tx AIS
Enable
Tx LOS
Enable
Tx FAS
Source
Select
TxASourceSel[1:0]
TxNSourceSel[1:0]
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
0
0
Table 54 lists these octets and the corresponding
LAPD Message types.
Setting TxNSourceSel[1:0] to “10” configures the
Transmit E3 Framer block to use the LAPD Transmitter as the data source for the “N” bits. Hence, the “N”
bit, (within each outbound E3 frame) is now carrying
LAPD Messages to the remote terminal equipment.
STEP 3 - Write the PMDL Message into the remaining part of the Transmit LAPD Message Buffer.
STEP 2 - Specify the type of LAPD Message frame
to be Transmitted (within the Transmit LAPD Message Buffer)
The user must write in a specific octet value into the
first octet position within the Transmit LAPD Buffer
(e.g., at Address Location 0x86 within the Framer IC).
This octet is referred to as the LAPD Message Frame
ID octet. The value of this octet must correspond to
the type of LAPD Message frame that is desired to be
transmitted. This octet will ultimately be used by the
Remote Terminal Equipment in order to help it identify
the type of LAPD message frame that it is receiving.
The user must now write in his/her PMDL Message
into the remaining portion of the Transmit LAPD Message buffer (e.g., addresses 0x87 through 0x135
within the Framer IC).
STEP 4 - Specifying the Length of the LAPD Message
One of two different sizes of LAPD Messages can be
transmitted. This can be accomplished by writing the
appropriate data to bit 1 within the Tx E3 LAPD Configuration Register. The bit-format of this register is
presented below.
TRANSMIT E3 LAPD CONFIGURATION REGISTER (ADDRESS = 0X33)
BIT 7
BIT 6
BIT 5
BIT 4
Not Used
BIT 3
BIT2
BIT 1
BIT 0
Auto
Retransmit
Not Used
TxLAPD
Msg Length
TxLAPD
Enable
R/O
R/O
R/O
R/O
R/W
R/O
R/W
R/W
0
0
0
0
X
0
X
X
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The relationship between the contents of bit-fields 1
and the LAPD Message size is given in Table 54.
TABLE 54: RELATIONSHIP BETWEEN TXLAPD MSG LENGTH AND THE LAPD MESSAGE SIZE
TXLAPD MESSAGE LENGTH
LAPD MESSAGE LENGTH
0
LAPD Message size is 76 bytes
1
LAPD Message size is 82 bytes
NOTE: The Message Type selected must correspond with
the contents of the first byte of the Information (Payload)
portion, as presented in Table 53.
STEP 5 - Specify whether the LAPD Transmitter
should transmit the LAPD Message frame only
once, or an indefinite number of times at one-second intervals.
The Transmit E3 HDLC Control block allows the user
to configure the LAPD Transmitter to transmit this
LAPD Message frame only once, or an indefinite
number of times at one-second intervals. The user
implements this configuration by writing the appropriate value into Bit 3 (Auto Retransmit) within the Tx E3
LAPD Configuration Register (Address = 0x33), as
depicted below.
)
TXE3 LAPD CONFIGURATION REGISTER (ADDRESS = 0X33)
BIT 7
BIT 6
BIT 5
BIT 4
Not Used
BIT 3
BIT 2
BIT 1
BIT 0
Auto
Retransmit
Not Used
TxLAPD
Msg Length
TxLAPD
Enable
RO
RO
RO
RO
R/W
RO
R/W
R/W
0
0
0
0
1
0
0
0
If the user writes a “1” into this bit-field, then the
LAPD Transmitter will transmit the LAPD Message
frame repeatedly at one-second intervals until the
LAPD Transmitter is disabled.
If the user writes a “0” into this bit-field, then the
LAPD Transmitter will transmit the LAPD Message
frame only once. Afterwards, the LAPD Transmitter
will halt its transmission until the user invokes the
Transmit LAPD Message frame command, once
again.
STEP 5 - Enabling the LAPD Transmitter
Prior to the transmission of any data via the LAPD
Transmitter, the LAPD Transmitter must be enabled.
This is accomplished by writing a "1" to bit 0 (TxLAPD
Enable) of the Tx E3 LAPD Configuration Register, as
depicted below.
TRANSMIT E3 LAPD CONFIGURATION REGISTER (ADDRESS = 0X33)
BIT 7
BIT 6
BIT 5
BIT 4
Not Used
BIT 3
BIT2
BIT 1
BIT 0
Auto
Retransmit
Not Used
TxLAPD
Msg Length
TxLAPD
Enable
R/O
R/O
R/O
E/O
R/W
R/O
R/W
R/W
0
0
0
0
X
0
X
1
If the user writes a “0” into this bit-field, then the
LAPD Transmitter will be enabled, and the LAPD
Transmitter will immediately begin to transmit a continuous stream of Flag Sequence octets (0x7E), via
the “N” bit-field of each outbound E3 frame.
Conversely, if the user writes a “1” into this bit-field,
then the LAPD Transmitter will be disabled. The
Transmit E3 Framer block will automatically insert a
“1” into the “N” bit-field, within each outbound E3
frame. No transmission of PMDL data will occur.
STEP 7 - Initiate the Transmission
At this point, the user should have written the PMDL
message into the on-chip Transmit LAPD Message
buffer and the type of LAPD Message that is desired
to be transmitted should have been specified. Finally,
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the user should have enabled the LAPD Transmitter.
The only remaining to do is initiate the transmission of
this message. This process is initiated by writing a “1”
to Bit 3 (Tx DL Start) within the Tx E3 LAPD Status
and Interrupt Register (Address = 0x34), as depicted
below.
)
TXE3 LAPD STATUS AND INTERRUPT REGISTER (ADDRESS = 0X34)
BIT 7
BIT 6
BIT 5
BIT 4
Not Used
BIT 3
BIT 2
BIT 1
BIT 0
TxDL Start
TxDL Busy
TxLAPD
Interrupt
Enable
TxLAPD
Interrupt
Status
RO
RO
RO
RO
R/W
RO
R/W
RUR
0
0
0
0
0
0
0
0
A “0” to “1” transition in Bit 3 (Tx DL Start) in this register, initiates the transmission of LAPD Message
frames. At this point, the LAPD Transmitter will begin
to search through the PMDL message, which is residing within the Transmit LAPD Message buffer. If the
LAPD Transmitter finds any string of five (5) consecutive “1’s” in the PMDL Message then the LAPD Transmitter will insert a “0” immediately following these
strings of consecutive “1’s”. This procedure is known
as stuffing. The purpose of PMDL Message stuffing is
to insure that the user’s PMDL Message does not
contain strings of data that mimic the Flag Sequence
octet (e.g., six consecutive “1’s”) or the ABORT Sequence octet (e.g., seven consecutive “1’s”). Afterwards, the LAPD Transmitter will begin to encapsulate the PMDL Message, residing in the Transmit
LAPD Message buffer, into a LAPD Message frame.
Finally, the LAPD Transmitter will fragment the out-
bound LAPD Message frame into bits and will begin
to transport these bits via the N bit-field within each
outbound E3 frame.
While the LAPD Transmitter is transmitting this LAPD
Message frame, the TxDL Busy bit-field (Bit 2) within
the Tx E3 LAPD Status and Interrupt Register, will be
set to “1”. This bit-field allows the user to poll the status of the LAPD Transmitter. Once the LAPD Transmitter has completed the transmission of the LAPD
Message, then this bit-field will toggle back to “0”.
The user can configure the LAPD Transmitter to interrupt the local Microprocessor/Microcontroller upon
completion of transmission of the LAPD Message
frame, by setting bit-field “1” (TxLAPD Interrupt Enable) within the Tx E3 LAPD Status and Interrupt register (Address = 0x34). to “1” as depicted below.
)
TXE3 LAPD STATUS AND INTERRUPT REGISTER (ADDRESS = 0X34)
BIT 7
BIT 6
BIT 5
BIT 4
Not Used
BIT 3
BIT 2
BIT 1
BIT 0
TxDL Start
TxDL Busy
TxLAPD
Interrupt
Enable
TxLAPD
Interrupt
Status
RO
RO
RO
RO
R/W
RO
R/W
RUR
0
0
0
0
X
X
1
X
‘The purpose of t his interrupt is to let the Microprocessor/Microcontroller know that the LAPD Transmitter is available and ready to transmit a LAPD Message frame (which contains a new PMDL Message)
to the remote terminal equipment. Bit 0 (Tx LAPD Interrupt Status) within the Tx E3 LAPD Status and Interrupt Register will reflect the status for the Transmit
LAPD Interrupt.
NOTE: This bit-field will be reset upon reading this register.
Summary of Operating the LAPD Transmitter
Once the user has invoked the TxDL Start command,
the LAPD Transmitter will do the following.
• Generate the four octets of the LAPD Message
frame header (e.g., the Flag Sequence, SAPI, TEI,
Control, etc.,) and insert them into the header byte
positions within the LAPD Message frame.
• It will read in the contents of the Transmit LAPD
Message buffer (e.g., the PMDL Message data)
and insert it into the Information Payload portion of
the LAPD Message frame.
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• Compute the 16-bit Frame Check Sequence (FCS)
value of the LAPD Message frame (e.g, of the
LAPD Message header and Payload bytes) and
insert this value into the FCS value octet positions
within the LAPD Message frame.
• Append a trailer Flag Sequence octet to the end of
the LAPD Message frame (following the 16-bit FCS
octets).
• Fragment the resulting LAPD Message frame into
bits and begin inserting these bits into the “N” bitfield within each outbound E3 frame.
• Complete the transmission of the overhead bytes,
information payload byte, FCS value, and the trailing Flag Sequence octets via the Transmit E3
Framer block.
Once the LAPD Transmitter has completed its transmission of the LAPD Message frame, the Framer will
generate an Interrupt to the MIcroprocessor/Microcontroller (if enabled). Afterwards, the LAPD Transmitter will either halt its transmission of LAPD Message frames or will proceed to retransmit the LAPD
Message frame, repeatedly at one-second intervals.
In between these transmissions of the LAPD Message frames, the LAPD Transmitter will be sending a
continuous stream of Flag Sequence bytes. The
áç
LAPD Transmitter will continue this behavior until the
user has disabled the LAPD Transmitter by writing a
“1” into bit 3 (No Data Link) within the Tx E3 Configuration register.
NOTE: In order to prevent the user’s data (e.g., the PMDL
Message within the LAPD Message frame) from mimicking
the Flag Sequence byte or an ABORT Sequence, the LAPD
Transmitter will parse through the PMDL Message data and
insert a “0” into this data, immediately following the detection of five (5) consecutive “1’s” (this stuffing occurs while
the PMDL message data is being read in from the Transmit
LAPD Message frame. The Remote LAPD Receive (See
Section 4.3.5) will have the responsibility of checking the
newly received PMDL messages for a string of five (5) consecutive “1’s” and removing the subsequent “0” from the
payload portion of the incoming LAPD Message.
Figure 118 presents a flow chart diagram. Figure 118
depicts the procedure (in white boxes) that the user
should use in order to transmit a PMDL message via
the LAPD Transmitter, when the LAPD Transmitter is
configured to retransmit the LAPD Message frame,
repeatedly at One-Second intervals. This figure also
indicates (via the Shaded boxes) what the LAPD
Transmitter circuitry will do before and during message transmission.
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FIGURE 118. FLOW CHART DEPICTING HOW TO USE THE LAPD TRANSMITTER
LAPD Transmitter inserts Frame Header
octets in front of the user payload.
START
START
WRITE IN DATA LINK INFORMATION
The user accomplishes this by writing the information
that he/she wishes to transmit (via the LAPD
Transmitter) to locations 0x86through 0xDD, within the
Framer Address Space.
LAPD Transmitter computes the 16 bit FCS
(a CRC-16 value) and inserts it into the LAPD
Message, following the user payload
LAPD Transmitter appends a Flag Sequence
Trailer octet to the end of the LAPD Message
(after the 16 bit FCS).
CONFIGURE THE N-BIT to CARRYLAPD
Messages
This is accomplished by setting “TxNSourceSel[1:0]
= “1, 0”
Is
5 consecutive
“1s” detected
?
ENABLE THE LAPD
TRANSMITTER FOR TRANSMISSION
This is accomplished by writing 00000xx1bto the Tx
E3 LAPD Configuration Register.(where xx dictates
LAPD Message Type)
No
No
INITIATE TRANSMISSION OF LAPD
MESSAGE
NOTE: In Figure 118, the unshaded boxes depict the tasks
that the user must perform. The shaded boxes present the
resulting tasks that the Transmit HDLC Controller block will
perform.
The Mechanics of Transmitting a New LAPD Message frame, if the LAPD Transmitter has been
configured to re-transmit the LAPD Message
frame, repeatedly, at One-Second intervals.
If the LAPD Transmitter has been configured to retransmit the LAPD Message frame repeatedly at onesecond intervals, then it will do the following (at onesecond intervals).
• Stuff the PMDL Message.
• Read in the stuffed PMDL Message from the Transmit LAPD Message buffer.
• Transmit this LAPD Message frame to the Remote
Terminal Equipment.
Insert a “0” after the
string of 5 consecutive
“1s”
Yes
END
Generate Interrupt
LAPD Transmitter will
continue to transmit
Flag Sequence octets.
This is accomplished by writing 000010x0bto the Tx
E3 LAPD Status/InterruptRegister. (where x indicates
the user’s choiceto enable/disable “LAPD Message
Transfer Complete” Interrupt
• Encapsulate this stuffed PMDL Message into a
LAPD Message frame.
Is
Message
Transmission
Complete
?
Yes
If another (e.g., a different) PMDL Message is to be
transmitted to the Remote Terminal Equipment, this
new message will have to be written into the Transmit
LAPD Message buffer, via the Microprocessor Interface block of the Framer IC. However, care must be
taken when writing this new PMDL message. If this
message is written into the Transmit LAPD Message
buffer at the wrong time (with respect to these Onesecond LAPD Message frame transmissions), the user’s action could interfere with these transmissions,
thereby causing the LAPD Transmitter to transmit a
corrupted message to the Remote Terminal Equipment. In order to avoid this problem, while writing the
new message into the Transmit LAPD Message buffer, the user should do the following.
1. Configure the Framer to automatically reset activated interrupts.
The user can do this by writing a “1” into Bit 3 within
the Framer Operating Mode register (Address =
0x00), as depicted below.
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FRAMER OPERATING MODE REGISTER (ADDRESS = 0X00)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
Local Loopback
DS3/E3*
Internal
LOS
Enable
RESET
Interrupt
Enable Reset
Frame Format
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
1
0
1
0
1
1
This action will prevent the LAPD Transmitter from
generating its own One-Second interrupt (following
each transmission of the LAPD Message frame).
BIT 1
BIT 0
TimRefSel[1:0]
This can be done by writing a “1” into Bit 0 (One-Second Interrupt Enable) within the Block Interrupt Enable Register, as depicted below.
2. Enable the One-Second Interrupt
BLOCK INTERRUPT ENABLE REGISTER (ADDRESS = 0X04)
BIT 7
BIT 6
BIT 5
RxDS3/E3
Interrupt
Enable
BIT 4
BIT 3
BIT 2
Not Used
BIT 1
BIT 0
TxDS3/E3
Interrupt
Enable
One-Second
Interrupt
Enable
R/W
RO
RO
RO
RO
RO
R/W
R/W
0
0
0
0
0
0
0
0
3. Write the new message into the Transmit LAPD
Message buffer immediately after the occurrence
of the One-Second Interrupt
By synchronizing the writes to the Transmit LAPD
Message buffer to occur immediately after the occur-
rence of the One-Second Interrupt, the user avoids
conflicting with the One-Second transmission of the
LAPD Message frame, and will transmit the correct
(uncorrupted) PMDL Message to the Remote LAPD
Receiver.
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5.2.4
REV. P1.1.8
The Transmit E3 Framer Block
However, the Transmit E3 Framer block will accept
(and insert) data from the Transmit Overhead Data Input Interface for both the “A” and “N” bit-fields.
5.2.4.1 Brief Description of the Transmit E3
Framer
The Transmit E3 Framer block accepts data from any
of the following four sources, and uses it to form the
E3 data stream.
If the user's local Data Link Equipment activates the
Transmit Overhead Data Input Interface block and
writes data into this interface for these bits or bytes,
then the Transmit E3 Framer block will insert this data
into the appropriate overhead bit/byte-fields, within
the outbound E3 frames.
• The Transmit Payload Data Input block
• The Transmit Overhead Data Input block
• The Transmit HDLC Controller block
Handling of data from the Transmit HDLC Controller Block
• The Internal Overhead Data Generator
The manner in how the Transmit E3 Framer block
handles data from each of these sources is described
below.
The exact manner in how the Transmit E3 Framer
handles data from the Transmit HDLC Controller
block depends upon whether the Transmit HDLC
Controller is activated or not. If the Transmit DS3
HDLC Controller block is not activated, then the
Transmit E3 Framer block will insert a “1” into each
“N” bit-field, within each outbound E3 frame.
Handling of data from the Transmit Payload Data
Input Interface
For E3 applications, all data that is input to the Transmit Payload Data Input Interface will be inserted into
the payload bit positions within the outbound E3
frames.
If the Transmit E3 HDLC Controller block is activated,
then data will be inserted into the “N” bit-fields as described in Section 4.2.3.
Handling of data from the Internal Overhead Bit
Generator
By default, the Transmit E3 Framer block will internally generate the overhead bytes. However, if the Terminal Equipment inserts its own values for the overhead
bits or bytes (via the Transmit Overhead Data Input
Interface) or if the user enables and employs the
Transmit E3 HDLC Controller block, then these internally generated overhead bytes will be overwritten.
Handling of data from the Transmit Overhead Data Input Interface
5.2.4.2 Detailed Functional Description of the
Transmit E3 Framer Block
The Transmit E3 Framer receives data from the following three sources and combines them together to
form the E3 data stream.
• The Transmit Payload Data Input Interface block.
• The Transmit Overhead Data Input Interface block
• The Transmit HDLC Controller block.
• The Internal Overhead Data Generator.
For E3 applications, the Transmit E3 Framer block automatically generates and inserts the framing alignment bytes (e.g., the 10 bit FAS framing alignment
signal) into the outbound E3 frames. Hence, the
Transmit E3 Framer block will not accept data from
the Transmit OH Data Input Interface block for the
FAS signal.
Afterwards, this E3 data stream will be routed to the
Transmit E3 LIU Interface block, for further processing.
Figure 119 presents a simple illustration of the Transmit E3 Framer block, along with the associated paths
to the other functional blocks within the chip.
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FIGURE 119. A SIMPLE ILLUSTRATION OF THE TRANSMIT E3 FRAMER BLOCK AND THE ASSOCIATED PATHS TO
FUNCTIONAL BLOCKS
OTHER
Transmit HDLC
Controller/Buffer
Transmit
Transmit
E3
E3Framer
Framer
Block
Block
Transmit Overhead
Data Input Interface
To Transmit E3 LIU Interface Block
Transmit Payload Data
Input Interface
In addition to taking data from multiple sources and
multiplexing them, in appropriate manner, to create
the outbound E3 frames, the Transmit E3 Framer
block has the following roles.
• Generating Alarm Conditions
• Generating Errored Frames (for testing purposes)
• Routing outbound E3 frames to the Transmit E3 LIU
Interface block
Each of these additional roles are discussed below.
5.2.4.2.1 Generating Alarm Conditions
The Transmit E3 Framer block permits the user to, by
writing the appropriate data into the on-chip registers,
to override the data that is being written into the
Transmit Payload Data and Overhead Data Input Interfaces and transmit the following alarm conditions.
• Generate the Yellow Alarms (or FERF indicators)
• Manipulate the A-bit, by forcing it to “0”.
• Generate the AIS Pattern
• Generate the LOS pattern
• Generate FERF (Yellow) Alarms, in response to
detection of a Red Alarm condition (via the Receive
Section of the XRT72L53).
The procedure and results of generating any of these
alarm conditions is presented below.
The user can exercise each of these options by writing the appropriate data to the Tx E3 Configuration
Register (Address = 0x30). The bit format of this register is presented below.
TXE3 CONFIGURATION REGISTER (ADDRESS = 0X30)
BIT 7
Tx
BIP-4
Enable
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
Tx AIS
Enable
Tx LOS
Enable
Tx FAS
Source
Select
TxASourceSel[1:0]
TxNSourceSel[1:0]
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
0
0
Bit-fields 1 and 2 permit the user to transmit various
alarm conditions to the remote terminal equipment.
The role/function of each of these two bit-fields within
the register, are discussed below.
5.2.4.2.1.1 Tx AIS Enable - Bit 2
This read/write bit field permits the user to force the
transmission of an AIS (Alarm Indication Signal) pat-
tern to the remote terminal equipment via software
control. If the user opts to transmit an AIS pattern,
then the Transmit Section of the Framer IC will begin
to transmit an unframed all ones pattern to the remote terminal equipment. Table 55 presents the relationship between the contents of this bit-field, and the
resulting Framer action.
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TABLE 55: THE RELATIONSHIP BETWEEN THE CONTENTS OF BIT 2 (TX AIS ENABLE) WITHIN THE TX E3
CONFIGURATION REGISTER, AND THE RESULTING TRANSMIT E3 FRAMER BLOCK'S ACTION
BIT 2
TRANSMIT E3 FRAMER'S ACTION
Normal Operation:
0
The Transmit Section of the XRT72L53 Framer IC will transmit E3 traffic based upon data that it accepts via
the Transmit Payload Data Input Interface block, the Transmit Overhead Data Input Interface block, the Transmit HDLC Controller block and internally generated overhead bytes.
1
Transmit AIS Pattern:
The Transmit E3 Framer block will overwrite the E3 traffic, within an Unframed “All Ones” pattern.
NOTE: This bit is ignored whenever the TxLOS bit-field is
set.
5.2.4.2.1.2 Transmit LOS Enable - Bit 1
This read/write bit field allows the user to transmit an
LOS (Loss of Signal) pattern to the remote terminal,
upon software control. Table 56 relates the contents
of this bit field to the Transmit E3 Framer block's action.
TABLE 56: THE RELATIONSHIP BETWEEN THE CONTENTS OF BIT 1 (TX LOS) WITHIN THE TX E3 CONFIGURATION
REGISTER, AND THE RESULTING TRANSMIT E3 FRAMER BLOCK'S ACTION
BIT 1
0
TRANSMIT E3 FRAMER'S ACTION
Normal Operation:
The Overhead bits are either internally generated, or they are inserted via the Transmit Overhead Data Input
Interface or the Transmit HDLC Controller blocks. The Payload bits are received from the Transmit Payload
Data Input Interface.
1
Transmit LOS Pattern:
When this command is invoked the Transmit E3 Framer will do the following.
• Set all of the overhead bytes to "0" (including the FA1 and FA2 bytes)
Overwrite the E3 payload bits with an "all zeros" pattern.
NOTE: When this bit is set, it overrides all of the other bits in
this register.
5.2.4.2.1.3 Transmitting FERF (Far-End
Receive Failure) Indicator or Yellow Alarm
The XRT72L53 Framer IC permits the user to control
the state of the “A” bit-field, within each outbound E3
frame. This can be achieved by writing the appropriate data into the TxASource[1:0] bit-fields within the
Tx E3 Configuration Register, as illustrated below.
TXE3 CONFIGURATION REGISTER (ADDRESS = 0X30)
BIT 7
Tx
BIP-4
Enable
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
Tx AIS
Enable
Tx LOS
Enable
Tx FAS
Source
Select
TxASourceSel[1:0]
TxNSourceSel[1:0]
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
X
X
0
0
0
0
0
The following table presents the relationship between
the contents of TxASource[1:0] and the resulting
source of the “A” bit.
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TXASOURCESEL[1:0]
SOURCE OF A BIT
00
TxE3 Service Bits Register (Address = 0x35)
01
Transmit Overhead Data Input Interface
10
Transmit Payload Data Input Interface
11
Functions as a FEBE (Far-End-Block Error) bit-field.
This bit-field is set to "0", if the Near-End Receive Section (within this chip) detects no BIP-4
Errors within the incoming E3 frames.
This bit-field is set to "1", if the Near-End Receive Section (within this chip) detects a BIP-4
Error within the incoming E3 frame.
STEP 1 - Write a “1” into Bit 1 (A Bit) within the Tx
E3 Service Bits Register, as indicated below.
Hence, if a Yellow Alarm condition needs to be transmitted to the Remote Terminal Equipment, this can be
accomplished by executing the following steps.
TXE3 SERVICE BITS REGISTER (ADDRESS = 0X35)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
A Bit
N Bit
Not Used
RO
RO
RO
RO
RO
RO
R/W
R/W
0
0
0
0
0
0
1
0
STEP 2 - Write the value “00” into the TxASource[1:0] bit-fields within the Tx E3 Configuration Register, as indicated below.
TXE3 CONFIGURATION REGISTER (ADDRESS = 0X30)
BIT 7
Tx BIP-4
Enable
BIT 6
BIT 5
TxASourceSel[1:0]
BIT 4
BIT 3
TxNSourceSel[1:0]
BIT 2
BIT 1
BIT 0
Tx AIS
Enable
Tx LOS
Enable
Tx FAS
Source Select
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
X
0
0
X
X
X
X
X
These two steps will cause the Transmit E3 Framer
block to read in the contents of Bit 1 (within the Tx E3
Service Bit register) and insert it into the “A” bit-field
within the outbound E3 data stream. Hence, the “A”
bit will be set to “1”, which will be interpreted as an
Alarm Condition, by the Remote Terminal Equipment.
The XRT72L53 Framer IC permits the user to (1) configure the Transmit Section of the device to insert the
BIP-4 value into each outbound E3 frame and (2) to
configure the Receive Section of the device to compute and verify the BIP-4 value, within each inbound’
E3 frame.
5.2.4.2.2 Configuring the Transmit E3 Framer
block to insert the BIP-4 nibble into each outbound E3 frame.
These two configurations are accomplished by setting
bit 7 (Tx BIP-4 Enable), within the Tx E3 Configuration Register, to “1”, as indicated below.
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TXE3 CONFIGURATION REGISTER (ADDRESS = 0X30)
BIT 7
Tx
BIP-4
Enable
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
Tx AIS
Enable
Tx LOS
Enable
Tx FAS
Source
Select
TxASourceSel[1:0]
TxNSourceSel[1:0]
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
1
X
X
X
X
X
X
X
Setting this bit-field to “1” accomplishes the following.
• TxE3 FAS Error Mask Register - 0
• It configures the Transmit E3 Framer block to compute the BIP-4 value of a given E3 frame, and insert
in to the very last nibble, within the very next outbound E3 frame. (Hence, bits 1533 through 1536,
within each E3 frame, will function as the BIP-4
value)
• TxE3 FAS Error Mask Register - 1
• It configures the Receive E3 Framer block to compute and verify the BIP-4 value of each incoming
E3 frame.
5.2.4.2.3 Generating Errored E3 Frames
The Transmit E3 Framer block permits the user to insert errors into the framing and error detection overhead bites (e.g., the FAS pattern, and the BIP-4 nibble) of the outbound E3 data stream in order to support Remote Terminal Equipment testing. The user
can exercise this option by writing data into any of the
following registers.
• TxE3 BIP-4 Error Mask Register
Inserting Errors into the FAS pattern of the outbound’ E3 frames.
The user can insert errors into the FAS pattern bits, of
each outbound E3 frame, by writing the appropriate
data into either the TxE3 FAS Error Mask Register - 0
or TxE3 FAS Error Mask Register - 1.
As the Transmit E3 Framer block formulates the outbound E3 frames, the contents of the FAS pattern bits
are automatically XORed with the contents of these
two registers. The results of this XOR operation is
written back into the corresponding bit-field within the
outbound E3 frame, and is transmitted to the Remote
Terminal Equipment. Therefore, if the user does not
wish to modify any of these bits, then these registers
must contain all “0’s” (the default value).
TXE3 FAS ERROR MASK REGISTER - 0 (ADDRESS = 0X48)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
Not Used
BIT 2
BIT 1
BIT 0
TxFAS_Error_Mask_Upper[4:0]
RO
RO
RO
R/W
R/W
R/W
R/W
R/W
0
0
0
X
X
X
X
X
BIT 2
BIT 1
BIT 0
TXE3 FAS ERROR MASK REGISTER - 1 (ADDRESS = 0X49)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
Not Used
TxFAS_Error_Mask_Lower[4:0]
RO
RO
RO
R/W
R/W
R/W
R/W
R/W
0
0
0
X
X
X
X
X
Inserting Errors into the BIP-4 nibble, within each
outbound E3 frame.
The user can insert errors into the BIP-4 nibble, within
each outbound E3 frame, by writing the appropriate
data into the TxE3 BIP-4 Error Mask Register.
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Equipment. Therefore, if the user does not wish to
modify any of these bits, then this register must contain all “0’s” (the default value).
As the Transmit E3 Framer block formulates the outbound E3 frames, the contents of the BIP-4 bits are
automatically XORed with the contents of this register. The results of this XOR operation is written back
into the corresponding bit-field within the outbound
E3 frame, and is transmitted to the Remote Terminal
NOTE: This register is only active if the XRT72L53 Framer
IC has been configured to insert the BIP-4 nibble into each
outbound E3 frame.
TXE3 BIP-4 ERROR MASK REGISTER (ADDRESS = 0X4A)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
Not Used
BIT 2
BIT 1
BIT 0
TxBIP-4 Mask[3:0]
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
0
0
5.2.5 The Transmit E3 Line Interface Block
The XRT72L53 Framer IC is a digital device that
takes E3 payload and overhead bit information from
some terminal equipment, processes this data and ultimately, multiplexes this information into a series of
outbound E3 frames. However, the XRT72L53 Framer IC lacks the current drive capability to be able to directly transmit this E3 data stream through some
transformer-coupled coax cable with enough signal
strength for it to be received by the remote receiver.
Therefore, in order to get around this problem, the
Framer IC requires the use of an LIU (Line Interface
Unit) IC. An LIU is a device that has sufficient drive
capability, along with the necessary pulse-shaping
circuitry to be able to transmit a signal through the
transmission medium in a manner that it can be reliably received by the far-end receiver. Figure 120 presents a circuit drawing depicting the Framer IC interfacing to an LIU (XRT7300 DS3/E3/STS-1 Transmit
LIU).
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FIGURE 120. APPROACH TO INTERFACING THE XRT72L53 FRAMER IC TO THE XRT73L03 DS3/E3/STS-1 LIU
RxAVDD_0
TxAVDD_0
DVDD_0
C3
C4
0.01uF
C5
0.01uF
0.01uF
C2
0.01uF
U21
Rx_AIS_Ch_0
RxRED_ALARM_0
Rx_OOF_Ch_0
Rx_LOS_Ch_0
F20
D20
F19
T20
RxFRAME_0
RxFRAME_CLK_0
RxDATA_IN_0
48
RxAIS_0
RxRED_0
RxOOF_0
RxLOS_0
RxFrame_0
RxClk_0
RxSer_0
MOTO
R8 4.7K
RxPOS_0
RxNEG_0
F2
67
42
51
R7 100
F3
50
F1
49
B8
D9
57
55
C7
A5
C6
C9
C3
61
62
63
64
96
RxAVDD0
TxAVDD0
RxDVDD0
TxAVDD0
28
37
LOSTHR_0
HOST/HW
RPOS0
RTIP0
J1
72
6 T2 1
RNEG0
D[7:0]
D7
D6
D5
D4
D3
D2
D1
D0
A[10:0]
M20
M19
M18
M17
N20
N19
N18
P20
P19
P18
R20
J17
R19
V20
P17
R18
H20
READY_OUT*
ALE
RD*
WR*
XRT72L53_CS*
XRT72L53_INT*
T19
HW_RESET*
R9
T18
A10
A9
A8
A7
A6
A5
A4
A3
A2
A1
A0
Rdy_Dtck
ALE_AS
RDB_DS
WRB_RW
CSB
INT
RESETB
RxLineClk_0
RLOL_0
ExtLOS_0
LLOOP_0
REQB_0
TAOS_0
DMO_0
TxLEV_0
RLOOP_0
ENCODIS_0 (TxOFF_0)
TxPOS_0
B7
RCLK0
RRING0
TxLineClk_0
3
T3001
R2
R1
37.4
37.4
RLOL_0
RLOS_0
CS
SCLK
SDI
SDO
REG_RESET*
C1
0.01uF
XRT71D03_CS* (Optional)
B2
117
C1
33
TxOFF_0
TPDATA_0
TTIP0
R3
29
D1
32
E2
34
47
J2
1 T1 6
TNDATA_0
TCLK_0
EXCLK_0
TRING0
MTIP0
NIBBLEINTF
R4
27
30
1
BNC
3
4
T3001
R5
36
270
100
TxFRAME_0
44.736MHz
TxDATA_OUT_0
4
71
36
TxNEG_0
BNC
2
J19
J20
K17
K18
K19
K20
L20
L18
1
2
70
U19
C5
B5
A3
C4
E20
G 4 TxFrame_0
E18 TxInClk_0
TxSER_0
MRING0
31
R6
270
54
73
RxDGND0
RxAGND0
TxAGND0
TxAGND0
39
26
XRT72L53_Ch_0
XRT73L03IV_Ch_0
The Transmit Section of the XRT72L53 contains a
block which is known as the Transmit E3 LIU Interface
block. The purpose of the Transmit E3 LIU Interface
block is to take the outbound E3 data stream, from
the Transmit E3 Framer block, and to do the following:
1. Encode this data into one of the following line
codes
a. Unipolar (e.g., Single-Rail)
b. AMI (Alternate Mark Inversion)
c. HDB3 (High Density Bipolar - 3)
2. And to transmit this data to the LIU IC.
Figure 121 presents a simple illustration of the Transmit E3 LIU Interface block.
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FIGURE 121. A SIMPLE ILLUSTRATION OF THE TRANSMIT E3 LIU INTERFACE BLOCK
TxPOS
Transmit E3
LIU Interface
Block
From Transmit E3
Framer Block
TxNEG
TxLineClk
od, at the start of each new E3 frame, and will remain
"Low" for the remainder of the frame. Figure 122 presents an illustration of the TxPOS and TxNEG signals
during data transmission while the Transmit E3 LIU
Interface block is operating in the Unipolar mode. This
mode is sometimes referred to as Single Rail mode
because the data pulses only exist in one polarity:
positive.
The Transmit E3 LIU Interface block can transmit data
to the LIU IC or other external circuitry via two different output modes: Unipolar or Bipolar. If the user selects Unipolar (or Single Rail) mode, then the contents of the E3 Frame is output, in a binary (NRZ
manner) data stream via the TxPOS pin to the LIU IC.
The TxNEG pin will only be used to denote the frame
boundaries. TxNEG will pulse "High" for one bit peri-
FIGURE 122. THE BEHAVIOR OF TXPOS AND TXNEG SIGNALS DURING DATA TRANSMISSION WHILE THE TRANSMIT
DS3 LIU INTERFACE IS OPERATING IN THE UNIPOLAR MODE
Data
1
0
1
1
0
0
1
0
0
1
1
1
0
1
0
1
0
0
1
1
1
0
0
1
TxPOS
TxNEG
TxLineClk
Frame Boundary
When the Transmit E3 LIU Interface block is operating
in the Bipolar (or Dual Rail) mode, then the contents
of the E3 Frame is output via both the TxPOS and TxNEG pins. If the Bipolar mode is chosen, then E3 data can be transmitted to the LIU via one of two differ-
ent line codes: Alternate Mark Inversion (AMI) or High
Density Bipolar -3 (HDB3). Each one of these line
codes will be discussed below. Bipolar mode is sometimes referred to as Dual Rail because the data pulses occur in two polarities: positive and negative. The
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TxPOS - Transmit Positive Polarity Pulse: The
Transmit E3 LIU Interface block will assert this output
to the LIU IC when it desires for the LIU to generate
and transmit a positive polarity pulse to the remote
terminal equipment.
TxLineClk - Transmit Line Clock: The LIU IC uses
this signal from the Transmit E3 LIU Interface block to
sample the state of its TxPOS and TxNEG inputs.
The results of this sampling dictates the type of pulse
(positive polarity, zero, or negative polarity) that it will
generate and transmit to the remote Receive E3
Framer.
TxNEG - Transmit Negative Polarity Pulse: The
Transmit E3 LIU Interface block will assert this output
to the LIU IC when it desires for the LIU to generate
and transmit a negative polarity pulse to the remote
terminal equipment.
5.2.5.1 Selecting the various Line Codes
The user can select either the Unipolar Mode or Bipolar Mode by writing the appropriate value to Bit 3 of
the I/O Control Register (Address = 0x01), as shown
below.
role of the TxPOS, TxNEG and TxLineClk output
pins, for this mode are discussed below.
I/O CONTROL REGISTER (ADDRESS = 0X01)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT2
BIT 1
BIT 0
Disable TxLOC
LOC
Disable
RxLOC
AMI/ZeroSup*
Unipolar/
Bipolar*
TxLine CLK
Invert
RxLine CLK
Invert
Reframe
R/W
RO
R/W
R/W
R/W
R/W
R/W
R/W
1
0
1
0
0
0
0
0
Table 57 relates the value of this bit field to the Transmit E3 LIU Interface Output Mode.
TABLE 57: THE RELATIONSHIP BETWEEN THE CONTENT OF BIT 3 (UNIPOLAR/BIPOLAR*) WITHIN THE UNI I/O
CONTROL REGISTER AND THE TRANSMIT E3 FRAMER LINE INTERFACE OUTPUT MODE
BIT 3
TRANSMIT E3 FRAMER LIU INTERFACE OUTPUT MODE
0
Bipolar Mode: AMI or HDB3 Line Codes are Transmitted and Received
1
Unipolar (Single Rail) Mode of transmission and reception of E3 data is selected.
NOTES:
1. The default condition is the Bipolar Mode.
2. This selection also effects the operation of the
Receive E3 LIU Interface block
5.2.5.1.1 The Bipolar Mode Line Codes
If the Framer is set to operate in the Bipolar Mode,
then the DS3 data-stream can be set to be transmitted via the AMI (Alternate Mark Inversion) or the
HDB3 Line Codes. The definition of AMI and HDB3
line codes follow.
5.2.5.1.1.1 The AMI Line Code
AMI or Alternate Mark Inversion, means that consecutive "one's" pulses (or marks) will be of opposite polarity with respect to each other. The line code in-
volves the use of three different amplitude levels: +1,
0, and -1. +1 and -1 amplitude signals are used to
represent one's (or mark) pulses and the "0" amplitude pulses (or the absence of a pulse) are used to
represent zeros (or space) pulses. The general rule
for AMI is: if a given mark pulse is of positive polarity,
then the very next mark pulse will be of negative polarity and vice versa. This alternating-polarity relationship exists between two consecutive mark pulses, independent of the number of 'zeros' that may exist between these two pulses. Figure 123 presents an illustration of the AMI Line Code as would appear at the
TxPOS and TxNEG pins of the Framer, as well as the
output signal on the line.
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FIGURE 123. ILLUSTRATION OF AMI LINE CODE
Data 1 0 1 1 0 0 0 1 0 1 1 1 1 0 1 1 0 1 1 0 0 1 1 0 0 0 0 1
TxPOS
TxNEG
Line Signal
NOTE: One of the main reasons that the AMI Line Code
has been chosen for driving transformer-coupled media is
that this line code introduces no dc component, thereby
minimizing dc distortion in the line.
causing the clock and data recovery process of the
receiver to fail. Therefore, some approach is needed
to insure that such a long string of consecutive zeros
can never happen. One such technique is HDB3 encoding. HDB3 (or High Density Bipolar - 3) is a form
of AMI line coding that implements the following rule.
5.2.5.1.1.2 The HDB3 Line Code
The Transmit E3 Framer and the associated LIU IC
combine the data and timing information (originating
from the TxLineClk signal) into the line signal that is
transmitted to the remote receiver. The remote receiver has the task of recovering this data and timing
information from the incoming E3 data stream. Many
clock and data recovery schemes rely on the use of
Phase Locked Loop technology. Phase-Locked-Loop
(PLL) technology for clock recovery relies on transitions in the line signal, in order to maintain lock with
the incoming E3 data stream. However, PLL-based
clock recovery scheme, are vulnerable to the occurrence of a long stream of consecutive zeros (e.g., the
absence of transitions). This scenario can cause the
PLL to lose lock with the incoming E3 data, thereby
In general the HDB3 line code behaves just like AMI
with the exception of the case when a long string of
consecutive zeros occur on the line. Any string of 4
consecutive zeros will be replaced with either a
"000V" or a "B00V" where "B" refers to a Bipolar
pulse (e.g., a pulse with a polarity that is compliant
with the AMI coding rule). And "V" refers to a Bipolar
Violation pulse (e.g., a pulse with a polarity that violates the alternating polarity scheme of AMI.) The decision between inserting an "000V" or a "B00V" is
made to insure that an odd number of Bipolar (B)
pulses exist between any two Bipolar Violation (V)
pulses. Figure 124 presents a timing diagram that illustrates examples of HDB3 encoding.
FIGURE 124. ILLUSTRATION OF TWO EXAMPLES OF HDB3 ENCODING
Data
1
0
1
1
0
0
0
0
0
0
0
V
0
1
1
1
1
0
1
1
0
1
1
0
0
1
1
0
0
0
0
B
0
0
V
TxPOS
TxNEG
TxLineClk
Line Signal
The user chooses between AMI or HDB3 line coding
by writing to bit 4 of the I/O Control Register (Address
= 0x01), as shown below.
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I/O CONTROL REGISTER (ADDRESS = 0X01)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT2
BIT 1
BIT 0
Disable TxLOC
LOC
Disable
RxLOC
AMI/ZeroSup*
Unipolar/
Bipolar*
TxLine CLK
Invert
RxLine CLK
Invert
Reframe
R/W
RO
R/W
R/W
R/W
R/W
R/W
R/W
1
0
1
0
0
0
0
0
Table 58 relates the content of this bit-field to the Bipolar Line Code that E3 Data will be transmitted and
received at.
NOTES:
1. This bit is ignored if the Unipolar mode is selected.
2. This selection also effects the operation of the
Receive E3 LIU Interface block
TABLE 58: THE RELATIONSHIP BETWEEN BIT 4 (AMI/
HDB3*) WITHIN THE I/O CONTROL REGISTER AND THE
BIPOLAR LINE CODE THAT IS OUTPUT BY THE TRANSMIT
E3 LIU INTERFACE BLOCK
5.2.5.2 TxLineClk Clock Edge Selection
The Framer also allows the user to specify whether
the E3 output data (via TxPOS and/or TxNEG output
pins) is to be updated on the rising or falling edges of
the TxLineClk signal. This selection is made by writing to bit 2 of the I/O Control Register, as depicted below.
BIT 4
BIPOLAR LINE CODE
0
HDB3
1
AMI
II/O CONTROL REGISTER (ADDRESS = 0X01)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT2
BIT 1
BIT 0
Disable TxLOC
LOC
Disable
RxLOC
AMI/ZeroSup*
Unipolar/
Bipolar*
TxLine CLK
Invert
RxLine CLK
Invert
Reframe
R/W
RO
R/W
R/W
R/W
R/W
R/W
R/W
1
0
1
0
0
0
0
0
Table 59 relates the contents of this bit field to the
clock edge of TxClk that E3 Data is output on the TxPOS and/or TxNEG output pins.
TABLE 59: THE RELATIONSHIP BETWEEN THE CONTENTS OF BIT 2 (TXLINECLK INV) WITHIN THE I/O CONTROL
REGISTER AND THE TXLINECLK CLOCK EDGE THAT TXPOS AND TXNEG ARE UPDATED ON
BIT 2
0
RESULT
Rising Edge:
Outputs on TxPOS and/or TxNEG are updated on the rising edge of TxLineClk.
See Figure 125 for timing relationship between TxLineClk, TxPOS and TxNEG signals, for this selection.
1
Falling Edge:
Outputs on TxPOS and/or TxNEG are updated on the falling edge of TxLineClk.
See Figure 126 for timing relationship between TxLineClk, TxPOS and TxNEG signals, for this selection.
NOTE: The user will typically make the selection based
upon the set-up and hold time requirements of the Transmit
LIU IC.
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THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
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FIGURE 125. WAVEFORM/TIMING RELATIONSHIP BETWEEN TXLINECLK, TXPOS AND TXNEG - TXPOS AND
TXNEG ARE CONFIGURED TO BE UPDATED ON THE RISING EDGE OF TXLINECLK
t32
TxLineClk
t30
t33
TxPOS
TxNEG
FIGURE 126. WAVEFORM/TIMING RELATIONSHIP BETWEEN TXLINECLK, TXPOS AND TXNEG - TXPOS AND
TXNEG ARE CONFIGURED TO BE UPDATED ON THE FALLING EDGE OF TXLINECLK
t32
TxLineClk
t31
t33
TxPOS
TxNEG
5.2.6 Transmit Section Interrupt Processing
The Transmit Section of the XRT72L53 can generate
an interrupt to the Microprocessor/Microcontroller for
the following reasons.
• Completion of Transmission of LAPD Message
5.2.6.1 Enabling Transmit Section Interrupts
The Interrupt Structure, within the XRT72L53 contains two hierarchical levels:
• Block Level
• Source Level
The Block Level
The Enable State of the Block Level for the Transmit
Section Interrupts dictates whether or not interrupts
(enabled) at the source level, are actually enabled.
The user can enable or disable these Transmit Section interrupts, at the Block Level by writing the appropriate data into Bit 1 (Tx DS3/E3 Interrupt Enable)
within the Block Interrupt Enable register (Address =
0x04), as illustrated below.
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BLOCK INTERRUPT ENABLE REGISTER (ADDRESS = 0X04)
BIT 7
BIT 6
BIT 5
RxDS3/E3
Interrupt
Enable
BIT 4
BIT 3
BIT 2
Not Used
BIT 1
BIT 0
TxDS3/E3
Interrupt
Enable
One-Second
Interrupt
Enable
R/W
RO
RO
RO
RO
RO
R/W
R/W
0
0
0
0
0
0
0
0
Setting this bit-field to “1” enables the Transmit Section (at the Block Level) for Interrupt Generation. Conversely, setting this bit-field to “0” disables the Transmit Section for interrupt generation.
What does it mean for the Transmit Section Interrupts to be enabled or disabled at the Block Level?
Block level, then a given interrupt will still be disabled,
if it is disabled at the source level.
As mentioned earlier, the Transmit Section of the
XRT72L53 Framer IC contains the Completion of
Transmission of LAPD Message Interrupt.
The Enabling/Disabling and Servicing of this interrupt
is presented below.
If the Transmit Section is disabled (for interrupt generation) at the Block Level, then ALL Transmit Section
interrupts are disabled, independent of the interrupt
enable/disable state of the source level interrupts.
If the Transmit Section is enabled (for interrupt generation) at the block level, then a given interrupt will be
enabled at the source level. Conversely, if the Transmit Section is enabled (for interrupt generation) at the
5.2.6.1.1 The Completion of Transmission of
the LAPD Message Interrupt
If the Transmit Section interrupts have been enabled
at the Block level, then the user can enable or disable
the Completion of Transmission of a LAPD Message
Interrupt, by writing the appropriate value into Bit 1
(TxLAPD Interrupt Enable) within the Tx E3 LAPD
Status & Interrupt Register (Address = 0x34), as illustrated below.
TXE3 LAPD STATUS AND INTERRUPT REGISTER (ADDRESS = 0X34)
BIT 7
BIT 6
BIT 5
BIT 4
Not Used
BIT 3
BIT 2
BIT 1
BIT 0
TXDL Start
TXDL Busy
TxLAPD
Interrupt
Enable
TxLAPD
Interrupt
Status
RO
RO
RO
RO
R/W
RO
R/W
RUR
0
0
0
0
0
0
X
0
Setting this bit-field to “1’ enables the Completion of
Transmission of a LAPD Message Interrupt. Conversely, setting this bit-field to “0” disables the Completion of Transmission of a LAPD Message interrupt.
5.2.6.1.2 Servicing the Completion of Transmission of a LAPD Message Interrupt
As mentioned previously, once the user commands
the LAPD Transmitter to begin its transmission of a
LAPD Message, it will do the following.
2.
3.
4.
1. It will parse through the contents of the Transmit
LAPD Message Buffer (located at address locations 0x86 through 0xDD) and search for a string
of five (5) consecutive “1’s”. If the LAPD Transmitter finds a string of five consecutive “1’s” (within
300
5.
the content of the LAPD Message Buffer, then it
will insert a “0” immediately after this string.
It will compute the FCS (Frame Check Sequence)
value and append this value to the back-end of
the user-message.
It will read out of the content of the user (zerostuffed) message and will encapsulate this data
into a LAPD Message frame.
Finally, it will begin transmitting the contents of
this LAPD Message frame via the “N” bits, within
each outbound E3 frame.
Once the LAPD Transmitter has completed its
transmission of this LAPD Message frame (to the
Remote Terminal Equipment), the XRT72L53
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THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. P1.1.8
Framer IC will generate the Completion of Transmission of a LAPD Message Interrupt to the
Microcontroller/Microprocessor. Once the
XRT72L53 Framer IC generates this interrupt, it
will do the following.
• Assert the Interrupt Output pin (INT) by toggling it
“Low”.
• Set Bit 0 (TxLAPD Interrupt Status) within the TxE3
LAPD Status and Interrupt Register, to “1” as illustrated below.
TXE3 LAPD STATUS AND INTERRUPT REGISTER (ADDRESS = 0X34)
BIT 7
BIT 6
BIT 5
BIT 4
Not Used
BIT 3
BIT 2
BIT 1
BIT 0
TXDL Start
TXDL Busy
TxLAPD
Interrupt
Enable
TxLAPD
Interrupt
Status
RO
RO
RO
RO
R/W
RO
R/W
RUR
0
0
0
0
0
0
0
1
The purpose of this interrupt is to alert the Microcontroller/MIcroprocessor that the LAPD Transmitter has
completed its transmission of a given LAPD (or PMDL) Message, and is now ready to transmit the next
PMDL Message, to the Remote Terminal Equipment.
• Receive LIU Interface block
5.3 THE RECEIVE SECTION OF THE XRT72L53 (E3
MODE OPERATION)
When the XRT72L53 has been configured to operate
in the E3 Mode, the Receive Section of the
XRT72L53 consists of the following functional blocks.
• Receive Payload Data Output Interface block
• Receive HDLC Controller block
• Receive E3 Framer block
• Receive Overhead Data Output Interface block
Figure 127 presents a simple illustration of the Receive Section of the XRT72L53 Framer IC.
FIGURE 127. A SIMPLE ILLUSTRATION OF THE RECEIVE SECTION OF THE XRT72L53 CONFIGURED TO OPERATE IN
THE E3 MODE
RxOHFrame
RxOHEnable
RxOH
RxOHClk
RxOHInd
RxSer
RxNib[3:0]
RxClk
RxFrame
Receive Overhead
Input
Interface Block
Receive
Payload Data
Input
Interface Block
RxPOS
Receive DS3/E3
Framer Block
Receive LIU
Interface
Block
RxNEG
RxLineClk
From Microprocessor
Interface Block
Rx
RxE3
E3HDLC
HDLC
Controller/Buffer
Controller/Buffer
Each of these functional blocks will be discussed in
detail in this document.
5.3.1 The Receive E3 LIU Interface Block
The purpose of the Receive E3 LIU Interface block is
two-fold:
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THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
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1. To receive encoded digital data from the E3 LIU
IC.
2. To decode this data, convert it into a binary data
stream and to route this data to the Receive E3
Framer block.
Figure 128 presents a simple illustration of the Receive E3 LIU Interface block.
FIGURE 128. A SIMPLE ILLUSTRATION OF THE RECEIVE E3 LIU INTERFACE BLOCK
RxPOS
To Receive E3
Framer Block
Receive E3
LIU Interface
Block
RxNEG
RxLineClk
The Receive Section of the XRT72L53 will via the Receive E3 LIU Interface Block receive timing and data
information from the incoming E3 data stream. The
E3 Timing information will be received via the RxLineClk input pin and the E3 data information will be received via the RxPOS and RxNEG input pins. The
Receive E3 LIU Interface block is capable of receiving
E3 data pulses in unipolar or bipolar format. If the Receive E3 framer is operating in the bipolar format,
then it can be configured to decode either AMI or
HDB3 line code data. Each of these input formats and
line codes will be discussed in detail, below.
5.3.1.1 Unipolar Decoding
If the Receive E3 LIU Interface block is operating in
the Unipolar (single-rail) mode, then it will receive the
Single Rail NRZ DS3 data pulses via the RxPOS input pin. The Receive E3 LIU Interface block will also
receive its timing signal via the RxLineClk signal.
NOTE: The RxLineClk signal will function as the timing
source for the entire Receive Section of the XRT72L53.
No data pulses will be applied to the RxNEG input
pin. The Receive E3 LIU Interface block receives a
logic "1" when a logic "1" level signal is present at the
RxPOS pin, during the sampling edge of the RxLineClk signal. Likewise, a logic "0" is received when a
logic "0" level signal is applied to the RxPOS pin.
Figure 129 presents an illustration of the behavior of
the RxPOS, RxNEG and RxLineClk input pins when
the Receive E3 LIU Interface block is operating in the
Unipolar mode.
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FIGURE 129. BEHAVIOR OF THE RXPOS, RXNEG AND RXLINECLK SIGNALS DURING DATA RECEPTION OF UNIPODATA
LAR
Data
1
0
1
1
0
0
1
0
0
1
1
1
0
1
0
1
0
0
1
1
1
0
0
1
RxPOS
RxNEG
RxLineClk
The user can configure the Receive E3 LIU Interface
block to operate in either the Unipolar or the Bipolar
Mode by writing the appropriate data to the I/O Control Register, as depicted below.
I/O CONTROL REGISTER (ADDRESS = 0X01)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT2
BIT 1
BIT 0
Disable TxLOC
LOC
Disable
RxLOC
AMI/ZeroSup*
Unipolar/
Bipolar*
TxLine CLK
Invert
RxLine CLK
Invert
Reframe
R/W
RO
R/W
R/W
R/W
R/W
R/W
R/W
1
0
1
0
0
0
0
0
Table 60 relates the value of this bit-field to the Receive E3 LIU Interface Input Mode.
TABLE 60: THE RELATIONSHIP BETWEEN THE CONTENTS OF BIT 2 (TXLINECLK INV) WITHIN THE I/O CONTROL
REGISTER AND THE TXLINECLK CLOCK EDGE THAT TXPOS AND TXNEG ARE UPDATED ON
BIT 3
RECEIVE E3 LIU INTERFACE INPUT MODE
0
Bipolar Mode (Dual Rail): AMI or HDB3 Line Codes are Transmitted and Received.
1
Unipolar Mode (Single Rail) Mode of transmission and reception of E3 data is selected.
NOTES:
1. The default condition is the Bipolar Mode.
2. This selection also effects the Transmit E3 Framer
Line Interface Output Mode
5.3.1.2 Bipolar Decoding
If the Receive E3 LIU Interface block is operating in
the Bipolar Mode, then it will receive the E3 data puls-
es via both the RxPOS, RxNEG, and the RxLineClk
input pins. Figure 130 presents a circuit diagram illustrating how the Receive E3 LIU Interface block interfaces to the Line Interface Unit while the Framer is
operating in Bipolar mode. The Receive E3 LIU Interface block can be configured to decode either the AMI
or HDB3 line codes.
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FIGURE 130. ILLUSTRATION ON HOW A CHANNEL OF THE RECEIVE E3 FRAMER (WITHIN THE XRT72L53 FRAMER
IC) BEING INTERFACE TO THEXRT73L03 LINE INTERFACE UNIT, WHILE OPERATING IN BIPOLAR MODE
RxAVDD_0
TxAVDD_0
DVDD_0
C3
C4
0.01uF
C5
0.01uF
0.01uF
C2
0.01uF
U21
C5
B5
A3
C4
Rx_AIS_Ch_0
RxRED_ALARM_0
Rx_OOF_Ch_0
Rx_LOS_Ch_0
F20
D20
F19
T20
RxFRAME_0
RxFRAME_CLK_0
RxDATA_IN_0
48
RxAIS_0
RxRED_0
RxOOF_0
RxLOS_0
RxFrame_0
RxClk_0
RxSer_0
MOTO
R8 4.7K
RxPOS_0
RxNEG_0
F2
67
42
51
R7 100
F3
50
F1
49
B8
D9
57
55
C7
A5
C6
C9
C3
61
62
63
64
96
RxAVDD0
TxAVDD0
RxDVDD0
TxAVDD0
28
37
LOSTHR_0
HOST/HW
RPOS0
RTIP0
J1
72
6 T2 1
RNEG0
D[7:0]
4
D7
D6
D5
D4
D3
D2
D1
D0
A[10:0]
M20
M19
M18
M17
N20
N19
N18
P20
P19
P18
R20
J17
R19
V20
P17
R18
H20
READY_OUT*
ALE
RD*
WR*
XRT72L53_CS*
XRT72L53_INT*
T19
HW_RESET*
R9
T18
A10
A9
A8
A7
A6
A5
A4
A3
A2
A1
A0
Rdy_Dtck
ALE_AS
RDB_DS
WRB_RW
CSB
INT
RESETB
RxLineClk_0
RLOL_0
ExtLOS_0
LLOOP_0
REQB_0
TAOS_0
DMO_0
TxLEV_0
RLOOP_0
ENCODIS_0 (TxOFF_0)
TxPOS_0
B7
RCLK0
RRING0
71
TxLineClk_0
R2
R1
37.4
37.4
RLOL_0
RLOS_0
CS
SCLK
SDI
SDO
REG_RESET*
C1
0.01uF
XRT71D03_CS* (Optional)
B2
117
C1
33
TxOFF_0
TPDATA_0
TTIP0
R3
29
D1
32
E2
34
47
J2
1 T1 6
TNDATA_0
TCLK_0
EXCLK_0
TRING0
MTIP0
R4
27
30
NIBBLEINTF
1
BNC
3
4
T3001
R5
36
270
100
TxFRAME_0
44.736MHz
TxDATA_OUT_0
3
T3001
36
TxNEG_0
BNC
2
J19
J20
K17
K18
K19
K20
L20
L18
1
2
70
U19
E20
G 4 TxFrame_0
E18 TxInClk_0
TxSER_0
MRING0
31
R6
270
54
73
RxDGND0
RxAGND0
TxAGND0
TxAGND0
39
26
XRT72L53_Ch_0
XRT73L03IV_Ch_0
5.3.1.2.1 AMI Decoding
AMI or Alternate Mark Inversion, means that consecutive "one's" pulses (or marks) will be of opposite polarity with respect to each other. This line code involves the use of three different amplitude levels: +1,
0, and -1. The +1 and -1 amplitude signals are used
to represent one's (or mark) pulses and the "0" amplitude pulses (or the absence of a pulse) are used to
represent zeros (or space) pulses. The general rule
for AMI is: if a given mark pulse is of positive polarity,
then the very next mark pulse will be of negative polarity and vice versa. This alternating-polarity relationship exists between two consecutive mark pulses, independent of the number of zeros that exist between
these two pulses. Figure 131 presents an illustration
of the AMI Line Code as would appear at the RxPOS
and RxNEG pins of the Framer, as well as the output
signal on the line.
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FIGURE 131. ILLUSTRATION OF AMI LINE CODE
Data 1 0 1 1 0 0 0 1 0 1 1 1 1 0 1 1 0 1 1 0 0 1 1 0 0 0 0 1
Line Signal
RxPOS
RxNEG
NOTE: One of the reasons that the AMI Line Code has
been chosen for driving copper medium, isolated via transformers, is that this line code has no dc component, thereby
eliminating dc distortion in the line.
happen. One such technique is HDB3 (or High Density Bipolar -3) encoding.
In general the HDB3 line code behaves just like AMI
with the exception of the case when a long string of
consecutive zeros occurs on the line. Any 4 consecutive zeros will be replaced with either a "000V" or a
"B00V" where "B" refers to a Bipolar pulse (e.g., a
pulse with a polarity that is compliant with the AMI
coding rule). And "V" refers to a Bipolar Violation
pulse (e.g., a pulse with a polarity that violates the alternating polarity scheme of AMI.) The decision between inserting an "000V" or a "B00V" is made to insure that an odd number of Bipolar (B) pulses exist
between any two Bipolar Violation (V) pulses. The
Receive E3 LIU Interface block, when operating with
the HDB3 Line Code is responsible for decoding the
HD-encoded data back into a unipolar (binary-format). For instance, if the Receive E3 LIU Interface
block detects a "000V" or a "B00V" pattern in the incoming pattern, the Receive E3 LIU Interface block
will replace it with four (4) consecutive zeros.
Figure 132 presents a timing diagram that illustrates
examples of HDB3 decoding.
5.3.1.2.2 HDB3 Decoding
The Transmit E3 LIU Interface block and the associated LIU embed and combine the data and clocking information into the line signal that is transmitted to the
remote terminal equipment. The remote terminal
equipment has the task of recovering this data and
timing information from the incoming E3 data stream.
Most clock and data recovery schemes rely on the
use of Phase-Locked-Loop technology. One of the
problems of using Phase-Locked-Loop (PLL) technology for clock recovery is that it relies on transitions in
the line signal, in order to maintain lock with the incoming E3 data-stream. Therefore, these clock recovery scheme, are vulnerable to the occurrence of a
long stream of consecutive zeros (e.g., no transitions
in the line). This scenario can cause the PLL to lose
lock with the incoming E3 data, thereby causing the
clock and data recovery process of the receiver to fail.
Therefore, some approach is needed to insure that
such a long string of consecutive zeros can never
FIGURE 132. ILLUSTRATION OF TWO EXAMPLES OF HDB3 DECODING
0
0
0
V
Line Signal
B
0
0
V
0
0
0
0
RxPOS
RxNEG
Data
1
0
1
1
0
0
0
0
0
1
1
1
1
305
0
1
1
0
1
1
0
0
1
1
1
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THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. P1.1.8
5.3.1.2.3 Line Code Violations
The Receive E3 LIU Interface block will also check
the incoming E3 data stream for line code violations.
For example, when the Receive E3 LIU Interface
block detects a valid bipolar violation (e.g., in HDB3
line code), it will substitute four zeros into the binary
data stream. However, if the bipolar violation is invalid, then an LCV (Line Code Violation) is flagged
and the PMON LCV Event Count Register (Address =
0x50 and 0x51) will also be incremented. Additionally,
the LCV-One-Second Accumulation Registers (Address = 0x6E and 0x6F) will be incremented. For example: If the incoming E3 data is HDB3 encoded, the
Receive E3 LIU Interface block will also increment the
LCV One-Second Accumulation Register if three (or
more) consecutive zeros are received.
5.3.1.2.4 RxLineClk Clock Edge Selection
The incoming unipolar or bipolar data, applied to the
RxPOS and the RxNEG input pins are clocked into
the Receive E3 LIU Interface block via the RxLineClk
signal. The Framer IC allows the user to specify
which edge (e.g, rising or falling) of the RxLineClk
signal will sample and latch the signal at the RxPOS
and RxNEG input signals into the Framer IC. The user can make this selection by writing the appropriate
data to bit 1 of the I/O Control Register, as depicted
below.
II/O CONTROL REGISTER (ADDRESS = 0X01)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT2
BIT 1
BIT 0
Disable
TxLOC
LOC
Disable
RxLOC
AMI/ZeroSup*
Unipolar/
Bipolar*
TxLine CLK
Invert
RxLine CLK
Invert
Reframe
R/W
RO
R/W
R/W
R/W
R/W
R/W
R/W
1
0
1
0
0
0
0
0
Table 61 depicts the relationship between the value of
this bit-field to the sampling clock edge of RxLineClk.
TABLE 61: THE RELATIONSHIP BETWEEN THE CONTENTS OF BIT 1 (RXLINECLK INV) OF THE I/O CONTROL REGISTER,
AND THE SAMPLING EDGE OF THE RXLINECLK SIGNAL
RXCLKINV
(BIT 1)
0
RESULT
.Rising Edge:
RxPOS and RxNEG are sampled at the rising edge of RxLineClk. See Figure 133 for timing relationship
between RxLineClk, RxPOS, and RxNEG.
1
Falling Edge:
RxPOS and RxNEG are sampled at the falling edge of RxLineClk. See Figure 134 for timing relationship
between RxLineClk, RxPOS, and RxNEG.
Figure 133 and Figure 134 present the Waveform and
Timing Relationships between RxLineClk, RxPOS
and RxNEG for each of these configurations.
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THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
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FIGURE 133. WAVEFORM/TIMING RELATIONSHIP BETWEEN RXLINECLK, RXPOS AND RXNEG - WHEN RXPOS AND
RXNEG ARE TO BE SAMPLED ON THE RISING EDGE OF RXLINECLK
t42
RxLineClk
t39
t38
RxPOS
RxNEG
FIGURE 134. WAVEFORM/TIMING RELATIONSHIP BETWEEN RXLINECLK, RXPOS AND RXNEG - WHEN RXPOS AND
RXNEG ARE TO BE SAMPLED ON THE FALLING EDGE OF RXLINECLK
RxLineClk
t40
t41
RxPOS
RxNEG
5.3.2 The Receive E3 Framer Block
The Receive E3 Framer block accepts decoded E3
data from the Receive E3 LIU Interface block, and
routes data to the following destinations.
• The Receive Payload Data Output Interface Block
• The Receive E3 HDLC Controller Block
Figure 135 presents a simple illustration of the Receive E3 Framer block along with the associated
paths to the other functional blocks within the Framer
chip.
• The Receive Overhead Data Output Interface
Block.
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FIGURE 135. A SIMPLE ILLUSTRATION OF THE RECEIVE E3 FRAMER BLOCK AND THE ASSOCIATED PATHS TO THE
OTHER FUNCTIONAL BLOCKS
To Receive E3 HDLC
Buffer
Receive Overhead Data
Output Interface
Receive
ReceiveE3
E3Framer
Framer
Block
Block
From Receive E3
LIU Interface Block
Receive Payload Data
Output Interface
Once the HDB3 (or AMI) encoded data has been decoded into a binary data-stream, the Receive E3
Framer block will use portions of this data-stream in
order to synchronize itself to the remote terminal
equipment. At any given time, the Receive E3 Framer
block will be operating in one of two modes.
Frame Acquisition/Maintenance Algorithm per
Figure 136.
• The Frame Acquisition Mode: In this mode, the
Receive E3 Framer block is trying to acquire synchronization with the incoming E3 frame, or
• LOF Condition State
• The Frame Maintenance Mode: In this mode, the
Receive E3 Framer block is trying to maintain frame
synchronization with the incoming E3 Frames.
Figure 136 presents a State Machine diagram that
depicts the Receive E3 Framer block's E3/ITU-T
G.751 Frame Acquisition/Maintenance Algorithm.
5.3.2.1 The Framing Acquisition Mode
The Receive E3 Framer block is considered to be operating in the Frame Acquisition Mode, if it is operating in any one of the following states within the E3
• FAS Pattern Search State
• FAS Pattern Verification State
• OOF Condition State
Each of these Framing Acquisition states, within the
Receive E3 Framer Framing Acquisition/Maintenance
State Machine are discussed below.
The FAS Pattern Search State
When the Receive E3 Framer block is first powered
up, it will be operating in the FAS Pattern Search
state. While the Receive E3 Framer is operating in
this state, it will be performing a bit-by-bit search for
the FAS (Framing Alignment Signal) pattern, of
“1111010000”. Figure 137, which presents an illustration of the E3, ITU-T G.751 Framing Format, indicates that this framing alignment signal will occur at
the beginning of each E3 frame.
308
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XRT72L53
THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. P1.1.8
FIGURE 136. THE STATE MACHINE DIAGRAM FOR THE RECEIVE E3 FRAMER E3 FRAME ACQUISITION/MAINTENANCE
ALGORITHM
FAS pattern is
detected once
FAS
Pattern
Search
FAS
Pattern
Verification
FAS Pattern is
not detected
LOF
Condition
FAS Pattern is
verified once
8 or 24 framing periods
of operating in the
OOF condition
(user-selectable)
3 consecutive
Valid Frames
OOF
Condition
In Frame
4 consecutive
In-valid Frames
Frame Maintenance
Mode
FIGURE 137. ILLUSTRATION OF THE E3, ITU-T G.751 FRAMING FORMAT
1
10
Frame
Alignment
Signal
11
12
A
N
384 385
Data
768
Data
769
1152 1153
Data
1532
Data
1536
BIP-4
if Selected
Framing Alignment Signal Pattern = 1111010000
When the Receive E3 Framer block detects the FAS
pattern, it will then transition over to the FAS Pattern
Verification state, per Figure 137.
The FAS Pattern Verification State
Once the Receive E3 Framer block has detected an
“1111010000” pattern, it must verify that this pattern
is indeed the FAS pattern and not some other set of
bits, within the E3 frame, mimicking the FAS Pattern.
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THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. P1.1.8
Hence, the purpose of the FAS Pattern Verification
state.
the In-Frame state, can be found in Section 4.3.2.2
(The Framing Maintenance Mode).
When the Receive E3 Framer block enters this state,
it will then quit performing its bit-by-bit search for the
Frame Alignment Signaling bits. Instead, the Receive
E3 Framer block will read in the 10 bits that occur
1536 bit (e.g., one E3 frame period later) after the
candidate FAS pattern was first detected. If these ten
bits match the assigned values for the FAS Pattern
octets, then the Receive E3 Framer block will conclude that it has found the FAS pattern and will then
transition to the In-Frame state. However, if these two
bytes do not match the assigned values for the FAS
pattern then the Receive E3 Framer block will concluded that it has been fooled by data mimicking the
Frame Alignment bytes, and will transition back to the
FAS Pattern Search state.
OOF (Out of Frame) Condition State
In Frame State
The Receive E3 Framer block will inform the Microprocessor/Microcontroller of its transition from the InFrame state to the OOF Condition state, by generating a Change in OOF Condition Interrupt. When this
occurs, Bit 3 (OOF Interrupt Status), within the Rx E3
Interrupt Status Register - 1, will be set to “1”, as depicted below.
Once the Receive E3 Framer block enters the InFrame state, then it will cease performing Frame Acquisition functions, and will proceed to perform Framing Maintenance functions. Therefore, the operation
of the Receive E3 Framer block, while operating in
If the Receive E3 Framer while operating in the InFrame state detects four (4) consecutive frames,
which do not have the valid Frame Alignment Signaling (FAS) patterns, then it will transition into the OOF
Condition State. The Receive E3 Framer block’s operation, while in the OOF condition state is a unique mix
of Framing Maintenance and Framing Acquisition operation. The Receive E3 Framer block will exhibit
some Framing Acquisition characteristics by attempting to locate (once again) the FAS pattern. However,
the Receive E3 Framer block will also exhibit some
Frame Maintenance behavior by still using the most
recent frame synchronization for its overhead bits and
payload bits processing.
RXE3 INTERRUPT STATUS REGISTER - 1 (ADDRESS = 0X14)
BIT 7
BIT 6
BIT 5
Not Used
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
COFA
Interrupt
Status
OOF
Interrupt
Status
LOF
Interrupt
Status
LOS
Interrupt
Status
AIS
Interrupt
Status
RO
RO
RO
RUR
RUR
RUR
RUR
RUR
0
0
0
0
0
0
0
0
The Receive E3 Framer block will also inform the external circuitry of its transition into the OOF Condition
state, by toggling the RxOOF output pin "High”.
If the Receive E3 Framer block is capable of finding
the FAS pattern within a user-selectable number of
E3 frame periods, then it will transition back into the
In-Frame state. The Receive E3 Framer block will
then inform the Microprocessor/Microcontroller of its
transition back into the In-Frame state by generating
the Change in OOF Condition Interrupt.
However, if the Receive E3 Framer block resides in
the OOF Condition state for more than this user-selectable number of E3 frame periods, then it will automatically transition to the LOF (Loss of Frame) Condition state.
The user can select this user-selectable number of
E3 frame periods that the Receive E3 Framer block
will remain in the OOF Condition state by writing the
appropriate value into Bit 7 (RxLOF Algo) within the
Rx E3 Configuration & Status Register, as depicted
below.
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THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. P1.1.8
RXE3 CONFIGURATION & STATUS REGISTER - 2 (ADDRESS = 0X11)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
RxLOF
Algo
RxLOF
RxOOF
RxLOS
RxAIS
R/W
RO
RO
RO
RO
RO
RO
RO
0
1
1
0
0
1
1
1
Not Used
BIT 0
RxFERF
• The Receive E3 Framer block will make an unconditional transition to the FAS Pattern Search state.
Writing a “0” into this bit-field causes the Receive E3
Framer block to reside in the OOF Condition state for
at most 24 E3 frame periods. Writing a “1” into this
bit-field causes the Receive E3 Framer block to reside in the OOF Condition state for at most 8 E3
frame periods.
LOF (Loss of Framing) Condition State
If the Receive E3 Framer block enters the LOF Condition state, then the following things will happen.
• The Receive E3 Framer block will notify the Microprocessor/Microcontroller of its transition to the
LOF Condition state, by generating the Change in
LOF Condition interrupt. When this occurs, Bit 2
(LOF Interrupt Status), within the Rx E3 Interrupt
Status Register - 1 will be set to “1”, as depicted
below.
• The Receive E3 Framer block will discard the most
recent frame synchronization and,
RXE3 INTERRUPT STATUS REGISTER - 1 (ADDRESS = 0X14)
BIT 7
BIT 6
BIT 5
Not Used
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
COFA
Interrupt
Status
OOF
Interrupt
Status
LOF
Interrupt
Status
LOS
Interrupt
Status
AIS
Interrupt
Status
RO
RO
RO
RUR
RUR
RUR
RUR
RUR
0
0
0
0
0
1
0
0
Finally, the Receive E3 Framer block will also inform
the external circuitry of this transition to the LOF Condition state by toggling the RxLOF output pin "High”.
5.3.2.2 The Framing Maintenance Mode
Once the Receive E3 Framer block enters the InFrame state, then it will notify the Microprocessor/Mi-
crocontroller of this fact by generating both the
Change in OOF Condition and Change in LOF Condition Interrupts. When this happens, bits 2 and 3 (LOF
Interrupt Status and OOF Interrupt Status) will be set
to “1”, as depicted below.
RXE3 INTERRUPT STATUS REGISTER - 1 (ADDRESS = 0X14)
BIT 7
BIT 6
BIT 5
Not Used
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
COFA
Interrupt
Status
OOF
Interrupt
Status
LOF
Interrupt
Status
LOS
Interrupt
Status
AIS
Interrupt
Status
RO
RO
RO
RUR
RUR
RUR
RUR
RUR
0
0
0
0
1
1
0
0
Additionally, the Receive E3 Framer block will inform
the external circuitry of its transition to the In-Frame
state by toggling both the RxOOF and RxLOF output
pins "Low”.
Finally, the Receive E3 Framer block will negate both
the RxOOF and the RxLOF bit-fields within the Rx E3
Configuration & Status Register, as depicted below.
311
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XRT72L53
THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. P1.1.8
RXE3 CONFIGURATION & STATUS REGISTER - 2 (ADDRESS = 0X11)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
RxLOF
Algo
RxLOF
RxOOF
RxLOS
RxAIS
R/W
RO
RO
RO
RO
RO
RO
RO
0
0
0
0
0
1
1
1
Not Used
BIT 0
RxFERF
Since the Receive E3 Framer block requires the detection of an invalid FAS pattern in four consecutive
frames, in order for it to transition to the OOF Condition state, it can tolerate some errors in the Framing
Alignment bytes, and still remain in the In-Frame
state. However, each time the Receive E3 Framer
block detects an error in the FAS pattern, it will increment the PMON Framing Error Event Count Registers (Address = 0x52 and 0x53). The bit-format for
these two registers are depicted below.
When the Receive E3 Framer block is operating in the
In-Frame state, it will then begin to perform Frame
Maintenance operations, where it will continue to verify that the Frame Alignment signal (FAS pattern) is
present, and at its proper location. While the Receive
E3 Framer block is operating in the Frame Maintenance Mode, it will declare an Out-of-Frame (OOF)
Condition if it detects an invalid FAS pattern in four
consecutive frames.
PMON FRAMING BIT/BYTE ERROR COUNT REGISTER - MSB (ADDRESS = 0X52)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
Framing Bit/Byte Error Count - High Byte
RUR
RUR
RUR
RUR
RUR
RUR
RUR
RUR
0
0
0
0
0
0
0
0
BIT 2
BIT 1
BIT 0
PMON FRAMING BIT/BYTE ERROR COUNT REGISTER - LSB (ADDRESS = 0X53)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
Framing Bit/Byte Error Count - Low Byte
RUR
RUR
RUR
RUR
RUR
RUR
RUR
RUR
0
0
0
0
0
0
0
0
5.3.2.3 Forcing a Reframe via Software Command
The XRT72L53 Framer IC permits the user to command a reframe procedure with the Receive E3 Framer block via software command. If the user writes a
“1” into Bit 0 (Reframe) within the I/O Control Register
(Address = 0x01), as depicted below, then the Receive E3 Framer block will be forced into the FAS Pattern Search state, per Figure 138., and will begin its
search for the FAS Pattern.
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THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. P1.1.8
)
I/O CONTROL REGISTER (ADDRESS = 0X01)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
Disable
TxLOC
LOC
Disable
RxLOC
AMI/
ZeroSup*
Unipolar/
Bipolar*
TxLine
Clk
Invert
RxLine
Clk
Invert
Reframe
R/W
RO
R/W
R/W
R/W
R/W
R/W
R/W
1
0
1
0
0
0
0
1
2. Generating both the Change in OOF Status and
the Change in LOF Status interrupts to the Microprocessor.
3. Asserting both the RxLOF and RxOOF bit-fields
within the Rx E3 Configuration & Status Register,
as depicted below.
The Framer IC will respond to this command by doing
the following.
1. Asserting both the RxOOF and RxLOF output
pins.
RXE3 CONFIGURATION & STATUS REGISTER - 2 (ADDRESS = 0X11)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
RxLOF
Algo
RxLOF
RxOOF
RxLOS
RxAIS
R/W
RO
RO
RO
RO
RO
RO
RO
0
1
1
0
0
1
1
0
5.3.2.4 Performance Monitoring of the Frame
Synchronization Section, within the Receive E3
Framer block
The user can monitor the number of FAS pattern errors that have been detected by the Receive E3
Framer block. This is accomplished by periodically
reading the PMON Framing Bit/Byte Error Event
Count Registers (Address = 0x52 and 0x53). The
byte format of these registers are presented below.
BIT 2
BIT 1
Not Used
BIT 0
RxFERF
5.3.2.5 The RxOOF and RxLOF output pin.
The user can roughly determine the current framing
state that the Receive E3 Framer block is operating in
by reading the logic state of the RxOOF and the RxLOF output pins. Table 62 presents the relationship
between the state of the RxOOF and RxLOF output
pins, and the Framing State of the Receive E3 Framer
block.
TABLE 62: THE RELATIONSHIP BETWEEN THE LOGIC STATE OF THE RXOOF AND RXLOF OUTPUT PINS, AND THE
FRAMING STATE OF THE RECEIVE E3 FRAMER BLOCK
RXLOF
RXOOF
0
0
In Frame
0
1
OOF Condition (The Receive E3 Framer block is operating in the 3ms OOF period).
1
0
Invalid
1
1
LOF Condition
5.3.2.6
FRAMING STATE OF THE RECEIVE E3 FRAMER BLOCK
E3 Receive Alarms
5.3.2.7 The Loss of Signal (LOS) Alarm
Declaring an LOS Condition
The Receive E3 Framer block will declare a Loss of
Signal (LOS) Condition, when it detects 32 consecu-
tive incoming “0’s” via the RxPOS and RxNEG input
pins or if the ExtLOS input pin (from the XRT7300
DS3/E3/STS-1 LIU IC) is asserted. The Receive E3
Framer block will indicate that it is declaring an LOS
condition by.
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THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. P1.1.8
• Asserting the RxLOS output pin (e.g., toggling it
"High”).
• Setting Bit 4 (RxLOS) of the Rx E3 Configuration &
Status Register to “1” as depicted below.
RXE3 CONFIGURATION & STATUS REGISTER - 2 (ADDRESS = 0X11)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
RxLOF
Algo
RxLOF
RxOOF
RxLOS
RxAIS
R/W
RO
RO
RO
RO
RO
RO
RO
0
1
1
1
0
0
0
0
• The Receive E3 Framer block will generate a
Change in LOS Condition interrupt request. Upon
generating this interrupt request, the Receive E3
BIT 2
BIT 1
Not Used
BIT 0
RxFERF
Framer block will assert Bit 1 (LOS Interrupt Status
within the Rx E3 Framer Interrupt Status Register 1, as depicted below.
RXE3 INTERRUPT STATUS REGISTER - 1 (ADDRESS = 0X14)
BIT 7
BIT 6
BIT 5
Not Used
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
COFA
Interrupt
Status
OOF
Interrupt
Status
LOF
Interrupt
Status
LOS
Interrupt
Status
AIS
Interrupt
Status
RO
RO
RO
RUR
RUR
RUR
RUR
RUR
0
0
0
0
0
0
1
0
Clearing the LOS Condition
The Receive E3 Framer block will clear the LOS condition when it encounters a stream of 32 bits that
does not contain a string of 4 consecutive zeros.
• Generating the Change in LOS Condition Interrupt
to the Microprocessor.
• Clearing Bit 4 (RxLOS) within the Rx E3 Configuration & Status Register, as depicted below.
When the Receive E3 Framer block clears the LOS
condition, then it will notify the Microprocessor and
the external circuitry of this occurrence by:
RXE3 CONFIGURATION & STATUS REGISTER - 2 (ADDRESS = 0X11)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
RxLOF
Algo
RxLOF
RxOOF
RxLOS
RxAIS
R/W
RO
RO
RO
RO
RO
RO
RO
0
1
1
0
0
1
1
1
• Clear the RxLOS output pin (e.g., toggle it "Low”).
5.3.2.8 The AIS (Alarm Indication Status) Condition
Declaring the AIS Condition
The Receive E3 Framer block will identify and declare
an AIS condition, if it detects an All Ones” pattern in
the incoming E3 data stream. More specifically, the
Receive E3 Framer block will declare an AIS Condi-
BIT 2
BIT 1
Not Used
BIT 0
RxFERF
tion if 7 or less “0’s” are detected in each of 2 consecutive E3 frames.
If the Receive E3 Framer block declares an AIS Condition, then it will do the following.
• Generate the Change in AIS Condition Interrupt to
the Microprocessor. Hence, the Receive E3 Framer
block will assert Bit 0 (AIS Interrupt Status) within
the Rx E3 Framer Interrupt Status register - 1, as
depicted below.
314
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XRT72L53
THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. P1.1.8
RXE3 INTERRUPT STATUS REGISTER - 1 (ADDRESS = 0X14)
BIT 7
BIT 6
BIT 5
Not Used
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
COFA
Interrupt
Status
OOF
Interrupt
Status
LOF
Interrupt
Status
LOS
Interrupt
Status
AIS
Interrupt
Status
RO
RO
RO
RUR
RUR
RUR
RUR
RUR
0
0
0
0
0
0
0
1
• Assert the RxAIS output pin.
• Set Bit 3 (RxAIS) within the Rx E3 Configuration &
Status Register, as depicted below.
RXE3 CONFIGURATION & STATUS REGISTER - 2 (ADDRESS = 0X11)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
RxLOF
Algo
RxLOF
RxOOF
RxLOS
RxAIS
R/W
RO
RO
RO
RO
RO
RO
RO
0
1
1
0
1
1
1
1
Clearing the AIS Condition
The Receive E3 Framer block will clear the AIS condition when it detects two consecutive E3 frames, with
eight or more “zeros” in the incoming data stream.
The Receive E3 Framer block will inform the Microprocessor that the AIS Condition has been cleared
by:
BIT 2
BIT 1
Not Used
BIT 0
RxFERF
Framer block will assert Bit 0 (AIS Interrupt Status)
within the Rx E3 Framer Interrupt Status Register 1.
• Clearing the RxAIS output pin (e.g., toggling it
"Low”).
• Setting the RxAIS bit-field, within the Rx E3 Configuration & Status Register to “0”, as depicted below.
• Generating the Change in AIS Condition Interrupt
to the Microprocessor. Hence, the Receive E3
RXE3 CONFIGURATION & STATUS REGISTER - 2 (ADDRESS = 0X11)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
RxLOF
Algo
RxLOF
RxOOF
RxLOS
RxAIS
R/W
RO
RO
RO
RO
RO
RO
RO
0
1
1
0
1
0
0
X
5.3.2.9 The Far-End-Receive Failure (FERF)
Condition
Declaring the FERF Condition
The Receive E3 Framer block will declare a Far-End
Receive Failure (FERF) condition if it detects a user-
BIT 2
BIT 1
Not Used
BIT 0
RxFERF
selectable number of consecutive incoming E3
frames, with the “A” bit-field set to “1”.
This User-selectable number of E3 frames is either 3
or 5, depending upon the value that has been written
into Bit 4 (RxFERF Algo) within the Rx E3 Configuration & Status Register, as depicted below.
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THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. P1.1.8
RXE3 CONFIGURATION & STATUS REGISTER - 1 G.751 (ADDRESS = 0X10)
BIT 7
BIT 6
BIT 5
Reserved
BIT 4
BIT 3
RxFERF
Algo
BIT 2
BIT 1
Reserved
BIT 0
RxBIP4
RO
RO
RO
R/W
RO
RO
RO
R/W
0
0
0
0
0
0
0
0
Whenever the Receive E3 Framer block declares a
FERF condition, then it will do the following.
Writing a “0” into this bit-field causes the Receive E3
Framer block to declare a FERF condition, if it detects
3 consecutive incoming E3 frames, that have the “A”
bit set to “1”.
• Generate a Change in FERF Condition interrupt to
the MIcroprocessor. Hence, the Receive E3 Framer
block will assert Bit 3 (FERF Interrupt Status) within
the Rx E3 Framer Interrupt Status register - 2, as
depicted below.
Writing a “1” into this bit-field causes the Receive E3
Framer block to declare a FERF condition, if it detects
5 consecutive incoming E3 frames, that have the “A”
bit set to “1”.
RXE3 INTERRUPT STATUS REGISTER - 2 (ADDRESS = 0X15)
BIT 7
BIT 6
BIT 5
BIT 4
Not Used
BIT 3
BIT 2
BIT 1
BIT 0
FERF
Interrupt
Status
BIP-4
Error
Interrupt
Status
Framing
Error
Interrupt
Status
Not Used
RO
RO
RO
RO
RUR
RUR
RUR
RUR
0
0
0
0
1
0
0
0
BIT 2
BIT 1
BIT 0
• Set the RxFERF bit-field, within the Rx E3 Configuration/Status Register to “1”, as depicted below.
RXE3 CONFIGURATION & STATUS REGISTER - 2 (ADDRESS = 0X11)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
RxLOF
Algo
RxLOF
RxOOF
RxLOS
RxAIS
R/W
RO
RO
RO
RO
RO
RO
RO
0
1
1
0
0
0
0
0
Clearing the FERF Condition
The Receive E3 Framer block will clear the FERF
condition once it has received a User-Selectable
number of E3 frames with the “A” bit-field being set to
“0” (e.g., no FERF condition). This User-Selectable
number of E3 frames is either 3 or 5 depending upon
the value that has been written into Bit 4 (RxFERF Al-
Not Used
RxFERF
go) of the Rx E3 Configuration/Status Register, as
discussed above.
Whenever the Receive E3 Framer clears the FERF
status, then it will do the following:
316
1. Generate a Change in the FERF Status Interrupt
to the Microprocessor.
2. Clear the Bit 0 (RxFERF) within the Rx E3 Configuration & Status register, as depicted below.
áç
XRT72L53
THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. P1.1.8
RXE3 CONFIGURATION & STATUS REGISTER - 2 (ADDRESS = 0X11)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
RxLOF
Algo
RxLOF
RxOOF
RxLOS
RxAIS
R/W
RO
RO
RO
RO
RO
RO
RO
0
1
1
0
0
1
1
1
5.3.2.10 Error Checking of the Incoming E3
Frames
The Receive E3 Framer block can be configured to
performs error-checking on the incoming E3 frame
data that it receives from the Remote Terminal Equipment. If configured accordingly, the Receive E3 Framer block will performs this error-checking by computing the BIP-4 value of an incoming E3 frame. Once
the Receive E3 Framer block has obtained this value,
it will compare this value with that of the BIP-4 value
that it receives, within the very next E3 frame. If the
locally computed BIP-4 value matches the EM byte of
the corresponding E3 frame, then the Receive E3
Framer block will conclude that this particular frame
has been properly received. The Receive E3 Framer
block will then inform the Remote Terminal Equip-
BIT 2
BIT 1
Not Used
BIT 0
RxFERF
ment of this fact by having the Local Terminal Equipment Transmit E3 Framer block send the Remote Terminal an E3 frame, with the “A” bit-field, set to “0”.
This procedure is illustrated in Figure 138 and
Figure 139, below.
Figure 138 illustrates the Local Receive E3 Framer
receiving an error-free E3 frame. In this figure, the locally computed BIP-4 value of “0xA” matches that received from the Remote Terminal, within the EM bytefield. Figure 139 illustrates the subsequent action of
the Local Transmit E3 Framer block, which will transmit an E3 frame, with the A bit-field set to “0”, to the
Remote Terminal. This signaling indicates that the
Local Receive E3 Framer has received an error-free
E3 frame.
FIGURE 138. ILLUSTRATION OF THE LOCAL RECEIVE E3 FRAMER BLOCK, RECEIVING AN E3 FRAME (FROM THE
REMOTE TERMINAL) WITH A CORRECT BIP-4 VALUE .
Local Terminal
Transmit E3
Framer
BIP-4 Nibble
Receive E3
Framer
0xA
0xA
Locally Calculated
BIP-4 Nibble
317
Remote
Terminal
áç
XRT72L53
THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. P1.1.8
FIGURE 139. ILLUSTRATION OF THE LOCAL RECEIVE E3 FRAMER BLOCK, TRANSMITTING AN E3 FRAME (TO THE
REMOTE TERMINAL) WITH THE “A” BIT SET TO “0”
Local Terminal
Value = 0
Transmit E3
Framer
Remote
Terminal
A Bit
Receive E3
Framer
However, if the locally computed BIP-4 value does not
match the BIP-4 value of the corresponding E3 frame,
then the Receive E3 Framer block will do the following.
• It will inform the Remote Terminal of this fact by
having the Local Transmit E3 Framer block send
the Remote Terminal an E3 frame, with the “A” bitfield set to “1”. This phenomenon is illustrated
below in Figure 140 and Figure 141.
Figure 140 illustrates the Local Receive E3 Framer
receiving an errored E3 frame. In this figure, the Local
Receive E3 Frame block is receiving an E3 frame with
an BIP-4 containing the value “0xA”. This value does
not match the locally computed BIP-4 value of “0xB”.
Consequently, there is an error in the previous E3
frame.
Figure 141 illustrates the subsequent action of the
Local Transmit E3 Framer block, which will transmit
an E3 frame, with the A bit-field set to “1” to the Remote Terminal. This signaling indicates that the Local
Receive E3 Framer block has received an errored E3
frame.
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THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. P1.1.8
FIGURE 140. ILLUSTRATION OF THE LOCAL RECEIVE E3 FRAMER BLOCK, RECEIVING AN E3 FRAME (FROM THE
REMOTE TERMINAL) WITH AN INCORRECT BIP-4 VALUE.
Local Terminal
Transmit E3
Framer
BIP-4 Nibble
Remote
Terminal
Receive E3
Framer
0xA
0xB
Locally Calculated
BIP-4 Nibble
FIGURE 141. ILLUSTRATION OF THE LOCAL RECEIVE E3 FRAMER BLOCK, TRANSMITTING AN E3 FRAME (TO THE
REMOTE TERMINAL) WITH THE “A” BIT-FIELD SET TO “1”
Local Terminal
Value = 1
Transmit E3
Framer
A Bit
Remote
Terminal
Receive E3
Framer
In additional to the FEBE bit-field signaling, the Receive E3 Framer block will generate the BIP-4 Error
Interrupt to the Microprocessor. Hence, it will set bit 2
(BIP-8 Error Interrupt Status) to “1”, as depicted below.
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THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. P1.1.8
RXE3 INTERRUPT STATUS REGISTER - 2 (ADDRESS = 0X15)
BIT 7
BIT 6
BIT 5
BIT 4
Not Used
BIT 3
BIT 2
BIT 1
BIT 0
FERF
Interrupt
Status
BIP-4
Error
Interrupt
Status
Framing
Error
Interrupt
Status
Not Used
RO
RO
RO
RO
RUR
RUR
RUR
RUR
0
0
0
0
0
1
0
0
BIT 2
BIT 1
BIT 0
Finally, the Receive E3 Framer block will increment
the PMON Parity Error Count registers. The byte format of these registers are presented below.
PMON PARITY ERROR COUNT REGISTER - MSB (ADDRESS = 0X54)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
Parity Error Count - High Byte
RUR
RUR
RUR
RUR
RUR
RUR
RUR
RUR
0
0
0
0
0
0
0
0
BIT 2
BIT 1
BIT 0
PMON PARITY ERROR COUNT REGISTER - LSB (ADDRESS = 0X55)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
Parity Error Count - Low Byte
RUR
RUR
RUR
RUR
RUR
RUR
RUR
RUR
0
0
0
0
0
0
0
0
The user can determine the number of BIP-4 Errors
that have been detected by the Receive E3 Framer
block, since the last read of these registers. These
registers are reset-upon-read.
In order to perform BIP-4 checking of each E3 frame,
the user must configure the XRT72L53 Framer IC accordingly, by executing the following steps.
1. Configure the Transmit Section (of the XRT72L53
Framer IC) to insert the BIP-4 value into the outbound E3 frames. This is accomplished by writing
a “1” into bit-field 7 (Tx BIP-4 Enable) within the
TxE3 Configuration Register, as illustrated below.
Configuring the XRT72L53 Framer IC to support
BIP-4 Error Detection
TXE3 CONFIGURATION REGISTER (ADDRESS = 0X30)
BIT 7
Tx
BIP-4
Enable
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
Tx AIS
Enable
Tx LOS
Enable
Tx FAS
Source
Select
TxASourceSel[1:0]
TxNSourceSel[1:0]
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
1
0
0
0
0
0
0
0
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THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. P1.1.8
2. Enable the BIP-4 Error Interrupt. This is accomplished by writing a “1” into bit-field 2 (BIP-4 Error
Interrupt Enable) within the RxE3 Interrupt
Enable Register, as illustrated below.
RXE3 INTERRUPT ENABLE REGISTER - 2 (ADDRESS = 0X13)
BIT 7
BIT 6
BIT 5
BIT 4
Not Used
BIT 3
BIT 2
BIT 1
FERF
BIP-4 Error
Framing Error
Interrupt Enable Interrupt Enable Interrupt Enable
BIT 0
Not Used
R/W
RO
RO
RO
R/W
R/W
R/W
RO
0
0
0
0
0
1
0
0
After doing this, the XRT72L53 Framer IC will generate an interrupt to the Microprocessor/Microcontroller
anytime the Receive Section detects a BIP-4 error.
• Framing to the incoming LAPD Messages
5.3.3 The Receive HDLC Controller Block
The Receive E3 HDLC Controller block can be used
to receive message-oriented signaling (MOS) type
data link messages from the remote terminal equipment.
• Storing the Frame Message into the Receive LAPD
Message Buffer
• Filtering out stuffed "0’s" (within the information
payload)
• Perform Frame Check Sequence (FCS) Verification
• Provide status indicators for
End of Message (EOM)
The MOS types of HDLC message processing is discussed in detail below.
Flag Sequence Byte detected
Abort Sequence detected
The Message Oriented Signaling (e.g., LAP-D)
Processing via the Receive E3 HDLC Controller
block
Message Type
C/R Type
The LAPD Receiver (within the Receive E3 HDLC
Controller block) allows the user to receive PMDL
messages from the remote terminal equipment, via
the inbound E3 frames. In this case, the inbound
message bits will be carried by the “N” bit-field within
each inbound E3 Frame. The remote LAPD Transmitter will transmit a LAPD Message to the Local Receiver via either the “N” bit within each E3 Frame. The
LAPD Receiver will receive and store the information
portion of the received LAPD frame into the Receive
LAPD Message Buffer, which is located at addresses:
0xDE through 0x135 within the on-chip RAM. The
LAPD Receiver has the following responsibilities.
The occurrence of FCS Errors
The LAPD receiver's actions are facilitated via the following two registers.
• Rx E3 LAPD Control Register
• Rx E3 LAPD Status Register
Operation of the LAPD Receiver
The LAPD Receiver, once enabled, will begin searching for the boundaries of the incoming LAPD message. The LAPD Message Frame boundaries are delineated via the Flag Sequence octets (0x7E), as depicted in Figure 142.
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THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. P1.1.8
FIGURE 142. LAPD MESSAGE FRAME FORMAT
Flag Sequence (8 bits)
C/R
SAPI (6-bits)
EA
EA
TEI (7 bits)
Control (8-bits)
76 or 82 Bytes of Information (Payload)
FCS - MSB
FCS - LSB
Flag Sequence (8-bits)
IDLE Signal Identification = 0x34 (76 bytes)
Where: Flag Sequence = 0x7E
SAPI + CR + EA = 0x3C or 0x3E
Test Signal Identification = 0x32 (76 bytes)
TEI + EA = 0x01
ITU-T Path Identification = 0x3F (82 bytes)
Control = 0x03
Enabling and Configuring the LAPD Receiver
The 16 bit FCS is calculated using CRC-16, x16 +
x12 + x5 + 1
Before the LAPD Receiver can begin to receive and
process incoming LAPD Message frames, the user
must do two things.
The local µP (at the remote terminal), while assembling the LAPD Message frame, will insert an additional byte at the beginning of the information (payload) field. This first byte of the information field indicates the type and size of the message being transferred. The value of this information field and the
corresponding message type/size follow:
CL Path Identification
1. Enabling the LAPD Receiver
The LAPD Receiver must be enabled before it can
begin receiving and processing any LAPD Message
frames. The LAPD Receiver can be enabled by writing a “1” to Bit 2 (RxLAPD Enable) of the Rx E3 LAPD
Control Register, as indicated below.
= 0x38 (76 bytes)
)
RXE3 LAPD CONTROL REGISTER (ADDRESS = 0X18
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
Not Used
BIT 2
BIT 1
BIT 0
RxLAPD
Enable
RxLAPD
Interrupt Enable
RxLAPD
Interrupt Enable
RO
RO
RO
RO
RO
R/W
R/W
RUR
0
0
0
0
0
0
0
0
Once the LAPD Receiver has been enabled, it will begin searching for the Flag Sequence octet (0x7E), in
the “N” bit-fields within each incoming E3 frame.
When the LAPD Receiver finds the flag sequence
byte, it will assert the Flag Present bit (Bit 0) within
the Rx E3 LAPD Status Register, as depicted below.
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THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
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REV. P1.1.8
RXE3 LAPD STATUS REGISTER (ADDRESS = 0X19)
BIT 7
BIT 6
BIT 5
Not Used
RxABORT
RO
RO
RO
0
0
0
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
RxCR
Type
RxFCS
Error
End of
Message
Flag
Present
RO
RO
RO
RO
RO
0
0
0
0
1
RxLAPDType[1:0]
The receipt of the Flag Sequence octet can mean
one of two things.
1. This Flag Sequence byte may be marking the
beginning or end of an incoming LAPD Message
frame.
2. The Received Flag Sequence octet could be just
one of many Flag Sequence octets that are transmitted via the E3 Transport Medium, during idle
periods between the transmission of LAPD Message frames.
The LAPD Receiver will negate the Flag Present bit
as soon as it has received an octet that is something
other than the Flag Sequence octet. Once this happens, the LAPD Receiver should be receiving either
octet # 2 of the incoming LAPD Message, or an
ABORT Sequence (e.g., a string of seven or more
consecutive “1’s”). If this next set of data is an
ABORT Sequence, then the LAPD Receiver will assert the RxABORT bit-field (Bit 6) within the Rx E3
LAPD Status Register, as depicted below.
RXE3 LAPD STATUS REGISTER (ADDRESS = 0X19)
BIT 7
BIT 6
BIT 5
Not Used
RxABORT
RO
RO
RO
0
1
0
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
RxCR
Type
RxFCS
Error
End of
Message
Flag
Present
RO
RO
RO
RO
RO
0
0
0
0
0
RxLAPDType[1:0]
However, if this next octet is Octet #2 of an incoming
LAPD Message frame, then the LAPD Receiver is beginning to receive a LAPD Message frame.
As the LAPD Receiver receives this LAPD Message
frame, it is reading in the LAPD Message frame octets, from “N” bit-fields within each incoming E3
frame. Secondly, it is reassembling these bits into a
LAPD Message frame.
Once the LAPD Receiver has received the complete
LAPD Message frame, then it will proceed to perform
the following five (5) steps.
1. PMDL Message Extraction
The LAPD Receiver will extract out the PMDL Message, from the newly received LAPD Message frame.
The LAPD Receiver will then write this PMDL Message into the Receive LAPD Message buffer within
the Framer IC.
NOTE: As the LAPD Receiver is extracting the PMDL Message, from the newly received LAPD Message frame, the
LAPD Receiver will also check the PMDL data for the
occurrence of stuff bits (e.g., “0’s” that were inserted into
the PMDL Message by the Remote LAPD Transmitter, in
order to prevent this data from mimicking the Flag
Sequence byte or an ABORT Sequence), and remove them
prior to writing the PMDL Message into the Receive LAPD
Message Buffer. Specifically, the LAPD Receiver will search
through the PMDL Message data and will remove any “0”
that immediately follows a string of 5 consecutive “1’s”.
NOTE: For more information on how the LAPD Transmitter
inserted these stuff bits, please see Section 4.2.3.1.
2. FCS (Frame Check Sequence) Word Verification
The LAPD Receiver will compute the CRC-16 value
of the header octets and the PMDL Message octets,
within this LAPD Message frame and will compare it
with the value of the two octets, residing in the FCS
word-field of this LAPD Message frame. If the FCS
value of the newly received LAPD Message frame
matches the locally-computed CRC-16 value, then
the LAPD Receiver will conclude that it has received
this LAPD Message frame in an error-free manner.
However, if the FCS value does not match the locallycomputed CRC-16 value, then the LAPD Receiver
will conclude that this LAPD Message frame is erred.
The LAPD Receiver will indicate the results of this
FCS Verification process by setting Bit 2 (RxFCS Er323
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THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. P1.1.8
ror) within the Rx E3 LAPD Status Register, to the appropriate value as tabulated below.
RXE3 LAPD STATUS REGISTER (ADDRESS = 0X19)
BIT 7
BIT 6
BIT 5
Not Used
RxABORT
RO
RO
RO
0
0
0
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
RxCR
Type
RxFCS
Error
End of
Message
Flag
Present
RO
RO
RO
RO
RO
0
0
1
0
0
RxLAPDType[1:0]
the Receive LAPD Message buffer, by first checking the
state of this bit-field.
If the LAPD Receiver detects an error in the FCS value, then it will set the RxFCS Error bit-field to “1”.
Conversely, if the LAPD Receiver does not detect an
error in the FCS value, then it will clear the RxFCS
Error bit-field to “0”.
3. Check and Report the State of the “C/R” Bit-field
After receiving the LAPD Message frame, the LAPD
Receiver will check the state of the “C/R” bit-field,
within octet # 2 of the LAPD Message frame header
and will reflect this value in Bit 3 (Rx CR Type) within
the Rx E3 LAPD Status Register, as depicted below.
NOTE: The LAPD Receiver will extract and write the PMDL
Message into the Receive LAPD Message buffer independent of the results of FCS Verification. Hence, the user is
urged to validate each PMDL Message that is read in from
RXE3 LAPD STATUS REGISTER (ADDRESS = 0X19)
BIT 7
BIT 6
BIT 5
Not Used
RxABORT
RO
RO
RO
0
0
0
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
RxCR
Type
RxFCS
Error
End of
Message
Flag
Present
RO
RO
RO
RO
RO
0
1
0
0
0
RxLAPDType[1:0]
Transmit LAPD Message buffer. The value of this byte
corresponds to the type of LAPD Message frame/PMDL Message that is to be transmitted to the Remote
LAPD Receiver. This Message-Type Identification octet is transported to the Remote LAPD Receiver,
along with the rest of the LAPD frame. From this Message Type Identification octet, the LAPD Receiver will
know the type of size of the newly received PMDL
Message. The LAPD Receiver will then reflect this information in Bits 4 and 5 (RxLAPDType[1:0]) within
the Rx E3 LAPD Status Register, as depicted below.
When this bit-field is “0”, it means that this LAPD
Message frame is originating from a customer installation. When this bit-field is “1”, it means that this
LAPD Message frame is originating from a network
terminal.
4. Identify the Type of LAPD Message Frame/PMDL
Message
Next, the LAPD Receiver will check the value of the
first octet within the PMDL Message field, of the
LAPD Message frame. When operating the LAPD
Transmitter, the user is required to write in a byte of a
specific value into the first octet position within the
RXE3 LAPD STATUS REGISTER (ADDRESS = 0X19)
BIT 7
BIT 6
BIT 5
Not Used
RxABORT
RO
RO
RO
0
0
0
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
RxCR
Type
RxFCS
Error
End of
Message
Flag
Present
RO
RO
RO
RO
RO
0
0
0
0
0
RxLAPDType[1:0]
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THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. P1.1.8
Table 63 presents the relationship between the contents of RxLAPDType[1:0] and the type of message
received by the LAPD Receiver.
TABLE 63: THE RELATIONSHIP BETWEEN THE CONTENTS OF RXLAPDTYPE[1:0] BIT-FIELDS AND THE PMDL
MESSAGE TYPE/SIZE
RXLAPDTYPE[1:0]
PMDL MESSAGE TYPE
PMDL MESSAGE SIZE
00
Test Signal Identification
76 Bytes
01
Idle Signal Identification
76 Bytes
10
CL Path Identification
76 Bytes
11
ITU-T Path Identification
82 Bytes
NOTE: Prior to reading in the PMDL Message from the
Receive LAPD Message buffer, the user is urged to read
the state of the RxLAPDType[1:0] bit-fields in order to determine the size of this message.
5. Inform the Local Microprocessor/External Circuitry of the receipt of the new LAPD Message
frame.
Finally, after the LAPD Receiver has received and
processed the newly received LAPD Message frame
(per steps 1 through 4, as described above), it will inform the local Microprocessor that a LAPD Message
frame has been received and is ready for user-system handling. The LAPD Receiver will inform the Mi-
croprocessor/Microcontroller and the external circuitry by:
• Generating a LAPD Message Frame Received
interrupt to the Microprocessor. The purpose of this
interrupt is to let the Microprocessor know that the
Receive LAPD Message buffer contains a new
PMDL Message that needs to be read and processed. When the LAPD Receiver generates this
interrupt, it will set bit 0 (RxLAPD Interrupt Status)
within the Rx E3 LAPD Control Register to “1” as
depicted below.
)
RXE3 LAPD CONTROL REGISTER (ADDRESS = 0X18
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
Not Used
BIT 2
BIT 1
BIT 0
RxLAPD
Enable
RxLAPD
Interrupt Enable
RxLAPD
Interrupt Status
RO
RO
RO
RO
RO
R/W
R/W
RUR
0
0
0
0
0
0
0
1
• Setting Bit 1 (End of Message) within the Rx E3
LAPD Status Register, to “1” as depicted below.
RXE3 LAPD STATUS REGISTER (ADDRESS = 0X19)
BIT 7
BIT 6
BIT 5
Not Used
RxABORT
RO
RO
RO
0
0
0
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
RxCR
Type
RxFCS
Error
End of
Message
Flag
Present
RO
RO
RO
RO
RO
0
0
0
1
0
RxLAPDType[1:0]
In summary, Figure 143 presents a flow chart depicting how the LAPD Receiver functions.
325
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XRT72L53
THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. P1.1.8
FIGURE 143. FLOW CHART DEPICTING THE FUNCTIONALITY OF THE LAPD RECEIVER
START
START
LAPD
LAPDReceiver
Receiverisisreading
readinginina aLAPD
LAPD
Message
MessageFrame,
Frame,containing
containinga aPMDL
PMDL
Message.
Message.
ENABLE THE LAPD RECEIVER
This is done by writing the value “xxxx x1xx” into
the RxLAPD Control Register (Address = 0x18)
Does
Does
the
theLAPD
LAPD
Receiver
Receiverdetect
detect66
consecutive
consecutive
Zeros
Zeros
??
NO
LAPD Receiver begins reading in the N bits
from each inbound E3 frame
VERIFY
VERIFYTHE
THEFCS
FCSVALUE
VALUE
Report results in the RxLAPD
Report results in the RxLAPD
Status
StatusRegister..
Register..
“Un-stuff
“Un-stuffcontents
contentsofofReceived
Received
Message”
Message”
YES
Does
Does
the
theLAPD
LAPD
Receiver detect 6
Receiver detect 6
consecutive
consecutive
Zeros
Zeros
?
?
1
1
YES
Does
Does
the LAPD
the LAPD
Receiver detect 7
Receiver detect 7
consecutive
consecutive
Zeros
Zeros
?
?
NO
ABORT Sequence
ABORT Sequence
YES
YES
NO
End
EndofofMessage
Message(EOM)
(EOM)
Generate
Generate“Received
“ReceivedLAPD
LAPD
Interrupt”
Interrupt”
Does
Does
the
theLAPD
LAPD
Receiver
Receiverdetect
detect77
consecutive
consecutive
Zeros
Zeros
??
Execute
ExecuteReceive
ReceiveLAPD
LAPD
Interrupt
InterruptService
ServiceRoutine
Routine
NO
11
Write
WriteReceived
ReceivedPMDL
PMDLMessage
Message
into
the
Receive
LAPD
into the Receive LAPDMessage
Message
Buffer
Buffer(Addresses
(Addresses0xDE
0xDE- -0x135)
0x135)
Flag Sequence
Flag Sequence
5.3.4
face
The Receive Overhead Data Output Inter-
Figure 144 presents a simple illustration of the Receive Overhead Data Output Interface block within
the XRT72L53.
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THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. P1.1.8
FIGURE 144. A SIMPLE ILLUSTRATION OF THE RECEIVE OVERHEAD OUTPUT INTERFACE BLOCK
RxOHFrame
RxOH
RxOHClk
Receive
ReceiveOverhead
Overhead
Output
Interface
Output Interface
Block
Block
From Receive
E3 Framer Block
RxOHEnable
• Method 2 - Using the RxClk and RxOHEnable output signals.
The E3, ITU-T G.751 frame consists of 1536 bits. Of
these bytes, 1524 bits are payload bits and the remaining 12 bits are overhead bits. The XRT72L53
has been designed to handle and process both the
payload type and overhead type bits for each E3
frame.
Each of these methods are described below.
Within the Receive Section of the XRT72L53, the Receive Payload Data Output Interface block has been
designed to handle the payload bits. Likewise, the
Receive Overhead Data Output Interface block has
been designed to handle and process the overhead
bits.
The Receive Overhead Data Output Interface block
unconditionally outputs the contents of all overhead
bits. The XRT72L53 does not offer the user a means
to shut off this transmission of data. However, the Receive Overhead Output Interface block does provide
the user with the appropriate output signals for external Data Link Layer equipment to sample and process these overhead bits, via the following two methods.
• Method 1- Using the RxOHClk clock signal.
5.3.4.1 Method 1 - Using the RxOHClk Clock
signal
The Receive Overhead Data Output Interface block
consists of four (4) signals. Of these four signals, the
following three signals are to be used when sampling
the E3 overhead bits via Method 1.
• RxOH
• RxOHClk
• RxOHFrame
Each of these signals are listed and described below
in Table 64.
Interfacing the Receive Overhead Data Output Interface block to the Terminal Equipment (Method
1)
Figure 145 illustrates how one should interface the
Receive Overhead Data Output Interface block to the
Terminal Equipment when using Method 1 to sample
and process the overhead bits from the inbound E3
data stream.
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THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. P1.1.8
FIGURE 145. ILLUSTRATION OF HOW TO INTERFACE THE TERMINAL EQUIPMENT TO THE RECEIVE OVERHEAD DATA
OUTPUT INTERFACE BLOCK (FOR METHOD 1).
RxOHClk
E3_OH_Clock_In
RxOH
E3_OH_In
RxOHFrame
Rx_Start_of_Frame
Terminal Equipment
XRT72L5x E3 Framer IC
2. Keep track of the number of rising clock edges
that have occurred in the RxOHClk (e.g., the
E3_OH_Clock_In) signal, since the last time the
RxOHFrame signal was sampled "High”. By
doing this, the Terminal Equipment will be able to
keep track of which overhead byte is being output
via the RxOH output pin. Based upon this information, the Terminal Equipment will be able to
derive some meaning from these overhead bits.
Method 1 Operation of the Terminal Equipment
If the Terminal Equipment intends to sample any
overhead data from the inbound E3 data stream (via
the Receive Overhead Data Output Interface block)
then it is expected to do the following:
1. Sample the state of the RxOHFrame signal (e.g.,
the Rx_Start_of_Frame input signal) on the rising
edge of the RxOHClk (e.g., the
E3_OH_Clock_In) signal.
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THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. P1.1.8
TABLE 64: LISTING AND DESCRIPTION OF THE PIN ASSOCIATED WITH THE RECEIVE OVERHEAD DATA OUTPUT
INTERFACE BLOCK (FOR METHOD 1)
SIGNAL NAME
TYPE
RxOH
Output
DESCRIPTION
Receive Overhead Data Output pin:
The XRT72L53 will output the overhead bits, within the incoming E3 frames, via this pin.
The Receive Overhead Data Output Interface block will output a given overhead bit, upon the
falling edge of RxOHClk. Hence, the external data link equipment should sample the data, at
this pin, upon the rising edge of RxOHClk.
NOTE: The XRT72L53 will always output the E3 Overhead bits via this output pin. There are no
external input pins or register bit settings available that will disable this output pin.
RxOHClk
Output
Receive Overhead Data Output Interface Clock Signal:
The XRT72L53 will output the Overhead bits (within the incoming E3 frames), via the RxOH
output pin, upon the falling edge of this clock signal.
As a consequence, the user's data link equipment should use the rising edge of this clock signal to sample the data on both the RxOH and RxOHFrame output pins.
NOTE: This clock signal is always active.
RxOHFrame
Output
Receive Overhead Data Output Interface - Start of Frame Indicator:
The XRT72L53 will drive this output pin "High” (for one period of the RxOHClk signal) whenever
the first overhead bit within a given E3 frame is being driven onto the RxOH output pin.
Table 65 relates the number of rising clock edges (in
the RxOHClk signal, since the RxOHFrame signal
was last sampled "High”) to the E3 Overhead bit that
is being output via the RxOH output pin.
TABLE 65: THE RELATIONSHIP BETWEEN THE NUMBER OF RISING CLOCK EDGES IN RXOHCLK, (SINCE
RXOHFRAME WAS LAST SAMPLED "HIGH”) TO THE E3 OVERHEAD BIT, THAT IS BEING OUTPUT VIA THE RXOH
OUTPUT PIN
NUMBER OF RISING CLOCK EDGES IN RXOHCLK
THE OVERHEAD BIT BEING OUTPUT BY THE
XRT72L53
0 (Clock edge is coincident with RxOHFrame being detected "High”)
FAS Pattern - Bit 9
1
FAS Pattern - Bit 8
2
FAS Pattern - Bit 7
3
FAS Pattern - Bit 6
4
FAS Pattern - Bit 5
5
FAS Pattern - Bit 4
6
FAS Pattern - Bit 3
7
FAS Pattern - Bit 2
8
FAS Pattern - Bit 1
9
FAS Pattern - Bit 0
10
A Bit
11
N Bit
Figure 146 presents the typical behavior of the Receive Overhead Data Output Interface block, when
Method 1 is being used to sample the incoming E3
overhead bits.
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FIGURE 146. ILLUSTRATION OF THE SIGNALS THAT ARE OUTPUT VIA THE RECEIVE OVERHEAD OUTPUT INTERFACE
(FOR METHOD 1).
RxOHClk
RxOHFrame
RxOH
FAS, Bit 9
FAS, Bit 8
Terminal Equipment should sample
the “RxOHFrame” and “RxOH” signals
here.
FAS, Bit 7
FAS, Bit 6
FAS, Bit 5
Recommended Sampling Edges
Method 2 - Using RxOutClk and the RxOHEnable
signals
• RxOH
Method 1 requires that the Terminal Equipment be
able to handle an additional clock signal, RxOHClk.
However, there may be a situation in which the Terminal Equipment circuitry does not have the means to
deal with this extra clock signal, in order to use the
Receive Overhead Data Output Interface. Method 2
involves the use of the following signals.
• RxOHEnable
• RxOutClk
• RxOHFrame
Each of these signals are listed and described below
in Table 66.
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TABLE 66: LISTING AND DESCRIPTION OF THE PIN ASSOCIATED WITH THE RECEIVE OVERHEAD DATA OUTPUT
INTERFACE BLOCK (METHOD 2)
SIGNAL NAME
TYPE
RxOH
Output
DESCRIPTION
Receive Overhead Data Output pin:
The XRT72L53 will output the overhead bits, within the incoming E3 frames, via this pin.
The Receive Overhead Output Interface will pulse the RxOHEnable output pin (for one RxOutClk period) at approximately the middle of the RxOH bit period. The user is advised to design
the Terminal Equipment to latch the contents of the RxOH output pin, whenever the RxOHEnable output pin is sampled "High” on the falling edge of RxOutClk.
RxOHEnable
Output
Receive Overhead Data Output Enable - Output pin:
The XRT72L53 will assert this output signal for one RxOutClk period when it is safe for the Terminal Equipment to sample the data on the RxOH output pin.
RxOHFrame
Output
Receive Overhead Data Output Interface - Start of Frame Indicator:
The XRT72L53 will drive this output pin "High” (for one period of the RxOH signal), whenever
the first overhead bit, within a given E3 frame is being driven onto the RxOH output pin.
RxOutClk
Output
Receive Section Output Clock Signal:
This clock signal is derived from the RxLineClk signal (from the LIU) for loop-timing applications, and the TxInClk signal (from a local oscillator) for local-timing applications. For E3 applications, this clock signal will operate at 34.368MHz.
The user is advised to design the Terminal Equipment to latch the contents of the RxOH pin,
anytime the RxOHEnable output signal is sampled "High” on the falling edge of this clock signal.
Interfacing the Receive Overhead Data Output Interface block to the Terminal Equipment (Method
2)
Figure 147 illustrates how one should interface the
Receive Overhead Data Output Interface block to the
Terminal Equipment, when using Method 2 to sample
and process the overhead bits from the inbound E3
data stream.
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FIGURE 147. ILLUSTRATION OF HOW TO INTERFACE THE TERMINAL EQUIPMENT TO THE RECEIVE OVERHEAD DATA
OUTPUT INTERFACE BLOCK (FOR METHOD 2).
E3_OH_In
RxOH
E3_OH_Enable_In
RxOHEnable
E3_Clk_In
RxOutClk
Rx_Start_of_Frame
RxOHFrame
Terminal Equipment
XRT72L5x E3 Framer IC
Method 2 Operation of the Terminal Equipment
"High”. By doing this, the Terminal Equipment will
be able to keep track of which overhead bit is
being output via the RxOH output pin. Based
upon this information, the Terminal Equipment
will be able to derive some meaning from these
overhead bits.
3. Table 67 relates the number of RxOHEnable output pulses (that have occurred since both the
RxOHFrame and the RxOHEnable pins were
both sampled "High”) to the E3 overhead bit that
is being output via the RxOH output pin.
If the Terminal Equipment intends to sample any
overhead data from the inbound E3 data stream (via
the Receive Overhead Data Output Interface), then it
is expected to do the following.
1. Sample the state of the RxOHFrame signal (e.g.,
the Rx_Start_of_Frame input) on the falling edge
of the RxOutClk clock signal, whenever the RxOHEnable output signal is also sampled "High”.
2. Keep track of the number of times that the RxOHEnable signal has been sampled "High” since
the last time the RxOHFrame was also sampled
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TABLE 67: THE RELATIONSHIP BETWEEN THE NUMBER OF RXOHENABLE OUTPUT PULSES (SINCE RXOHFRAME WAS
LAST SAMPLED "HIGH") TO THE E3 OVERHEAD BIT, THAT IS BEING OUTPUT VIA THE RXOH OUTPUT PIN
NUMBER OF RXOHENABLE OUTPUT PULSES
THE OVERHEAD BIT BEING OUTPUT BY THE
XRT72L53
0 (Clock edge is coincident with RxOHFrame being detected "High”)
FAS Pattern - Bit 9
1
FAS Pattern - Bit 8
2
FAS Pattern - Bit 7
3
FAS Pattern - Bit 6
4
FAS Pattern - Bit 5
5
FAS Pattern - Bit 4
6
FAS Pattern - Bit 3
7
FAS Pattern - Bit 2
8
FAS Pattern - Bit 1
9
FAS Pattern - Bit 0
10
A Bit
11
N Bit
Figure 148 presents the typical behavior of the Receive Overhead Data Output Interface block, when
Method 2 is being used to sample the incoming E3
overhead bits.
FIGURE 148. ILLUSTRATION OF THE SIGNALS THAT ARE OUTPUT VIA THE RECEIVE OVERHEAD DATA OUTPUT INTERFACE BLOCK (FOR METHOD 2).
RxOutClk
RxOHEnable
Recommended
Sampling
Edges
RxOHFrame
RxOH
BIP - 4, Bit 0
FAS, Bit 9
FAS, Bit 8
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5.3.5
face
REV. P1.1.8
The Receive Payload Data Output Inter-
Figure 149 presents a simple illustration of the Receive Payload Data Output Interface block.
FIGURE 149. A SIMPLE ILLUSTRATION OF THE RECEIVE PAYLOAD DATA OUTPUT INTERFACE BLOCK
RxOHInd
RxSer
RxNib[3:0]
RxClk
Receive
ReceivePayload
Payload
Data
Output
Data Output
Interface
Interface
From Receive E3
Framer Block
RxOutClk
RxFrame
Each of the output pins of the Receive Payload Data
Output Interface block are listed in Table 68 and described below. The exact role that each of these out-
put pins assume, for a variety of operating scenarios
are described throughout this section.
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TABLE 68: LISTING AND DESCRIPTION OF THE PIN ASSOCIATED WITH THE RECEIVE PAYLOAD DATA OUTPUT
INTERFACE BLOCK
SIGNAL NAME
RxSer
TYPE
Output
DESCRIPTION
Receive Serial Payload Data Output pin:
If the user opts to operate the XRT72L53 in the serial mode, then the chip will output the payload data, of the incoming E3 frames, via this pin. The XRT72L53 will output this data upon the
rising edge of RxClk.
The user is advised to design the Terminal Equipment such that it will sample this data on the
falling edge of RxClk.
This signal is only active if the NibInt input pin is pulled "Low".
RxNib[3:0]
Output
Receive Nibble-Parallel Payload Data Output pins:
If the user opts to operate the XRT72L53 in the nibble-parallel mode, then the chip will output
the payload data, of the incoming E3 frames, via these pins. The XRT72L53 will output data
via these pins, upon the falling edge of the RxClk output pin.
The user is advised to design the Terminal Equipment such that it will sample this data upon
the rising edge of RxClk.
NOTE: These pins are only active if the NibInt input pin is pulled "High".
RxClk
Output
Receive Payload Data Output Clock pin:
The exact behavior of this signal depends upon whether the XRT72L53 is operating in the
Serial or in the Nibble-Parallel-Mode.
Serial Mode Operation
In the serial mode, this signal is a 34.368MHz clock output signal. The Receive Payload Data
Output Interface will update the data via the RxSer output pin, upon the rising edge of this
clock signal.
The user is advised to design (or configure) the Terminal Equipment to sample the data on the
RxSer pin, upon the falling edge of this clock signal.
Nibble-Parallel Mode Operation
In this Nibble-Parallel Mode, the XRT72L53 will derive this clock signal, from the RxLineClk
signal. The XRT72L53 will pulse this clock 1060 times for each inbound E3 frame. The
Receive Payload Data Output Interface will update the data, on the RxNib[3:0] output pins
upon the falling edge of this clock signal.
The user is advised to design (or configure) the Terminal Equipment to sample the data on the
RxNib[3:0] output pins, upon the rising edge of this clock signal
RxOHInd
Output
Receive Overhead Bit Indicator Output:
This output pin will pulse "High" whenever the Receive Payload Data Output Interface outputs
an overhead bit via the RxSer output pin. The purpose of this output pin is to alert the Terminal
Equipment that the current bit, (which is now residing on the RxSer output pin), is an overhead
bit and should not be processed by the Terminal Equipment.
The XRT72L53 will update this signal, upon the rising edge of RxOHInd.
The user is advised to design (or configure) the Terminal Equipment to sample this signal
(along with the data on the RxSer output pin) on the falling edge of the RxClk signal.
NOTE: For E3 applications, this output pin is only active if the XRT72L53 is operating in the
Serial Mode. This output pin will be "Low" if the device is operating in the Nibble-Parallel Mode.
RxFrame
Output
Receive Start of Frame Output Indicator:
The exact behavior of this pin, depends upon whether the XRT72L53 has been configured to
operate in the Serial Mode or the Nibble-Parallel Mode.
Serial Mode Operation:
The Receive Section of the XRT72L53 will pulse this output pin "High" (for one bit period)
when the Receive Payload Data Output Interface block is driving the very first bit (or Nibble) of
a given E3 frame, onto the RxSer output pin.
Nibble-Parallel Mode Operation:
The Receive Section of the XRT72L53 will pulse this output pin "High" for one nibble period,
when the Receive Payload Data Output Interface is driving the very first nibble of a given E3
frame, onto the RxNib[3:0] output pins.
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Operation of the Receive Payload Data Output Interface block
The XRT72L53 will output the payload data, of the incoming E3 frames via the RxSer output pin, upon the
rising edge of RxClk.
The Receive Payload Data Output Interface permits
the user to read out the payload data of inbound E3
frames, via either of the following modes.
Delineation of inbound E3 Frames
The XRT72L53 will pulse the RxFrame output pin
"High" for one bit-period coincident with it driving the
first bit within a given E3 frame, via the RxSer output
pin.
• Serial Mode
• Nibble-Parallel Mode
Each of these modes are described in detail, below.
5.3.5.1 Serial Mode Operation Behavior of the
XRT72L53
If the XRT72L53 has been configured to operate in
this mode, then the XRT72L53 will behave as follows.
Payload Data Output
Interfacing the XRT72L53 to the Receive Terminal
Equipment
Figure 150 presents a simple illustration as how the
user should interface the XRT72L53 to that terminal
equipment which processes Receive Direction payload data.
FIGURE 150. ILLUSTRATION OF THE TERMINAL EQUIPMENT BEING INTERFACED TO THE RECEIVE PAYLOAD DATA
INPUT INTERFACE BLOCK OF THE XRT72L53 FRAMER IC (SERIAL MODE OPERATION)
Rx_E3_Clock_In
34.368 MHz Clock Signal
34.368 MHz
Clock Source
RxClk
RxSer
E3_Data_In
RxLineClk
RxFrame
Rx_Start_of_Frame
RxOHInd
Rx_E3_OH_Ind
Terminal Equipment
(Receive Payload Section)
XRT72L5x E3 Framer
Required Operation of the Terminal Equipment
The XRT72L53 will update the data on the RxSer output pin, upon the rising edge of RxClk. Hence, the
Terminal Equipment should sample the data on the
RxSer output pin (or the E3_Data_In pin at the Terminal Equipment) upon the rising edge of RxClk. As the
Terminal Equipment samples RxSer with each rising
edge of RxClk it should also be sampling the following signals.
• RxFrame
• RxOHInd
The Need for sampling RxFrame
The XRT72L53 will pulse the RxFrame output pin
"High" coincident with it driving the very first bit of a
given E3 frame onto the RxSer output pin. If knowl-
edge of the E3 Frame Boundaries is important for the
operation of the Terminal Equipment, then this is a
very important signal for it to sample.
The Need for sampling RxOHInd
The XRT72L53 will indicate that it is currently driving
an overhead bit onto the RxSer output pin, by pulsing
the RxOHInd output pin "High". If the Terminal Equipment samples this signal "High", then it should know
that the bit, that it is currently sampling via the RxSer
pin is an overhead bit and should not be processed.
The Behavior of the Signals between the Receive
Payload Data Output Interface block and the Terminal Equipment
The behavior of the signals between the XRT72L53
and the Terminal Equipment for E3 Serial Mode Operation is illustrated in Figure 151.
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FIGURE 151. AN ILLUSTRATION OF THE BEHAVIOR OF THE SIGNALS BETWEEN THE RECEIVE PAYLOAD DATA OUTPUT INTERFACE BLOCK OF THE XRT72L53 AND THE TERMINAL EQUIPMENT
Terminal Equipment Signals
E3_Clock_In
E3_Data_Out
Payload[1522]
Payload[1523]
FAS , Bit 9
FAS, Bit 8
FAS, Bit 9
FAS, Bit 8
Rx_Start_of_Frame
E3_Overhead_Ind
XRT72L5x Receive Payload Data I/F Signals
RxClk
RxSer
Payload[1522]
Payload[1523]
RxFrame
RxOH_Ind
E3 Frame Number N
E3 Frame Number N + 1
Note: RxFrame pulses high to denote
E3 Frame Boundary.
Note: RxOH_Ind pulses high for 12
bit-periods in order to denote
Overhead Data (e.g., the FAS pattern,
the A and N bits).
2. Unlike Serial Mode operation, the duty cycle of
RxClk, in Nibble-Parallel Mode operation is approximately 25%.
5.3.5.2 Nibble-Parallel Mode Operation Behavior of the XRT72L53
If the XRT72L53 has been configured to operate in
the Nibble-Parallel Mode, then the XRT72L53 will behave as follows.
Delineation of Inbound E3 Frames
Payload Data Output
The XRT72L53 will output the payload data of the incoming E3 frames, via the RxNib[3:0] output pins, upon the rising edge of RxClk.
NOTES:
1. In this case, RxClk will function as the Nibble Clock
signal between the XRT72L53 the Terminal Equipment. The XRT72L53 will pulse the RxClk output
signal "High" 1060 times, for each inbound E3
frame.
Note: FAS pattern will not be processed by the
Transmit Payload Data Input Interface.
The XRT72L53 will pulse the RxFrame output pin
"High" for one nibble-period coincident with it driving
the very first nibble, within a given inbound E3 frame,
via the RxNib[3:0] output pins.
Interfacing the XRT72L53 the Terminal Equipment.
Figure 152 presents a simple illustration as how the
user should interface the XRT72L53 to that terminal
equipment which processes Receive Direction payload data.
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FIGURE 152. ILLUSTRATION OF THE XRT72L53 DS3/E3 FRAMER IC BEING INTERFACED TO THE RECEIVE SECTION
TERMINAL EQUIPMENT (NIBBLE-PARALLEL MODE OPERATION)
OF THE
34.368 MHz
Clock Source
8.592 MHz Clock Signal
Rx_E3_Clock_In
RxClk
RxNib[3:0]
E3_Data_In[3:0]
RxLineClk
RxFrame
Rx_Start_of_Frame
Rx_E3_OH_Ind
RxOH_Ind
Terminal Equipment
(Receive Payload Section)
XRT72L5x E3 Framer
Required Operation of the Terminal Equipment
The XRT72L53 will update the data on the RxNib[3:0]
line, upon the rising edge of RxClk. Hence, the Terminal Equipment should sample the data on the RxNib[3:0] output pins (or the E3_Data_In[3:0] input
pins at the Terminal Equipment) upon the rising edge
of RxClk. As the Terminal Equipment samples RxSer
with each rising edge of RxClk it should also be sampling the RxFrame signal.
The Need for Sampling RxFrame
The XRT72L53 will pulse the RxFrame output pin
"High" coincident with it driving the very first nibble of
a given E3 frame, onto the RxNib[3:0] output pins. If
knowledge of the E3 Frame Boundaries is important
for the operation of the Terminal Equipment, then this
is a very important signal for it to sample.
The Behavior of the Signals between the Receive
Payload Data Output Interface block and the Terminal Equipment
The behavior of the signals between the XRT72L53
and the Terminal Equipment for E3 Nibble-Mode operation is illustrated in Figure 153.
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FIGURE 153. ILLUSTRATION OF THE SIGNALS THAT ARE OUTPUT VIA THE RECEIVE PAYLOAD DATA OUTPUT INTERNIBBLE-PARALLEL MODE OPERATION).
FACE BLOCK (FOR
Terminal Equipment Signals
RxOutClk
Rx_E3_Clock_In
E3_Data_In[3:0]
Overhead Nibble [0]
Overhead Nibble [1]
Rx_Start_of_Frame
Rx_E3_OH_Ind
XRT72L5x Receive Payload Data I/F Signals
RxOutClk
RxClk
RxNib[3:0]
Overhead Nibble [0]
Overhead Nibble [1]
RxFrame
RxOH_Ind
E3 Frame Number N
E3 Frame Number N + 1
Note: RxFrame pulses high to denote
E3 Frame Boundary.
Recommended Sampling Edge of Terminal
Equipment
5.3.6 Receive Section Interrupt Processing
The Receive Section of the XRT72L53 can generate
an interrupt to the MIcrocontroller/Microprocessor for
the following reasons.
5.3.6.1 Enabling Receive Section Interrupts
As mentioned in Section 1.6, the Interrupt Structure
within the XRT72L53 contains two hierarchical levels.
• Change in Receive LOS Condition
• Source Level
• Change in Receive OOF Condition
The Block Level
• Change in Receive LOF Condition
The Enable state of the Block level for the Receive
Section Interrupts dictates whether or not interrupts
(if enabled at the source level), are actually enabled.
• Change in Receive AIS Condition
• Change in Receive FERF Condition
• Change of Framing Alignment
• Detection of FEBE (Far-End Block Error) Event
• Detection of BIP-4 Error
• Detection of Framing Error
• Block Level
The user can enable or disable these Receive Section interrupts, at the Block Level by writing the appropriate data into Bit 7 (Rx DS3/E3 Interrupt Enable)
within the Block Interrupt Enable register (Address =
0x04), as illustrated below.
• Reception of a new LAPD Message
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BLOCK INTERRUPT ENABLE REGISTER (ADDRESS = 0X04)
BIT 7
BIT 6
BIT 5
RxDS3/E3
Interrupt
Enable
BIT 4
BIT 3
BIT 2
Not Used
BIT 1
BIT 0
TxDS3/E3
Interrupt
Enable
One-Second
Interrupt
Enable
R/W
RO
RO
RO
RO
RO
R/W
R/W
X
0
0
0
0
0
0
0
• If the XRT7300 LIU IC declares an LOS condition,
and drives the RLOS input pin (of the XRT72L53
Framer IC) “High”.
Setting this bit-field to “1” enables the Receive Section at the Block Level) for interrupt generation. Conversely, setting this bit-field to “0” disables the Receive Section for interrupt generation.
5.3.6.2 Enabling/Disabling and Servicing Interrupts
As mentioned previously, the Receive Section of the
XRT72L53 Framer IC contains numerous interrupts.
The Enabling/Disabling and Servicing of each of
these interrupts is described below.
5.3.6.2.1 The Change in Receive LOS Condition Interrupt
If the Change in Receive LOS Condition Interrupt is
enabled, then the XRT72L53 Framer IC will generate
an interrupt in response to either of the following conditions.
1. When the XRT72L53 Framer IC declares an LOS
(Loss of Signal) Condition, and
2. When the XRT72L53 Framer IC clears the LOS
condition.
Conditions causing the XRT72L53 Framer IC to
declare an LOS Condition.
• If the XRT72L53 Framer IC detects 32 consecutive
“0”, via the RxPOS and RxNEG input pins.
Conditions causing the XRT72L53 Framer IC to
clear the LOS Condition.
• If the XRT7300 LIU IC clears the LOS condition and
drives the RLOS input pin (of the XRT72L53
Framer IC) “Low”.
• If the XRT72L53 Framer IC detects a string of 32
consecutive bits (via the RxPOS and RxNEG input
pins) that does NOT contain a string of 4 consecutive “0’s”.
Enabling and Disabling the Change in Receive
LOS Condition Interrupt
The user can enable or disable the Change in Receive LOS Condition Interrupt, by writing the appropriate value into Bit 1 (LOS Interrupt Enable), within
the RxE3 Interrupt Enable Register - 1, as indicated
below.
RXE3 INTERRUPT ENABLE REGISTER - 1 (ADDRESS = 0X12)
BIT 7
BIT 6
BIT 5
Not Used
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
COFA
Interrupt
Enable
OOF
Interrupt
Enable
LOF
Interrupt
Enable
LOS
Interrupt
Enable
AIS
Interrupt
Enable
RO
RO
RO
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
X
0
Setting this bit-field to “1” enables this interrupt. Conversely, setting this bit-field to “0” disables this interrupt.
Servicing the Change in Receive LOS Condition
Interrupt
Whenever the XRT72L53 Framer IC detects this interrupt, it will do all of the following.
• It will assert the Interrupt Request output pin (INT),
by driving it “Low”.
• It will set Bit 1 (LOS Interrupt Status), within the Rx
E3 Interrupt Status Register - 1 to “1”, as indicated
below.
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RXE3 INTERRUPT STATUS REGISTER - 1 (ADDRESS = 0X14)
BIT 7
BIT 6
BIT 5
Not Used
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
COFA
OOF
LOF
LOS
AIS
Interrupt Status Interrupt Status Interrupt Status Interrupt Status Interrupt Status
RO
RO
RO
RUR
RUR
RUR
RUR
RUR
0
0
0
0
0
0
1
0
declares or clears the LOS defect. Hence, the
user can determine the current state of the LOS
defect by reading the state of Bit 4 (RxLOS)
within the Rx E3 Configuration and Status Register - 2, as illustrated below.
Whenever the user’s system encounters the Change
in Receive LOS Condition Interrupt, then it should do
the following.
1. It should determine the current state of the LOS
condition. Recall, that this interrupt can be generated, whenever the XRT72L53 Framer IC
RXE3 CONFIGURATION & STATUS REGISTER - 2 (ADDRESS = 0X11)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
RxLOF
Algo
RxLOF
RxOOF
RxLOS
RxAIS
R/W
RO
RO
RO
RO
RO
RO
RO
0
1
1
0
0
1
1
1
BIT 1
Not Used
BIT 0
RxFERF
2. When the XRT72L53 Framer IC clears the OOF
condition.
Conditions causing the XRT72L53 Framer IC to
declare an OOF Condition.
If the LOS state is TRUE
1. It should transmit a FERF (Far-End-Receive Failure) indicator to the Remote Terminal Equipment.
Please see Section 4.2.4.2.1.3 on how to configure the XRT72L53 to transmit a FERF indicator to
the Remote Terminal Equipment.
If the LOS state is FALSE
• If the Receive E3 Framer block (within the
XRT72L53 Framer IC) detects Framing bit errors,
within four consecutive incoming E3 frames.
Conditions causing the XRT72L53 Framer IC to
clear the OOF Condition.
1. It should cease transmitting the FERF indication
to the Remote Terminal Equipment. Please see
Section 4.2.4.2.1.3 on how to control the state of
the “A” bit, which is transmitted on each outbound
E3 frame.
5.3.6.2.2 The Change in Receive OOF Condition Interrupt
If the Change in Receive OOF Condition Interrupt is
enabled, then the XRT72L53 Framer IC will generate
an interrupt in response to either of the following conditions.
1. When the XRT72L53 Framer IC declares an OOF
(Out of Frame) Condition, and
BIT 2
• If the Receive E3 Framer block (within the
XRT72L53 Framer IC) transitions from the FAS Pattern Verification state to the In-Frame state (see
Figure 115).
• If the Receive E3 Framer block transitions from the
OOF Condition state to the In-Frame state (see Figure 115).
Enabling and Disabling the Change in Receive
OOF Condition Interrupt
The user can enable or disable the Change in Receive OOF Condition Interrupt, by writing the appropriate value into Bit 3 (OOF Interrupt Enable), within
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the RxE3 Interrupt Enable Register - 1, as indicated
below.
RXE3 INTERRUPT ENABLE REGISTER - 1 (ADDRESS = 0X12)
BIT 7
BIT 6
BIT 5
Not Used
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
COFA
Interrupt
Enable
OOF
Interrupt
Enable
LOF
Interrupt
Enable
LOS
Interrupt
Enable
AIS
Interrupt
Enable
RO
RO
RO
R/W
R/W
R/W
R/W
R/W
0
0
0
0
X
0
X
0
• It will assert the Interrupt Request output pin (INT),
by driving it “Low”.
Setting this bit-field to “1” enables this interrupt. Conversely, setting this bit-field to “0” disables this interrupt.
• It will set Bit 3 (OOF Interrupt Status), within the Rx
E3 Interrupt Status Register - 1 to “1”, as indicated
below.
Servicing the Change in Receive OOF Condition
Interrupt
Whenever the XRT72L53 Framer IC detects this interrupt, it will do all of the following.
RXE3 INTERRUPT STATUS REGISTER - 1 (ADDRESS = 0X14)
BIT 7
BIT 6
BIT 5
Not Used
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
COFA
Interrupt
Status
OOF
Interrupt
Status
LOF
Interrupt
Status
LOS
Interrupt
Status
AIS
Interrupt
Status
RO
RO
RO
RUR
RUR
RUR
RUR
RUR
0
0
0
0
1
0
0
0
declares or clears the OOF defect. Hence, the
user can determine the current state of the LOS
defect by reading the state of Bit 5 (RxOOF)
within the Rx E3 Configuration and Status Register - 2, as illustrated below.
Whenever the user’s system encounters the Change
in Receive OOF Condition Interrupt, then it should do
the following.
1. It should determine the current state of the OOF
condition. Recall, that this interrupt can be generated, whenever the XRT72L53 Framer IC
RXE3 CONFIGURATION & STATUS REGISTER 2 (ADDRESS = 0X11)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
RxLOF Algo
RxLOF
RxOOF
RxLOS
RxAIS
RxPld Unstab
Rx
TMark
RxFERF
R/W
RO
RO
RO
RO
RO
RO
RO
X
X
X
X
X
X
X
X
If the OOF state is TRUE
If the OOF state is FALSE
1. It should transmit a FERF (Far-End-Receive Failure) indicator to the Remote Terminal Equipment.
Please see Section 4.2.4.2.1.3 on how to configure the XRT72L53 to transmit the FERF indicator
to the Remote Terminal Equipment.
1. It should cease transmitting the FERF indication
to the Remote Terminal Equipment. Please see
Section 4.2.4.2.1.3 on how to control the state of
the “A” bit, which is transmitted via each outbound E3 frame.
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5.3.6.2.3 The Change in Receive LOF Condition Interrupt
If the Change in Receive LOF Condition Interrupt is
enabled, then the XRT72L53 Framer IC will generate
an interrupt in response to either of the following conditions.
1. When the XRT72L53 Framer IC declares an LOF
(Out of Frame) Condition, and
2. When the XRT72L53 Framer IC clears the LOF
condition.
Conditions causing the XRT72L53 Framer IC to
declare an LOF Condition.
not capable of transition back into the In-Frame
state within a 1ms or 3ms period.
Conditions causing the XRT72L53 Framer IC to
clear the LOF Condition.
• If the Receive E3 Framer block transitions from the
OOF Condition state to the LOF Condition state
(see Figure 115).
• If the Receive E3 Framer block transitions back into
the In-Frame state.
Enabling and Disabling the Change in Receive
LOF Condition Interrupt
The user can enable or disable the Change in Receive LOF Condition Interrupt, by writing the appropriate value into Bit 3 (LOF Interrupt Enable), within the
RxE3 Interrupt Enable Register - 1, as indicated below.
• If the Receive E3 Framer block (within the
XRT72L53 Framer IC) detects Framing Bit errors,
within four consecutive incoming E3 frames, and is
RXE3 INTERRUPT ENABLE REGISTER - 1 (ADDRESS = 0X12)
BIT 7
BIT 6
BIT 5
Not Used
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
COFA
Interrupt
Enable
OOF
Interrupt
Enable
LOF
Interrupt
Enable
LOS
Interrupt
Enable
AIS
Interrupt
Enable
RO
RO
RO
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
X
0
• It will assert the Interrupt Request output pin (INT),
by driving it “Low”.
Setting this bit-field to “1” enables this interrupt. Conversely, setting this bit-field to “0” disables this interrupt.
• It will set Bit 6 (LOF Interrupt Status), within the Rx
E3 Interrupt Status Register - 1 to “1”, as indicated
below.
Servicing the Change in Receive LOF Condition
Interrupt
Whenever the XRT72L53 Framer IC detects this interrupt, it will do all of the following.
RXE3 CONFIGURATION & STATUS REGISTER - 2 (ADDRESS = 0X11)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
RxLOF
Algo
RxLOF
RxOOF
RxLOS
RxAIS
R/W
RO
RO
RO
RO
RO
RO
RO
0
1
1
0
0
1
1
1
Not Used
BIT 0
RxFERF
5.3.6.2.4 The Change in Receive AIS Condition
Interrupt
If the Change in Receive AIS Condition Interrupt is
enabled, then the XRT72L53 Framer IC will generate
an interrupt in response to either of the following conditions.
2. When the XRT72L53 Framer IC clears the AIS
condition.
Conditions causing the XRT72L53 Framer IC to
declare an AIS Condition.
1. When the XRT72L53 Framer IC declares an AIS
(Loss of Signal) Condition, and
Conditions causing the XRT72L53 Framer IC to
clear the AIS Condition.
• If the XRT72L53 Framer IC detects 7 or less “0”
within 2 consecutive E3 frames.
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PRELIMINARY
REV. P1.1.8
• If the XRT72L53 Framer IC detects 2 consecutive
E3 frames that each contain 8 or more “0’s”.
The user can enable or disable the Change in Receive LOS Condition Interrupt, by writing the appropriate value into Bit 0 (AIS Interrupt Enable), within
the RxE3 Interrupt Enable Register - 1, as indicated
below.
Enabling and Disabling the Change in Receive
AIS Condition Interrupt
RXE3 INTERRUPT ENABLE REGISTER - 1 (ADDRESS = 0X12)
BIT 7
BIT 6
BIT 5
Not Used
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
COFA
Interrupt
Enable
OOF
Interrupt
Enable
LOF
Interrupt
Enable
LOS
Interrupt
Enable
AIS
Interrupt
Enable
RO
RO
RO
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
X
0
Setting this bit-field to “1” enables this interrupt. Conversely, setting this bit-field to “0” disables this interrupt.
Whenever the user’s system encounters the Change
in Receive AIS Condition Interrupt, then it should do
the following.
Servicing the Change in Receive AIS Condition
Interrupt
1. It should determine the current state of the AIS
condition. Recall, that this interrupt can be generated, whenever the XRT72L53 Framer IC
declares or clears the AIS defect. Hence, the
user can determine the current state of the AIS
defect by reading the state of Bit 3 (RxAIS) within
the Rx E3 Configuration and Status Register - 2,
as illustrated below.
Whenever the XRT72L53 Framer IC detects this interrupt, it will do all of the following.
• It will assert the Interrupt Request output pin (INT),
by driving it “Low”.
• It will set Bit 0 (AIS Interrupt Status), within the Rx
E3 Interrupt Status Register - 1 to “1”, as indicated
below.
RXE3 CONFIGURATION & STATUS REGISTER - 2 (ADDRESS = 0X11)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
RxLOF
Algo
RxLOF
RxOOF
RxLOS
RxAIS
R/W
RO
RO
RO
RO
RO
RO
RO
0
1
1
0
0
1
1
1
If the AIS Condition is TRUE
Not Used
BIT 0
RxFERF
NOTE: This interrupt is typically accompanied with the
Change in Receive OOF Condition interrupt as well.
2. It should cease transmitting the FERF indication
to the Remote Terminal Equipment. Please see
Section 4.2.4.2.1.3 for instructions on how to control the state of the “A” bit-field, within each outbound E3 frame.
The Change of Framing Alignment
BIT 1
If the Change of Framing Alignment Interrupt is enabled then the XRT72L53 Framer IC will generate an
interrupt any time the Receive E3 Framer block detects an abrupt change of framing alignment.
1. It should begin transmitting the FERF indication
to the Remote Terminal Equipment. Please see
Section 4.2.4.2.1.3 for instructions on how to
transmit a FERF condition.
If the AIS Condition is FALSE
5.3.6.2.5
Interrupt
BIT 2
Conditions causing the XRT72L53 Framer IC to
generate this interrupt.
If the XRT72L53 Framer detects receives at least four
consecutive E3 frames, within its Framing Alignment
bytes in Error, then the XRT72L53 Framer IC will declare an OOF condition. However, while the
XRT72L53 Framer IC is operating in the OOF condi-
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PRELIMINARY
REV. P1.1.8
tion, it will still rely on the old framing alignment for E3
payload data extraction, etc.
Enabling and Disabling the Change of Framing
Alignment Interrupt
However, if the Receive E3 Framer had to change
alignment, in order to re-acquire frame synchronization, then this interrupt will occur.
The user can enable or disable the Change of Framing Alignment Interrupt by writing the appropriate value into Bit 4 (COFA Interrupt Enable), within the Rx
E3 Interrupt Enable Register - 1.
RXE3 INTERRUPT ENABLE REGISTER - 1 (ADDRESS = 0X12)
BIT 7
BIT 6
BIT 5
Not Used
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
COFA
Interrupt
Enable
OOF
Interrupt
Enable
LOF
Interrupt
Enable
LOS
Interrupt
Enable
AIS
Interrupt
Enable
RO
RO
RO
R/W
R/W
R/W
R/W
R/W
0
0
0
X
0
0
0
0
Writing a “1” into this bit-field enables the Change of
Framing Alignment Interrupt. Conversely, writing a “0”
into this bit-field disables the Change of Framing
Alignment Interrupt.
Whenever the XRT72L53 Framer IC generates this
interrupt, it will do the following.
Servicing the Change of Framing Alignment Interrupt
• It will set Bit 4 (COFA Interrupt Status), within the
Rx E3 Interrupt Status Register -1, to “1”, as indicated below.
• It will assert the Interrupt Request output pin (INT)
by driving it “Low”.
RXE3 INTERRUPT STATUS REGISTER - 1 (ADDRESS = 0X14)
BIT 7
BIT 6
BIT 5
Not Used
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
COFA
Interrupt
Status
OOF
Interrupt
Status
LOF
Interrupt
Status
LOS
Interrupt
Status
AIS
Interrupt
Status
RO
RO
RO
RUR
RUR
RUR
RUR
RUR
0
0
0
1
0
0
0
0
5.3.6.2.6 The Change in Receive FERF Condition Interrupt
If the Change in Receive FERF Condition Interrupt is
enabled, then the XRT72L53 Framer IC will generate
an interrupt in response to either of the following conditions.
• If the XRT72L53 Framer IC begins receiving E3
frames which have the “A” bit set to “1”).
1. When the XRT72L53 Framer IC declares a FERF
(Far-End Receive Failure) Condition, and
2. When the XRT72L53 Framer IC clears the FERF
condition.
Conditions causing the XRT72L53 Framer IC to
declare an FERF Condition.
Enabling and Disabling the Change in Receive
AIS Condition Interrupt
Conditions causing the XRT72L53 Framer IC to
clear the AIS Condition.
• If the XRT72L53 Framer IC begins receiving E3
frames that do NOT have the “A” bit set to “1”.
The user can enable or disable the Change in Receive FERF Condition Interrupt, by writing the appropriate value into Bit 3 (FERF Interrupt Enable), within
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REV. P1.1.8
the RxE3 Interrupt Enable Register - 2, as indicated
below.
RXE3 INTERRUPT ENABLE REGISTER - 2 (ADDRESS = 0X13)
BIT 7
BIT 6
BIT 5
BIT 4
Not Used
BIT 3
BIT 2
BIT 1
BIT 0
FERF
Interrupt
Enable
BIP-4 Error
Interrupt
Enable
Framing Error
Interrupt
Enable
Not Used
R/W
RO
RO
RO
R/W
R/W
R/W
RO
0
0
0
0
0
0
0
0
• It will assert the Interrupt Request output pin (INT),
by driving it “Low”.
Setting this bit-field to “1” enables this interrupt. Conversely, setting this bit-field to “0” disables this interrupt.
• It will set Bit 3 (FERF Interrupt Status), within the
Rx E3 Interrupt Status Register - 2 to “1”, as indicated below.
Servicing the Change in Receive FERF Condition
Interrupt
Whenever the XRT72L53 Framer IC detects this interrupt, it will do all of the following.
RXE3 INTERRUPT STATUS REGISTER - 2 (ADDRESS = 0X15)
BIT 7
BIT 6
BIT 5
BIT 4
Not Used
BIT 3
BIT 2
BIT 1
BIT 0
FERF
Interrupt
Status
BIP-4
Error
Interrupt
Status
Framing
Error
Interrupt
Status
Not Used
RO
RO
RO
RO
RUR
RUR
RUR
RUR
0
0
0
0
1
0
0
0
declares or clears the FERF defect. Hence, the
user can determine the current state of the LOS
defect by reading the state of Bit 0 (RxFERF)
within the Rx E3 Configuration and Status Register - 2, as illustrated below.
Whenever the user’s system encounters the Change
in Receive FERF Condition Interrupt, then it should
do the following.
1. It should determine the current state of the FERF
condition. Recall, that this interrupt can be generated, whenever the XRT72L53 Framer IC
RXE3 CONFIGURATION & STATUS REGISTER - 2 (ADDRESS = 0X11)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
RxLOF
Algo
RxLOF
RxOOF
RxLOS
RxAIS
R/W
RO
RO
RO
RO
RO
RO
RO
0
1
1
0
0
1
1
1
5.3.6.2.7 The Detection of BIP-4 Error Interrupt
If the Detection of BIP-4 Error Interrupt is enabled,
then the XRT72L53 Framer IC will generate an interrupt, anytime the Receive E3 Framer block has de-
BIT 2
BIT 1
Not Used
BIT 0
RxFERF
tected an error in the BIP-4 Nibble, within an incoming E3 frame.
NOTE: This interrupt is only active if the XRT72L53 Framer
IC has been configured to process the BIP-4 nibble within
each incoming and outbound E3 frame.
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REV. P1.1.8
Enabling and Disabling the Detection of FEBE
Event Interrupt
Bit 2 (BIP-4 Interrupt Enable) within the Rx E3 Interrupt Enable Register - 2, as indicated below.
The user can enable or disable the Detection of BIP-4
Error’ interrupt by writing the appropriate value into
RXE3 INTERRUPT ENABLE REGISTER - 2 (ADDRESS = 0X13)
BIT 7
BIT 6
BIT 5
BIT 4
Not Used
BIT 3
BIT 2
BIT 1
BIT 0
FERF
Interrupt
Enable
BIP-4 Error
Interrupt
Enable
Framing Error
Interrupt
Enable
Not Used
R/W
RO
RO
RO
R/W
R/W
R/W
RO
0
0
0
0
0
X
0
0
• It will assert the Interrupt Request output pin (INT),
by driving it “High”.
Setting this bit-field to “1” enables this interrupt. Conversely, setting this bit-field to “0” disables this interrupt.
• It will set the Bit 2 (BIP-4 Interrupt Status), within
the RxE3 Interrupt Status Register - 2 as indicated
below.
Servicing the Detection of the BIP-4 Error Interrupt
Whenever the XRT72L53 Framer IC detects this interrupt, it will do the following.
RXE3 INTERRUPT STATUS REGISTER - 2 (ADDRESS = 0X15)
BIT 7
BIT 6
BIT 5
BIT 4
Not Used
BIT 3
BIT 2
BIT 1
BIT 0
FERF
Interrupt
Status
BIP-4
Error
Interrupt
Status
Framing
Error
Interrupt
Status
Not Used
RO
RO
RO
RO
RUR
RUR
RUR
RUR
0
0
0
0
0
1
0
0
Whenever the Terminal Equipment encounters the
Detection of BIP-4 Error Interrupt, it should do the following.
• It should read the contents of the PMON Parity
Error Event Count Registers (located at Addresses
0x54 and 0x55) in order to determine the number of
BIP-4 Errors that have been received by the
XRT72L53 Framer IC.
5.3.6.2.8
rupt
The Detection of Framing Error Inter-
If the Detection of Framing Error Interrupt is enabled,
then the XRT72L53 Framer IC will generate an interrupt, anytime the Receive E3 Framer block has received an E3 frame with an incorrect FAS pattern value.
Enabling and Disabling the Detection of FEBE
Event Interrupt
The user can enable or disable the Detection of
Framing Error’ interrupt by writing the appropriate value into Bit 1 (Framing Error Interrupt Enable) within
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PRELIMINARY
REV. P1.1.8
the Rx E3 Interrupt Enable Register - 2, as indicated
below.
RXE3 INTERRUPT ENABLE REGISTER - 2 (ADDRESS = 0X13)
BIT 7
BIT 6
BIT 5
BIT 4
Not Used
BIT 3
BIT 2
BIT 1
BIT 0
FERF
Interrupt
Enable
BIP-4 Error
Interrupt
Enable
Framing Error
Interrupt
Enable
Not Used
R/W
RO
RO
RO
R/W
R/W
R/W
RO
0
0
0
0
0
0
X
0
• It will assert the Interrupt Request output pin (INT),
by driving it “High”.
Setting this bit-field to “1” enables this interrupt. Conversely, setting this bit-field to “0” disables this interrupt.
Servicing the Detection of Framing Error Interrupt
Whenever the XRT72L53 Framer IC detects this interrupt, it will do the following.
• It will set the Bit 1 (Framing Error Interrupt Status),
within the RxE3 Interrupt Status Register - 2 as
indicated below.
RXE3 INTERRUPT STATUS REGISTER - 2 (ADDRESS = 0X15)
BIT 7
BIT 6
BIT 5
BIT 4
Not Used
BIT 3
BIT 2
BIT 1
BIT 0
FERF
Interrupt
Status
BIP-4
Error
Interrupt
Status
Framing
Error
Interrupt
Status
Not Used
RO
RO
RO
RO
RUR
RUR
RUR
RUR
0
0
0
0
0
0
0
0
rupt anytime the Receive HDLC Controller block has
received a new LAPD Message frame from the Remote Terminal Equipment, and has stored the contents of this message into the Receive LAPD Message buffer.
Whenever the Terminal Equipment encounters the
Detection of Framing Error Interrupt, it should do the
following.
• It should read the contents of the PMON Framing
Bit/Byte Error Count Registers (located at
Addresses 0x52 and 0x53) in order to determine
the number of Framing errors that have been
received by the XRT72L53 Framer IC.
Enabling/Disabling the Receive LAPD Message
Interrupt
The user can enable or disable the Receive LAPD
Message Interrupt by writing the appropriate data into
Bit 1 (RxLAPD Interrupt Enable) within the Rx E3
LAPD Control Register, as indicated below.
5.3.6.2.9 The Receipt of New LAPD Message
Interrupt
If the Receive LAPD Message Interrupt is enabled,
then the XRT72L53 Framer IC will generate an inter-
RXE3 LAPD CONTROL REGISTER (ADDRESS = 0X18)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
Not Used
BIT 2
BIT 1
BIT 0
RxLAPD
Enable
RxLAPD
Interrupt Enable
RxLAPD
Interrupt Enable
RO
RO
RO
RO
RO
R/W
R/W
RUR
0
0
0
0
0
0
0
0
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REV. P1.1.8
Writing a “1” into this bit-field enables the Receive
LAPD Message Interrupt. Conversely, writing a “0” into this bit-field disables the Receive LAPD Message
Interrupt.
Servicing the Receive LAPD Message Interrupt
• It will assert the Interrupt Request output pin (INT),
by driving it “Low”.
• It will set Bit 0 (RxLAPD Interrupt Status), within the
Rx E3 LAPD Control register to “1”, as indicated
below.
Whenever the XRT72L53 Framer IC generates this
interrupt, it will do the following.
RXE3 LAPD CONTROL REGISTER (ADDRESS = 0X18)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
Not Used
BIT 2
BIT 1
BIT 0
RxLAPD
Enable
RxLAPD
Interrupt Enable
RxLAPD
Interrupt Enable
RO
RO
RO
RO
RO
R/W
R/W
RUR
0
0
0
0
0
0
0
0
• It will write the contents of the newly Received
LAPD Message into the Receive LAPD Message
buffer (located at 0xDE through 0x135).
Whenever the Terminal Equipment encounters the
Receive LAPD Message Interrupt, then it should read
out the contents of the Receive LAPD Message buffer, and respond accordingly.
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REV. P1.1.8
6.0 E3/ITU-T G.832 OPERATION OF THE
XRT72L53
Configuring the XRT72L53 to Operate in the E3,
ITU-T G.832 Mode
The XRT72L53 can be configured to operate in the
E3/ITU-T G.832 Mode by writing a “0” into bit-field 6
and a “1” into bit-field 2, within the Framer Operating
Mode register, as illustrated below.
FRAMER OPERATING MODE REGISTER (ADDRESS = 0X00)
BIT 7
BIT 6
BIT 5
BIT 4
Local Loopback
DS3/E3*
Internal
LOS Enable
RESET
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
x
0
x
0
x
1
x
x
Prior to describing the functional blocks within the
Transmit and Receive Sections of the XRT72L53, it is
important to describe the E3, ITU-T G.832 framing
format.
6.1 DESCRIPTION OF THE E3, ITU-T G.832 FRAMES
AND ASSOCIATED OVERHEAD BYTES
The role of the various overhead bytes are best described by discussing the E3, ITU-T G.832 Frame
Format as a whole. The E3, ITU-T G.832 Frame con-
BIT 3
BIT2
Interrupt
Frame Format
Enable Reset
BIT 1
BIT 0
TimRefSel[1:0]
tains 537 bytes, of which 7 bytes are overhead and
the remaining 530 bytes are payload bytes.
These 537 octets are arranged in 9 rows of 60 columns each, except for the last three rows which contain only 59 columns. The frame repetition rate for this
type of E3 frame is 8000 times per second, thereby
resulting in the standard E3 bit rate of 34.368 Mbps.
Figure 154 presents an illustration of the E3, ITU-T
G.832 Frame Format.
FIGURE 154. ILLUSTRATION OF THE E3, ITU-T G.832 FRAMING FORMAT.
60 Columns
FA1
FA2
EM
TR
MA
NR
530 Octet Payload
9 Rows
GC
1 Byte
6.1.1 Definition of the Overhead Bytes
The seven (7) overhead bytes are shown in
Figure 154, as FA1, FA2, EM, TR, MA, NR and GC.
59 Bytes
Each of these Overhead Bytes are further defined below.
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REV. P1.1.8
FRAMER OPERATING MODE REGISTER (ADDRESS = 0X00)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
Local Loopback
DS3/E3*
Internal LOS
Enable
RESET
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
x
1
x
0
x
x
x
x
6.1.1.1 Frame Alignment (FA1 and FA2) Bytes
FA1 and FA2 are known as the frame alignment
bytes. The Receive E3 Framer, while trying to acquire
or maintain framing synchronization with its incoming
E3 frames, will attempt to locate these two bytes. FA1
is assigned the value “0xF6” and FA2 is assigned the
value “0x28”.
BIT2
Interrupt
Frame Format
Enable Reset
BIT 1
BIT 0
TimRefSel[1:0]
very next E3 frame. If the two EM byte values are
equal, then the Receive E3 Framer will conclude that
this E3 frame was received in an error-free manner.
Further, the Receive E3 Framer will block will inform
the Remote Terminal Equipment of this fact by having
the Local Terminal Equipment set the FEBE (FarEnd-Block Error) bit, within the MA Byte of an Outbound E3 frame (to the Remote Terminal Equipment)
to “0”. Please see Section 5.1.1 for a discussion of
the MA Byte.
6.1.1.2 Error Monitor (EM) Byte
The EM byte contains the results of BIP-8 (Bit-Interleaved Parity) calculations over an entire E3 frame.
The Bit Interleaved Parity (BIP-8) byte field supports
error detection, during the transmission of E3 frames,
between the Local Terminal Equipment and the Remote Terminal Equipment.
However, if the Receive E3 Framer block detects an
error in the incoming EM byte, then it will conclude
that the corresponding E3 frame is errored. Further,
the Receive E3 Framer block will inform the Remote
Terminal (e.g., the source of this erred E3 frame) of
this fact by having the Local Terminal Equipment
(e.g., the Transmit E3 Framer block) set the FEBE bit,
within an Outbound E3 frame (destined to the Remote Terminal) to “1”.
The Transmit E3 Framer will compute the BIP-8 value
over the 537 octet structure, within each E3 frame.
The resulting BIP-8 value is then inserted into the EM
byte-field within the very next E3 frame. BIP-8 is an
eight bit code in which the nth bit of the BIP-8 code
reflects the even-parity bit calculated with the nth bit
of each of the 537 octets within the E3 frame. Thus,
the BIP-8 value presents the results for 8 separate
even-bit parity calculations.
NOTE: A detailed discussion on the practical use of the EM
byte is presented in Section 5.2.2.
The Receive E3 Framer will compute its own version
of the EM bytes for each E3 frame that it receives. Afterwards, it will compare the value of its locally computed EM byte with the EM byte that it receives in the
6.1.1.3 The Trail-Trace Buffer (TTB) Byte
This byte-field is used to repetitively transmit a Trailaccess point identifier so that a trail receiving terminal
can verify its continued connection to the intended
transmitter. The trail access point identifier uses the
16-byte numbering format as tabulated in Table 69.
TABLE 69: DEFINITION OF THE TRAIL TRACE BUFFER BYTES, WITHIN THE E3, ITU-T G.832 FRAMING FORMAT
TRAIL TRACE BITS
BYTE NUMBER
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
1 (Frame Start
Marker)
1
C6
C5
C4
C3
C2
C1
C0
2
X
X
X
X
X
X
X
X
*
X
X
X
X
X
X
X
X
*
X
X
X
X
X
X
X
X
16
X
X
X
X
X
X
X
X
351
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XRT72L53
THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. P1.1.8
6.1.1.4 Maintenance and Adaptation (MA) Byte
The MA byte is responsible for carrying the FERF
(Far-End Receive Failure) and the FEBE (Far-End
Block Error) status indicators from one terminal to another. The MA byte-field also carries the Payload
Type, the Payload Dependent and the Timing Marker
indicators. The byte format for the MA byte is presented below.
The first byte of this 16-byte string is a frame start
marker and is typically of the form [1, C6, C5, C4, C3,
C2, C1, C0]. The “1” in the MSB (most significant bit)
of this first byte is used to identify this byte as the
frame start marker (e.g., the first byte of the 16-byte
Trail Trace Buffer Sequence). The bits: C6 through C0
are the results of a CRC-7 calculation over the previous 16-byte frame. The subsequent 15 bytes are
used for the transport of 15 ASCII characters required
for the E.164 numbering format.
THE MAINTENANCE AND ADAPTATION (MA) BYTE FORMAT
BIT 7
BIT 6
FERF
FEBE
BIT 5
BIT 4
BIT 3
Payload Type
BIT 2
BIT 1
Payload Dependent
BIT 0
Timing Marker
NOTE: A detailed discussion into the practical use of the
FERF bit-field is presented in Section 5.2.4.2.
Bit 7 - FERF (Far-End Receive Failure)
If the Receive E3 Framer block (at a Local Terminal)
is experiencing problems receiving E3 frame data
from a Remote Terminal (e.g., an LOS, OOF or AIS
condition), then it will inform the Remote Terminal
Equipment of this fact by commanding the Local
Transmit E3 Framer block to set the FERF bit-field
(within the MA byte) of an Outbound E3 frame, to “1”.
The Local Transmit E3 Framer block will continue to
set the FERF bit-field (within the subsequent Outbound E3 frames) to “1” until the Receive E3 Framer
block no longer experiences problems in receiving the
E3 frame data. If the Remote Terminal Equipment receives a certain number of consecutive E3 frames,
with the FERF bit-field set to “1”, then the Remote
Terminal Equipment will interpret this signaling as an
indication of a Far-End Receive Failure (e.g., a problem with the Local Terminal Equipment).
Bit 6 - FEBE (Far-End Block Error)
If a Local Receive E3 Framer block detects an error in
the EM byte, within an incoming E3 frame that it has
received from the Remote Terminal Equipment, then
it will inform the Remote Terminal Equipment of this
error by commanding the Local Transmit E3 Framer
block to set the FEBE bit-field (within the MA bytefield) of an Outbound E3 frame (which is destined for
the Remote Terminal Equipment) to “1”. The Remote
Terminal Equipment will interpret this signaling as an
indication that the E3 frames that it is transmitting
back out to the Local Receive E3 Framer block are
erred.
Conversely, if the Receive E3 Framer block (at a Local Terminal Equipment) is not experiencing any
problems receiving E3 frame data from a Remote Terminal Equipment, then it will also inform the Remote
Terminal Equipment of this fact by commanding the
Local Transmit E3 Framer block to set the FERF bitfield (within the MA byte-field) of an Outbound E3
frame (which is destined for the Remote Terminal) to
“0”. The Remote Terminal Equipment will interpret
this form of signaling as an indication of a normal operation.
Conversely, if the Local Receive E3 Framer block
does not detect any errors in the EM byte, within the
incoming E3 frame, then it will also inform the Remote Terminal Equipment of this fact by commanding
the Local Transmit E3 Framer block to set the FEBE
bit-field of an Outbound E3 frame (which is destined
for the Remote Terminal Equipment) to “0”.
NOTE: A detailed discussion into the practical use of the
FEBE bit-field is presented in Section 5.2.4.2.
Bits 5 - 3 Payload Type
These bit-fields indicates to the Remote Terminal
Equipment, what kind of data is being transported in
the 530 bytes of E3 frame payload data. Some of the
defined payload type values are tabulated in
Table 70.
352
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XRT72L53
THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. P1.1.8
TABLE 70: A LISTING OF THE VARIOUS PAYLOAD TYPE VALUES AND THEIR CORRESPONDING MEANING
PAYLOAD TYPE
VALUE
MEANING
000
Unequipped
001
Equipped
010
ATM Cells
011
SDH TU-12s
Bits 2 - 1 Payload Dependent
minal Equipment) at a data rate of 64kbps (1 byte per
E3 frame).
To be provided later.
This bit-field is set to “0” to indicate that the timing
source is traceable to a Primary Reference Clock.
Otherwise, this bit-field is set to “1”.
If the user opts not to use the GC byte to transport
these LAPD Message frames, then the Transmit E3
Framer block will read in the contents of the Tx GC
Byte Register (Address = 0x35), and insert this value
into the GC byte-field of each Outbound E3 frame.
6.1.1.5 The Network Operator (NR) Byte
The NR byte or the GC byte can be configured to
transport LAP-D Message frame octets from the
LAPD Transmitter to the LAPD Receiver (of the Remote Terminal Equipment) at a data rate of 64kbps (1
byte per E3 frame).
The Receive E3 Framer block will read in the contents
of the GC byte-field, within each incoming E3 frame,
and will write it into the RxGC Byte register. Consequently, the user can determine the value of the GC
byte, within the most recently received E3 frame, by
reading the Rx GC Byte register (Address = 0x1B).
If the user opts not to use the NR byte to transport
these LAPD Message frames, then the Transmit E3
Framer block will read in the contents of the TxNR
Byte Register (Address = 0x37), and insert this value
into the NR byte-field of each Outbound E3 frame.
The Receive E3 Framer block will read in the contents
of the NR byte-field within each incoming E3 frame
and will write it into the RxNR Byte register. Consequently, the user can determine the value of the NR
byte, within the most recently received E3 frame by
reading the Rx NR Byte Register (Address = 0x1A).
6.2 THE TRANSMIT SECTION OF THE XRT72L53 (E3
MODE OPERATION)
When the XRT72L53 has been configured to operate
in the E3, ITU-T G.832 Mode, the Transmit Section of
the XRT72L53 consists of the following functional
blocks.
6.1.1.6 The General Purpose Communications Channel (GC) Byte
The NR byte or the GC byte can be configured to
transport LAPD Message frames from the LAPD
Transmitter to the LAPD Receiver (of the Remote Ter-
• Transmit LIU Interface block
Bit 0 - Timing Marker
• Transmit Payload Data Input Interface block
• Transmit Overhead Data Input Interface block
• Transmit E3 Framer block
• Transmit HDLC Controller block
Figure 155 presents a simple illustration of the Transmit Section of the XRT72L53 Framer IC.
353
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XRT72L53
THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. P1.1.8
FIGURE 155. A SIMPLE ILLUSTRATION OF THE TRANSMIT SECTION, WITHIN THE XRT72L53, WHEN IT HAS BEEN
E3 MODE
CONFIGURED TO OPERATE IN THE
TxOHFrame
TxOHEnable
TxOH
TxOHClk
TxOHIns
TxOHInd
TxSer
TxNib[3:0]
TxInClk
TxNibClk
TxFrame
Transmit Overhead
Input
Interface Block
Transmit
Payload Data
Input
Interface Block
TxPOS
Transmit DS3/E3
Framer Block
Transmit LIU
Interface
Block
TxNEG
TxLineClk
From Microprocessor
Interface Block
Tx E3 HDLC
Tx E3 HDLC
Controller/Buffer
Controller/Buffer
Each of these functional blocks will be discussed in
detail in this document.
6.2.1 The Transmit Payload Data Input Interface
Block
Figure 156 presents a simple illustration of the Transmit Payload Data Input Interface block.
354
XRT72L53
THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
áç
PRELIMINARY
REV. P1.1.8
FIGURE 156. A SIMPLE ILLUSTRATION OF THE TRANSMIT PAYLOAD DATA INPUT INTERFACE BLOCK
TxOH_Ind
TxSer
TxNib[3:0]
TxInClk
Transmit
TransmitPayload
Payload
Data
DataInput
Input
Interface
InterfaceBlock
Block
To Transmit E3 Framer Block
TxNibClk
TxFrame
TxFrameRef
Each of the input and output pins of the Transmit Payload Data Input Interface are listed in Table 71 and
described below. The exact role that each of these in-
puts and output pins assume, for a variety of operating scenarios are described throughout this section.
355
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XRT72L53
THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. P1.1.8
TABLE 71: LISTING AND DESCRIPTION OF THE PINS ASSOCIATED WITH THE TRANSMIT PAYLOAD DATA INPUT
INTERFACE
SIGNAL NAME
TYPE
TxSer
Input
DESCRIPTION
Transmit Serial Payload Data Input Pin:
If the user opts to operate the XRT72L53 in the serial mode, then the Terminal Equipment is
expected to apply the payload data (that is to be transported via the Outbound E3 data stream)
to this input pin. The XRT72L53 will sample the data that is at this input pin upon the rising
edge either the RxOutClk or the TxInClk signal (whichever is appropriate).
NOTE: This signal is only active if the NibInt input pin is pulled "Low".
TxNib[3:0]
Input
Transmit Nibble-Parallel Payload Data Input pins:
If the user opts to operate the XRT72L53 in the Nibble-Parallel mode, then the Terminal Equipment is expected to apply the payload data (that is to be transported via the Outbound E3 data
stream) to these input pins. The XRT72L53 will sample the data that is at these input pins upon
the rising edge of the TxNibClk signal.
NOTE: These pins are only active if the NibInt input pin is pulled "High".
TxInClk
Input
Transmit Section Timing Reference Clock Input pin:
The Transmit Section of the XRT72L53 can be configured to use this clock signal as the Timing
Reference. If the user has made this configuration selection, then the XRT72L53 will use this
clock signal to sample the data on the TxSer input pin.
NOTE: If this configuration is selected, then a 34.368 MHz clock signal must be applied to this
input pin.
TxNibClk
Output Transmit Nibble Mode Output
If the user opts to operate the XRT72L53 in the Nibble-Parallel mode, then the XRT72L53 will
derive this clock signal from the selected Timing Reference for the Transmit Section of the chip
(e.g., either the TxInClk or the RxLineClk signals).
The XRT72L53 will use this signal to sample the data on the TxNib[3:0] input pins.
TxOHInd
Output Transmit Overhead Bit Indicator Output:
This output pin will pulse "High" one-bit period prior to the time that the Transmit Section of the
XRT72L53 will be processing an Overhead bit. The purpose of this output pin is to warn the
Terminal Equipment that, during the very next bit-period, the XRT72L53 is going to be processing an Overhead bit and will be ignoring any data that is applied to the TxSer input pin.
TxFrame
Output Transmit End of Frame Output Indicator:
The Transmit Section of the XRT72L53 will pulse this output pin "High" (for one bit-period),
when the Transmit Payload Data Input Interface is processing the last bit of a given E3 frame.
The purpose of this output pin is to alert the Terminal Equipment that it needs to begin transmission of a new E3 frame to the XRT72L53 (e.g., to permit the XRT72L53 to maintain Transmit
E3 framing alignment control over the Terminal Equipment).
TxFrameRef
RxOutClk
Input Transmit Frame Reference Input:
The XRT72L53 permits the user to configure the Transmit Section to use this input pin as a
frame reference. If the user makes this configuration selection, then the Transmit Section will
initiate its transmission of a new E3 frame, upon the rising edge of this signal.
The purpose of this input pin is to permit the Terminal Equipment to maintain Transmit E3 Framing alignment control over the XRT72L53.
Output Loop-Timed Timing Reference Clock Output pin:
The Transmit Section of the XRT72L53 can be configured to use the RxLineClk signal as the
Timing Reference (e.g., loop-timing). If the user has made this configuration selection, then the
XRT72L53 will:
• Output a 34.368 MHz clock signal via this pin, to the Terminal Equipment.
• Sample the data on the TxSer input pin, upon the rising edge of this clock signal.
356
XRT72L53
THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. P1.1.8
Operation of the Transmit Payload Data Input Interface
Since the XRT72L53 is configured to operate in the
loop-timed mode, the Transmit Section (of the
XRT72L53) will use the RxLineClk input clock signal
(e.g., the Recovered Clock signal, from the LIU) as its
timing source. When the XRT72L53 is operating in
this mode it will do the following.
The Transmit Terminal Input Interface is extremely
flexible, in that it permits the user to make the following configuration options.
• The Serial or the Nibble-Parallel Interface Mode
1. It will ignore any signal at the TxInClk input pin.
2. The XRT72L53 will output a 34.368MHz clock
signal via the RxOutClk output pin. This clock signal functions as the Transmit Payload Data Input
Interface block clock signal.
3. The XRT72L53 will use the rising edge of the
RxOutClk signal to latch in the data residing on
the TxSer input pin.
B. Serial Mode
• The Loop-Timing or the TxInClk (Local Timing)
Mode
Further, if the XRT72L53 has been configured to operate in the TxInClk mode, then the user has two additional options.
• The XRT72L53 is the Frame Master (e.g., it dictates
when the Terminal Equipment will initiate the transmission of data within a new E3 frame).
• The XRT72L53 is the Frame Slave (e.g., the Terminal Equipment will dictate when the XRT72L53 initiates the transmission of a new E3 frame).
The XRT72L53 will accept the E3 payload data from
the Terminal Equipment, in a serial-manner, via the
TxSer input pin The Transmit Payload Data Input Interface will latch this data into its circuitry, on the rising edge of the RxOutClk output clock signal.
Given these three set of options, the Transmit Terminal Input Interface can be configured to operate in
one of the six (6) following modes.
C. Delineation of Outbound E3 frames
• Mode 1 - Serial/Loop-Timed Mode
The XRT72L53 will pulse the TxFrame output pin
"High" for one bit-period, coincident with the
XRT72L53 processing the last bit of a given E3
frame.
• Mode 2 - Serial/Local-Timed/Frame Slave Mode
• Mode 3 - Serial/Local-Timed/Frame Master Mode
• Mode 4 - Nibble/Loop-Timed Mode
D. Sampling of Payload Data, from the Terminal
Equipment
• Mode 5 - Nibble/Local-Timed/Frame Slave Mode
• Mode 6 - Nibble/Local-Timed/Frame Master Mode
In Mode 1, the XRT72L53 will sample the data at the
TxSer input, on the rising edge of RxOutClk.
Each of these modes are described, in detail, below.
6.2.1.1 Mode 1 - The Serial/Loop-Timing Mode
The Behavior of the XRT72L53
If the XRT72L53 has been configured to operate in
this mode, then the XRT72L53 will behave as follows.
A. Loop-Timing (Uses the RxLineClk signal as the
Timing Reference)
áç
Interfacing the Transmit Payload Data Input Interface block of the XRT72L53 to the Terminal Equipment for Mode 1 Operation
Figure 157 presents an illustration of the Transmit
Payload Data Input Interface block (within the
XRT72L53) being interfaced to the Terminal Equipment, for Mode 1 operation.
357
áç
XRT72L53
THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. P1.1.8
FIGURE 157. ILLUSTRATION OF THE TERMINAL EQUIPMENT BEING INTERFACED TO THE TRANSMIT PAYLOAD DATA
INPUT INTERFACE BLOCK OF THE XRT72L53 FOR MODE 1 (SERIAL/LOOP-TIMED) OPERATION
E3_Clock_In
34.368 MHz Clock Signal
RxOutClk
TxSer
E3_Data_Out
TxFrame
Tx_Start_of_Frame
TxOH_Ind
E3_OH_Ind
NibInt
Terminal Equipment
(Receive Payload Section)
Mode 1 Operation of the Terminal Equipment
When the XRT72L53 is operating in this mode it will
function as the source of the 34.368MHz clock signal.
This clock signal will be used as the Terminal Equipment Interface clock by both the XRT72L53 IC and
the Terminal Equipment.
The Terminal Equipment will serially output the payload data of the Outbound E3 data stream via its
E3_Data_Out pin. The Terminal Equipment will update the data on the E3_Data_Out pin upon the rising
edge of the 34.368 MHz clock signal, at its
E3_Clock_In input pin (as depicted in Figures 19 and
20).
The XRT72L53 will latch the Outbound E3 data
stream (from the Terminal Equipment) on the rising
edge of the RxOutClk signal.
The XRT72L53 will indicate that it is processing the
last bit, within a given Outbound E3 frame, by pulsing
its TxFrame output pin “High” for one bit-period.
XRT72L5x E3 Framer
When the Terminal Equipment detects this pulse at its
Tx_Start_of_Frame input, it is expected to begin
transmission of the very next Outbound E3 frame to
the XRT72L53 via the E3_Data_Out (or TxSer pin).
Finally, the XRT72L53 will indicate that it is about to
process an overhead bit by pulsing the TxOH_Ind
output pin "High" one bit period prior to its processing
of an OH (Overhead) bit. In Figure 157, the
TxOH_Ind output pin is connected to the
E3_Overhead_Ind input pin, of the Terminal Equipment. Whenever the E3_Overhead_Ind pin is pulsed
"High" the Terminal Equipment is expected to not
transmit a E3 payload bit upon the very next clock
edge. Instead, the Terminal Equipment is expected to
delay its transmission of the very next payload bit, by
one clock cycle.
The behavior of the signals, between the XRT72L53
and the Terminal Equipment, for E3 Mode 1 operation
is illustrated in Figure 158.
358
áç
XRT72L53
THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. P1.1.8
FIGURE 158. BEHAVIOR OF THE TERMINAL INTERFACE SIGNALS BETWEEN THE TRANSMIT PAYLOAD DATA INPUT
INTERFACE BLOCK OF THE XRT72L53 AND THE TERMINAL EQUIPMENT (FOR MODE 1 OPERATION)
Terminal Equipment Signals
E3_Clock_In
Payload[4238]
E3_Data_Out
Payload[4239]
FA1, Bit 7
FA1, Bit 6
FA1, Bit 7
FA1, Bit 6
Tx_Start_of_Frame
E3_Overhead_Ind
XRT72L5x Transmit Payload Data I/F Signals
RxOutClk
Payload[4238]
TxSer
Payload[4239]
TxFrame
TxOH_Ind
E3 Frame Number N
E3 Frame Number N + 1
Note: TxFrame pulses high to denote
E3 Frame Boundary.
Note: The FA1 byte will not be processed by the
Transmit Payload Data Input Interface.
Note: TxOH_Ind pulses high for
16 bit periods in order to
denote Overhead Data
(e.g., the FA1 and FA2 bytes)
How to configure the XRT72L53 into the Serial/
Loop-Timed/Non-Overhead Interface Mode
2. Set the TimRefSel[1:0] bit fields (within the
Framer Operating Mode Register) to "00" as illustrated below.
1. Set the NibIntf input pin "Low".
FRAMER OPERATING MODE REGISTER (ADDRESS = 0X00)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT2
BIT 1
BIT 0
Local Loopback
DS3/E3*
Internal LOS
Enable
RESET
Interrupt
Enable Reset
Frame Format
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
1
0
1
0
0
0
TimRefSel[1:0]
3. Interface the XRT72L53, to the Terminal Equipment, as illustrated in Figure 157.
In this mode, the Transmit Section of the XRT72L53
will use the TxInClk signal as its timing reference.
6.2.1.2 Mode 2 - The Serial/Local-Timed/
Frame-Slave Mode Behavior of the XRT72L53
If the XRT72L53 has been configured to operate in
this mode, then the XRT72L53 will function as follows.
B. Serial Mode
A. Local Timing - Uses the TxInClk signal as the
Timing Reference
The XRT72L53 will receive the E3 payload data, in a
serial manner, via the TxSer input pin. The Transmit
Payload Data Input Interface (within the XRT72L53)
will latch this data into its circuitry, on the rising edge
of the TxInClk input clock signal.
C. Delineation of Outbound E3 frames (Frame
Slave Mode)
359
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XRT72L53
THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. P1.1.8
The Transmit Section of the XRT72L53 will use the
TxInClk input as its timing reference, and will use the
TxFrameRef input signal as its framing reference. In
other words, the Transmit Section of the XRT72L53
will initiate frame generation upon the rising edge of
the TxFrameRef input signal).
D. Sampling of payload data, from the Terminal
Equipment
In Mode 2, the XRT72L53 will sample the data, at the
TxSer input pin, on the rising edge of TxInClk.
Interfacing the Transmit Payload Data Input Interface block of the XRT72L53 to the Terminal Equipment for Mode 2 Operation
Figure 159 presents an illustration of the Transmit
Payload Data Input Interface block (within the
XRT72L53) being interfaced to the Terminal Equipment, for Mode 2 operation.
FIGURE 159. ILLUSTRATION OF THE TERMINAL EQUIPMENT BEING INTERFACED TO THE TRANSMIT PAYLOAD DATA
INPUT INTERFACE BLOCK OF THE XRT72L53 FOR MODE 2 (SERIAL/LOCAL-TIMED/FRAME-SLAVE) OPERATION
34.368MHz
Clock Source
E3_Clock_In
TxInClk
E3_Data_Out
TxSer
Tx_Start_of_Frame
TxFrameRef
E3_Overhead_Ind
TxOH_Ind
NibInt
Terminal Equipment
Mode 2 Operation of the Terminal Equipment
As shown in Figure 159, both the Terminal Equipment
and the XRT72L53 will be driven by an external
34.368MHz clock signal. The Terminal Equipment will
receive the 34.368MHz clock signal via its
E3_Clock_In input pin, and the XRT72L53 Framer IC
will receive the 34.368MHz clock signal via the TxInClk input pin.
The Terminal Equipment will serially output the payload data of the Outbound E3 data stream, via the
E3_Data_Out output pin, upon the rising edge of the
signal at the E3_Clock_In input pin.
NOTE: The E3_Data_Out output pin of the Terminal Equipment is electrically connected to the TxSer input pin). The
XRT72L53 Framer IC will latch the data, residing on the
TxSer input line, on the rising edge of the TxInClk signal.
In this case, the Terminal Equipment has the responsibility of providing the framing reference signal by
pulsing its Tx_Start_of_Frame output signal (and in
turn, the TxFrameRef input pin of the XRT72L53),
“High” for one-bit period, coincident with the first bit of
XRT72L5x E3 Framer
a new E3 frame. Once the XRT72L53 detects the rising edge of the input at its TxFrameRef input pin, it
will begin generation of a new E3 frame.
NOTES:
1. In this case, the Terminal Equipment is controlling
the start of Frame Generation, and is therefore
referred to as the Frame Master. Conversely, since
the XRT72L53 does not control the generation of a
new E3 frame, but is rather driven by the Terminal
Equipment, the XRT72L53 is referred to as the
Frame Slave.
2. If the user opts to configure the XRT72L53 to operate in Mode 2, it is imperative that the
Tx_Start_of_Frame (or TxFrameRef) signal is synchronized to the TxInClk input clock signal.
Finally, the XRT72L53 will pulse its TxOH_Ind output
pin, one bit-period prior to it processing a given overhead bit, within the Outbound E3 frame. Since the
TxOH_Ind output pin (of the XRT72L53) is electrically
connected to the E3_Overhead_Ind, whenever the
XRT72L53 pulses the TxOH_Ind output pin "High", it
will also be driving the E3_Overhead_Ind input pin (of
360
áç
XRT72L53
THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. P1.1.8
the Terminal Equipment) "High". Whenever the Terminal Equipment detects this pin toggling "High", it
should delay transmission of the very next E3 frame
payload bit by one clock cycle.
The behavior of the signals between the XRT72L53
and the Terminal Equipment for E3 Mode 2 Operation
is illustrated in Figure 160.
FIGURE 160. BEHAVIOR OF THE TERMINAL INTERFACE SIGNALS BETWEEN THE XRT72L53 AND THE TERMINAL
EQUIPMENT (MODE 2 OPERATION)
Terminal Equipment Signals
E3_Clock_In
Payload[4238]
E3_Data_Out
Payload[4239]
FA1, Bit 7
FA1, Bit 6
FA1, Bit 7
FA1, Bit 6
Tx_Start_of_Frame
E3_Overhead_Ind
XRT7250 Transmit Payload Data I/F Signals
TxInClk
Payload[4238]
TxSer
Payload[4239]
TxFrameRef
TxOH_Ind
E3 Frame Number N
E3 Frame Number N + 1
Note: The FA1 byte will not be processed by the
Transmit Payload Data Input Interface.
Note: TxOH_Ind pulses high for
16 bit periods in order to
denote Overhead Data
(e.g., the FA1 and FA2 bytes)
Note: TxFrameRef pulses high to denote
E3 Frame Boundary.
How to configure the XRT72L53 to operate in this
mode.
2. Set the TimRefSel[1:0] bit-fields (within the
Framer Operating Mode Register) to "01" as
depicted below.
1. Set the NibIntf input pin "Low".
FRAMER OPERATING MODE REGISTER (ADDRESS = 0X00)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT2
BIT 1
BIT 0
Local Loopback
DS3/E3*
Internal LOS
Enable
RESET
Interrupt
Enable Reset
Frame Format
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
1
0
1
0
0
1
TimRefSel[1:0]
3. Interface the XRT72L53, to the Terminal Equipment, as illustrated in Figure 159.
A. Local Timed - Uses the TxInClk signal as the
Timing Reference
6.2.1.3 Mode 3 - The Serial/Local-Timed/
Frame-Master Mode Behavior of the XRT72L53
If the XRT72L53 has been configured to operate in
this mode, then the XRT72L53 will function as follows.
In this mode, the Transmit Section of the XRT72L53
will use the TxInClk signal as its timing reference.
B. Serial Mode
361
áç
XRT72L53
THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. P1.1.8
The XRT72L53 will receive the E3 payload data, in a
serial manner, via the TxSer input pin. The Transmit
Payload Data Input Interface (within the XRT72L53)
will latch this data into its circuitry, on the rising edge
of the TxInClk input clock signal.
C. Delineation of Outbound DS3 frames (Frame
Master Mode)
The Transmit Section of the XRT72L53 will use the
TxInClk signal as its timing reference, and will initiate
E3 frame generation, asynchronously with respect to
any externally applied signal. The XRT72L53 will
pulse its TxFrame output pin "High" whenever its it
processing the very last bit-field within a given E3
frame.
D. Sampling of payload data, from the Terminal
Equipment
In Mode 3, the XRT72L53 will sample the data, at the
TxSer input pin, on the rising edge of TxInClk.
Interfacing the Transmit Payload Data Input Interface block of the XRT72L53 to the Terminal Equipment for Mode 3 Operation
Figure 161 presents an illustration of the Transmit
Payload Data Input Interface block (within the
XRT72L53) being interfaced to the Terminal Equipment, for Mode 3 operation.
FIGURE 161. ILLUSTRATION OF THE TERMINAL EQUIPMENT BEING INTERFACED TO THE TRANSMIT PAYLOAD DATA
INPUT INTERFACE BLOCK OF THE XRT72L53 FOR MODE 3 (SERIAL/LOCAL-TIMED/FRAME-MASTER) OPERATION
34.368 MHz
34.368
MHz
Clock
Source
Clock Source
E3_Clock_In
E3_Clock_In
E3_Data_Out
E3_Data_Out
TxStart_of_Frame
TxStart_of_Frame
E3_Overhead_Ind
E3_Overhead_Ind
TxInClk
TxInClk
TxSer
TxSer
TxFrameRef
TxFrameRef
TxOH_Ind
TxOH_Ind
NibInt
NibInt
Terminal Equipment
Mode 3 Operation of the Terminal Equipment
In Figure 161, both the Terminal Equipment and the
XRT72L53 are driven by an external 34.368 MHz
clock signal. This clock signal is connected to the
E3_Clock_In input of the Terminal Equipment and the
TxInClk input pin of the XRT72L53.
The Terminal Equipment will serially output the payload data on its E3_Data_Out output pin, upon the
rising edge of the signal at the E3_Clock_In input pin.
Similarly, the XRT72L53 will latch the data, residing
on the TxSer input pin, on the rising edge of TxInClk.
The XRT72L53 will pulse the TxFrame output pin
"High" for one bit-period, coincident while it is processing the last bit-field within a given Outbound E3
frame. The Terminal Equipment is expected to moni-
XRT72L5X E3 Framer
tor the TxFrame signal (from the XRT72L53) and to
place the first bit, within the very next Outbound E3
frame on the TxSer input pin.
NOTE: In this case, the XRT72L53 dictates exactly when
the very next E3 frame will be generated. The Terminal
Equipment is expected to respond appropriately by providing the XRT72L53 with the first bit of the new E3 frame,
upon demand. Hence, in this mode, the XRT72L53 is
referred to as the Frame Master and the Terminal Equipment is referred to as the Frame Slave.
Finally, the XRT72L53 will pulse its TxOH_Ind output
pin, one bit-period prior to it processing a given overhead bit, within the Outbound E3 frame. Since the
TxOH_Ind output pin of the XRT72L53 is electrically
connected to the E3_Overhead_Ind whenever the
XRT72L53 pulses the TxOH_Ind output pin "High", it
362
áç
XRT72L53
THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. P1.1.8
will also be driving the E3_Overhead_Ind input pin (of
the Terminal Equipment) "High". Whenever the Terminal Equipment detects this pin toggling "High", it
should delay transmission of the very next DS3 frame
payload bit by one clock cycle.
The behavior of the signal between the XRT72L53
and the Terminal Equipment for E3 Mode 3 Operation
is illustrated in Figure 162.
FIGURE 162. BEHAVIOR OF THE TERMINAL INTERFACE SIGNALS BETWEEN THE XRT72L53 AND THE TERMINAL
EQUIPMENT (E3 MODE 3 OPERATION)
Terminal Equipment Signals
E3_Clock_In
Payload[4238]
E3_Data_Out
Payload[4239]
FA1, Bit 7
FA1, Bit 6
FA1, Bit 7
FA1, Bit 6
Tx_Start_of_Frame
E3_Overhead_Ind
XRT72L5x Transmit Payload Data I/F Signals
TxInClk
Payload[4238]
TxSer
Payload[4239]
TxFrame
TxOH_Ind
E3 Frame Number N
E3 Frame Number N + 1
Note: TxFrame pulses high to denote
E3 Frame Boundary.
Note: The FA1 byte will not be processed by the
Transmit Payload Data Input Interface.
Note: TxOH_Ind pulses high for
16 bit periods in order to
denote Overhead Data
(e.g., the FA1 and FA2 bytes)
How to configure the XRT72L53 to operate in this
mode.
2. Set the TimRefSel[1:0] bit-fields (within the
Framer Operating Mode Register) to "01".
1. Set the NibIntf input pin "Low".
FRAMER OPERATING MODE REGISTER (ADDRESS = 0X00)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT2
BIT 1
BIT 0
Local Loopback
DS3/E3*
Internal LOS
Enable
RESET
Interrupt
Enable Reset
Frame Format
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
1
0
1
0
0
0
TimRefSel[1:0]
3. Interface the XRT72L53, to the Terminal Equipment, as illustrated in Figure 162.
A. Looped Timing (Uses the RxLineClk as the
Timing Reference)
6.2.1.4 Mode 4 - The Nibble-Parallel/LoopTimed Mode Behavior of the XRT72L53
If the XRT72L53 has been configured to operate in
this mode, then the XRT72L53 will behave as follows.
In this mode, the Transmit Section of the XRT72L53
will use the RxLineClk signal as its timing reference.
When the XRT72L53 is operating in the Nibble-Mode,
it will internally divide the RxLineClk signal, by a fac-
363
áç
XRT72L53
THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. P1.1.8
tor of four (4) and will output this signal via the TxNibClk output pin.
B. Nibble-Parallel Mode
The XRT72L53 will accept the E3 payload data, from
the Terminal Equipment in a nibble-parallel manner,
via the TxNib[3:0] input pins. The Transmit Terminal
Equipment Input Interface block will latch this data into its circuitry, on the rising edge of the TxNibClk output signal.
The E3 Frame consists of 537 bytes or 1074 nibbles.
Therefore, the XRT72L53 will supply 1074 TxNibClk
pulses between the rising edges of two consecutive
TxNibFrame pulses. The E3 Frame repetition rate is
8.0kHz. Hence, 1074 TxNibClk pulses for each E3
frame period amounts to TxNibClk running at approximately 8.592 MHz. The method by which the 1074
TxNibClk pulses are distributed throughout the E3
frame period is presented below.
C. Delineation of the Outbound E3 frames
The XRT72L53 will pulse the TxNibFrame output pin
"High" for one bit-period, coincident with the
XRT72L53 processing the last nibble of a given E3
frame.
Nominally, the Transmit Section within the XRT72L53
will generate a TxNibClk pulse for every 4 RxOutClk
(or TxInClk) periods.
D. Sampling of payload data, from the Terminal
Equipment
In Mode 4, the XRT72L53 will sample the data, at the
TxNib[3:0] input pins, on the third rising edge of the
RxOutClk clock signal, following a pulse in the TxNibClk signal (see Figure 164).
NOTE: The TxNibClk signal, from the XRT72L53, operates
nominally at 11.184 MHz (e.g., 44.736 MHz divided by 4).
However, for reasons described below, TxNibClk effectively
operates at a lower clock frequency. The Transmit Payload
Data Input Interface is only used to accept the payload
data, which is intended to be carried by Outbound DS3
frames. The Transmit Payload Data Input Interface is not
designed to accommodate the entire DS3 data stream.
Interfacing the Transmit Payload Data Input Interface block of the XRT72L53 to the Terminal Equipment for Mode 4 Operation
Figure 163 presents an illustration of the Transmit
Payload Data Input Interface block (within the
XRT72L53) being interfaced to the Terminal Equipment, for Mode 4 Operation.
FIGURE 163. ILLUSTRATION OF THE TERMINAL EQUIPMENT BEING INTERFACED TO THE TRANSMIT PAYLOAD DATA
INPUT INTERFACE BLOCK OF THE XRT72L53 FOR MODE 4 (NIBBLE-PARALLEL/LOOP-TIMED) OPERATION
VCC
8.592 MHz
E3_Nib_Clock_In
E3_Data_Out[3:0]
TxNibClk
NibInt
4
TxNib[3:0]
Tx_Start_of_Frame
TxNibFrame
TxOH_Ind
E3_Overhead_Ind
Terminal Equipment
Mode 4 Operation of the Terminal Equipment
When the XRT72L53 is operating in this mode, it will
function as the source of the 8.592MHz (e.g., the
34.368MHz clock signal divided by 4) clock signal
that will be used as the Terminal Equipment Interface
clock by both the XRT72L53 and the Terminal Equipment.
The Terminal Equipment will output the payload data
of the Outbound E3 data stream via its
E3_Data_Out[3:0] pins on the rising edge of the
34.368MHz
RxLineClk
XRT72L5X E3 Framer
8.592MHz clock signal at the E3_Nib_Clock_In input
pin.
The XRT72L53 will latch the Outbound E3 data
stream (from the Terminal Equipment) on the rising
edge of the TxNibClk output clock signal. The
XRT72L53 will indicate that it is processing the last
nibble, within a given E3 frame, by pulsing its TxNibFrame output pin "High" for one TxNibClk clock period. When the Terminal Equipment detects a pulse at
its Tx_Start_of_Frame input pin, it is expected to
transmit the first nibble, of the very next Outbound E3
364
áç
XRT72L53
THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. P1.1.8
frame to the XRT72L53 via the E3_Data_Out[3:0] (or
TxNib[3:0] pins).
Finally, for the Nibble-Parallel Mode operation, the
XRT72L53 will pulse the TxOHInd output pin “High”
for a total of 14 nibble periods (e.g., for the 7 overhead bytes, within each of the E3, ITU-T G.832
frames). At the beginning of an E3 frame, the
XRT72L53 will pulse the TxOHInd output pin “High”
for 4 nibble periods. These four nibbles represent the
“FA1” and “FA2” bytes within each E3 frame.
Throughout the remainder of the E3 framing period,
the XRT72L53 will pulse the TxOHInd output pin 5
times. The width (or duration) of each of these pulses
will be two nibbles. Clearly, each of these 5 pulses
corresponds to the five remaining overhead bytes,
within the E3, ITU-T G.832 framing structure.
The behavior of the signals between the XRT72L53
and the Terminal Equipment for E3 Mode 4 Operation
is illustrated in Figure 164.
FIGURE 164. BEHAVIOR OF THE TERMINAL INTERFACE SIGNALS BETWEEN THE XRT72L53 AND THE TERMINAL
EQUIPMENT (MODE 4 OPERATION)
Terminal Equipment Signals
RxOutClk
E3_Nib_Clock_In
Payload Nibble [1059]
E3_Data_Out[3:0]
Overhead Nibble [0]
Tx_Start_of_Frame
E3_Overhead_Ind
XRT72L5x Transmit Payload Data I/F Signals
RxOutClk
TxNibClk
Nibble [1059]
TxNib[3:0]
Overhead Nibble [0]
TxNibFrame
TxOH_Ind
Note: TxNibFrame pulses high to denote
E3 Frame Boundary.
E3 Frame Number N + 1
E3 Frame Number N
TxOH_Ind pulses high for 4 Nibble periods
How to configure the XRT72L53 into Mode 4
2. Set the TimRefSel[1:0] bit-fields (within the
Framer Operating Mode Register) to "00" as illustrated below.
1. Set the NibIntf input pin "High".
FRAMER OPERATING MODE REGISTER (ADDRESS = 0X00)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT2
Local Loopback
DS3/E3*
Internal LOS
Enable
RESET
Interrupt
Enable Reset
Frame Format
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
1
0
1
0
0
0
365
BIT 1
BIT 0
TimRefSel[1:0]
áç
XRT72L53
THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. P1.1.8
3. Interface the XRT72L53, to the Terminal Equipment, as illustrated in Figure 163.
circuitry, on the rising edge of the TxNibClk output
signal.
6.2.1.5 Mode 5 - The Nibble-Parallel/LocalTime/Frame-Slave Interface Mode Behavior of the
XRT72L53
If the XRT72L53 has been configured to operate in
this mode, then the XRT72L53 will function as follows:
C. Delineation of Outbound E3 Frames
A. Local Timing - Uses the TxInClk signal as the
Timing Reference
D. Sampling of payload data, from the Terminal
Equipment
In this mode, the Transmit Section of the XRT72L53
will use the TxInClk signal at its timing reference. Further, the chip will internally divide the TxInClk clock
signal by a factor of 4 and will output this divided
clock signal via the TxNibClk output pin. The Transmit
Terminal Equipment Input Interface block (within the
XRT72L53) will use the rising edge of the TxNibClk
signal, to latch the data, residing on the TxNib[3:0] into its circuitry.
In Mode 5, the XRT72L53 will sample the data, at the
TxNib[3:0] input pins, on the third rising edge of the
TxInClk clock signal, following a pulse in the TxNibClk
signal (see Figure 166).
The Transmit Section will use the TxInClk input signal
as its timing reference and will use the TxFrameRef
input signal as its Framing Reference (e.g., the Transmit Section of the XRT72L53 initiates frame generation upon the rising edge of the TxFrameRef signal).
B. Nibble-Parallel Mode
NOTE: The TxNibClk signal, from the XRT72L53 operates
nominally at 8.592 MHz (e.g., 34.368 MHz divided by 4).
Interfacing the Transmit Payload Data Input Interface block of the XRT72L53 to the Terminal Equipment for Mode 5 Operation
Figure 165 presents an illustration of the Transmit
Payload Data Input Interface block (within the
XRT72L53) being interfaced to the Terminal Equipment, for Mode 5 Operation.
The XRT72L53 will accept the DS3 payload data,
from the Terminal Equipment, in a parallel manner,
via the TxNib[3:0] input pins. The Transmit Terminal
Equipment Input Interface will latch this data into its
FIGURE 165. ILLUSTRATION OF THE TERMINAL EQUIPMENT BEING INTERFACED TO THE TRANSMIT PAYLOAD DATA
INPUT INTERFACE BLOCK OF THE XRT72L53 FOR MODE 5 (NIBBLE-PARALLEL/LOCAL-TIME/FRAME-SLAVE) OPERATION
34.368MHz Clock Source
VCC
TxInClk
E3_Nib_Clock_In
NibInt
8.592MHz
TxNibClk
4
E3_Data_Out[3:0]
TxNib[3:0]
Tx_Start_of_Frame
TxFrameRef
E3_Overhead_Ind
TxOH_Ind
XRT72L5x E3 Framer
Terminal Equipment
Mode 5 Operation of the Terminal Equipment
In Figure 165 both the Terminal Equipment and the
XRT72L53 will be driven by an external 8.592MHz
clock signal. The Terminal Equipment will receive the
8.592MHz clock signal via the E3_Nib_Clock_In input
pin. The XRT72L53 will output the 8.592MHz clock
signal via the TxNibClk output pin.
The Terminal Equipment will serially output the data
on the E3_Data_Out[3:0] pins, upon the rising edge
of the signal at the E3_Clock_In input pin.
NOTE: The E3_Data_Out[3:0] output pins of the Terminal
Equipment is electrically connected to the TxNib[3:0] input
pins.
366
áç
XRT72L53
THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. P1.1.8
ing edge of the input at its TxFrameRef input pin, it
will begin generation of a new E3 frame.
The XRT72L53 will latch the data, residing on the TxNib[3:0] input pins, on the rising edge of the TxNibClk
signal.
Finally, the XRT72L53 will always internally generate
the Overhead bits, when it is operating in both the E3
and Nibble-parallel modes. The XRT72L53 will pull
the TxOHInd input pin "Low".
In this case, the Terminal Equipment has the responsibility of providing the framing reference signal by
pulsing the Tx_Start_of_Frame output pin (and in
turn, the TxFrameRef input pin of the XRT72L53)
"High" for one bit-period, coincident with the first bit of
a new E3 frame. Once the XRT72L53 detects the ris-
The behavior of the signals between the XRT72L53
and the Terminal Equipment for E3 Mode 5 Operation
is illustrated in Figure 166.
FIGURE 166. BEHAVIOR OF THE TERMINAL INTERFACE SIGNALS BETWEEN THE XRT72L53 AND THE TERMINAL
EQUIPMENT (E3 MODE 5 OPERATION)
Terminal Equipment Signals
RxOutClk
E3_Nib_Clock_In
Payload Nibble [1059]
E3_Data_Out[3:0]
Overhead Nibble [0]
Tx_Start_of_Frame
E3_Overhead_Ind
XRT72L5x Transmit Payload Data I/F Signals
p
RxOutClk
TxNibClk
Nibble [1059]
TxNib[3:0]
Overhead Nibble [0]
TxFrameRef
TxOH_Ind
E3 Frame Number N
Note: Terminal Equipment pulses
“TxFrameRef” in order to denote
the E3 Frame Boundary.
E3 Frame Number N + 1
TxOH_Ind pulses high for 4 Nibble periods
How to configure the XRT72L53 into Mode 5
2. Set the TimRefSel[1:0] bit-fields (within the
Framer Operating Mode Register) to "01" as illustrated below.
1. Set the NibIntf input pin "High".
FRAMER OPERATING MODE REGISTER (ADDRESS = 0X00)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
Local Loopback
DS3/E3*
Internal LOS
Enable
RESET
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
1
0
1
0
0
1
367
BIT2
Interrupt Enable Frame Format
Reset
BIT 1
BIT 0
TimRefSel[1:0]
áç
XRT72L53
THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. P1.1.8
3. Interface the XRT72L53, to the Terminal Equipment, as illustrated in Figure 165.
ment Input Interface will latch this data into its circuitry, on the rising edge of the TxNibClk output signal.
6.2.1.6 Mode 6 - The Nibble-Parallel/LocalTimed/Frame-Master Interface Mode Behavior of
the XRT72L53
If the XRT72L53 has been configured to operate in
this mode, then the XRT72L53 will function as follows:
C. Delineation of Outbound E3 Frames
The Transmit Section will use the TxInClk input signal
as its timing reference and will initiate the generation
of E3 frames, asynchronous with respect to any external signal. The XRT72L53 will pulse the TxFrame
output pin "High" whenever it is processing the last
bit, within a given Outbound E3 frame.
A. Local Timing - Uses the TxInClk signal as the
Timing Reference
In this mode, the Transmit Section of the XRT72L53
will use the TxInClk signal at its timing reference. Further, the chip will internally divide the TxInClk clock
signal by a factor of 4 and will output this divided
clock signal via the TxNibClk output pin. The Transmit
Terminal Equipment Input Interface block (within the
XRT72L53) will use the rising edge of the TxNibClk
signal, to latch the data, residing on the TxNib[3:0] into its circuitry.
B. Nibble-Parallel Mode
The XRT72L53 will accept the E3 payload data, from
the Terminal Equipment, in a parallel manner, via the
TxNib[3:0] input pins. The Transmit Terminal Equip-
D. Sampling of payload data, from the Terminal
Equipment
In Mode 6, the XRT72L53 will sample the data, at the
TxNib[3:0] input pins, on the third rising edge of the
TxInClk clock signal, following a pulse in the TxNibClk
signal (see Figure 168).
NOTE: The TxNibClk signal, from the XRT72L53 operates
nominally at 8.592 MHz (e.g., 34.368 MHz divided by 4).
Interfacing the Transmit Payload Data Input Interface block of the XRT72L53 to the Terminal Equipment for Mode 6 Operation
Figure 167 presents an illustration of the Transmit
Payload Data Input Interface block (within the
XRT72L53) being interfaced to the Terminal Equipment, for Mode 6 Operation.
FIGURE 167. ILLUSTRATION OF THE TERMINAL EQUIPMENT BEING INTERFACED TO THE TRANSMIT PAYLOAD DATA
INPUT INTERFACE BLOCK OF THE XRT72L53 FOR MODE 6 OPERATION
34.368MHz Clock Source
VCC
TxInClk
E3_Nib_Clock_In
NibInt
8.592MHz
TxNibClk
4
E3_Data_Out[3:0]
TxNib[3:0]
Tx_Start_of_Frame
TxNibFrame
E3_Overhead_Ind
TxOH_Ind
Terminal Equipment
Mode 6 Operation of the Terminal Equipment
In Figure 167 both the Terminal Equipment and the
XRT72L53 will be driven by an external 8.592MHz
clock signal. The Terminal Equipment will receive the
8.592MHz clock signal via the E3_Nib_Clock_In input
pin. The XRT72L53 will output the 8.592MHz clock
signal via the TxNibClk output pin.
XRT72L5x E3 Framer
The Terminal Equipment will serially output the data
on the E3_Data_Out[3:0] pins upon the rising edge of
the signal at the E3_Clock_In input pin. The
XRT72L53 will latch the data, residing on the TxNib[3:0] input pins, on the rising edge of the TxNibClk
signal.
368
áç
XRT72L53
THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. P1.1.8
Finally, the XRT72L53 will always internally generate
the Overhead bits, when it is operating in both the E3
and Nibble-parallel modes. The XRT72L53 will pull
the TxOHInd input pin "Low".
In this case the XRT72L53 has the responsibility of
providing the framing reference signal by pulsing the
TxFrame output pin (and in turn the
Tx_Start_of_Frame input pin of the Terminal Equipment) "High" for one bit-period, coincident with the
last bit within a given E3 frame.
The behavior of the signals between the XRT72L53
and the Terminal Equipment for E3 Mode 6 Operation
is illustrated in Figure 168.
FIGURE 168. BEHAVIOR OF THE TERMINAL INTERFACE SIGNALS BETWEEN THE XRT72L53 AND THE TERMINAL
EQUIPMENT (E3 MODE 6 OPERATION)
Terminal Equipment Signals
TxInClk
E3_Nib_Clock_In
Payload Nibble [1059]
E3_Data_Out[3:0]
Overhead Nibble [0]
Tx_Start_of_Frame
E3_Overhead_Ind
XRT72L5x Transmit Payload Data I/F Signals
TxInClk
TxNibClk
Nibble [1059]
TxNib[3:0]
Overhead Nibble [0]
TxNibFrame
TxOH_Ind
E3 Frame Number N + 1
E3 Frame Number N
Note: TxNibFrame pulses high to denote
E3 Frame Boundary.
TxOH_Ind pulses high for 4 Nibble periods
How to configure the XRT72L53 into Mode 6
2. Set the TimRefSel[1:0] bit-fields (within the
Framer Operating Mode Register) to "1X" as illustrated below.
1. Set the NibInt input pin "High".
FRAMER OPERATING MODE REGISTER (ADDRESS = 0X00)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
Local Loopback
DS3/E3*
Internal LOS
Enable
RESET
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
1
0
1
0
1
x
3. Interface the XRT72L53, to the Terminal Equipment, as illustrated in Figure 167.
Interrupt
Frame Format
Enable Reset
6.2.2
face
369
BIT2
BIT 1
BIT 0
TimRefSel[1:0]
The Transmit Overhead Data Input Inter-
áç
XRT72L53
THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. P1.1.8
Figure 169 presents a simple illustration of the Transmit Overhead Data Input Interface block within the
XRT72L53.
FIGURE 169. SIMPLE ILLUSTRATION OF THE TRANSMIT OVERHEAD DATA INPUT INTERFACE BLOCK
TxOHFrame
TxOHEnable
TxOH
Transmit
Transmit
Overhead
Overhead
Data
DataInput
Input
Interface
InterfaceBlock
Block
To Transmit E3 Framer Block
TxOHClk
TxOHIns
The E3, ITU-T G.832 Frame consists of 537 bytes. Of
these bytes, 530 bytes are payload bytes and the remaining 7 are overhead bytes. The XRT72L53 has
been designed to handle and process both the payload type and overhead type bits for each E3 frame.
Within the Transmit Section within the XRT72L53, the
Transmit Payload Data Input Interface has been designed to handle the payload data. Likewise, the
Transmit Overhead Input Interface has been designed to handle and process the overhead bits.
The Transmit Section of the XRT72L53 generates or
processes the various overhead bits within the E3
frame, in the following manner.
The Frame Alignment Overhead Bytes (e.g., the
“FA1” and “FA2” bytes)
The "FA1" and "FA2" bytes are always internally generated by the Transmit Section of the XRT72L53.
Hence, the user cannot insert his/her value for the
"FA1" and "FA2" bytes into the Outbound DS3 data
stream, via the Transmit Overhead Data Input Interface.
The Error Monitoring (EM) Overhead Byte
The EM byte is always internally generated by the
Transmit Section of the XRT72L53. Hence, the user
cannot insert his/her value for the EM byte into the
Outbound E3 data stream, via the Transmit Overhead
Data Input Interface.
The Alarm and signaling related Overhead bytes
Bytes that are used to transport the alarm conditions
can be either internally generated by the Transmit
Section within the XRT72L53, or can be externally
generated and inserted into the Outbound E3 data
stream, via the Transmit Overhead Data Input Interface. The E3 frame overhead bits that fall into this category are:
• The "MA” byte
• The "TR” byte
The Data Link Related Overhead Bits
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THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
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PRELIMINARY
REV. P1.1.8
The E3 frame structure also contains bits which can
be used to transport User Data Link information and
Path Maintenance Data Link information. The UDL
(User Data Link) bits are only accessible via the
Transmit Overhead Data Input Interface. The Path
Maintenance Data Link (PMDL) bits can either be
sourced from the Transmit LAPD Controller/Buffer or
via the Transmit Overhead Data Input Interface.
Table 72 lists the Overhead Bits within the DS3
frame. Additionally, this table also indicates whether
or not these overhead bits can be sourced by the
Transmit Overhead Data Input Interface or not.
TABLE 72: A LISTING OF THE OVERHEAD BITS WITHIN THE E3 FRAME, AND THEIR POTENTIAL SOURCES, WITHIN THE
XRT72L53 IC
OVERHEAD BIT
INTERNALLY GENERATED
ACCESSIBLE VIA THE TRANSMIT OVERHEAD
DATA INPUT INTERFACE
BUFFER/REGISTER
ACCESSIBLE
FA1 - Bit 7
Yes
No
Yes*
FA1 - Bit 6
Yes
No
Yes
FA1 - Bit 5
Yes
No
Yes*
FA1 - Bit 4
Yes
No
Yes*
FA1 - Bit 3
Yes
No
Yes
FA1 - Bit 2
Yes
No
Yes
FA1 - Bit 1
Yes
No
Yes+
FA1 - Bit 0
Yes
No
Yes
FA2 - Bit 7
Yes
No
Yes
FA2 - Bit 6
Yes
No
Yes
FA2 - Bit 5
Yes
No
Yes
FA2 - Bit 4
Yes
No
Yes
FA2 - Bit 3
Yes
No
Yes
FA2 - Bit 2
Yes
No
Yes
FA2 - Bit 1
Yes
No
Yes
FA2 - Bit 0
Yes
No
Yes
EM - Bit 7
Yes
Yes
Yes
EM - Bit 6
Yes
Yes
Yes
EM - Bit 5
Yes
Yes
Yes
EM - Bit 4
Yes
Yes
Yes
EM - Bit 3
Yes
Yes
Yes
EM - Bit 2
Yes
Yes
Yes
EM - Bit 1
Yes
Yes
Yes
EM - Bit 0
Yes
Yes
Yes
TR - Bit 7
No
Yes
Yes
TR - Bit 6
No
Yes
Yes
371
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THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. P1.1.8
TABLE 72: A LISTING OF THE OVERHEAD BITS WITHIN THE E3 FRAME, AND THEIR POTENTIAL SOURCES, WITHIN THE
XRT72L53 IC
OVERHEAD BIT
INTERNALLY GENERATED
ACCESSIBLE VIA THE TRANSMIT OVERHEAD
DATA INPUT INTERFACE
BUFFER/REGISTER
ACCESSIBLE
TR - Bit 5
No
Yes
Yes
TR - Bit 4
No
Yes
Yes
TR - Bit 3
No
Yes
Yes
TR - Bit 2
No
Yes
Yes
TR - Bit 1
No
Yes
Yes
TR - Bit 0
No
Yes
Yes
MA - Bit 7
Yes
Yes
Yes
MA - Bit 6
Yes
Yes
Yes
MA - Bit 5
Yes
Yes
Yes
MA - Bit 4
Yes
Yes
Yes
MA - Bit 3
Yes
Yes
Yes
MA - Bit 2
Yes
Yes
Yes
MA - Bit 1
Yes
Yes
Yes
MA - Bit 0
Yes
Yes
Yes
NR - Bit 7
No
Yes
Yes
NR - Bit 6
No
Yes
Yes
NR - Bit 5
No
Yes
Yes
NR - Bit 4
No
Yes
Yes
NR - Bit 3
No
Yes
Yes
NR - Bit 2
No
Yes
Yes
NR - Bit 1
No
Yes
Yes
NR - Bit 0
No
Yes
Yes
GC - Bit 7
No
Yes
Yes
GC - Bit 6
No
Yes
Yes
GC - Bit 5
No
Yes
Yes
GC - Bit 4
No
Yes
Yes
GC - Bit 3
No
Yes
Yes
GC - Bit 2
No
Yes
Yes
GC - Bit 1
No
Yes
Yes
GC - Bit 0
No
Yes
Yes
NOTES:
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THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
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REV. P1.1.8
1. The XRT72L53 contains mask register bits that
permit the user to alter the state of the internally
generated value for these bits.
2. The Transmit LAPD Controller/Buffer can be configured to be the source of the DL bits, within the Outbound E3 data stream.
In all, the Transmit Overhead Data Input Interface
permits the user to insert overhead data into the Outbound E3 frames via the following two different methods.
áç
6.2.2.1 Method 1 - Using the TxOHClk Clock
Signal
The Transmit Overhead Data Input Interface consists
of the five signals. Of these five (5) signals, the following four (4) signals are to be used when implementing Method 1.
• TxOH
• TxOHClk
• TxOHFrame
• Method 1 - Using the TxOHClk clock signal
• TxOHIns
• Method 2 - Using the TxInClk and the TxOHEnable
signals.
Each of these signals are listed and described below.
Table 73.
Each of these methods are described below.
373
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THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
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REV. P1.1.8
TABLE 73: DESCRIPTION OF METHOD 1 TRANSMIT OVERHEAD INPUT INTERFACE SIGNALS
NAME
TYPE
TxOHIns
Input
DESCRIPTION
Transmit Overhead Data Insert Enable input pin.
Asserting this input signal (e.g., setting it "High") enables the Transmit Overhead Data Input Interface to accept overhead data from the Terminal Equipment. In other words, while this input pin is
"High", the Transmit Overhead Data Input Interface will sample the data at the TxOH input pin, on
the falling edge of the TxOHClk output signal.
Conversely, setting this pin "Low" configures the Transmit Overhead Data Input Interface to NOT
sample (e.g., ignore) the data at the TxOH input pin, on the falling edge of the TxOHClk output
signal.
NOTE: If the Terminal Equipment attempts to insert an overhead bit that cannot be accepted by
the Transmit Overhead Data Input Interface (e.g., if the Terminal Equipment asserts the TxOHIns
signal, at a time when one of these non-insertable overhead bits are being processed), that particular insertion effort will be ignored.
TxOH
Input
Transmit Overhead Data Input pin:
The Transmit Overhead Data Input Interface accepts the overhead data via this input
pin, and inserts into the overhead bit position within the very next Outbound E3 frame. If
the TxOHIns pin is pulled "High", the Transmit Overhead Data Input Interface will sample the data at this input pin (TxOH), on the falling edge of the TxOHClk output pin. Conversely, if the TxOHIns pin is pulled "Low", then the Transmit Overhead Data Input Interface will NOT sample the data at this input pin (TxOH). Consequently, this data will be
ignored.
TxOHClk
Output
Transmit Overhead Input Interface Clock Output signal:
This output signal serves two purposes:
1. The Transmit Overhead Data Input Interface will provide a rising clock edge on this signal, one
bit-period prior to the instant that the Transmit Overhead Data Input Interface is processing an
overhead bit.
2. The Transmit Overhead Data Input Interface will sample the data at the TxOH input, on the falling edge of this clock signal (provided that the TxOHIns input pin is "High").
NOTE: The Transmit Overhead Data Input Interface will supply a clock edge for all overhead bits
within the DS3 frame (via the TxOHClk output signal). This includes those overhead bits that the
Transmit Overhead Data Input Interface will not accept from the Terminal Equipment.
TxOHFrame
Output
Transmit Overhead Input Interface Frame Boundary Indicator Output:
This output signal pulses "High" when the XRT72L53 is processing the last bit within a
given E3 frame.
The purpose of this output signal is to alert the Terminal Equipment that the Transmit
Overhead Data Input Interface block is about to begin processing the overhead bits for a
new E3 frame.
374
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THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. P1.1.8
Interfacing the Transmit Overhead Data Input Interface to the Terminal Equipment.
Figure 170 illustrates how one should interface the
Transmit Overhead Data Input Interface to the Terminal Equipment, when using Method 1.
FIGURE 170. ILLUSTRATION OF THE TERMINAL EQUIPMENT BEING INTERFACED TO THE TRANSMIT OVERHEAD DATA
INPUT INTERFACE (METHOD 1)
34.368MHz Clock Source
TxInClk
E3_OH_Clock_In
TxOHClk
E3_OH_Out
TxOH
RxLineCl,k
TxFrame
Tx_Start_of_Frame
Insert_OH
TxOHIns
Terminal Equipment
XRT72L5x E3 Framer
Method 1 Operation of the Terminal Equipment
If the Terminal Equipment intends to insert any overhead data into the Outbound E3 data stream, (via the
Transmit Overhead Data Input Interface), then it is expected to do the following.
1. To sample the state of the TxOHFrame signal
(e.g., the Tx_Start_of_Frame input signal) on the
rising edge of the TxOHClk (e.g., the
E3_OH_Clock_In signal).
2. To keep track of the number of rising clock edges
that have occurred, via the TxOHClk (e.g., the
E3_OH_Clock_In signal) since the last time the
TxOHFrame signal was sampled "High". By doing
this the Terminal Equipment will be able to keep
34.368MHz
Clock Source
track of which overhead bit is being processed by
the Transmit Overhead Data Input Interface block
at any given time. When the Terminal Equipment
knows which overhead bit is being processed, at
a given TxOHClk period, it will know when to
insert a desired overhead bit value into the Outbound E3 data stream. From this, the Terminal
Equipment will know when it should assert the
TxOHIns input pin and place the appropriate
value on the TxOH input pin (of the XRT72L53).
Table 74 relates the number of rising clock edges (in
the TxOHClk signal, since TxOHFrame was sampled
"High") to the E3 Overhead Bit, that is being processed.
375
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THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. P1.1.8
TABLE 74: THE RELATIONSHIP BETWEEN THE NUMBER OF RISING CLOCK EDGES IN TXOHCLK, (SINCE
"TXOHFRAME" WAS LAST SAMPLED "HIGH") TO THE E3 OVERHEAD BIT, THAT IS BEING PROCESSED
NUMBER OF RISING CLOCK EDGES IN
TXOHCLK
THE OVERHEAD BIT EXPECTED BY THE CAN THIS OVERHEAD BIT BE ACCEPTED BY
THE XRT72L53?
"XRT72L53"
0 (Clock edge is coincident with TxOHFrame being detected “High”)
FA1 Byte - Bit 7
No
1
FA1 Byte - Bit 6
No
2
FA1 Byte - Bit 5
No
3
FA1 Byte - Bit 4
No
4
FA1 Byte - Bit 3
No
5
FA1 Byte - Bit 2
No
6
FA1 Byte - Bit 1
No
7
FA1 Byte - Bit 0
No
8
FA2 Byte - Bit 7
No
9
FA2 Byte - Bit 6
No
10
FA2 Byte - Bit 5
No
11
FA2 Byte - Bit 4
No
12
FA2 Byte - Bit 3
No
13
FA2 Byte - Bit 2
No
14
FA2 Byte - Bit 1
No
15
FA2 Byte - Bit 0
No
16
EM Byte - Bit 7
No
17
EM Byte - Bit 6
No
18
EM Byte - Bit 5
No
19
EM Byte - Bit 4
No
20
EM Byte - Bit 3
No
21
EM Byte - Bit 2
No
22
EM Byte - Bit 1
No
23
EM Byte - Bit 0
No
24
TR Byte - Bit 7
Yes
25
TR Byte - Bit 6
Yes
26
TR Byte - Bit 5
Yes
27
TR Byte - Bit 4
Yes
28
TR Byte - Bit 3
Yes
29
TR Byte - Bit 2
Yes
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THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
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PRELIMINARY
REV. P1.1.8
TABLE 74: THE RELATIONSHIP BETWEEN THE NUMBER OF RISING CLOCK EDGES IN TXOHCLK, (SINCE
"TXOHFRAME" WAS LAST SAMPLED "HIGH") TO THE E3 OVERHEAD BIT, THAT IS BEING PROCESSED
NUMBER OF RISING CLOCK EDGES IN
TXOHCLK
THE OVERHEAD BIT EXPECTED BY THE CAN THIS OVERHEAD BIT BE ACCEPTED BY
THE XRT72L53?
"XRT72L53"
30
TR Byte - Bit 1
Yes
31
TR Byte - Bit 0
Yes
32
MA Byte - Bit 7
Yes (FERF Bit)
33
MA Byte - Bit 6
Yes (FEBE Bit)
34
MA Byte - Bit 5
Yes
35
MA Byte - Bit 4
Yes
36
MA Byte - Bit 3
Yes
37
MA Byte - Bit 2
Yes
38
MA Byte - Bit 1
Yes
39
MA Byte - Bit 0
Yes
40
NR Byte - Bit 7
Yes
41
NR Byte - Bit 6
Yes
42
NR Byte - Bit 5
Yes
43
NR Byte - Bit 4
Yes
44
NR Byte - Bit 3
Yes
45
NR Byte - Bit 2
Yes
46
NR Byte - Bit 1
Yes
47
NR Byte - Bit 0
Yes
48
GC Byte - Bit 7
Yes
49
GC Byte - Bit 6
Yes
50
GC Byte - Bit 5
Yes
51
GC Byte - Bit 4
Yes
52
GC Byte - Bit 3
Yes
53
GC Byte - Bit 2
Yes
54
GC Byte - Bit 1
Yes
55
GC Byte - Bit 0
Yes
3. After the Terminal Equipment has waited the
appropriate number of clock edges (from the
TxOHFrame signal being sampled "High"), it
should assert the TxOHIns input signal. Concurrently, the Terminal Equipment should also place
the appropriate value (of the inserted overhead
bit) onto the TxOH signal.
4. The Terminal Equipment should hold both the
TxOHIns input pin "High" and the value of the
TxOH signal, stable until the next rising edge of
TxOHClk is detected.
Case Study: The Terminal Equipment intends to
insert the appropriate overhead bits into the
Transmit Overhead Data Input Interface (using
377
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XRT72L53
THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. P1.1.8
Method 1) in order to transmit a Yellow Alarm to
the remote terminal equipment.
Yellow Alarm is transmitted by setting the FERF bit
(within the MA Byte) to "0".
In this example, the Terminal Equipment intends to insert the appropriate overhead bits, into the Transmit
Overhead Data Input Interface, such that the
XRT72L53 will transmit a Yellow Alarm to the remote
terminal equipment. Recall that, for E3 Applications, a
If one assumes that the connection between the Terminal Equipment and the XRT72L53 are as illustrated
in Figure 170 then Figure 171 presents an illustration
of the signaling that must go on between the Terminal
Equipment and the XRT72L53.
FIGURE 171. ILLUSTRATION OF THE SIGNAL THAT MUST OCCUR BETWEEN THE TERMINAL EQUIPMENT AND THE
XRT72L53, IN ORDER TO CONFIGURE THE XRT72L53 TO TRANSMIT A YELLOW ALARM TO THE REMOTE TERMINAL
EQUIPMENT
Terminal Equipment/XRT72L5x Interface Signals
0
1
26
27
28
29
30
31
32
TxOHClk
TxOHFrame
TxOHIns
TxOH
Remaining Overhead Bits with E3 Frame
MA, Bit 7
TxOHFrame is sample “high”
Terminal Equipment asserts TxOHIns and
Data on TxOH line.
XRT72L5x Framer samples TxOHIns and
TxOHIns signal
In Figure 171 the Terminal Equipment samples the
TxOHFrame signal being "High" at rising clock edge #
“0". From this point, the Terminal Equipment waits until it has detected 32 rising edges in the TxOHClk signal. At this point, the Terminal Equipment knows that
the XRT72L53 is just about to process the FERF bit
within the MA byte (in a given Outbound E3 frame).
Additionally, according to Table 74, the 32nd overhead bit to be processed is the FERF bit. In order to
facilitate the transmission of the Yellow Alarm, the
Terminal Equipment must set this FERF bit to "1".
Hence, the Terminal Equipment starts this process by
implementing the following steps concurrently.
a. Assert the TxOHIns input pin by setting it "High".
b. Set the TxOH input pin to "0".
After the Terminal Equipment has applied these signals, the XRT72L53 will sample the data on both the
TxOHIns and TxOH signals upon the very next falling
edge of TxOHClk (designated at 32- in Figure 171).
Once the XRT72L53 has sampled this data, it will
then insert a "1" into the FERF bit position, in the Outbound E3 frame.
Upon detection of the very next rising edge of the TxOHClk clock signal (designated as clock edge 1 in
Figure 171), the Terminal Equipment will negate the
TxOHIns signal (e.g., toggles it "Low") and will cease
inserting data into the Transmit Overhead Data Input
Interface.
6.2.2.2 Method 2 - Using the TxInClk and
TxOHEnable Signals
Method 1 requires the use of an additional clock signal, TxOHClk. However, there may be a situation in
which the user does not wish to add this extra clock
signal to their design, in order to use the Transmit
Overhead Data Input Interface. Hence, Method 2 is
available. When using Method 2, either the TxInClk or
RxOutClk signal is used to sample the overhead bits
and signals which are input to the Transmit Overhead
378
XRT72L53
THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
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PRELIMINARY
REV. P1.1.8
Data Input Interface. Method 2 involves the use of the
following signals:
• TxOHFrame
• TxOH
Each of these signals are listed and described in
Table 75.
• TxInClk
• TxOHEnable
TABLE 75: DESCRIPTION OF METHOD 1 TRANSMIT OVERHEAD INPUT INTERFACE SIGNALS
NAME
TYPE
TxOHEnable
Output
DESCRIPTION
Transmit Overhead Data Enable Output pin
The XRT72L53 will assert this signal, for one TxInClk period, just prior to the instant that
the Transmit Overhead Data Input Interface is processing an overhead bit.
TxOHFrame
Output
Transmit Overhead Input Interface Frame Boundary Indicator Output:
This output signal pulses "High" when the XRT72L53 is processing the last bit within a
given DS3 frame.
TxOHIns
Input
Transmit Overhead Data Insert Enable input pin.
Asserting this input signal (e.g., setting it "High") enables the Transmit Overhead Data Input Interface to accept overhead data from the Terminal Equipment. In other words, while this input pin is
"High", the Transmit Overhead Data Input Interface will sample the data at the TxOH input pin, on
the falling edge of the TxInClk output signal.
Conversely, setting this pin "Low" configures the Transmit Overhead Data Input Interface to NOT
sample (e.g., ignore) the data at the TxOH input pin, on the falling edge of the TxOHClk output
signal.
NOTE: If the Terminal Equipment attempts to insert an overhead bit that cannot be accepted by
the Transmit Overhead Data Input Interface (e.g., if the Terminal Equipment asserts the TxOHIns
signal, at a time when one of these non-insertable overhead bits are being processed), that particular insertion effort will be ignored.
TxOH
Input
Transmit Overhead Data Input pin:
The Transmit Overhead Data Input Interface accepts the overhead data via this input
pin, and inserts into the overhead bit position within the very next Outbound DS3 frame.
If the TxOHIns pin is pulled "High", the Transmit Overhead Data Input Interface will sample the data at this input pin (TxOH), on the falling edge of the TxOHClk output pin. Conversely, if the TxOHIns pin is pulled "Low", then the Transmit Overhead Data Input Interface will NOT sample the data at this input pin (TxOH). Consequently, this data will be
ignored.
Interfacing the Transmit Overhead Data Input Interface
to the Terminal Equipment
Figure 172 illustrates how one should interface the
Transmit Overhead Data Input Interface to the Terminal Equipment when using Method 2.
379
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XRT72L53
THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. P1.1.8
FIGURE 172. ILLUSTRATION OF THE TERMINAL EQUIPMENT BEING INTERFACED TO THE TRANSMIT OVERHEAD DATA
INPUT INTERFACE (METHOD 2)
34.368MHz Clock Source
E3_Clock_In
TxInClk
TxOHEnable
E3_OH_Enable
E3_OH_Out
TxOH
Tx_Start_of_Frame
RxLineCl,k
TxOHFrame
Insert_OH
TxOHIns
Terminal Equipment
XRT72L5x E3 Framer
Method 2 Operation of the Terminal Equipment
If the Terminal Equipment intends to insert any overhead data into the Outbound E3 data stream (via the
Transmit Overhead Data Input Interface), then it is expected to do the following.
1. To sample the state of both the TxOHFrame and
the TxOHEnable input signals, via the
E3_Clock_In (e.g., either the TxInClk or the
RxOutClk signal of the XRT72L53) signal. If the
Terminal Equipment samples the TxOHEnable
signal "High", then it knows that the XRT72L53 is
about to process an overhead bit. Further, if the
Terminal Equipment samples both the TxOHFrame and the TxOHEnable pins "High" (at the
same time) then the Terminal Equipment knows
that the XRT72L53 is about to process the first
overhead bit, within a new E3 frame.
34.368MHz
Clock Source
2. To keep track of the number of times that the
TxOHEnable signal has been sampled "High"
since the last time both the TxOHFrame and the
TxOHEnable signals were sampled "High". By
doing this, the Terminal Equipment will be able to
keep track of which overhead bit the Transmit
Overhead Data Input Interface is about ready to
process. From this, the Terminal Equipment will
know when it should assert the TxOHIns input pin
and place the appropriate value on the TxOH
input pins of the XRT72L53.
Table 76 also relates the number of TxOHEnable output pulses (that have occurred since both the TxOHFrame and TxOHEnable pins were sampled "High")
to the E3 overhead bit, that is being processed.
380
XRT72L53
THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
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PRELIMINARY
REV. P1.1.8
TABLE 76: THE RELATIONSHIP BETWEEN THE NUMBER OF TXOHENABLE PULSES (SINCE THE LAST OCCURRENCE OF
THE TXOHFRAME PULSE) TO THE E3 OVERHEAD BIT, THAT IS BEING PROCESSED BY THE XRT72L53
NUMBER OF TXOHENABLE PULSES
THE OVERHEAD BIT EXPECTED BY THE CAN THIS OVERHEAD BIT BE ACCEPTED BY
THE XRT72L53?
XRT72L53
0 (Clock edge is coincident with TxOHFrame being detected “High”)
FA1 Byte - Bit 7
Yes
1
FA1 Byte - Bit 6
No
2
FA1 Byte - Bit 5
No
3
FA1 Byte - Bit 4
No
4
FA1 Byte - Bit 3
No
5
FA1 Byte - Bit 2
No
6
FA1 Byte - Bit 1
No
7
FA1 Byte - Bit 0
No
8
FA2 Byte - Bit 7
No
9
FA2 Byte - Bit 6
No
10
FA2 Byte - Bit 5
No
11
FA2 Byte - Bit 4
No
12
FA2 Byte - Bit 3
No
13
FA2 Byte - Bit 2
No
14
FA2 Byte - Bit 1
No
15
FA2 Byte - Bit 0
No
16
EM Byte - Bit 7
No
17
EM Byte - Bit 6
No
18
EM Byte - Bit 5
No
19
EM Byte - Bit 4
No
20
EM Byte - Bit 3
No
21
EM Byte - Bit 2
No
22
EM Byte - Bit 1
No
23
EM Byte - Bit 0
No
24
TR Byte - Bit 7
Yes
25
TR Byte - Bit 6
Yes
26
TR Byte - Bit 5
Yes
27
TR Byte - Bit 4
Yes
28
TR Byte - Bit 3
Yes
29
TR Byte - Bit 2
Yes
381
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XRT72L53
THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. P1.1.8
TABLE 76: THE RELATIONSHIP BETWEEN THE NUMBER OF TXOHENABLE PULSES (SINCE THE LAST OCCURRENCE OF
THE TXOHFRAME PULSE) TO THE E3 OVERHEAD BIT, THAT IS BEING PROCESSED BY THE XRT72L53
NUMBER OF TXOHENABLE PULSES
THE OVERHEAD BIT EXPECTED BY THE CAN THIS OVERHEAD BIT BE ACCEPTED BY
THE XRT72L53?
XRT72L53
30
TR Byte - Bit 1
Yes
31
TR Byte - Bit 0
Yes
32
MA Byte - Bit 7 (FERF)
Yes
33
MA Byte - Bit 6 (FEBE)
Yes
34
MA Byte - Bit 5
Yes
35
MA Byte - Bit 4
Yes
36
MA Byte - Bit 3
Yes
37
MA Byte - Bit 2
Yes
38
MA Byte - Bit 1
Yes
39
MA Byte - Bit 0
Yes
40
NR Byte - Bit 7
Yes
41
NR Byte - Bit 6
Yes
42
NR Byte - Bit 5
Yes
43
NR Byte - Bit 4
Yes
44
NR Byte - Bit 3
Yes
45
NR Byte - Bit 2
Yes
46
NR Byte - Bit 1
Yes
47
NR Byte - Bit 0
Yes
48
GC Byte - Bit 7
Yes
49
GC Byte - Bit 6
Yes
50
GC Byte - Bit 5
Yes
51
GC Byte - Bit 4
Yes
52
GC Byte - Bit 3
Yes
53
GC Byte - Bit 2
Yes
54
GC Byte - Bit 1
Yes
55
GC Byte - Bit 0
Yes
3. After the Terminal Equipment has waited through
the appropriate number of pulses via the TxOHEnable pin, it should then assert the TxOHIns
input signal. Concurrently, the Terminal Equipment should also place the appropriate value (of
the inserted overhead bit) onto the TxOH signal.
4. The Terminal Equipment should hold both the
TxOHIns input pin "High" and the value of the
TxOH signal stable, until the next TxOHEnable
pulse is detected.
Case Study: The Terminal Equipment intends to
insert the appropriate overhead bits into the
Transmit Overhead Data Input Interface (using
382
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XRT72L53
THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. P1.1.8
Method 2) in order to transmit a Yellow Alarm to
the remote terminal equipment.
tions, a Yellow Alarm is transmitted by setting the
FERF bit (within the MA byte) to "1".
In this case, the Terminal Equipment intends to insert
the appropriate overhead bits, into the Transmit Overhead Data Input Interface such that the XRT72L53
will transmit a Yellow Alarm to the remote terminal
equipment. Recall that, for E3, ITU-T G.832 applica-
If one assumes that the connection between the Terminal Equipment and the XRT72L53 is as illustrated
in Figure 172 then, Figure 173 presents an illustration
of the signaling that must go on between the Terminal
Equipment and the XRT72L53.
FIGURE 173. BEHAVIOR OF TRANSMIT OVERHEAD DATA INPUT INTERFACE SIGNALS BETWEEN THE XRT72L53 AND
TERMINAL EQUIPMENT (FOR METHOD 2)
THE
TxInClk
TxOHFrame
TxOHEnable Pulse # 32
TxOHEnable Pulse # 0
TxOHEnable
TxOHIns
TxOH
MA Byte, Bit 7
Terminal Equipment
samples “TxOHFrame” and
“TxOHEnable” being “HIGH”
Terminal Equipment counts the number of
TxOHEnable pulses. At “pulse # 32” the Terminal
Equipment asserts the “TxOHIns” signal and places the
desired data on TxOH.
6.2.3 The Transmit E3 HDLC Controller
The Transmit E3 HDLC Controller block can be used
to transport Message-Oriented Signaling (MOS) type
messages to the remote terminal equipment as discussed in detail below.
NOTE: While executing this particular write operation, the
user should write the binary value "000xx110b" into the Tx
Controller block), please see Section 5.3.3.1.
6.2.3.1 Message-Oriented Signaling (e.g.,
LAP-D) processing via the Transmit DS3 HDLC
Controller
The LAPD Transmitter (within the Transmit E3 HDLC
Controller Block) allows the user to transmit path
XRT72L5x samples TxOH
here.
maintenance data link (PMDL) messages to the remote terminal via the Outbound E3 Frames. In this
case the message bits are either inserted into and
carried by the “NR” or the “GC” bytes, within the Outbound E3 frames. The on-chip LAPD transmitter supports both the 76 byte and 82 byte length message
formats, and the Framer IC allocates 88 bytes of onchip RAM (e.g., the Transmit LAPD Message buffer)
to store the message to be transmitted. The message
format complies with ITU-T Q.921 (LAP-D) protocol
with different addresses and is presented below in
Figure 174.
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THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. P1.1.8
FIGURE 174. LAPD MESSAGE FRAME FORMAT
Flag Sequence (8 bits)
SAPI (6-bits)
C/R
EA
EA
TEI (7 bits)
Control (8-bits)
76 or 82 Bytes of Information (Payload)
FCS - MSB
FCS - LSB
Flag Sequence (8-bits)
Where: Flag Sequence = 0x7E
SAPI + CR + EA = 0x3C or 0x3E
TEI + EA = 0x01
Control = 0x03
The following sections defines each of these bit/bytefields within the LAPD Message Frame Format.
Flag Sequence Byte
Information Payload
The Information Payload is the 76 bytes or 82 bytes of
data (e.g., the PMDL Message) that the user has written into the on-chip Transmit LAPD Message buffer
(which is located at addresses 0x86 through 0xDD).
The Flag Sequence byte is of the value 0x7E, and is
used to denote the boundaries of the LAPD Message
Frame.
SAPI - Service Access Point Identifier
The SAPI bit-fields are assigned the value of
"001111b" or 15 (decimal).
TEI - Terminal Endpoint Identifier
The TEI bit-fields are assigned the value of 0x00. The
TEI field is used in N-ISDN systems to identify a terminal out of multiple possible terminal. However,
since the Framer IC transmits data in a point-to-point
manner, the TEI value is unimportant.
Control
The Control identifies the type of frame being transmitted. There are three general types of frame formats: Information, Supervisory, and Unnumbered.
The Framer assigned the Control byte the value 03h.
Hence, the Framer will be transmitting and receiving
Unnumbered LAPD Message frames.
It is important to note that the user must write in a
specific octet value into the first byte position within
the Transmit LAPD Message buffer (located at Address = 0x86, within the Framer). The value of this octet depends upon the type of LAPD Message frame/
PMDL Message that the user wishes to transmit.
Table 77 presents a list of the various types of LAPD
Message frames/PMDL Messages that are supported
by the XRT72L53 Framer device and the corresponding octet value that the user must write into the first
octet position within the Transmit LAPD Message
buffer.
TABLE 77: THE LAPD MESSAGE TYPE AND THE CORRESPONDING VALUE OF THE FIRST BYTE, WITHIN THE
INFORMATION PAYLOAD
LAPD MESSAGE TYPE
VALUE OF FIRST BYTE, WITHIN
INFORMATION PAYLOAD OF MESSAGE
MESSAGE SIZE
CL Path Identification
0x38
76 bytes
IDLE Signal Identification
0x34
76 bytes
Test Signal Identification
0x32
76 bytes
ITU-T Path Identification
0x3F
82 bytes
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THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. P1.1.8
STEP 1 - Specify the type of LAPD Message frame
to be Transmitted (within the Transmit LAPD Message Buffer)
Frame Check Sequence Bytes
The 16 bit FCS (Frame Check Sequence) is calculated over the LAPD Message Header and Information
Payload bytes, by using the CRC-16 polynomial, x16
+ x12 + x5 + 1.
Operation of the LAPD Transmitter
If a message is to be transmitted via the LAPD Transmitter then, the information portion (or the body) of
the message must be written into the Transmit LAPD
Message Buffer, which is located at 0x86 through
0xDD in on-chip RAM via the Microprocessor Interface. Afterwards, the user must do three things:
1. Specify the length of LAPD message to be transmitted.
2. Specify which bit-field (within the E3 frame) that
the LAPD Message frame is to be transported on
(e.g., either the “GC” or the “NR” byte).
3. Specify whether the LAPD Transmitter should
transmit this LAPD Message frame only once, or
an indefinite number of times at One-Second
intervals.
4. Enable the LAPD Transmitter.
5. Initiate the Transmission of the PMDL Message.
Each of these steps will be discussed in detail.
The user must write in a specific octet value into the
first octet position within the Transmit LAPD Buffer
(e.g., at Address Location 0x86 within the Framer IC).
This octet is referred to as the LAPD Message Frame
ID octet. The value of this octet must correspond to
the type of LAPD Message frame that is to be transmitted. This octet will ultimately be used by the Remote Terminal Equipment in order to help it identify
the type of LAPD message frame that it is receiving.
Table 77 lists these octets and the corresponding
LAPD Message types.
STEP 2 - Write the PMDL Message into the remaining part of the Transmit LAPD Message Buffer.
The user must now write in his/her PMDL Message
into the remaining portion of the Transmit LAPD Message buffer (e.g., addresses 0x87 through 0x135
within the Framer IC).
STEP 3 - Specifying the Length of the LAPD Message
One of two different sizes of LAPD Messages can be
transmitted, by writing the appropriate data to bit 1
within the Tx E3 LAPD Configuration Register. The
bit-format of this register is presented below.
TRANSMIT E3 LAPD CONFIGURATION REGISTER (ADDRESS = 0X33)
BIT 7
BIT 6
BIT 5
BIT 4
Not Used
BIT 3
BIT2
BIT 1
BIT 0
Auto
Retransmit
Not Used
TxLAPD
Msg Length
TxLAPD
Enable
R/O
R/O
R/O
R/O
R/W
R/O
R/W
R/W
0
0
0
0
X
0
X
X
The relationship between the contents of bit-fields 1
and the LAPD Message size is given in Table 78.
TABLE 78: RELATIONSHIP BETWEEN TXLAPD MSG LENGTH AND THE LAPD MESSAGE SIZE
TXLAPD MESSAGE LENGTH
LAPD MESSAGE LENGTH
0
LAPD Message size is 76 bytes
1
LAPD Message size is 82 bytes
NOTE: The Message Type selected must correspond with
the contents of the first byte of the Information (Payload)
portion, as presented in Table 77.
STEP 4 - Specifying which byte-field (within the
E3 frame) that the LAPD Message frame octets
are to be transported on.
The Transmit E3 Framer block allows the user to
transport the LAPD Message frame octets via either
the “NR” byte or the “GC” byte-field, within each Outbound E3 frame. The user makes this selection by
writing the appropriate value to bit-field 4 (DLinNR),
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THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. P1.1.8
within the Tx E3 Configuration Register, as depicted
below.
)
TXE3 CONFIGURATION REGISTER (ADDRESS = 0X30)
BIT 7
BIT 6
BIT 5
Not Used
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
TxDL
in NR
Not Used
TxAIS
Enable
TxLOS
Enable
TxMARx
RO
RO
RO
R/W
RO
R/W
R/W
R/W
0
0
0
0
0
0
0
0
STEP 5 - Specify whether the LAPD Transmitter
should transmit the LAPD Message frame only
once, or an indefinite number of times at OneSecond intervals.
If the user writes a “0” into this bit-field, then the
LAPD Transmitter will transmit the comprising octets
of the Outbound LAPD Message frame via the GC
byte field. Additionally, the Transmit E3 Framer block
will insert the contents of the TxNR Byte Register
(Address = 0x37) into the “NR” byte of each Outbound E3 frame.
Conversely, if the user writes a “1” into this bit-field,
then the LAPD Transmitter will transmit the Outbound
LAPD Message frame octets via the NR byte-field,
within each Outbound E3 frame. Additionally, the
Transmit E3 Framer will insert the contents of the Tx
GC Byte Register (Address = 0x35) into the GC bytefield of each Outbound E3 frame.
The Transmit E3 HDLC Control block allows the user
to configure the LAPD Transmitter to transmit this
LAPD Message frame only once, or an indefinite
number of times at One-Second intervals. The user
implements this configuration by writing the appropriate value into Bit 3 (Auto Retransmit) within the Tx E3
LAPD Configuration Register (Address = 0x33), as
depicted below.
)
TXE3 LAPD CONFIGURATION REGISTER (ADDRESS = 0X33)
BIT 7
BIT 6
BIT 5
BIT 4
Not Used
BIT 3
BIT 2
BIT 1
BIT 0
Auto
Retransmit
Not Used
TxLAPD
Msg Length
TxLAPD
Enable
RO
RO
RO
RO
R/W
RO
R/W
R/W
0
0
0
0
1
0
0
0
If the user writes a “1” into this bit-field, then the
LAPD Transmitter will transmit the LAPD Message
frame repeatedly at One-Second intervals until the
LAPD Transmitter is disabled.
If the user writes a “0” into this bit-field, then the
LAPD Transmitter will transmit the LAPD Message
frame only once. Afterwards, the LAPD Transmitter
will halt its transmission until the user invokes the
Transmit LAPD Message frame command, once
again.
STEP 6 - Enabling the LAPD Transmitter
Prior to the transmission of any data via the LAPD
Transmitter, the LAPD Transmitter must be enabled
by writing a "1" to bit 0 (TxLAPD Enable) of the Tx E3
LAPD Configuration Register, as depicted below.
TRANSMIT E3 LAPD CONFIGURATION REGISTER (ADDRESS = 0X33)
BIT 7
BIT 6
BIT 5
BIT 4
Not Used
BIT 3
BIT2
BIT 1
BIT 0
Auto
Retransmit
Not Used
TxLAPD
Msg Length
TxLAPD
Enable
R/O
R/O
R/O
R/O
R/W
R/O
R/W
R/W
0
0
0
0
X
0
X
X
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XRT72L53
THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. P1.1.8
STEP 7 - Initiate the Transmission
If the user writes a “0” into this bit-field, then the
LAPD Transmitter will be enabled, and the LAPD
Transmitter will immediately begin to transmit a continuous stream of Flag Sequence octets (0x7E), via
either the “GC” or the “NR” byte-field of each Outbound E3 frame (depending upon which byte has
been selected to carry the PMDL channel).
Conversely, if the user writes a “1” into this bit-field,
then the LAPD Transmitter will be disabled. The
Transmit E3 Framer block will insert the contents of
the Tx GC Byte Register into the “GC” byte-field for
each Outbound E3 frame. Likewise, the Transmit E3
Framer block will also insert the contents of the Tx
NR Byte Register into the NR” byte-field for each Outbound E3 frame. No transmission of PMDL data will
occur.
At this point, the user should have written the PMDL
message into the on-chip Transmit LAPD Message
buffer and should have specified the type of LAPD
Message that is to be transmitted. The user should
have also specified whether the LAPD Transmitter will
transport the LAPD Message frame octets via the
GC-byte field or via the NR-byte field of each Outbound E3 frame. Finally the LAPD Transmitter should
have been enabled. Then initiate the transmission of
this message by writing a “1” to Bit 3 (Tx DL Start)
within the Tx E3 LAPD Status and Interrupt Register
(Address = 0x34), as depicted below.
)
TXE3 LAPD STATUS AND INTERRUPT REGISTER (ADDRESS = 0X34)
BIT 7
BIT 6
BIT 5
BIT 4
Not Used
BIT 3
BIT 2
BIT 1
BIT 0
TxDL Start
TxDL Busy
TxLAPD
Interrupt
Enable
TxLAPD
Interrupt
Status
RO
RO
RO
RO
R/W
RO
R/W
RUR
0
0
0
0
0
0
0
0
A “0” to “1” transition in Bit 3 (TxDL Start) in this register, initiates the transmission of LAPD Message
frames. At this point, the LAPD Transmitter will begin
to search through the PMDL message, which is residing within the Transmit LAPD Message buffer. If the
LAPD Transmitter finds any string of five (5) consecutive “1’s” in the PMDL Message, then the LAPD
Transmitter will insert a “0” immediately following
these strings of consecutive “1’s”. This procedure is
known as stuffing. The purpose of PMDL Message
stuffing is to insure that the user’s PMDL Message
does not contain strings of data that mimic the Flag
Sequence octet (e.g., six consecutive “1’s”) or the
ABORT Sequence octet (e.g., seven consecutive
“1’s”). Afterwards, the LAPD Transmitter will begin to
encapsulate the PMDL Message, residing in the
Transmit LAPD Message buffer, into a LAPD Message frame. Finally, the LAPD Transmitter will frag-
ment the Outbound LAPD Message frame into octets
and will begin to transport these octets via the GC or
the NR byte-fields (depending upon the user’s selection) of each Outbound E3 frame.
While the LAPD Transmitter is transmitting this LAPD
Message frame, the TxDL Busy bit-field (Bit 2) within
the Tx E3 LAPD Status and Interrupt Register, will be
set to “1”. This bit-field allows the user to poll the status of the LAPD Transmitter. Once the LAPD Transmitter has completed the transmission of the LAPD
Message, then this bit-field will toggle back to “0”.
The user can configure the LAPD Transmitter to interrupt the local Microprocessor/Microcontroller upon
completion of transmission of the LAPD Message
frame, by setting bit-field 1 (TxLAPD Interrupt Enable)
within the Tx E3 LAPD Status and Interrupt register
(Address = 0x34). to “1” as depicted below.
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XRT72L53
THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. P1.1.8
TXE3 LAPD STATUS AND INTERRUPT REGISTER (ADDRESS = 0X34)
BIT 7
BIT 6
BIT 5
BIT 4
Not Used
BIT 3
BIT 2
BIT 1
BIT 0
TxDL Start
TxDL Busy
TxLAPD
Interrupt
Enable
TxLAPD
Interrupt
Status
RO
RO
RO
RO
R/W
RO
R/W
RUR
0
0
0
0
0
0
0
0
‘The purpose of t his interrupt is to let the Microprocessor/Microcontroller know that the LAPD Transmitter is available and ready to transmit a LAPD Message frame (which contains a new PMDL Message)
to the remote terminal equipment. Bit 0 (Tx LAPD Interrupt Status) within the Tx E3 LAPD Status and Interrupt Register will reflect the status for the Transmit
LAPD Interrupt.
NOTE: This bit-field will be reset upon reading this register.
Summary of Operating the LAPD Transmitter
Once the user has invoked the TxDL Start command,
the LAPD Transmitter will do the following.
• Generate the four octets of the LAPD Message
frame header (e.g., the Flag Sequence, SAPI, TEI,
Control, etc.,) and insert them into the header byte
positions within the LAPD Message frame.
• It will read in the contents of the Transmit LAPD
Message buffer (e.g., the PMDL Message data)
and insert it into the Information Payload portion of
the LAPD Message frame.
• Compute the 16-bit Frame Check Sequence (FCS)
value of the LAPD Message frame (e.g, of the
LAPD Message header and Payload bytes) and
insert this value into the FCS value octet positions
within the LAPD Message frame.
• Append a trailer Flag Sequence octet to the end of
the LAPD Message frame (following the 16-bit FCS
octets).
• Fragment the resulting LAPD Message frame into
octets and begin inserting these octets into either
the GC or NR byte-fields within the Outbound E3
frames (depending upon the user’s selection).
• Complete the transmission of the overhead bytes,
information payload byte, FCS value, and the trail-
ing Flag Sequence octets via the Transmit E3
Framer block.
Once the LAPD Transmitter has completed its transmission of the LAPD Message frame, the Framer will
generate an Interrupt to the MIcroprocessor/Microcontroller (if enabled). Afterwards, the LAPD Transmitter will either halt its transmission of LAPD Message frames or will proceed to retransmit the LAPD
Message frame, repeatedly at One-Second intervals.
In between these transmissions of the LAPD Message frames, the LAPD Transmitter will be sending a
continuous stream of Flag Sequence bytes. The
LAPD Transmitter will continue this behavior until the
user has disabled the LAPD Transmitter by writing a
“1” into bit 3 (No Data Link) within the Tx E3 Configuration register.
NOTE: In order to prevent the user’s data (e.g., the PMDL
Message within the LAPD Message frame) from mimicking
the Flag Sequence byte or an ABORT Sequence, the LAPD
Transmitter will parse through the PMDL Message data and
insert a “0” into this data, immediately following the detection of five (5) consecutive “1’s” (this stuffing occurs while
the PMDL message data is being read in from the Transmit
LAPD Message frame. The Remote LAPD Receive (See
Section 5.3.5) will have the responsibility of checking the
newly received PMDL messages for a string of five (5) consecutive “1’s” and removing the subsequent “0” from the
payload portion of the incoming LAPD Message.
Figure 175 is a flow chart that depicts the procedure
(in white boxes) that the user should use in order to
transmit a PMDL message via the LAPD Transmitter,
when the LAPD Transmitter is configured to retransmit the LAPD Message frame, repeatedly at OneSecond intervals. This figure also indicates (via the
Shaded boxes) what the LAPD Transmitter circuitry
will do before and during message transmission.
388
XRT72L53
THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
áç
PRELIMINARY
REV. P1.1.8
FIGURE 175. FLOW CHART DEPICTING HOW TO USE THE LAPD TRANSMITTER (LAPD TRANSMITTER IS CONFIGURED
LAPD MESSAGE FRAME REPEATEDLY AT ONE-SECOND INTERVALS)
TO RE-TRANSMIT THE
Start
Initiate the LAPD Message frame transmission.
Write the “LAPD Message frame identification”
octet into the first octet position within the
“Transmit LAPD Message” buffer (Address = 0x86).
LAPD Transmitter will “stuff” the contents of the
PMDL Message (residing within the “Transmit
LAPD Message” buffer).
Write the PMDL Message into the remaining
portion of the “Transmit LAPD Message” buffer
(from 0x87 to 0xDD).
LAPD Transmitter will read out “stuff” PMDL
Message and encapsulate it into a LAPD Message
frame.
Specify the type/size of the LAPD Message frame
to be transmitted.
Write in the appropriate value into bits 5 and 6
within the Tx E3 LAPD Configuration Register
LAPD Transmitter will compute and insert the
FCS value, into the LAPD Message frame.
Specify whether the “outbound” LAPD Message
frame is to be transported via the GC or the NR
byte-fields, within each “outbound” E3 Frame
LAPD Transmitter will fragment LAPD Message
frame into “octets” and begin to insert these octets into
the GC or NR byte-field (depending upon user’s
selection) into each “outbound” E3 frame.
Enable the LAPD Transmitter
Complete transmission of LAPD Message frame.
Configure the LAPD Transmitter to repeat transmissions
of the LAPD Message frame at one-second intervals.
Generate “Completion of Transmission of LAPD
Message frame Interrupt.
LAPD Transmitter will generate a continuous
string of “Flag Sequence” bytes. These bytes will
be transported via either the GC or the NR byte
field (depending upon user’s selection).
Figure 176 presents the procedure (in white boxes)
which the user should use in order to transmit a PMDL Message via the LAPD Transmitter, when the
Wait One Second. Generate a continuous
string of Flag Sequence Bytes
LAPD Transmitter is configured to transmit a LAPD
Message frame only once, and then halt transmission.
389
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XRT72L53
THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. P1.1.8
FIGURE 176. FLOW CHART DEPICTING HOW TO USE THE LAPD TRANSMITTER (LAPD TRANSMITTER IS CONFIGURED
LAPD MESSAGE FRAME ONLY ONCE).
TO TRANSMIT A
Start
Initiate the LAPD Message frame transmission.
Write the “LAPD Message frame identification”
octet into the first octet position within the
“Transmit LAPD Message” buffer (Address = 0x86).
LAPD Transmitter will “stuff” the contents of the
PMDL Message (residing within the “Transmit
LAPD Message” buffer).
Write the PMDL Message into the remaining
portion of the “Transmit LAPD Message” buffer
(from 0x87 to 0xDD).
LAPD Transmitter will read out “stuff” PMDL Message
and encapsulate it into a LAPD Message frame.
Specify the type/size of the LAPD Message frame
to be transmitted.
Write in the appropriate value into bits 5 and 6
within the Tx E3 LAPD Configuration Register
LAPD Transmitter will compute and insert the
FCS value, into the LAPD Message frame.
Specify whether the “outbound” LAPD Message
frame is to be transported via the GC or the NR
byte-fields, within each “outbound” E3 Frame
LAPD Transmitter will fragment LAPD Message
frame into “octets” and begin to insert these octets into
the GC or NR byte-field (depending upon user’s
selection) into each “outbound” E3 frame.
Configure the LAPD Transmitter to transmit
LAPD Message Frame Only Once
Complete transmission of LAPD Message frame.
Enable the LAPD Transmitter
Generate “Completion of Transmission of LAPD
Message frame Interrupt.
LAPD Transmitter will generate a continuous
string of “Flag Sequence” bytes. These bytes will
be transported via either the GC or the NR byte
field (depending upon user’s selection).
Halt Transmission for an “indefinite period.
Wait until the user initiates “LAPD Message
Frame Transmission” again.
The Mechanics of Transmitting a New LAPD Message frame, if the LAPD Transmitter has been
configured to re-transmit the LAPD Message
frame, repeatedly, at One-Second intervals.
• Transmit this LAPD Message frame to the Remote
Terminal Equipment.
If the LAPD Transmitter has been configured to retransmit the LAPD Message frame repeatedly at
One-Second intervals, then it will do the following (at
One-Second intervals).
• Stuff the PMDL Message.
• Read in the stuffed PMDL Message from the Transmit LAPD Message buffer.
• Encapsulate this stuffed PMDL Message into a
LAPD Message frame.
If another (e.g., a different) PMDL Message is to be
transmitted to the Remote Terminal Equipment this
new message will have to be written into the Transmit
LAPD Message buffer, via the Microprocessor Interface block of the Framer IC. However, care must be
taken when writing this new PMDL message. If this
message is written into the Transmit LAPD Message
buffer at the wrong time (with respect to these OneSecond LAPD Message frame transmissions), the
user’s action could interfere with these transmissions,
thereby causing the LAPD Transmitter to transmit a
corrupted message to the Remote Terminal Equip-
390
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XRT72L53
THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. P1.1.8
ment. In order to avoid this problem, while writing the
new message into the Transmit LAPD Message buffer, the user should do the following.
The user can do this by writing a “1” into Bit 3 within
the Framer Operating Mode register (Address =
0x00), as depicted below.
1. Configure the Framer to automatically reset activated interrupts.
FRAMER OPERATING MODE REGISTER (ADDRESS = 0X00)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
Local Loopback
DS3/E3*
Internal
LOS
Enable
RESET
Interrupt
Enable Reset
Frame Format
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
1
0
1
0
1
1
This action will prevent the LAPD Transmitter from
generating its own One-Second interrupt (following
each transmission of the LAPD Message frame).
BIT 1
BIT 0
TimRefSel[1:0]
This can be done by writing a “1” into Bit 0 (One-Second Interrupt Enable) within the Block Interrupt Enable Register, as depicted below.
2. Enable the One-Second Interrupt
BLOCK INTERRUPT ENABLE REGISTER (ADDRESS = 0X04)
BIT 7
BIT 6
BIT 5
RxDS3/E3
Interrupt
Enable
BIT 4
BIT 3
BIT 2
Not Used
BIT 1
BIT 0
TxDS3/E3
Interrupt
Enable
One-Second
Interrupt
Enable
R/W
RO
RO
RO
RO
RO
R/W
R/W
0
0
0
0
0
0
0
0
3. Write the new message into the Transmit LAPD
Message buffer immediately after the occurrence
of the One-Second Interrupt
By synchronizing the writes to the Transmit LAPD
Message buffer to occur immediately after the occurrence of the One-Second Interrupt, the user avoids
conflicting with the One-Second transmission of the
LAPD Message frame, and will transmit the correct
(uncorrupted) PMDL Message to the Remote LAPD
Receiver.
6.2.4
The Transmit E3 Framer Block
6.2.4.1 Brief Description of the Transmit E3
Framer
The Transmit E3 Framer block accepts data from any
of the following three sources, and uses it to form the
E3 data stream.
• The Transmit Payload Data Input block
• The Transmit Overhead Data Input block
• The Transmit HDLC Controller block
• The Internal Overhead Data Generator
The manner in how the Transmit E3 Framer block
handles data from each of these sources is described
below.
Handling of data from the Transmit Payload Data
Input Interface
For E3 applications, all data that is input to the Transmit Payload Data Input Interface will be inserted into
the payload bit positions within the Outbound E3
frames.
Handling of data from the Internal Overhead Bit
Generator
By default, the Transmit E3 Framer block will internally generate the overhead bytes. However, if the Terminal Equipment inserts its own values for the overhead
bits or bytes (via the Transmit Overhead Data Input
Interface) or, if the user enables and employs the
Transmit E3 HDLC Controller block, then these internally generated overhead bytes will be overwritten.
Handling of data from the Transmit Overhead Data Input Interface
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XRT72L53
THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. P1.1.8
For E3 applications, the Transmit E3 Framer block automatically generates and inserts the framing alignment bytes (e.g., the "FA1” and “FA2” framing alignment bytes) into the Outbound E3 frames. Further,
the Transmit E3 Framer block will automatically compute and insert the EM byte into the Outbound E3
frames. Hence, the Transmit E3 Framer block will not
accept data from the Transmit OH Data Input Interface block for the "FA1”, “FA2” and “EM” bytes.
However, the Transmit E3 Framer block will accept
(and insert) data from the Transmit Overhead Data Input Interface for the following byte-fields.
writes data into this interface for these bits or bytes,
then the Transmit E3 Framer block will insert this data
into the appropriate overhead bit/byte-fields, within
the Outbound E3 frames.
6.2.4.2 Detailed Functional Description of the
Transmit E3 Framer Block
The Transmit E3 Framer receives data from the following three sources and combines them together to
form a E3 data stream.
• The Transmit Payload Data Input Interface block.
• The Transmit Overhead Data Input Interface block
• MA byte
• The Transmit HDLC Controller block.
• TR byte
Afterwards, this E3 data stream will be routed to the
Transmit E3 LIU Interface block, for further processing.
• NR byte
• GC byte
If the user's local Data Link Equipment activates the
Transmit Overhead Data Input Interface block and
Figure 177 presents a simple illustration of the Transmit E3 Framer block, along with the associated paths
to the other functional blocks within the chip.
FIGURE 177. A SIMPLE ILLUSTRATION OF THE TRANSMIT E3 FRAMER BLOCK AND THE ASSOCIATED PATHS TO
FUNCTIONAL BLOCKS
OTHER
Transmit HDLC
Controller/Buffer
Transmit Overhead
Data Input Interface
Transmit
Transmit
E3
E3Framer
Framer
Block
Block
To Transmit E3 LIU Interface Block
Transmit Payload Data
Input Interface
In addition to taking data from multiple sources and
multiplexing them, in appropriate manner, to create
the Outbound E3 frames, the Transmit E3 Framer
block has the following roles.
to override the data that is being written into the
Transmit Payload Data and Overhead Data Input Interfaces and transmit the following alarm conditions.
• Generating Alarm Conditions
• Manipulate the FERF-bit, within the MA byte (set
them to "0")
• Generating Errored Frames (for testing purposes)
• Generate the Yellow Alarms (or FERF indicators)
• Routing Outbound E3 frames to the Transmit E3
LIU Interface block
• Generate the AIS Pattern
Each of these additional roles are discussed below.
• Generate FERF (Yellow) Alarms, in response to
detection of a Red Alarm condition (via the Receive
Section of the XRT72L53).
6.2.4.2.1 Generating Alarm Conditions
The Transmit E3 Framer block permits the user to, by
writing the appropriate data into the on-chip registers,
• Generate the LOS pattern
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XRT72L53
THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. P1.1.8
• Generate and transmit a desired value for the
FEBE (Far-End-Block Error) bit, within the MA byte.
The procedure and results of generating any of these
alarm conditions is presented below.
The user can exercise each of these options by writing the appropriate data to the Tx E3 Configuration
Register (Address = 0x30). The bit format of this register is presented below.
TXE3 CONFIGURATION REGISTER (ADDRESS = 0X30)
BIT 7
BIT 6
BIT 5
Not Used
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
TxDL
in NR
Not Used
TxAIS
Enable
TxLOS
Enable
TxMARx
RO
RO
RO
R/W
RO
R/W
R/W
R/W
0
0
0
0
0
0
0
0
Bit-field 2 through 0 permit the user to transmit various alarm conditions to the remote terminal equipment. The role/function of each of these three bitfields within the register, are discussed below.
6.2.4.2.1.1 Tx AIS Enable - Bit 2
This read/write bit field permits the user to force the
transmission of an AIS (Alarm Indication Signal) pat-
tern to the remote terminal equipment via software
control. If the user opts to transmit an AIS pattern,
then the Transmit Section of the Framer IC will begin
to transmit an unframed all ones pattern to the remote terminal equipment. Table 79 presents the relationship between the contents of this bit-field, and the
resulting Framer action.
TABLE 79: THE RELATIONSHIP BETWEEN THE CONTENTS OF BIT 2 (TX AIS ENABLE) WITHIN THE TX E3
CONFIGURATION REGISTER, AND THE RESULTING TRANSMIT E3 FRAMER BLOCK'S ACTION
BIT 2
0
TRANSMIT E3 FRAMER'S ACTION
Normal Operation:
The Transmit Section of the XRT72L53 Framer IC will transmit E3 traffic based upon data that it accepts via
the Transmit Payload Data Input Interface block, the Transmit Overhead Data Input Interface block, the Transmit HDLC Controller block and internally generated overhead bytes.
1
Transmit AIS Pattern:
The Transmit E3 Framer block will overwrite the E3 traffic, within an Unframed All Ones pattern.
NOTE: This bit is ignored whenever the TxLOS bit-field is
set.
6.2.4.2.1.2 Transmit LOS Enable - Bit 1
This read/write bit field allows the user to transmit an
LOS (Loss of Signal) pattern to the remote terminal,
upon software control. Table 80 relates the contents
of this bit field to the Transmit E3 Framer block's action.
TABLE 80: THE RELATIONSHIP BETWEEN THE CONTENTS OF BIT 1 (TX LOS) WITHIN THE TX E3 CONFIGURATION
REGISTER, AND THE RESULTING TRANSMIT E3 FRAMER BLOCK'S ACTION
BIT 1
0
TRANSMIT E3 FRAMER'S ACTION
Normal Operation:
The Overhead bits are either internally generated, or they are inserted via the Transmit Overhead Data Input
Interface or the Transmit HDLC Controller blocks. The Payload bits are received from the Transmit Payload
Data Input Interface.
1
Transmit LOS Pattern:
When this command is invoked the Transmit E3 Framer will do the following.
• Set all of the overhead bytes to "0" (including the FA1 and FA2 bytes)
Overwrite the E3 payload bits with an "all zeros" pattern.
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THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. P1.1.8
NOTE: When this bit is set, it overrides all of the other bits in
this register.
the Tx TTB-0 register, and repeating the above-mentioned procedure.
6.2.4.2.1.3 TxMARx - Bit 0
This read/write bit-field permits the user to force the
XRT72L53 Framer IC to transmit either a FERF (FarEnd Receive Failure) or a FEBE (Far-End Block Error) indication to the remote terminal equipment.
The contents of the Tx TTB-0 register will typically be
of the form [1, C6, C5, C4, C3, C2, C1, C0]. The “1” in
the MSB (Most Significant bit) position of this byte is
used to designate that this octet is the frame-start
marker (e.g., is the first of the 16 TR bytes, within a
Trail Trace Buffer super-frame). The remaining Trail
Trace Buffer registers (TxTTB-1 through TxTTB-15)
will typically contain a “0” in their MSB positions. The
remaining bits within the Tx TTB-0 register C6
through C0 are the CRC-7 bits calculated over the
contents of all 16 TR bytes, within the previous Trail
Trace Buffer super-frame. The contents of the remaining Trail Trace Buffer registers (e.g., Tx TTB-1 through
Tx TTB-15) will typically contain the 15 ASCII characters required for the E.164 numbering format.
6.2.4.2.2 Configuring the Transmit Trail Trace
Buffer Message
The XRT72L53 Framer IC contains 16 bytes worth of
Transmit Trail Trace Buffer registers and 16 bytes
worth of Receive Trail Trace Buffer registers. The role
of the Receive Trail Trace Buffer registers are described in Section 5.3.7.
The XRT72L53 Framer IC contains 16 Transmit Trail
Trace Buffer registers (e.g., Tx TTB-0 through TxTTB15). The purpose of these registers are to provide a
16-byte Trail Access Point Identifier to the Remote
Terminal Equipment. The Remote Terminal Equipment will use this information in order to verify that it
is still receiving data from its intended transmitter.
The specific use of these registers follows.
For Trail Trace Buffer Message purposes, the Transmit E3 Framer block will group 16 consecutive E3
frames, into a Trail Trace Buffer super-frame. When
the Transmit E3 Framer block is generating the first
E3 frame, within a Trail Trace Buffer super-frame, it
will read in the contents of the Tx TTB-0 Register (Address = 0x38) and insert this value into the “TR” bytefield of this very first Outbound E3 frame. When the
Transmit E3 Framer is generating the very next E3
frame (e.g., the second E3 frame, within the Trail
Trace Buffer super-frame), it will read in the contents
of the Tx TTB-1 register (Address = 0x39) and insert
this value into the TR byte-field of this Outbound E3
frame. As the Transmit E3 Framer block is creating
each subsequent E3 frame, within this Trail Trace
Buffer super frame, it will continue to increment to the
very next Transmit Trail Trace Buffer register. The
Transmit E3 Framer block will then read in the contents of this particular Transmit Trail Trace Buffer register (Tx TTB-n) and insert this value into the TR bytefield of the very next Outbound E3 frame. After the
Transmit E3 Framer block has created the 16th E3
frame, within a given Trail Trace Buffer super-frame
(e.g., it has read in the contents of Tx TTB-15 register
and has inserted this value into the “TR” byte of the
16th E3 frame), it will begin to create a new Trail
Trace Buffer super-frame, by reading the contents of
NOTES:
1. The XRT72L53 Framer IC will not compute the
CRC-7 value, to be written into the Tx TTB-0 register. The user’s system must compute this value
prior to writing it into the Tx TTB-0 register.
2. The user, when writing data into the Tx TTB registers, must take care to insure that only the Tx TTB0 register contains an octet with a “1” in the MSB
(most significant bit) position. All remaining Tx TTB
registers (e.g., Tx TTB-1 through Tx TTB-15) must
contain octets with a “0” in the MSB position. The
reason for this cautionary note is presented in Section 5.3.2.9.
6.2.5 The Transmit E3 Line Interface Block
The XRT72L53 Framer IC is a digital device that
takes E3 payload and overhead bit information from
some terminal equipment, processes this data and ultimately, multiplexes this information into a series of
Outbound E3 frames. However, the XRT72L53 Framer IC lacks the current drive capability to be able to directly transmit this E3 data stream through some
transformer-coupled coax cable with enough signal
strength for it to be received by the remote receiver.
Therefore, in order to get around this problem, the
Framer IC requires the use of an LIU (Line Interface
Unit) IC. An LIU is a device that has sufficient drive
capability, along with the necessary pulse-shaping
circuitry to be able to transmit a signal through the
transmission medium in a manner that it can be reliably received by the far-end receiver. Figure 178 presents a circuit drawing depicting the Framer IC interfacing to an LIU (XRT7300 DS3/E3/STS-1 Transmit
LIU).
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XRT72L53
THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. P1.1.8
FIGURE 178. APPROACH TO INTERFACING THE XRT72L53 FRAMER IC DEVICE TO THE XRT73L03 DS3/E3/STS-1
LIU
RxAVDD_0
TxAVDD_0
DVDD_0
C3
C4
0.01uF
C5
0.01uF
0.01uF
C2
0.01uF
U21
Rx_AIS_Ch_0
RxRED_ALARM_0
Rx_OOF_Ch_0
Rx_LOS_Ch_0
F20
D20
F19
T20
RxFRAME_0
RxFRAME_CLK_0
RxDATA_IN_0
48
RxAIS_0
RxRED_0
RxOOF_0
RxLOS_0
RxFrame_0
RxClk_0
RxSer_0
MOTO
R8
RxPOS_0
RxNEG_0
F2
R7
4.7K
67
42
51
100
F3
50
F1
49
B8
D9
57
55
C7
A5
C6
C9
C3
61
62
63
64
96
RxAVDD0
TxAVDD0
RxDVDD0
TxAVDD0
28
37
LOSTHR_0
HOST/HW
RPOS0
RTIP0
J1
72
6
4
A[10:0]
M20
M19
M18
M17
N20
N19
N18
P20
P19
P18
R20
J17
R19
V20
P17
R18
H20
READY_OUT*
ALE
RD*
WR*
XRT72L53_CS*
XRT72L53_INT*
T19
HW_RESET*
R9
T18
D7
D6
D5
D4
D3
D2
D1
D0
A10
A9
A8
A7
A6
A5
A4
A3
A2
A1
A0
Rdy_Dtck
ALE_AS
RDB_DS
WRB_RW
CSB
INT
RESETB
RxLineClk_0
RLOL_0
ExtLOS_0
LLOOP_0
REQB_0
TAOS_0
DMO_0
TxLEV_0
RLOOP_0
ENCODIS_0 (TxOFF_0)
TxPOS_0
B7
RCLK0
RRING0
71
R2
R1
37.4
37.4
RLOL_0
RLOS_0
CS
SCLK
SDI
SDO
REG_RESET*
C1
0.01uF
XRT71D03_CS* (Optional)
B2
117
C1
33
TxOFF_0
TPDATA_0
TTIP0
R3
29
TxLineClk_0
D1
32
E2
34
47
J2
1
T1 6
TNDATA_0
TCLK_0
EXCLK_0
TRING0
MTIP0
R4
27
30
NIBBLEINTF
1
BNC
3
4
T3001
R5
36
270
100
E20
G4
E18
3
T3001
36
TxNEG_0
BNC
2
J19
J20
K17
K18
K19
K20
L20
L18
1
RNEG0
D[7:0]
TxFRAME_0
44.736MHz
TxDATA_OUT_0
T2 1
2
70
U19
C5
B5
A3
C4
MRING0
TxFrame_0
TxInClk_0
TxSER_0
31
R6
270
54
73
RxDGND0
RxAGND0
TxAGND0
TxAGND0
39
26
XRT72L53_Ch_0
XRT73L03IV_Ch_0
The Transmit Section of the XRT72L53 contains a
block which is known as the Transmit E3 LIU Interface
block. The purpose of the Transmit E3 LIU Interface
block is to take the Outbound E3 data stream, from
the Transmit E3 Framer block, and to do the following:
1. Encode this data into one of the following line
codes
a. Unipolar (e.g., Single-Rail)
b. AMI (Alternate Mark Inversion)
c. HDB3 (High Density Bipolar - 3)
2. And to transmit this data to the LIU IC.
Figure 179 presents a simple illustration of the Transmit E3 LIU Interface block.
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XRT72L53
THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. P1.1.8
FIGURE 179. A SIMPLE ILLUSTRATION OF THE TRANSMIT E3 LIU INTERFACE BLOCK
TxPOS
Transmit E3
LIU Interface
Block
From Transmit E3
Framer Block
TxNEG
TxLineClk
od, at the start of each new E3 frame, and will remain
"Low" for the remainder of the frame. Figure 180 presents an illustration of the TxPOS and TxNEG signals
during data transmission while the Transmit E3 LIU
Interface block is operating in the Unipolar mode. This
mode is sometimes referred to as Single Rail mode
because the data pulses only exist in one polarity:
positive.
The Transmit E3 LIU Interface block can transmit data
to the LIU IC or other external circuitry via two different output modes: Unipolar or Bipolar. If the user selects Unipolar (or Single Rail) mode, then the contents of the E3 Frame is output, in a binary (NRZ
manner) data stream via the TxPOS pin to the LIU IC.
The TxNEG pin will only be used to denote the frame
boundaries. TxNEG will pulse "High" for one bit peri-
FIGURE 180. THE BEHAVIOR OF TXPOS AND TXNEG SIGNALS DURING DATA TRANSMISSION WHILE THE TRANSMIT
DS3 LIU INTERFACE IS OPERATING IN THE UNIPOLAR MODE
Data
1
0
1
1
0
0
1
0
0
1
1
1
0
1
0
1
0
0
1
1
1
0
0
1
TxPOS
TxNEG
TxLineClk
Frame Boundary
When the Transmit E3 LIU Interface block is operating
in the Bipolar (or Dual Rail) mode, then the contents
of the E3 Frame is output via both the TxPOS and TxNEG pins. If the Bipolar mode is chosen, then the E3
data can be transmitted to the LIU via one of two different line codes: Alternate Mark Inversion (AMI) or
High Density Bipolar -3 (HDB3). Each one of these
line codes will be discussed below. Bipolar mode is
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XRT72L53
THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. P1.1.8
TxLineClk - Transmit Line Clock: The LIU IC uses
this signal from the Transmit E3 LIU Interface block to
sample the state of its TxPOS and TxNEG inputs.
The results of this sampling dictates the type of pulse
(positive polarity, zero, or negative polarity) that it will
generate and transmit to the remote Receive E3
Framer.
sometimes referred to as Dual Rail because the data
pulses occur in two polarities: positive and negative.
The role of the TxPOS, TxNEG and TxLineClk output
pins, for this mode are discussed below.
TxPOS - Transmit Positive Polarity Pulse: The
Transmit E3 LIU Interface block will assert this output
to the LIU IC when it desires for the LIU to generate
and transmit a positive polarity pulse to the remote
terminal equipment.
6.2.5.1 Selecting the various Line Codes
The user can select either the Unipolar Mode or Bipolar Mode by writing the appropriate value to Bit 3 of
the I/O Control Register (Address = 0x01), as shown
below.
TxNEG - Transmit Negative Polarity Pulse: The
Transmit E3 LIU Interface block will assert this output
to the LIU IC when it desires for the LIU to generate
and transmit a negative polarity pulse to the remote
terminal equipment.
I/O CONTROL REGISTER (ADDRESS = 0X01)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT2
BIT 1
BIT 0
Disable TxLOC
LOC
Disable
RxLOC
AMI/ZeroSup*
Unipolar/
Bipolar*
TxLine CLK
Invert
RxLine CLK
Invert
Reframe
R/W
RO
R/W
R/W
R/W
R/W
R/W
R/W
1
0
1
0
0
0
0
0
Table 81 relates the value of this bit field to the Transmit E3 LIU Interface Output Mode.
TABLE 81: THE RELATIONSHIP BETWEEN THE CONTENT OF BIT 3 (UNIPOLAR/BIPOLAR*) WITHIN THE UNI I/O
CONTROL REGISTER AND THE TRANSMIT E3 FRAMER LINE INTERFACE OUTPUT MODE
BIT 3
TRANSMIT E3 FRAMER LIU INTERFACE OUTPUT MODE
0
Bipolar Mode: AMI or HDB3 Line Codes are Transmitted and Received
1
Unipolar (Single Rail) Mode of transmission and reception of E3 data is selected.
NOTES:
1. The default condition is the Bipolar Mode.
2. This selection also effects the operation of the
Receive E3 LIU Interface block
6.2.5.1.1 The Bipolar Mode Line Codes
If the Framer is selected to operate in the Bipolar
Mode, then the DS3 data-stream can be transmitted
via the AMI (Alternate Mark Inversion) or the HDB3
Line Codes. The definition of AMI and HDB3 line
codes follow.
6.2.5.1.1.1 The AMI Line Code
AMI or Alternate Mark Inversion, means that consecutive "one's" pulses (or marks) will be of opposite polarity with respect to each other. The line code in-
volves the use of three different amplitude levels: +1,
0, and -1. +1 and -1 amplitude signals are used to
represent one's (or mark) pulses and the "0" amplitude pulses (or the absence of a pulse) are used to
represent zeros (or space) pulses. The general rule
for AMI is: if a given mark pulse is of positive polarity,
then the very next mark pulse will be of negative polarity and vice versa. This alternating-polarity relationship exists between two consecutive mark pulses, independent of the number of 'zeros' that may exist between these two pulses. Figure 181 presents an illustration of the AMI Line Code as would appear at the
TxPOS and TxNEG pins of the Framer, as well as the
output signal on the line.
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THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. P1.1.8
FIGURE 181. ILLUSTRATION OF AMI LINE CODE
Data 1 0 1 1 0 0 0 1 0 1 1 1 1 0 1 1 0 1 1 0 0 1 1 0 0 0 0 1
TxPOS
TxNEG
Line Signal
NOTE: One of the main reasons that the AMI Line Code
has been chosen for driving transformer-coupled media is
that this line code introduces no dc component, thereby
minimizing dc distortion in the line.
causing the clock and data recovery process of the
receiver to fail. Therefore, some approach is needed
to insure that such a long string of consecutive zeros
can never happen. One such technique is HDB3 encoding. HDB3 (or High Density Bipolar - 3) is a form
of AMI line coding that implements the following rule.
6.2.5.1.1.2 The HDB3 Line Code
The Transmit E3 Framer and the associated LIU IC
combine the data and timing information (originating
from the TxLineClk signal) into the line signal that is
transmitted to the remote receiver. The remote receiver has the task of recovering this data and timing
information from the incoming E3 data stream. Many
clock and data recovery schemes rely on the use of
Phase Locked Loop technology. Phase-Locked-Loop
(PLL) technology for clock recovery relies on transitions in the line signal, in order to maintain lock with
the incoming E3 data stream. However, PLL-based
clock recovery scheme, are vulnerable to the occurrence of a long stream of consecutive zeros (e.g., the
absence of transitions). This scenario can cause the
PLL to lose lock with the incoming E3 data, thereby
In general the HDB3 line code behaves just like AMI
with the exception of the case when a long string of
consecutive zeros occur on the line. Any string of 4
consecutive zeros will be replaced with either a
"000V" or a "B00V" where "B" refers to a Bipolar
pulse (e.g., a pulse with a polarity that is compliant
with the AMI coding rule). And "V" refers to a Bipolar
Violation pulse (e.g., a pulse with a polarity that violates the alternating polarity scheme of AMI.) The decision between inserting an "000V" or a "B00V" is
made to insure that an odd number of Bipolar (B)
pulses exist between any two Bipolar Violation (V)
pulses. Figure 182 presents a timing diagram that illustrates examples of HDB3 encoding.
FIGURE 182. ILLUSTRATION OF TWO EXAMPLES OF HDB3 ENCODING
Data
1
0
1
1
0
0
0
0
0
0
0
V
0
1
1
1
1
0
1
1
0
1
1
0
0
1
1
0
0
0
0
B
0
0
V
TxPOS
TxNEG
TxLineClk
Line Signal
The user chooses between AMI or HDB3 line coding
by writing to bit 4 of the I/O Control Register (Address
= 0x01), as shown below.
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THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. P1.1.8
I/O CONTROL REGISTER (ADDRESS = 0X01)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT2
BIT 1
BIT 0
Disable TxLOC
LOC
Disable
RxLOC
AMI/ZeroSup*
Unipolar/
Bipolar*
TxLine CLK
Invert
RxLine CLK
Invert
Reframe
R/W
RO
R/W
R/W
R/W
R/W
R/W
R/W
1
0
1
0
0
0
0
0
Table 82 relates the content of this bit-field to the Bipolar Line Code which E3 Data will be transmitted
and received at.
NOTES:
1. This bit is ignored if the Unipolar mode is selected.
2. This selection also effects the operation of the
Receive E3 LIU Interface block
TABLE 82: THE RELATIONSHIP BETWEEN BIT 4 (AMI/
HDB3*) WITHIN THE I/O CONTROL REGISTER AND THE
BIPOLAR LINE CODE THAT IS OUTPUT BY THE TRANSMIT
E3 LIU INTERFACE BLOCK
6.2.5.2 TxLineClk Clock Edge Selection
The Framer also allows the user to specify whether
the E3 output data (via TxPOS and/or TxNEG output
pins) is to be updated on the rising or falling edges of
the TxLineClk signal. This selection is made by writing to bit 2 of the I/O Control Register, as depicted below.
BIT 4
BIPOLAR LINE CODE
0
HDB3
1
AMI
II/O CONTROL REGISTER (ADDRESS = 0X01)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT2
BIT 1
BIT 0
Disable TxLOC
LOC
Disable
RxLOC
AMI/ZeroSup*
Unipolar/
Bipolar*
TxLine CLK
Invert
RxLine CLK
Invert
Reframe
R/W
RO
R/W
R/W
R/W
R/W
R/W
R/W
1
0
1
0
0
0
0
0
Table 83 relates the contents of this bit field to the
clock edge of TxClk that E3 Data is output on the TxPOS and/or TxNEG output pins.
TABLE 83: THE RELATIONSHIP BETWEEN THE CONTENTS OF BIT 2 (TXLINECLK INV) WITHIN THE I/O CONTROL
REGISTER AND THE TXLINECLK CLOCK EDGE THAT TXPOS AND TXNEG ARE UPDATED ON
BIT 2
0
RESULT
Rising Edge:
Outputs on TxPOS and/or TxNEG are updated on the rising edge of TxLineClk.
See Figure 183 for timing relationship between TxLineClk, TxPOS and TxNEG signals, for this selection.
1
Falling Edge:
Outputs on TxPOS and/or TxNEG are updated on the falling edge of TxLineClk.
See Figure 184 for timing relationship between TxLineClk, TxPOS and TxNEG signals, for this selection.
NOTE: The user will typically make the selection based
upon the set-up and hold time requirements of the Transmit
LIU IC.
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XRT72L53
THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. P1.1.8
FIGURE 183. WAVEFORM/TIMING RELATIONSHIP BETWEEN TXLINECLK, TXPOS AND TXNEG - TXPOS AND
TXNEG ARE CONFIGURED TO BE UPDATED ON THE RISING EDGE OF TXLINECLK
t32
TxLineClk
t30
t33
TxPOS
TxNEG
FIGURE 184. WAVEFORM/TIMING RELATIONSHIP BETWEEN TXLINECLK, TXPOS AND TXNEG - TXPOS AND
TXNEG ARE CONFIGURED TO BE UPDATED ON THE FALLING EDGE OF TXLINECLK
t32
TxLineClk
t31
t33
TxPOS
TxNEG
6.2.6 Transmit Section Interrupt Processing
The Transmit Section of the XRT72L53 can generate
an interrupt to the Microprocessor/Microcontroller for
the following reasons.
The Block Level
• Completion of Transmission of LAPD Message
The user can enable or disable these Transmit Section interrupts, at the Block Level by writing the appropriate data into Bit 1 (Tx DS3/E3 Interrupt Enable)
within the Block Interrupt Enable register (Address =
0x04), as illustrated below.
The Enable State of the Block Level for the Transmit
Section Interrupts dictates whether or not interrupts
(enabled) at the source level, are actually enabled.
6.2.6.1 Enabling Transmit Section Interrupts
As mentioned in Section 36, the Interrupt Structure,
within the XRT72L53 contains two hierarchical levels:
• Block Level
• Source Level
400
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XRT72L53
THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. P1.1.8
BLOCK INTERRUPT ENABLE REGISTER (ADDRESS = 0X04)
BIT 7
BIT 6
BIT 5
RxDS3/E3
Interrupt
Enable
BIT 4
BIT 3
BIT 2
Not Used
BIT 1
BIT 0
TxDS3/E3
Interrupt
Enable
One-Second
Interrupt
Enable
R/W
RO
RO
RO
RO
RO
R/W
R/W
0
0
0
0
0
0
0
0
Setting this bit-field to “1” enables the Transmit Section (at the Block Level) for Interrupt Generation. Conversely, setting this bit-field to “0” disables the Transmit Section for interrupt generation.
What does it mean for the Transmit Section Interrupts to be enabled or disabled at the Block Level?
Block level, then a given interrupt will still be disabled,
if it is disabled at the source level.
As mentioned earlier, the Transmit Section of the
XRT72L53 Framer IC contains the Completion of
Transmission of LAPD Message Interrupt.
The Enabling/Disabling and Servicing of this interrupt
is presented below.
If the Transmit Section is disabled (for interrupt generation) at the Block Level, then ALL Transmit Section
interrupts are disabled, independent of the interrupt
enable/disable state of the source level interrupts.
If the Transmit Section is enabled (for interrupt generation) at the block level, then a given interrupt will be
enabled at the source level. Conversely, if the Transmit Section is enabled (for interrupt generation) at the
6.2.6.1.1 The Completion of Transmission of
the LAPD Message Interrupt
If the Transmit Section interrupts have been enabled
at the Block level, then the user can enable or disable
the Completion of Transmission of a LAPD Message
Interrupt by writing the appropriate value into Bit 1
(TxLAPD Interrupt Enable) within the Tx E3 LAPD
Status & Interrupt Register (Address = 0x34), as illustrated below.
TXE3 LAPD STATUS AND INTERRUPT REGISTER (ADDRESS = 0X34)
BIT 7
BIT 6
BIT 5
BIT 4
Not Used
BIT 3
BIT 2
BIT 1
BIT 0
TXDL Start
TXDL Busy
TxLAPD
Interrupt
Enable
TxLAPD
Interrupt
Status
RO
RO
RO
RO
R/W
RO
R/W
RUR
0
0
0
0
0
0
X
0
Setting this bit-field to “1” enables the Completion of
Transmission of a LAPD Message Interrupt. Conversely, setting this bit-field to “0” disables the Completion of Transmission of a LAPD Message interrupt.
6.2.6.1.2 Servicing the Completion of Transmission of a LAPD Message Interrupt
As mentioned previously, once the user commands
the LAPD Transmitter to begin its transmission of a
LAPD Message, it will do the following.
2.
3.
4.
1. It will parse through the contents of the Transmit
LAPD Message Buffer (located at address locations 0x86 through 0xDD) and search for a string
of five (5) consecutive “1’s”. If the LAPD Transmitter finds a string of five consecutive “1’s” (within
401
5.
the content of the LAPD Message Buffer, then it
will insert a “0” immediately after this string.
It will compute the FCS (Frame Check Sequence)
value and append this value to the back-end of
the user-message.
It will read out of the content of the user (zerostuffed) message and will encapsulate this data
into a LAPD Message frame.
Finally, it will begin transmitting the contents of
this LAPD Message frame via the “N” bits, within
each Outbound E3 frame.
Once the LAPD Transmitter has completed its
transmission of this LAPD Message frame (to the
Remote Terminal Equipment), the XRT72L53
Framer IC will generate the Completion of Trans-
áç
XRT72L53
THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. P1.1.8
mission of a LAPD Message Interrupt to the
Microcontroller/Microprocessor. Once the
XRT72L53 Framer IC generates this interrupt, it
will do the following.
• Assert the Interrupt Output pin (INT) by toggling it
“Low”.
• Set Bit 0 (TxLAPD Interrupt Status) within the TxE3
LAPD Status and Interrupt Register, to “1” as illustrated below.
TXE3 LAPD STATUS AND INTERRUPT REGISTER (ADDRESS = 0X34)
BIT 7
BIT 6
BIT 5
BIT 4
Not Used
BIT 3
BIT 2
BIT 1
BIT 0
TXDL Start
TXDL Busy
TxLAPD
Interrupt
Enable
TxLAPD
Interrupt
Status
RO
RO
RO
RO
R/W
RO
R/W
RUR
0
0
0
0
0
0
0
1
The purpose of this interrupt is to alert the Microcontroller/MIcroprocessor that the LAPD Transmitter has
completed its transmission of a given LAPD (or PMDL) Message, and is now ready to transmit the next
PMDL Message, to the Remote Terminal Equipment.
• Receive LIU Interface block
6.3 THE RECEIVE SECTION OF THE XRT72L53 (E3
MODE OPERATION)
When the XRT72L53 has been configured to operate
in the E3 Mode, the Receive Section of the
XRT72L53 consists of the following functional blocks.
• Receive Payload Data Output Interface block
• Receive HDLC Controller block
• Receive E3 Framer block
• Receive Overhead Data Output Interface block
Figure 185 presents a simple illustration of the Receive Section of the XRT72L53 Framer IC.
FIGURE 185. A SIMPLE ILLUSTRATION OF THE RECEIVE SECTION OF THE XRT72L53, WHEN IT HAS BEEN CONFIGURED TO OPERATE IN THE E3 MODE
RxOHFrame
RxOHEnable
RxOH
RxOHClk
RxOHInd
RxSer
RxNib[3:0]
RxClk
RxFrame
Receive Overhead
Input
Interface Block
Receive
Payload Data
Input
Interface Block
RxPOS
Receive DS3/E3
Framer Block
RxNEG
RxLineClk
From Microprocessor
Interface Block
Rx
RxE3
E3HDLC
HDLC
Controller/Buffer
Controller/Buffer
Each of these functional blocks will be discussed in
detail in this document.
6.3.1
Receive LIU
Interface
Block
The purpose of the Receive E3 LIU Interface block is
two-fold:
1. To receive encoded digital data from the E3 LIU
IC.
The Receive E3 LIU Interface Block
402
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XRT72L53
THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. P1.1.8
2. To decode this data, convert it into a binary data
stream and to route this data to the Receive E3
Framer block.
Figure 186 presents a simple illustration of the Receive E3 LIU Interface block.
FIGURE 186. A SIMPLE ILLUSTRATION OF THE RECEIVE E3 LIU INTERFACE BLOCK
RxPOS
To Receive DS3
Framer Block
Receive DS3
LIU Interface
Block
RxNEG
RxLineClk
The Receive Section of the XRT72L53 will via the Receive E3 LIU Interface Block receive timing and data
information from the incoming E3 data stream. The
E3 Timing information will be received via the RxLineClk input pin and the E3 data information will be received via the RxPOS and RxNEG input pins. The
Receive E3 LIU Interface block is capable of receiving
E3 data pulses in unipolar or bipolar format. If the Receive E3 framer is operating in the bipolar format,
then it can be configured to decode either AMI or
HDB3 line code data. Each of these input formats and
line codes will be discussed in detail, below.
6.3.1.1 Unipolar Decoding
If the Receive E3 LIU Interface block is operating in
the Unipolar (single-rail) mode, then it will receive the
Single Rail NRZ DS3 data pulses via the RxPOS input pin. The Receive E3 LIU Interface block will also
receive its timing signal via the RxLineClk signal.
NOTE: The RxLineClk signal will function as the timing
source for the entire Receive Section of the XRT72L53.
No data pulses will be applied to the RxNEG input
pin. The Receive E3 LIU Interface block receives a
logic "1" when a logic "1" level signal is present at the
RxPOS pin, during the sampling edge of the RxLineClk signal. Likewise, a logic "0" is received when a
logic "0" level signal is applied to the RxPOS pin.
Figure 187 presents an illustration of the behavior of
the RxPOS, RxNEG and RxLineClk input pins when
the Receive E3 LIU Interface block is operating in the
Unipolar mode.
403
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XRT72L53
THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. P1.1.8
FIGURE 187. BEHAVIOR OF THE RXPOS, RXNEG AND RXLINECLK SIGNALS DURING DATA RECEPTION OF UNIPODATA
LAR
Data
1
0
1
1
0
0
1
0
0
1
1
1
0
1
0
1
0
0
1
1
1
0
0
1
RxPOS
RxNEG
RxLineClk
The user can configure the Receive E3 LIU Interface
block to operate in either the Unipolar or the Bipolar
Mode by writing the appropriate data to the I/O Control Register, as depicted below.
II/O CONTROL REGISTER (ADDRESS = 0X01)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT2
BIT 1
BIT 0
Disable TxLOC
LOC
Disable
RxLOC
AMI/ZeroSup*
Unipolar/
Bipolar*
TxLine CLK
Invert
RxLine CLK
Invert
Reframe
R/W
RO
R/W
R/W
R/W
R/W
R/W
R/W
1
0
1
0
0
0
0
0
Table 84 relates the value of this bit-field to the Receive E3 LIU Interface Input Mode.
TABLE 84: THE RELATIONSHIP BETWEEN THE CONTENTS OF BIT 2 (TXLINECLK INV) WITHIN THE I/O CONTROL
REGISTER AND THE TXLINECLK CLOCK EDGE THAT TXPOS AND TXNEG ARE UPDATED ON
BIT 3
RECEIVE E3 LIU INTERFACE INPUT MODE
0
.Bipolar Mode (Dual Rail): AMI or HDB3 Line Codes are Transmitted and Received.
1
Unipolar Mode (Single Rail) Mode of transmission and reception of E3 data is selected.
NOTES:
1. The default condition is the Bipolar Mode.
2. This selection also effects the Transmit E3 Framer
Line Interface Output Mode
6.3.1.2 Bipolar Decoding
If the Receive E3 LIU Interface block is operating in
the Bipolar Mode, then it will receive the E3 data puls-
es via both the RxPOS, RxNEG, and the RxLineClk
input pins. Figure 188 presents a circuit diagram illustrating how the Receive E3 LIU Interface block interfaces to the Line Interface Unit while the Framer is
operating in Bipolar mode. The Receive E3 LIU Interface block can be configured to decode either the AMI
or HDB3 line codes.
404
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XRT72L53
THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. P1.1.8
FIGURE 188. ILLUSTRATION ON HOW THE XRT72L53 RECEIVE E3 FRAMER IS INTERFACED TO THE XRT73L03 LINE
INTERFACE UNIT WHILE OPERATING IN THE BIPOLAR MODE (ONE CHANNEL SHOWN)
RxAVDD_0
TxAVDD_0
DVDD_0
C3
C4
0.01uF
C5
0.01uF
0.01uF
C2
0.01uF
U21
C5
B5
A3
C4
Rx_AIS_Ch_0
RxRED_ALARM_0
Rx_OOF_Ch_0
Rx_LOS_Ch_0
F20
D20
F19
T20
RxFRAME_0
RxFRAME_CLK_0
RxDATA_IN_0
48
RxAIS_0
RxRED_0
RxOOF_0
RxLOS_0
RxFrame_0
RxClk_0
RxSer_0
MOTO
R8 4.7K
RxPOS_0
RxNEG_0
F2
67
42
51
R7 100
F3
50
F1
49
B8
D9
57
55
C7
A5
C6
C9
C3
61
62
63
64
96
RxAVDD0
TxAVDD0
RxDVDD0
TxAVDD0
28
37
LOSTHR_0
HOST/HW
RPOS0
RTIP0
J1
72
6 T2 1
RNEG0
D[7:0]
4
D7
D6
D5
D4
D3
D2
D1
D0
A[10:0]
M20
M19
M18
M17
N20
N19
N18
P20
P19
P18
R20
J17
R19
V20
P17
R18
H20
READY_OUT*
ALE
RD*
WR*
XRT72L53_CS*
XRT72L53_INT*
T19
HW_RESET*
R9
T18
A10
A9
A8
A7
A6
A5
A4
A3
A2
A1
A0
Rdy_Dtck
ALE_AS
RDB_DS
WRB_RW
CSB
INT
RESETB
RxLineClk_0
RLOL_0
ExtLOS_0
LLOOP_0
REQB_0
TAOS_0
DMO_0
TxLEV_0
RLOOP_0
ENCODIS_0 (TxOFF_0)
TxPOS_0
B7
RCLK0
RRING0
71
TxLineClk_0
R2
R1
37.4
37.4
RLOL_0
RLOS_0
CS
SCLK
SDI
SDO
REG_RESET*
C1
0.01uF
XRT71D03_CS* (Optional)
B2
117
C1
33
TxOFF_0
TPDATA_0
TTIP0
R3
29
D1
32
E2
34
47
J2
1 T1 6
TNDATA_0
TCLK_0
EXCLK_0
TRING0
MTIP0
R4
27
30
NIBBLEINTF
1
BNC
3
4
T3001
R5
36
270
100
TxFRAME_0
44.736MHz
TxDATA_OUT_0
3
T3001
36
TxNEG_0
BNC
2
J19
J20
K17
K18
K19
K20
L20
L18
1
2
70
U19
E20
G 4 TxFrame_0
E18 TxInClk_0
TxSER_0
MRING0
31
R6
270
54
73
RxDGND0
RxAGND0
TxAGND0
TxAGND0
39
26
XRT72L53_Ch_0
XRT73L03IV_Ch_0
6.3.1.2.1 AMI Decoding
AMI or Alternate Mark Inversion, means that consecutive "one's" pulses (or marks) will be of opposite polarity with respect to each other. This line code involves the use of three different amplitude levels: +1,
0, and -1. The +1 and -1 amplitude signals are used
to represent one's (or mark) pulses and the "0" amplitude pulses (or the absence of a pulse) are used to
represent zeros (or space) pulses. The general rule
for AMI is: if a given mark pulse is of positive polarity,
then the very next mark pulse will be of negative polarity and vice versa. This alternating-polarity relationship exists between two consecutive mark pulses, independent of the number of zeros that exist between
these two pulses. Figure 189 presents an illustration
of the AMI Line Code as would appear at the RxPOS
and RxNEG pins of the Framer, as well as the output
signal on the line.
405
áç
XRT72L53
THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. P1.1.8
FIGURE 189. ILLUSTRATION OF AMI LINE CODE
Data 1 0 1 1 0 0 0 1 0 1 1 1 1 0 1 1 0 1 1 0 0 1 1 0 0 0 0 1
Line Signal
RxPOS
RxNEG
NOTE: One of the reasons that the AMI Line Code has
been chosen for driving copper medium, isolated via transformers, is that this line code has no dc component, thereby
eliminating dc distortion in the line.
happen. One such technique is HDB3 (or High Density Bipolar -3) encoding.
In general the HDB3 line code behaves just like AMI
with the exception of the case when a long string of
consecutive zeros occurs on the line. Any 4 consecutive zeros will be replaced with either a "000V" or a
"B00V" where "B" refers to a Bipolar pulse (e.g., a
pulse with a polarity that is compliant with the AMI
coding rule). And "V" refers to a Bipolar Violation
pulse (e.g., a pulse with a polarity that violates the alternating polarity scheme of AMI.) The decision between inserting an "000V" or a "B00V" is made to insure that an odd number of Bipolar (B) pulses exist
between any two Bipolar Violation (V) pulses. The
Receive E3 LIU Interface block, when operating with
the HDB3 Line Code is responsible for decoding the
HD-encoded data back into a unipolar (binary-format). For instance, if the Receive E3 LIU Interface
block detects a "000V" or a "B00V" pattern in the incoming pattern, the Receive E3 LIU Interface block
will replace it with four (4) consecutive zeros.
Figure 190 presents a timing diagram that illustrates
examples of HDB3 decoding.
6.3.1.2.2 HDB3 Decoding
The Transmit E3 LIU Interface block and the associated LIU embed and combine the data and clocking information into the line signal that is transmitted to the
remote terminal equipment. The remote terminal
equipment has the task of recovering this data and
timing information from the incoming E3 data stream.
Most clock and data recovery schemes rely on the
use of Phase-Locked-Loop technology. One of the
problems of using Phase-Locked-Loop (PLL) technology for clock recovery is that it relies on transitions in
the line signal, in order to maintain lock with the incoming E3 data-stream. Therefore, these clock recovery scheme, are vulnerable to the occurrence of a
long stream of consecutive zeros (e.g., no transitions
in the line). This scenario can cause the PLL to lose
lock with the incoming E3 data, thereby causing the
clock and data recovery process of the receiver to fail.
Therefore, some approach is needed to insure that
such a long string of consecutive zeros can never
FIGURE 190. ILLUSTRATION OF TWO EXAMPLES OF HDB3 DECODING
0
0
0
V
Line Signal
B
0
0
V
0
0
0
0
RxPOS
RxNEG
Data
1
0
1
1
0
0
0
0
0
1
1
1
1
406
0
1
1
0
1
1
0
0
1
1
1
áç
XRT72L53
THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. P1.1.8
6.3.1.2.3 Line Code Violations
The Receive E3 LIU Interface block will also check
the incoming E3 data stream for line code violations.
For example, when the Receive E3 LIU Interface
block detects a valid bipolar violation (e.g., in HDB3
line code), it will substitute four zeros into the binary
data stream. However, if the bipolar violation is invalid, then an LCV (Line Code Violation) is flagged
and the PMON LCV Event Count Register (Address =
0x50 and 0x51) will also be incremented. Additionally,
the LCV-One-Second Accumulation Registers (Address = 0x6E and 0x6F) will be incremented. For example: If the incoming E3 data is HDB3 encoded, the
Receive E3 LIU Interface block will also increment the
LCV One-Second Accumulation Register if three (or
more) consecutive zeros are received.
6.3.1.2.4 RxLineClk Clock Edge Selection
The incoming unipolar or bipolar data, applied to the
RxPOS and the RxNEG input pins are clocked into
the Receive E3 LIU Interface block via the RxLineClk
signal. The Framer IC allows the user to specify
which edge (e.g, rising or falling) of the RxLineClk
signal will sample and latch the signal at the RxPOS
and RxNEG input signals into the Framer IC. The user can make this selection by writing the appropriate
data to bit 1 of the I/O Control Register, as depicted
below.
II/O CONTROL REGISTER (ADDRESS = 0X01)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT2
BIT 1
BIT 0
Disable
TxLOC
LOC
Disable
RxLOC
AMI/ZeroSup*
Unipolar/
Bipolar*
TxLine CLK
Invert
RxLine CLK
Invert
Reframe
R/W
RO
R/W
R/W
R/W
R/W
R/W
R/W
1
0
1
0
0
0
0
0
Table 85 depicts the relationship between the value of
this bit-field to the sampling clock edge of RxLineClk.
TABLE 85: THE RELATIONSHIP BETWEEN THE CONTENTS OF BIT 1 (RXLINECLK INV) OF THE I/O CONTROL REGISTER,
AND THE SAMPLING EDGE OF THE RXLINECLK SIGNAL
RXCLKINV
(BIT 1)
0
RESULT
.Rising Edge:
RxPOS and RxNEG are sampled at the rising edge of RxLineClk. See Figure 191 for timing relationship
between RxLineClk, RxPOS, and RxNEG.
1
Falling Edge:
RxPOS and RxNEG are sampled at the falling edge of RxLineClk. See Figure 192 for timing relationship
between RxLineClk, RxPOS, and RxNEG.
Figure 191 and Figure 192 present the Waveform and
Timing Relationships between RxLineClk, RxPOS
and RxNEG for each of these configurations.
407
áç
XRT72L53
THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. P1.1.8
FIGURE 191. WAVEFORM/TIMING RELATIONSHIP BETWEEN RXLINECLK, RXPOS AND RXNEG - WHEN RXPOS AND
RXNEG ARE TO BE SAMPLED ON THE RISING EDGE OF RXLINECLK
t42
RxLineClk
t39
t38
RxPOS
RxNEG
FIGURE 192. WAVEFORM/TIMING RELATIONSHIP BETWEEN RXLINECLK, RXPOS AND RXNEG - WHEN RXPOS AND
RXNEG ARE TO BE SAMPLED ON THE FALLING EDGE OF RXLINECLK
RxLineClk
t40
t41
RxPOS
RxNEG
6.3.2 The Receive E3 Framer Block
The Receive E3 Framer block accepts decoded E3
data from the Receive E3 LIU Interface block, and
routes data to the following destinations.
• The Receive Payload Data Output Interface Block
• The Receive E3 HDLC Controller Block
Figure 193 presents a simple illustration of the Receive E3 Framer block, along with the associated
paths to the other functional blocks within the Framer
chip.
• The Receive Overhead Data Output Interface
Block.
408
áç
XRT72L53
THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. P1.1.8
FIGURE 193. A SIMPLE ILLUSTRATION OF THE RECEIVE E3 FRAMER BLOCK AND THE ASSOCIATED PATHS TO THE
OTHER FUNCTIONAL BLOCKS
To Receive E3 HDLC
Buffer
Receive Overhead Data
Output Interface
Receive
ReceiveE3
E3Framer
Framer
Block
Block
From Receive E3
LIU Interface Block
Receive Payload Data
Output Interface
Once the HDB3 (or AMI) encoded data has been decoded into a binary data-stream, the Receive E3
Framer block will use portions of this data-stream in
order to synchronize itself to the remote terminal
equipment. At any given time, the Receive E3 Framer
block will be operating in one of two modes.
• The Frame Acquisition Mode: In this mode, the
Receive E3 Framer block is trying to acquire synchronization with the incoming E3 frame, or
• The Frame Maintenance Mode: In this mode, the
Receive E3 Framer block is trying to maintain frame
synchronization with the incoming E3 Frames.
Figure 194 presents a State Machine diagram that
depicts the Receive E3 Framer block's E3/ITU-T
G.832 Frame Acquisition/Maintenance Algorithm.
6.3.2.1 The Framing Acquisition Mode
The Receive E3 Framer block is considered to be operating in the Frame Acquisition Mode, if it is operating in any one of the following states within the E3
Frame Acquisition/Maintenance Algorithm per
Figure 194.
• FA1, FA2 Octet Search State
• FA1, FA2 Octet Verification State
• OOF Condition State
• LOF Condition State
Each of these Framing Acquisition states, within the
Receive E3 Framer Framing Acquisition/Maintenance
State Machine are discussed below.
The FA1, FA2 Octet Search State
When the Receive E3 Framer block is first powered
up, it will be operating in the FA1, FA2 Octet Search
state. While the Receive E3 Framer is operating in
this state, it will be performing a bit-by-bit search for
the FA1 and FA2 Framing Alignment octets. FA1 is
assigned the value “0xF6”, and FA2 is assigned the
value of “0x28”. Figure 195, which presents an illustration of the E3, ITU-T G.832 Framing Format, indicates that these two octets will occur at the beginning
of each E3 frame, and that the FA2 octet will appear
immediately after the FA1 octet.
409
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XRT72L53
THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. P1.1.8
FIGURE 194. THE STATE MACHINE DIAGRAM FOR THE RECEIVE E3 FRAMER E3 FRAME ACQUISITION/MAINTENANCE
ALGORITHM
FA1 and FA2 octets are
detected once
FA1, FA2
Octet
Verification
FA1, FA2
Octet
Search
FA1 and FA2 octets are
not detected
LOF
Condition
1 or 3 ms of operating
in the OOF condition
(user-selectable)
FA1 and FA2 octets
are verified once
OOF
Condition
3 consecutive
Valid Frames
In Frame
4 consecutive
In-valid Frames
410
Frame Maintenance
Mode
XRT72L53
THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
áç
PRELIMINARY
REV. P1.1.8
FIGURE 195. ILLUSTRATION OF THE E3, ITU-T G.832 FRAMING FORMAT
60 Columns
FA1
FA2
EM
TR
MA
NR
530 Octet Payload
9 Rows
GC
1 Byte
59 Bytes
In Frame State
When the Receive E3 Framer block detects the “FA1”
octet, and determines that this octet is immediately
followed by the “FA2” octet, then it will transition to the
FA1, FA2 Octet Verification state, per Figure 195.
Once the Receive E3 Framer block enters the InFrame state, then it will cease performing Frame Acquisition functions, and will proceed to perform Framing Maintenance functions. Therefore, the operation
of the Receive E3 Framer block, while operating in
the In-Frame state, can be found in Section 5.3.2.2
(The Framing Maintenance Mode).
The FA1, FA2 Octet Verification State
Once the Receive E3 Framer block has detected an
“0xF628” pattern (e.g., the concatenation of the FA1
and FA2 octets), it must verify that this pattern is indeed the “FA1” and “FA2” octets and not some other
set of bytes, within the E3 frame, mimicking the
Frame Alignment bytes. Hence, the purpose of the
FA1, FA2 Octet Verification state.
OOF (Out of Frame) Condition State
When the Receive E3 Framer block enters this state,
it will then quit performing its bit-by-bit search for the
Frame Alignment bytes. Instead, the Receive E3
Framer block will read in the two octets that occur 537
bytes (e.g., one E3 frame period later) after the candidate Frame Alignment patterns were first detected. If
these two bytes match the assigned values for the
“FA1” and “FA2” octets, then the Receive E3 Framer
block will conclude that it has found the Frame Alignment bytes and will then transition to the In-Frame
state. However, if these two bytes do not match the
assigned values for the “FA1” and “FA2” octets then
the Receive E3 Framer block will concluded that it
has been fooled by data mimicking the Frame Alignment bytes, and will transition back to the FA1, FA2
Octet Search state.
If the Receive E3 Framer while operating in the InFrame state detects four (4) consecutive frames,
which do not have the valid Frame Alignment (FA1
and FA2 octet) patterns, then it will transition into the
OOF Condition State. The Receive E3 Framer block’s
operation, while in the OOF condition state is a
unique mix of Framing Maintenance and Framing Acquisition operation. The Receive E3 Framer block will
exhibit some Framing Acquisition characteristics by
attempting to locate (once again) the Frame Alignment octets. However, the Receive E3 Framer block
will also exhibit some Frame Maintenance behavior
by still using the most recent frame synchronization
for its overhead byte and payload byte processing.
The Receive E3 Framer block will inform the Microprocessor/Microcontroller of its transition from the InFrame state to the OOF Condition state, by generating a Change in OOF Condition Interrupt. When this
occurs, Bit 3 (OOF Interrupt Status), within the Rx E3
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THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. P1.1.8
Interrupt Status Register - 1, will be set to “1”, as depicted below.
RXE3 INTERRUPT STATUS REGISTER - 1 (ADDRESS = 0X14)
BIT 7
BIT 6
BIT 5
Not Used
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
COFA
Interrupt
Status
OOF
Interrupt
Status
LOF
Interrupt
Status
LOS
Interrupt
Status
AIS
Interrupt
Status
RO
RO
RO
RUR
RUR
RUR
RUR
RUR
0
0
0
0
0
0
0
0
However, if the Receive E3 Framer block resides in
the OOF Condition state for more than this user-selectable number of E3 frame periods, then it will automatically transition to the LOF (Loss of Frame) Condition state.
The Receive E3 Framer block will also inform the external circuitry of its transition into the OOF Condition
state, by toggling the RxOOF output pin “High”.
If the Receive E3 Framer block is capable of finding
the Framing Alignment octets within a user-selectable
number of E3 frame periods, then it will transition
back into the In-Frame state. The Receive E3 Framer
block will then inform the Microprocessor/Microcontroller of its transition back into the In-Frame state by
generating the Change in OOF Condition Interrupt.
The user can select this user-selectable number of
E3 frame periods that the Receive E3 Framer block
will remain in the OOF Condition state by writing the
appropriate value into Bit 7 (RxLOF Algo) within the
Rx E3 Configuration & Status Register, as depicted
below.
RXE3 CONFIGURATION & STATUS REGISTER 2 (ADDRESS = 0X11)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
Rx LOF Algo
RxLOF
RxOOF
RxLOS
RxAIS
RxPld Unstab
Rx
TMark
RxFERF
R/W
RO
RO
RO
RO
RO
RO
RO
0
1
1
1
1
1
1
1
• The Receive E3 Framer block will make an unconditional transition to the FA1, FA2 Octet Search
state.
Writing a “0” into this bit-field causes the Receive E3
Framer block to reside in the OOF Condition state for
at most 24 E3 frame periods (3 ms). Writing a “1” into
this bit-field causes the Receive E3 Framer block to
reside in the OOF Condition state for at most 8 E3
frame periods (1 ms).
LOF (Loss of Framing) Condition State
If the Receive E3 Framer block enters the LOF Condition state, then the following things will happen.
• The Receive E3 Framer block will discard the most
recent frame synchronization and
• The Receive E3 Framer block will notify the Microprocessor/Microcontroller of its transition to the
LOF Condition state, by generating the Change in
LOF Condition interrupt. When this occurs, Bit 2
(LOF Interrupt Status), within the Rx E3 Interrupt
Status Register - 1 will be set to “1”, as depicted
below.
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THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
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REV. P1.1.8
RXE3 INTERRUPT STATUS REGISTER - 1 (ADDRESS = 0X14)
BIT 7
BIT 6
BIT 5
Not Used
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
COFA
Interrupt
Status
OOF
Interrupt
Status
LOF
Interrupt
Status
LOS
Interrupt
Status
AIS
Interrupt
Status
RO
RO
RO
RUR
RUR
RUR
RUR
RUR
0
0
0
0
0
0
0
0
Finally, the Receive E3 Framer block will also inform
the external circuitry of this transition to the LOF Condition state by toggling the RxLOF output pin “High”.
6.3.2.2 The Framing Maintenance Mode
Once the Receive E3 Framer block enters the InFrame state, then it will notify the Microprocessor/Mi-
crocontroller of this fact by generating both the
Change in OOF Condition and Change in LOF Condition Interrupts. When this happens, bits 2 and 3 (LOF
Interrupt Status and OOF Interrupt Status) will be set
to “1”, as depicted below.
RXE3 INTERRUPT STATUS REGISTER - 1 (ADDRESS = 0X14)
BIT 7
BIT 6
BIT 5
Not Used
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
COFA
Interrupt
Status
OOF
Interrupt
Status
LOF
Interrupt
Status
LOS
Interrupt
Status
AIS
Interrupt
Status
RO
RO
RO
RUR
RUR
RUR
RUR
RUR
0
0
0
0
1
1
0
0
Finally, the Receive E3 Framer block will negate both
the RxOOF and the RxLOF bit-fields within the Rx E3
Configuration & Status Register, as depicted below.
Additionally, the Receive E3 Framer block will inform
the external circuitry of its transition to the In-Frame
state by toggling both the RxOOF and RxLOF output
pins "Low”.
RXE3 CONFIGURATION & STATUS REGISTER 2 (ADDRESS = 0X11)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
Rx LOF Algo
RxLOF
RxOOF
RxLOS
RxAIS
RxPld Unstab
Rx
TMark
RxFERF
R/W
RO
RO
RO
RO
RO
RO
RO
0
1
1
0
0
0
0
0
When the Receive E3 Framer block is operating in the
In-Frame state, it will then begin to perform Frame
Maintenance operations, where it will continue to verify that the Frame Alignment octets (FA1, FA2) are
present, at their proper locations. While the Receive
E3 Framer block is operating in the Frame Maintenance Mode, it will declare an Out-of-Frame (OOF)
Condition if it detects invalid Framing Alignment bytes
in four consecutive frames.
Since the Receive E3 Framer block requires the detection of invalid Frame Alignment bytes in four consecutive frames, in order for it to transition to the OOF
Condition state, it can tolerate some errors in the
Framing Alignment bytes, and still remain in the InFrame state. However, each time the Receive E3
Framer block detects an error in the Frame Alignment
bytes, it will increment the PMON Framing Error
Event Count Registers (Address = 0x52 and 0x53).
The bit-format for these two registers are depicted below.
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THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. P1.1.8
PMON FRAMING BIT/BYTE ERROR COUNT REGISTER - MSB (ADDRESS = 0X52)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
Framing Bit/Byte Error Count - High Byte
RUR
RUR
RUR
RUR
RUR
RUR
RUR
RUR
0
0
0
0
0
0
0
0
BIT 2
BIT 1
BIT 0
PMON FRAMING BIT/BYTE ERROR COUNT REGISTER - LSB (ADDRESS = 0X53)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
Framing Bit/Byte Error Count - Low Byte
RUR
RUR
RUR
RUR
RUR
RUR
RUR
RUR
0
0
0
0
0
0
0
0
6.3.2.3 Forcing a Reframe via Software Command
The XRT72L53 Framer IC permits the user to command a reframe procedure with the Receive E3 Framer block via software command. If the user writes a
“1” into Bit 0 (Reframe) within the I/O Control Register
(Address = 0x01), as depicted below, then the Receive E3 Framer block will be forced into the FA1, FA2
Octet Search state, per Figure 194, and will begin its
search for the “FA1” and “FA2” octets.)
I/O CONTROL REGISTER (ADDRESS = 0X01)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
Disable TxLOC
LOC
Disable
RxLOC
AMI/
ZeroSup*
Unipolar/Bipolar*
TxLine
Clk
Invert
RxLine
Clk
Invert
Reframe
R/W
RO
R/W
R/W
R/W
R/W
R/W
R/W
1
0
1
0
0
0
0
1
2. Generating both the Change in OOF Status and
the Change in LOF Status interrupts to the Microprocessor.
3. Asserting both the RxLOF and RxOOF bit-fields
within the Rx E3 Configuration & Status Register,
as depicted below.
The Framer IC will respond to this command by doing
the following.
1. Asserting both the RxOOF and RxLOF output
pins.
RXE3 CONFIGURATION & STATUS REGISTER 2 (ADDRESS = 0X11)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
Rx LOF Algo
RxLOF
RxOOF
RxLOS
RxAIS
RxPld Unstab
Rx
TMark
RxFERF
R/W
RO
RO
RO
RO
RO
RO
RO
0
1
1
1
1
1
1
1
6.3.2.4 Performance Monitoring of the Frame
Synchronization Section, within the Receive E3
Framer block
The user can monitor the number of framing bytes
(FA1 and FA2 bytes) errors that have been detected
by the Receive E3 Framer block. This is accom-
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THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. P1.1.8
plished by periodically reading the PMON Framing
Bit/Byte Error Event Count Registers (Address =
0x52 and 0x53). The byte format of these registers
are presented below.
6.3.2.5 The RxOOF and RxLOF output pin.
The user can roughly determine the current framing
state that the Receive E3 Framer block is operating in
by reading the logic state of the RxOOF and the RxLOF output pins. Table 86 presents the relationship
between the state of the RxOOF and RxLOF output
pins, and the Framing State of the Receive E3 Framer
block.
TABLE 86: THE RELATIONSHIP BETWEEN THE LOGIC STATE OF THE RXOOF AND RXLOF OUTPUT PINS, AND THE
FRAMING STATE OF THE RECEIVE E3 FRAMER BLOCK
RXLOF
RXOOF
0
0
In Frame
0
1
OOF Condition (The Receive E3 Framer block is operating in the 3ms OOF period).
1
0
Invalid
1
1
LOF Condition
6.3.2.6
FRAMING STATE OF THE RECEIVE E3 FRAMER BLOCK
E3 Receive Alarms
DS3/E3/STS-1 LIU IC) is asserted. The Receive E3
Framer block will indicate that it is declaring an LOS
condition by.
6.3.2.6.1 The Loss of Signal (LOS) Alarm
Declaring an LOS Condition
The Receive E3 Framer block will declare a Loss of
Signal (LOS) Condition, when it detects 32 consecutive incoming “0’s” via the RxPOS and RxNEG input
pins or if the ExtLOS input pin (from the XRT7300
• Asserting the RxLOS output pin (e.g., toggling it
“High”).
• Setting Bit 4 (RxLOS) of the Rx E3 Configuration &
Status Register to “1” as depicted below.
RXE3 CONFIGURATION & STATUS REGISTER 2 (ADDRESS = 0X11)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
Rx LOF Algo
RxLOF
RxOOF
RxLOS
RxAIS
RxPld Unstab
Rx
TMark
RxFERF
R/W
RO
RO
RO
RO
RO
RO
RO
0
0
0
1
0
0
0
0
• The Receive E3 Framer block will generate a
Change in LOS Condition interrupt request. Upon
generating this interrupt request, the Receive E3
Framer block will assert Bit 1 (LOS Interrupt Status
within the Rx E3 Framer Interrupt Status Register 1, as depicted below.
RXE3 INTERRUPT STATUS REGISTER - 1 (ADDRESS = 0X14)
BIT 7
BIT 6
BIT 5
Not Used
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
COFA
Interrupt
Status
OOF
Interrupt
Status
LOF
Interrupt
Status
LOS
Interrupt
Status
AIS
Interrupt
Status
RO
RO
RO
RUR
RUR
RUR
RUR
RUR
0
0
0
0
0
0
1
0
Clearing the LOS Condition
The Receive E3 Framer block will clear the LOS condition when it encounters a stream of 32 bits that
does not contain a string of 4 consecutive zeros.
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THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. P1.1.8
• Generating the Change in LOS Condition Interrupt
to the Microprocessor.
When the Receive E3 Framer block clears the LOS
condition, then it will notify the Microprocessor and
the external circuitry of this occurrence by:
• Clearing Bit 4 (RxLOS) within the Rx E3 Configuration & Status Register, as depicted below.
RXE3 CONFIGURATION & STATUS REGISTER 2 (ADDRESS = 0X11)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
Rx LOF Algo
RxLOF
RxOOF
RxLOS
RxAIS
RxPld Unstab
Rx
TMark
RxFERF
R/W
RO
RO
RO
RO
RO
RO
RO
0
0
0
1
0
0
0
0
• Clear the RxLOS output pin (e.g., toggle it "Low”).
tion if 7 or less “0s” are detected in each of 2 consecutive E3 frames.
6.3.2.6.2 The AIS (Alarm Indication Status)
Condition
Declaring the AIS Condition
If the Receive E3 Framer block declares an AIS Condition, then it will do the following.
• Generate the Change in AIS Condition Interrupt to
the Microprocessor. Hence, the Receive E3 Framer
block will assert Bit 1 (AIS Interrupt Status) within
the Rx E3 Framer Interrupt Status register - 1, as
depicted below.
The Receive E3 Framer block will identify and declare
an AIS condition, if it detects an “All Ones” pattern in
the incoming E3 data stream. More specifically, the
Receive E3 Framer block will declare an AIS Condi-
RXE3 INTERRUPT STATUS REGISTER - 1 (ADDRESS = 0X14)
BIT 7
BIT 6
BIT 5
Not Used
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
COFA
Interrupt
Status
OOF
Interrupt
Status
LOF
Interrupt
Status
LOS
Interrupt
Status
AIS
Interrupt
Status
RO
RO
RO
RUR
RUR
RUR
RUR
RUR
0
0
0
0
0
0
0
1
• Assert the RxAIS output pin.
• Set Bit 3 (Rx AIS) within the Rx E3 Configuration &
Status Register, as depicted below.
RXE3 CONFIGURATION & STATUS REGISTER 2 (ADDRESS = 0X11)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
Rx LOF Algo
RxLOF
RxOOF
RxLOS
RxAIS
RxPld Unstab
Rx
TMark
RxFERF
R/W
RO
RO
RO
RO
RO
RO
RO
0
0
0
0
1
0
0
0
Clearing the AIS Condition
The Receive E3 Framer block will clear the AIS condition when it detects two consecutive E3 frames, with
eight or more “zeros” in the incoming data stream.
The Receive E3 Framer block will inform the Micro-
processor that the AIS Condition has been cleared
by:
• Generating the Change in AIS Condition Interrupt
to the Microprocessor. Hence, the Receive E3
Framer block will assert Bit 1 (AIS Interrupt Status)
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THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. P1.1.8
• Setting the RxAIS bit-field, within the Rx E3 Configuration & Status Register to “0”, as depicted below.
within the Rx E3 Framer Interrupt Status Register 1.
• Clearing the RxAIS output pin (e.g., toggling it
"Low”).
RXE3 CONFIGURATION & STATUS REGISTER 2 (ADDRESS = 0X11)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
Rx LOF Algo
RxLOF
RxOOF
RxLOS
RxAIS
RxPld Unstab
Rx
TMark
RxFERF
R/W
RO
RO
RO
RO
RO
RO
RO
0
0
0
0
0
0
0
0
6.3.2.6.3 The Far-End-Receive Failure (FERF)
Condition
Declaring the FERF Condition
selectable number of consecutive incoming E3
frames, with the FERF bit-field (Bit 7, within the MA
Byte) set to “1”. Recall, the bit-format of the MA byte
is presented below.
The Receive E3 Framer block will declare a Far-End
Receive Failure (FERF) condition if it detects a user-
THE MAINTENANCE AND ADAPTATION (MA) BYTE FORMAT
BIT 7
BIT 6
FERF
FEBE
BIT 5
BIT 4
BIT 3
Payload Type
This User-selectable number of E3 frames is either 3
or 5, depending upon the value that has been written
BIT 2
BIT 1
Payload Dependent
BIT 0
Timing Marker
into Bit 4 (Rx FERF Algo) within the Rx E3 Configuration & Status Register, as depicted below.
RXE3 CONFIGURATION & STATUS REGISTER 1 - (E3, ITU-T G.832) (ADDRESS = 0X10)
BIT 7
BIT 6
BIT 5
RxPLDType[2:0]
BIT 4
BIT 3
RxFERF
Algo
RxTMark
Algo
BIT 2
BIT 1
BIT 0
RxPLDExp[2:0]
RO
RO
RO
RO
RO
RO
RO
RO
0
0
0
0
0
0
0
0
Writing a “0” into this bit-field causes the Receive E3
Framer block to declare a FERF condition, if it detects
3 consecutive incoming E3 frames, that have the
FERF bit (within the MA byte) set to “1”.
Writing a “1” into this bit-field causes the Receive E3
Framer block to declare a FERF condition, if it detects
5 consecutive incoming E3 frames, that have the
FERF bit (within the MA byte) set to “1”.
Whenever the Receive E3 Framer block declares a
FERF condition, then it will do the following.
• Generate a Change in FERF Condition interrupt to
the MIcroprocessor. Hence, the Receive E3 Framer
block will assert Bit 3 (FERF Interrupt Status) within
the Rx E3 Framer Interrupt Status register - 2, as
depicted below.
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THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
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REV. P1.1.8
RXE3 INTERRUPT ENABLE REGISTER - 2 (ADDRESS = 0X13)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
Not Used
TTB
Change
Interrupt
Enable
Not Used
FEBE
Interrupt
Enable
FERF
Interrupt
Enable
BIP-8
Error Interrupt
Enable
Framing
Byte Error
Interrupt
Enable
RxPld
Mis
Interrupt
Enable
RO
R/W
RO
R/W
R/W
R/W
R/W
R/W
0
0
0
0
1
0
0
0
• Set the Rx FERF bit-field, within the Rx E3 Configuration/Status Register to “1”, as depicted below.
RXE3 CONFIGURATION & STATUS REGISTER 2 (ADDRESS = 0X11)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
Rx LOF Algo
RxLOF
RxOOF
RxLOS
RxAIS
RxPld Unstab
Rx
TMark
RxFERF
R/W
RO
RO
RO
RO
RO
RO
RO
0
0
0
0
0
0
0
1
Clearing the FERF Condition
Whenever the Receive E3 Framer clears the FERF
status, then it will do the following:
The Receive E3 Framer block will clear the FERF
condition once it has received a User-Selectable
number of E3 frames is either 3 or 5 depending upon
the value that has been written into Bit 4 (Rx FERF
Algo) of the Rx E3 Configuration/Status Register, as
discussed above.
1. Generate a Change in the FERF Status Interrupt
to the Microprocessor.
2. Clear the Bit 0 (RxFERF) within the Rx E3 Configuration & Status register, as depicted below.
RXE3 CONFIGURATION & STATUS REGISTER 2 (ADDRESS = 0X11)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
Rx LOF Algo
RxLOF
RxOOF
RxLOS
RxAIS
RxPld Unstab
Rx
TMark
RxFERF
R/W
RO
RO
RO
RO
RO
RO
RO
0
0
0
0
0
0
0
1
6.3.2.7 Error Checking of the Incoming E3
Frames
The Receive E3 Framer block performs error-checking on the incoming E3 frame data that it receives
from the Remote Terminal Equipment. It performs this
error-checking by computing the BIP-8 value of an incoming E3 frame. Once the Receive E3 Framer block
has obtained this value, it will compare this value with
that of the “EM” byte that it receives, within the very
next E3 frame. If the locally computed BIP-8 value
matches the EM byte of the corresponding E3 frame,
then the Receive E3 Framer block will conclude that
this particular frame has been properly received. The
Receive E3 Framer block will then inform the Remote
Terminal Equipment of this fact by having the Local
Terminal Equipment Transmit E3 Framer block send
the Remote Terminal an E3 frame, with the FEBE bitfield, within the MA byte, set to “0”.
This procedure is illustrated in Figure 196 and
Figure 197.
Figure 196 illustrates the Local Receive E3 Framer
receiving an error-free E3 frame. In this figure, the locally computed BIP-8 value of “0x5A” matches that
received from the Remote Terminal, within the EM
byte-field. Figure 197 illustrates the subsequent ac-
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THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
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REV. P1.1.8
tion of the Local Transmit E3 Framer block, which will
transmit an E3 frame to the Remote Terminal, with
the FEBE bit-field set to “0”. This signaling indicates
that the Local Receive E3 Framer has received an error-free E3 frame.
FIGURE 196. ILLUSTRATION OF THE LOCAL RECEIVE E3 FRAMER BLOCK, RECEIVING AN E3 FRAME (FROM THE
REMOTE TERMINAL) WITH A CORRECT EM BYTE.
Local Terminal
Transmit E3
Framer
Remote
Terminal
EM Byte
Receive E3
Framer
0x5A
0x5A
Locally Calculated
EM Byte
FIGURE 197. ILLUSTRATION OF THE LOCAL RECEIVE E3 FRAMER BLOCK, TRANSMITTING AN E3 FRAME (TO THE
REMOTE TERMINAL) WITH THE FEBE BIT (WITHIN THE MA BYTE-FIELD) SET TO “0”
FEBE bit
Local Terminal
x0xxxxxx
Transmit E3
Framer
MA Byte
Remote
Terminal
Receive E3
Framer
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REV. P1.1.8
Receive E3 Frame block is receiving an E3 frame with
an EM byte containing the value “0x5A”. This value
does not match the locally computed EM byte value
of “0x5B”. Consequently, there is an error in this E3
frame.
However, if the locally computed BIP-8 value does not
match the EM byte of the corresponding E3 frame,
then the Receive E3 Framer block will do the following.
• It will inform the Remote Terminal of this fact by
having the Local Transmit E3 Framer block send
the Remote Terminal an E3 frame, with the FEBE
bit-field, within the MA byte, set to “1”. This phenomenon is illustrated below in Figure 198 and
Figure 199.
Figure 199 illustrates the subsequent action of the
Local Transmit E3 Framer block, which will transmit
an E3 frame, with the FEBE bit-field set to “1” to the
Remote Terminal. This signaling indicates that the
Local Receive E3 Framer block has received an errored E3 frame.
Figure 198 illustrates the Local Receive E3 Framer
receiving an errored E3 frame. In this figure, the Local
FIGURE 198. ILLUSTRATION OF THE LOCAL RECEIVE E3 FRAMER BLOCK, RECEIVING AN E3 FRAME (FROM THE
REMOTE TERMINAL) WITH AN INCORRECT EM BYTE.
Local Terminal
Transmit E3
Framer
Remote
Terminal
EM Byte
Receive E3
Framer
0x5A
0x5B
Locally Calculated
EM Byte
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THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. P1.1.8
FIGURE 199. ILLUSTRATION OF THE LOCAL RECEIVE E3 FRAMER BLOCK, TRANSMITTING AN E3 FRAME (TO THE
REMOTE TERMINAL) WITH THE FEBE BIT (WITHIN THE MA BYTE-FIELD) SET TO “1”
FEBE bit
Local Terminal
x1xxxxxx
Transmit E3
Framer
MA Byte
Remote
Terminal
Receive E3
Framer
In additional to the FEBE bit-field signaling, the Receive E3 Framer block will generate the BIP-8 Error
Interrupt to the Microprocessor. Hence, it will set bit 2
(BIP-8 Error Interrupt Status) to “1”, as depicted below.
RXE3 INTERRUPT STATUS REGISTER - 2 (ADDRESS = 0X15)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
Not Used
TTB
Change
Interrupt
Status
Not Used
FEBE
Interrupt
Status
FERF
Interrupt
Status
BIP-8
Error
Interrupt
Status
Framing
Byte Error
Interrupt
Status
RxPld
Mis
Interrupt
Status
RO
RUR
RO
RUR
RUR
RUR
RUR
RUR
0
0
0
0
0
0
0
0
BIT 2
BIT 1
BIT 0
Finally, the Receive E3 Framer block will increment
the PMON Parity Error Count registers. The byte format of these registers are presented below.
PMON PARITY ERROR COUNT REGISTER - MSB (ADDRESS = 0X54)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
Parity Error Count - High Byte
RUR
RUR
RUR
RUR
RUR
RUR
RUR
RUR
0
0
0
0
0
0
0
0
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THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. P1.1.8
PMON PARITY ERROR COUNT REGISTER - LSB (ADDRESS = 0X55)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
Parity Error Count - Low Byte
RUR
RUR
RUR
RUR
RUR
RUR
RUR
RUR
0
0
0
0
0
0
0
0
The user can determine the number of BIP-8 Errors
that have been detected by the Receive E3 Framer
block, since the last read of these registers. These
registers are reset-upon-read.
6.3.2.8 Processing of the Far-End-Block Error
(FEBE) Bit-fields
Whenever the Receive E3 Framer detects an error in
the incoming E3 frame, via EM byte verification, it will
inform the Local Transmit E3 Framer of this fact. The
Local Transmit E3 Framer will, in turn, notify the Remote Terminal (e.g., the source of the errored E3
frame) by transmitting an E3 frame, with the FEBE
bit-field (within the MA byte) set to “1”.
If the Receive E3 Framer receives any E3 frame, with
the FEBE bit-field set to “1”, then it will do the following.
• It will generate a FEBE Event interrupt to the Microprocessor/Microcontroller. Hence, the Receive E3
Framer block will set bit 4 (FEBE Interrupt Status)
within the Rx E3 Framer Interrupt Status Register 2, as depicted below.
RXE3 INTERRUPT STATUS REGISTER - 2 (ADDRESS = 0X15)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
Not Used
TTB Change
Interrupt Status
RO
RUR
RO
RUR
RUR
RUR
RUR
RUR
0
0
0
1
0
0
0
0
Not Used FEBE Interrupt FERF Interrupt BIP-8 Error
Framing Byte
RxPld Mis
Status
Status
Interrupt Status Error Interrupt Interrupt Status
Status
• Increment the PMON Received FEBE Event Count
register - MSB/LSB, which is located at 0x56 and
0x57 in the Framer Address space. The byte-format
of these registers are presented below.
PMON FEBE EVENT COUNT REGISTER - MSB (ADDRESS = 0X56)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
FEBE Event Count - High Byte
RUR
RUR
RUR
RUR
RUR
RUR
RUR
RUR
0
0
0
0
0
0
0
0
BIT 2
BIT 1
BIT 0
PMON FEBE EVENT COUNT REGISTER - LSB (ADDRESS = 0X57)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
FEBE Event Count - Low Byte
RUR
RUR
RUR
RUR
RUR
RUR
RUR
RUR
0
0
0
0
0
0
0
0
The user can determine the total number of FEBE
Events (e.g., E3 frames that have been received with
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THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. P1.1.8
the FEBE bit-field set to “1”) that have occurred since
the last read of this register. This register is reset-upon-read.
6.3.2.9 Receiving the Trail Trace Buffer Messages
The XRT72L53 Framer IC device contains 16 bytes
worth of Transmit Trail Trace Buffers, and 16 bytes
worth of Receive Trail Trace Buffers, as described below. The role of the Transmit Trail Trace Buffers are
described in Section 5.2.4.2.
For Trail Trace Buffer purposes, the Remote Transmit
E3 Framer block will group 16 consecutive E3 frames
into a Trail Trace Buffer super-frame. When the Remote Transmit E3 Framer is generating the first E3
frame, within a Trail Trace Buffer super-frame, it will
insert the value [1, C6, C5, C4, C3, C2, C1, C0], into
the TR byte-field of this Outbound E3 frame. The remaining 15 TR byte-fields (within this Trail Trace Buffer super-frame) will consists of ASCII characters that
are required for the E.164 numbering format.
When the Local Receive E3 Framer block receives an
E3 frame, containing a value in the TR byte that has a
“1” in the MSB position, then it (the Receive E3 Framer block) will write this value into the RxTTB-0 Register (Address = 0x1C). Once this occurs, the Receive
E3 Framer block will notify the Microprocessor of this
new incoming Trail Trace Buffer message by generating the Change in Trail Trace Buffer Message interrupt. The Receive E3 Framer block will also set bit 6
(TTB Change Interrupt Status) within the Rx E3
Framer Interrupt Status Register - 2, as depicted below.
The XRT72L53 DS3/E3 Framer IC contains 16 Receive Trail Trace Buffer registers (e.g., RxTTB-0
through RxTTB-15). The purpose of these registers
are to receive and store the incoming Trail Access
Point Identifier from the Remote Transmitting Terminal.
The Local Receiving Terminal will use this information
to verify that it is still receiving data from its intended
transmitter. The specific use of these registers follows.
RXE3 INTERRUPT STATUS REGISTER - 2 (ADDRESS = 0X15)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
Not Used
TTB
Change
Interrupt
Status
Not Used
FEBE
Interrupt
Status
FERF
Interrupt
Status
BIP-8
Error Interrupt
Status
Framing
Byte Error
Interrupt
Status
RxPld
Mis
Interrupt
Status
RO
RUR
RO
RUR
RUR
RUR
RUR
RUR
0
0
0
0
0
0
0
0
through TxTTB-15) must contain octets with a “0” in
the MSB position.
3. The Framer IC will not verify the CRC-7 value that
is written into the Rx TTB-0” register. It is up to the
user’s system hardware and/or software to perform
this verification.
The contents of the TR byte-field, in the very next E3
frame will be written into the Rx TTB-1 Register (Address = 0x1D), and so on until all 16 bytes have been
received.
NOTES:
1. Anytime the Receive E3 Framer block receives an
E3 frame that contains an octet in the TR byte-field,
with a “1” in the MSB (Most Significant Bit) position,
then the Receive E3 Framer block will (1) write the
contents of the TR byte-field (in this E3 frame) into
the RxTTB-0 Register,
2. It will generate the Change in Trail Trace Buffer
Interrupt. The Receive E3 Framer will do these
things independent of the number of E3 frames that
have been received since the last occurrence of the
Change in Trail Trace Buffer Interrupt. Hence, the
user, when writing data into the Tx TTB registers,
must take care to insure that only the Tx TTB-0 register contains an octet with a “1” in the MSB position. All remaining Tx TTB registers (e.g., TxTTB-1
6.3.3 The Receive HDLC Controller Block
The Receive E3 HDLC Controller block can be used
to receive message-oriented signaling (MOS) type
data link messages from the remote terminal equipment.
The MOS types of HDLC message processing is discussed in detail below.
The Message Oriented Signaling (e.g., LAP-D)
Processing via the Receive DS3 HDLC Controller
block
The LAPD Receiver (within the Receive E3 HDLC
Controller block) allows the user to receive PMDL
messages from the remote terminal equipment, via
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THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. P1.1.8
End of Message (EOM)
the Inbound E3 frames. In this case, the Inbound
message bits will be carried by either the “GC” or the
“NR” byte-fields within each E3 Frame. The remote
LAPD Transmitter will transmit a LAPD Message to
the Near-End Receiver via either one of these bytes
within each E3 Frame. The LAPD Receiver will receive and store the information portion of the received LAPD frame into the Receive LAPD Message
Buffer, which is located at addresses: 0xDE through
0x135 within the on-chip RAM. The LAPD Receiver
has the following responsibilities.
Flag Sequence Byte detected
Abort Sequence detected
Message Type
C/R Type
The occurrence of FCS Errors
The LAPD receiver's actions are facilitated via the following two registers.
• Rx E3 LAPD Control Register
• Framing to the incoming LAPD Messages
• Rx E3 LAPD Status Register
• Filtering out stuffed "0’s" (within the information
payload)
Operation of the LAPD Receiver
The LAPD Receiver, once enabled, will begin searching for the boundaries of the incoming LAPD message. The LAPD Message Frame boundaries are delineated via the Flag Sequence octets (0x7E), as depicted in Figure 200.
• Storing the Frame Message into the Receive LAPD
Message Buffer
• Perform Frame Check Sequence (FCS) Verification
• Provide status indicators for
FIGURE 200. LAPD MESSAGE FRAME FORMAT
Flag Sequence (8 bits)
SAPI (6-bits)
C/R
EA
EA
TEI (7 bits)
Control (8-bits)
76 or 82 Bytes of Information (Payload)
FCS - MSB
FCS - LSB
Flag Sequence (8-bits)
Where: Flag Sequence = 0x7E
ITU-T Path Identification = 0x3F (82 bytes)
SAPI + CR + EA = 0x3C or 0x3E
Enabling and Configuring the LAPD Receiver
TEI + EA = 0x01
Before the LAPD Receiver can begin to receive and
process incoming LAPD Message frames, the user
must do two things.
Control = 0x03
The 16 bit FCS is calculated using CRC-16, x16 +
x12 + x5 + 1
The local µP (at the remote terminal), while assembling the LAPD Message frame, will insert an additional byte at the beginning of the information (payload) field. This first byte of the information field indicates the type and size of the message being transferred. The value of this information field and the
corresponding message type/size follow:
CL Path Identification
= 0x38 (76 bytes)
IDLE Signal Identification = 0x34 (76 bytes)
Test Signal Identification = 0x32 (76 bytes)
1. The byte-field within each E3 frame which will be
carrying the comprising octets of the LAPD Message frame must be specified and
2. The LAPD Receiver must be enabled.
Each of these steps are discussed in detail below.
1. Specifying which byte-field, within each E3 frame,
will be carrying the LAPD Message frame.
The LAPD Receiver can receive the LAPD Message
frame octets via either the GC-byte-field or the NRbyte-field, within each incoming E3 frame. The user
makes this selection by writing the appropriate bit to
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THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. P1.1.8
Bit 1 (DL from NR) within the Rx E3 LAPD Control
Register, as depicted below.
RXE3 LAPD CONTROL REGISTER (ADDRESS = 0X18)
BIT 7
BIT 6
BIT 5
BIT 4
Not Used
BIT 3
BIT 2
BIT 1
BIT 0
DL from NR
RxLAPD
Enable
RxLAPD
Interrupt
Enable
RxLAPD
Interrupt
Status
RO
RO
RO
RO
R/W
R/W
R/W
RUR
0
0
0
0
0
0
1
0
2. Enabling the LAPD Receiver
The LAPD Receiver must be enabled before it can
begin receiving and processing any LAPD Message
frames. The LAPD Receiver can be enabled by writing a “1” to Bit 2 (RxLAPD Enable) of the Rx E3 LAPD
Control Register, as indicated below.
Writing a “0” into this bit-field causes the LAPD Receiver to read in the octets from the GC byte-field of
each E3 frame and with these octets, reassembling
the LAPD Message frame. Writing a “1” into this bitfield causes the LAPD Receiver to receive the LAPD
Message frame octets from the NR byte-field of each
E3 frame.
RXE3 LAPD CONTROL REGISTER (ADDRESS = 0X18)
BIT 7
BIT 6
BIT 5
BIT 4
Not Used
BIT 3
BIT 2
BIT 1
BIT 0
DL from NR
RxLAPD
Enable
RxLAPD
Interrupt
Enable
RxLAPD
Interrupt
Status
RO
RO
RO
RO
R/W
R/W
R/W
RUR
0
0
0
0
0
1
1
0
Once the LAPD Receiver has been enabled, it will begin searching for the Flag Sequence octet (0x7E), in
either the “GC” or the “NR” byte-fields within each incoming E3 frame. When the LAPD Receiver finds the
flag sequence byte, it will assert the Flag Present bit
(Bit 0) within the Rx E3 LAPD Status Register, as depicted below.
RXE3 LAPD STATUS REGISTER (ADDRESS = 0X19)
BIT 7
BIT 6
BIT 5
Not Used
Rx ABORT
RO
RO
RO
0
0
0
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
RxCR
Type
RxFCS
Error
End of
Message
Flag
Present
RO
RO
RO
RO
RO
0
0
0
0
1
RxLAPDType[1:0]
The receipt of the Flag Sequence octet can mean
one of two things.
1. This Flag Sequence byte may be marking the
beginning or end of an incoming LAPD Message
frame.
2. The Received Flag Sequence octet could be just
one of many Flag Sequence octets that are transmitted via the E3 Transport Medium, during idle
periods between the transmission of LAPD Message frames.
The LAPD Receiver will negate the Flag Present bit
as soon as it has received an octet that is something
other than the Flag Sequence octet. Once this happens, the LAPD Receiver should be receiving either
octet # 2 of the incoming LAPD Message, or an
ABORT Sequence (e.g., a string of seven or more
consecutive “1’s”). If this next set of data is an
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THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. P1.1.8
ABORT Sequence, then the LAPD Receiver will assert the RxABORT bit-field (Bit 6) within the Rx E3
LAPD Status Register, as depicted below.
RXE3 LAPD STATUS REGISTER (ADDRESS = 0X19)
BIT 7
BIT 6
BIT 5
Not Used
Rx ABORT
RO
RO
RO
0
1
0
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
RxCR
Type
RxFCS
Error
End of
Message
Flag
Present
RO
RO
RO
RO
RO
0
0
0
0
0
RxLAPDType[1:0]
However, if this next octet is Octet #2 of an incoming
LAPD Message frame, then the LAPD Receiver is beginning to receive a LAPD Message frame.
As the LAPD Receiver receives this LAPD Message
frame, it is reading in the LAPD Message frame octets, from either the “GC” or the “NR” byte-fields within each incoming E3 frame. Secondly, it is reassembling these octets into a LAPD Message frame.
the PMDL Message into the Receive LAPD Message
Buffer. Specifically, the LAPD Receiver will search through
the PMDL Message data and will remove any “0” that
immediately follows a string of 5 consecutive “1’s”.
For more information on how the LAPD Transmitter
inserted these stuff bits, please see Section 5.2.3.1.
2. FCS (Frame Check Sequence) Word Verification
The LAPD Receiver will compute the CRC-16 value
of the header octets and the PMDL Message octets,
within this LAPD Message frame and will compare it
with the value of the two octets, residing in the FCS
word-field of this LAPD Message frame. If the FCS
value of the newly received LAPD Message frame
matches the locally-computed CRC-16 value, then
the LAPD Receiver will conclude that it has received
this LAPD Message frame in an error-free manner.
Once the LAPD Receiver has received the complete
LAPD Message frame, then it will proceed to perform
the following five (5) steps.
1. PMDL Message Extraction
The LAPD Receiver will extract out the PMDL Message, from the newly received LAPD Message frame.
The LAPD Receiver will then write this PMDL Message into the Receive LAPD Message buffer within
the Framer IC.
However, if the FCS value does not match the locallycomputed CRC-16 value, then the LAPD Receiver
will conclude that this LAPD Message frame is erred.
NOTE: As the LAPD Receiver is extracting the PMDL Message, from the newly received LAPD Message frame, the
LAPD Receiver will also check the PMDL data for the
occurrence of stuff bits (e.g., “0s” that were inserted into the
PMDL Message by the Remote LAPD Transmitter, in order
to prevent this data from mimicking the Flag Sequence byte
or an ABORT Sequence), and remove them prior to writing
The LAPD Receiver will indicate the results of this
FCS Verification process by setting Bit 2 (RxFCS Error) within the Rx E3 LAPD Status Register, to the appropriate value as tabulated below.
RXE3 LAPD STATUS REGISTER (ADDRESS = 0X19)
BIT 7
BIT 6
BIT 5
Not Used
Rx ABORT
RO
RO
RO
0
0
0
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
RxCR
Type
RxFCS
Error
End of
Message
Flag
Present
RO
RO
RO
RO
RO
0
0
1
0
0
RxLAPDType[1:0]
If the LAPD Receiver detects an error in the FCS value, then it will set the RxFCS Error bit-field to “1”.
Conversely, if the LAPD Receiver does not detect an
error in the FCS value, the it will clear the RxFCS Error bit-field to “0”.
NOTE: The LAPD Receiver will extract and write the PMDL
Message into the Receive LAPD Message buffer independent of the results of FCS Verification. Hence, the user is
urged to validate each PMDL Message that is read in from
the Receive LAPD Message buffer, by first checking the
state of this bit-field.
3. Check and Report the State of the “C/R” Bit-field
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THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. P1.1.8
After receiving the LAPD Message frame, the LAPD
Receiver will check the state of the “C/R” bit-field,
within octet # 2 of the LAPD Message frame header
and will reflect this value in Bit 3 (Rx CR Type) within
the Rx E3 LAPD Status Register, as depicted below.
RXE3 LAPD STATUS REGISTER (ADDRESS = 0X19)
BIT 7
BIT 6
BIT 5
Not Used
Rx ABORT
RO
RO
RO
0
0
0
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
RxCR
Type
RxFCS
Error
End of
Message
Flag
Present
RO
RO
RO
RO
RO
0
1
0
0
0
RxLAPDType[1:0]
first octet position within the Transmit LAPD Message
buffer. The value of this byte corresponds to the type
of LAPD Message frame/PMDL Message that is to be
transmitted to the Remote LAPD Receiver. This Message-Type Identification octet is transported to the
Remote LAPD Receiver, along with the rest of the
LAPD frame. From this Message Type Identification
octet, the LAPD Receiver will know the type of size of
the newly received PMDL Message. The LAPD Receiver will then reflect this information in Bits 4 and 5
(RxLAPDType[1:0]) within the Rx E3 LAPD Status
Register, as depicted below.
When this bit-field is “0”, it means that this LAPD
Message frame is originating from a customer installation. When this bit-field is “1”, it means that this
LAPD Message frame is originating from a network
terminal.
4. Identify the Type of LAPD Message Frame/PMDL
Message
Next, the LAPD Receiver will check the value of the
first octet within the PMDL Message field, of the
LAPD Message frame. Recall that from Section _,
that when operating the LAPD Transmitter, the user is
required to write in a byte of a specific value into the
RXE3 LAPD STATUS REGISTER (ADDRESS = 0X19)
BIT 7
BIT 6
BIT 5
Not Used
Rx ABORT
RO
RO
RO
0
0
0
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
RxCR
Type
RxFCS
Error
End of
Message
Flag
Present
RO
RO
RO
RO
RO
0
0
0
0
0
RxLAPDType[1:0]
Table 87 presents the relationship between the contents of RxLAPDType[1:0] and the type of message
received by the LAPD Receiver.
TABLE 87: THE RELATIONSHIP BETWEEN THE CONTENTS OF RXLAPDTYPE[1:0] BIT-FIELDS AND THE PMDL
MESSAGE TYPE/SIZE
RXLAPDTYPE[1:0]
PMDL MESSAGE TYPE
PMDL MESSAGE SIZE
00
Test Signal Identification
76 Bytes
01
Idle Signal Identification
76 Bytes
10
CL Path Identification
76 Bytes
11
ITU-T Path Identification
82 Bytes
NOTE: Prior to reading in the PMDL Message from the
Receive LAPD Message buffer, the user is urged to read
the state of the RxLAPDType[1:0] bit-fields in order to determine the size of this message.
427
5. Inform the Local Microprocessor/External Circuitry of the receipt of the new LAPD Message
frame.
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XRT72L53
THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. P1.1.8
• Generating a LAPD Message Frame Received
interrupt to the Microprocessor. The purpose of this
interrupt is to let the Microprocessor know that the
Receive LAPD Message buffer contains a new
PMDL Message that needs to be read and processed. When the LAPD Receiver generates this
interrupt, it will set bit 0 (RxLAPD Interrupt Status)
within the Rx E3 LAPD Control Register to “1” as
depicted below.
Finally, after the LAPD Receiver has received and
processed the newly received LAPD Message frame
(per steps 1 through 4, as described above), it will inform the local Microprocessor that a LAPD Message
frame has been received and is ready for user-system handling. The LAPD Receiver will inform the Microprocessor/Microcontroller and the external circuitry by:
RXE3 LAPD CONTROL REGISTER (ADDRESS = 0X18)
BIT 7
BIT 6
BIT 5
BIT 4
Not Used
BIT 3
BIT 2
BIT 1
BIT 0
DL from NR
RxLAPD
Enable
RxLAPD
Interrupt
Enable
RxLAPD
Interrupt
Status
RO
RO
RO
RO
R/W
R/W
R/W
RUR
0
0
0
0
0
0
0
1
BIT 3
BIT 2
BIT 1
BIT 0
RxCR
Type
RxFCS
Error
End of
Message
Flag
Present
• Setting Bit 1 (End of Message) within the Rx E3
LAPD Status Register, to “1” as depicted below.
RXE3 LAPD STATUS REGISTER (ADDRESS = 0X19)
BIT 7
BIT 6
BIT 5
BIT 4
Not Used
Rx ABORT
RO
RO
RO
RO
RO
RO
RO
RO
0
0
0
0
0
0
1
0
RxLAPDType[1:0]
In summary, Figure 201 presents a flow chart depicting how the LAPD Receiver functions.
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THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. P1.1.8
FIGURE 201. FLOW CHART DEPICTING THE FUNCTIONALITY OF THE LAPD RECEIVER
START
Set the “RxLAPDType[1:0] bit-fields to the appropriate value.
Indicate whether the LAPD Receiver should retrieve the
LAPD Message frame octets from the NR or GC byte-field,
within each incoming E3 Frame.
Continue to read in the LAPD Message frame octets
Enable the LAPD Receiver
Is
Abort Sequence
Detected?
The LAPD Receiver will begin searching for the Flag Sequence
octet (0x7E) in the “selected” byte-field (e.g., NR or GC) of each
incoming E3 frame.
No
No
No
Is
Flag Sequence
octet
Present?
Yes
A
Has
the last byte
of the LAPD Message
frame been
received?
Yes
Yes
Set the “End Of Message” bit-field within the “RxE3
LAPD Status Register (Address = 0x19)
Assert the “Flag Present” bit-field within the “Rx E3 LAPD
Status Register (Address = 0x19).
Unstuff the “PMDL” portion of the LAPD Message frame.
Is
non-Flag Sequence
octet detected
?
Yes
Goto Figure 185
No
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THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. P1.1.8
FIGURE 202. FLOW CHART DEPICTING THE FUNCTIONALITY OF THE LAPD RECEIVER (CONTINUED)
Generate the “Receive LAPD Message frame” interrupt.
From Figure 184
A
Compute “Frame Check Sequence (FCS)” value of incoming
LAPD Message Frame.
End
Compare “locally-computed” FCS value with that contained
within the newly received LAPD Message frames.
Do the
two FCS values
Match?
Yes
No
FCS Error Detected
Assert the “Rx FCS Error” bit-field within the “Rx E3
LAPD Status Register (Address = 0x19).
6.3.4
face
The Receive Overhead Data Output Inter-
Figure 203 presents a simple illustration of the Receive Overhead Data Output Interface block within
the XRT72L53.
FIGURE 203. A SIMPLE ILLUSTRATION OF THE RECEIVE OVERHEAD OUTPUT INTERFACE BLOCK
RxOHFrame
RxOH
RxOHClk
Receive
ReceiveOverhead
Overhead
Output
Interface
Output Interface
Block
Block
From Receive
E3 Framer Block
RxOHEnable
The E3, ITU-T G.832 frame consists of 537 bytes. Of
these bytes, 530 bytes are payload bits and the remaining 7 bytes are overhead bytes. The XRT72L53
has been designed to handle and process both the
payload type and overhead type bytes for each E3
frame.
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THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. P1.1.8
Within the Receive Section of the XRT72L53, the Receive Payload Data Output Interface block has been
designed to handle the payload bits. Likewise, the
Receive Overhead Data Output Interface block has
been designed to handle and process the overhead
bits.
6.3.4.1 Method 1 - Using the RxOHClk Clock
signal
The Receive Overhead Data Output Interface block
consists of four (4) signals. Of these four signals, the
following three signals are to be used when sampling
the E3 overhead bits via Method 1.
The Receive Overhead Data Output Interface block
unconditionally outputs the contents of all overhead
bits. The XRT72L53 does not offer the user a means
to shut off this transmission of data. However, the Receive Overhead Output Interface block does provide
the user with the appropriate output signals for external Data Link Layer equipment to sample and process these overhead bits, via the following two methods.
• RxOH
• Method 1- Using the RxOHClk clock signal.
Figure 204 illustrates how one should interface the
Receive Overhead Data Output Interface block to the
Terminal Equipment when using Method 1, to sample
and process the overhead bits from the Inbound E3
data stream.
• Method 2 - Using the RxClk and RxOHEnable output signals.
Each of these methods are described below.
• RxOHClk
• RxOHFrame
Each of these signals are listed and described below
in Table 88.
Interfacing the Receive Overhead Data Output Interface block to the Terminal Equipment (Method
1)
FIGURE 204. ILLUSTRATION OF HOW TO INTERFACE THE TERMINAL EQUIPMENT TO THE RECEIVE OVERHEAD DATA
OUTPUT INTERFACE BLOCK (FOR METHOD 1).
E3_OH_Clock_In
RxOHClk
E3_OH_In
RxOH
Rx_Start_of_Frame
RxOHFrame
Terminal Equipment
XRT72L5x E3 Framer
2. Keep track of the number of rising clock edges
that have occurred in the RxOHClk (e.g., the
E3_OH_Clock_In) signal, since the last time the
RxOHFrame signal was sampled “High”. By
doing this, the Terminal Equipment will be able to
keep track of which overhead byte is being output
via the RxOH output pin. Based upon this information, the Terminal Equipment will be able to
derive some meaning from these overhead bits.
Method 1 Operation of the Terminal Equipment
If the Terminal Equipment intends to sample any
overhead data from the Inbound E3 data stream (via
the Receive Overhead Data Output Interface block)
then it is expected to do the following:
1. Sample the state of the RxOHFrame signal (e.g.,
the Rx_Start_of_Frame input signal) on the rising
edge of the RxOHClk (e.g., the
E3_OH_Clock_In) signal.
431
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THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. P1.1.8
TABLE 88: LISTING AND DESCRIPTION OF THE PIN ASSOCIATED WITH THE RECEIVE OVERHEAD DATA OUTPUT
INTERFACE BLOCK
SIGNAL NAME
TYPE
DESCRIPTION
RxOH
Output
Receive Overhead Data Output pin:
The XRT72L53 will output the overhead bits, within the incoming E3 frames, via this pin.
The Receive Overhead Data Output Interface block will output a given overhead bit, upon the
falling edge of RxOHClk. Hence, the external data link equipment should sample the data, at
this pin, upon the rising edge of RxOHClk.
The XRT72L53 will always output the E3 Overhead bits via this output pin. There are no external input pins or register bit settings available that will disable this output pin.
RxOHClk
Output
Receive Overhead Data Output Interface Clock Signal:
The XRT72L53 will output the Overhead bits (within the incoming E3 frames), via the RxOH
output pin, upon the falling edge of this clock signal.
As a consequence, the user's data link equipment should use the rising edge of this clock signal to sample the data on both the RxOH and RxOHFrame output pins.
This clock signal is always active.
RxOHFrame
Output
Receive Overhead Data Output Interface - Start of Frame Indicator:
The XRT72L53 will drive this output pin "High" (for one period of the RxOHClk signal), whenever the first overhead bit within a given E3 frame is being driven onto the RxOH output pin.
Table 89 relates the number of rising clock edges (in
the RxOHClk signal, since the RxOHFrame signal
was last sampled “High”) to the E3 Overhead bit that
is being output via the RxOH output pin.
TABLE 89: THE RELATIONSHIP BETWEEN THE NUMBER OF RISING CLOCK EDGES IN RXOHCLK, (SINCE
RXOHFRAME WAS LAST SAMPLED "HIGH") TO THE E3 OVERHEAD BIT, THAT IS BEING OUTPUT VIA THE RXOH
OUTPUT PIN
NUMBER OF RISING CLOCK EDGES IN RXOHCLK
THE OVERHEAD BIT BEING OUTPUT BY THE
XRT72L53
0 (Clock edge is coincident with RxOHFrame being detected “High”)
FA1 Byte - Bit 7
1
FA1 Byte - Bit 6
2
FA1 Byte - Bit 5
3
FA1 Byte - Bit 4
4
FA1 Byte - Bit 3
5
FA1 Byte - Bit 2
6
FA1 Byte - Bit 1
7
FA1 Byte - Bit 0
8
FA2 Byte - Bit 7
9
FA2 Byte - Bit 6
10
FA2 Byte - Bit 5
11
FA2 Byte - Bit 4
12
FA2 Byte - Bit 3
13
FA2 Byte - Bit 2
14
FA2 Byte - Bit 1
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THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
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PRELIMINARY
REV. P1.1.8
TABLE 89: THE RELATIONSHIP BETWEEN THE NUMBER OF RISING CLOCK EDGES IN RXOHCLK, (SINCE
RXOHFRAME WAS LAST SAMPLED "HIGH") TO THE E3 OVERHEAD BIT, THAT IS BEING OUTPUT VIA THE RXOH
OUTPUT PIN
NUMBER OF RISING CLOCK EDGES IN RXOHCLK
THE OVERHEAD BIT BEING OUTPUT BY THE
XRT72L53
15
FA2 Byte - Bit 0
16
EM Byte - Bit 7
17
EM Byte - Bit 6
18
EM Byte - Bit 5
19
EM Byte - Bit 4
20
EM Byte - Bit 3
21
EM Byte - Bit 2
22
EM Byte - Bit 1
23
EM Byte - Bit 0
24
TR Byte - Bit 7
25
TR Byte - Bit 6
26
TR Byte - Bit 5
27
TR Byte - Bit 4
28
TR Byte - Bit 3
29
TR Byte - Bit 2
30
TR Byte - Bit 1
31
TR Byte - Bit 0
32
MA Byte - Bit 7
33
MA Byte - Bit 6
34
MA Byte - Bit 5
35
MA Byte - Bit 4
36
MA Byte - Bit 3
37
MA Byte - Bit 2
38
MA Byte - Bit 1
39
MA Byte - Bit 0
40
NR Byte - Bit 7
41
NR Byte - Bit 6
42
NR Byte - Bit 5
43
NR Byte - Bit 4
44
NR Byte - Bit 3
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XRT72L53
THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. P1.1.8
TABLE 89: THE RELATIONSHIP BETWEEN THE NUMBER OF RISING CLOCK EDGES IN RXOHCLK, (SINCE
RXOHFRAME WAS LAST SAMPLED "HIGH") TO THE E3 OVERHEAD BIT, THAT IS BEING OUTPUT VIA THE RXOH
OUTPUT PIN
NUMBER OF RISING CLOCK EDGES IN RXOHCLK
THE OVERHEAD BIT BEING OUTPUT BY THE
XRT72L53
45
NR Byte - Bit 2
46
NR Byte - Bit 1
47
NR Byte - Bit 0
48
GC Byte - Bit 7
49
GC Byte - Bit 6
50
GC Byte - Bit 5
51
GC Byte - Bit 4
52
GC Byte - Bit 3
53
GC Byte - Bit 2
54
GC Byte - Bit 1
55
GC Byte - Bit 0
Figure 205 presents the typical behavior of the Receive Overhead Data Output Interface block, when
Method 1 is being used to sample the incoming E3
overhead bits.
FIGURE 205. ILLUSTRATION OF THE SIGNALS THAT ARE OUTPUT VIA THE RECEIVE OVERHEAD OUTPUT INTERFACE
(FOR METHOD 1).
RxOHClk
RxOHFrame
RxOH
FA1, Bit 7
FA1, Bit 6
Terminal Equipment should sample
the “RxOHFrame” and “RxOH” signals
here.
6.3.4.2
FA1, Bit 5
FA1, Bit 4
Recommended Sampling Edges
Method 2 - Using RxOutClk and the
RxOHEnable signals
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FA1, Bit 3
XRT72L53
THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
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PRELIMINARY
REV. P1.1.8
Method 1 requires that the Terminal Equipment be
able to handle an additional clock signal, RxOHClk.
However, there may be a situation in which the Terminal Equipment circuitry does not have the means to
deal with this extra clock signal, in order to use the
Receive Overhead Data Output Interface. Method 2
involves the use of the following signals.
• RxOH
• RxOutClk
• RxOHEnable
• RxOHFrame
Each of these signals are listed and described in
Table 90.
TABLE 90: LISTING AND DESCRIPTION OF THE PIN ASSOCIATED WITH THE RECEIVE OVERHEAD DATA OUTPUT
INTERFACE BLOCK (METHOD 2)
SIGNAL NAME
TYPE
DESCRIPTION
RxOH
Output
Receive Overhead Data Output pin:
The XRT72L53 will output the overhead bits, within the incoming E3 frames, via this pin.
The Receive Overhead Output Interface will pulse the RxOHEnable output pin (for one RxOutClk period) at approximately the middle of the RxOH bit period. The user is advised to design
the Terminal Equipment to latch the contents of the RxOH output pin, whenever the RxOHEnable output pin is sampled “High” on the falling edge of RxOutClk.
RxOHEnable
Output
Receive Overhead Data Output Enable - Output pin:
The XRT72L53 will assert this output signal for one RxOutClk period when it is safe for the Terminal Equipment to sample the data on the RxOH output pin.
RxOHFrame
Output
Receive Overhead Data Output Interface - Start of Frame Indicator:
The XRT72L53 will drive this output pin “High” (for one period of the RxOH signal), whenever
the first overhead bit, within a given E3 frame is being driven onto the RxOH output pin.
RxOutClk
Output
Receive Section Output Clock Signal:
This clock signal is derived from the RxLineClk signal (from the LIU) for loop-timing applications, and the TxInClk signal (from a local oscillator) for local-timing applications. For E3 applications, this clock signal will operate at 34.368MHz.
The user is advised to design the Terminal Equipment to latch the contents of the RxOH pin,
anytime the RxOHEnable output signal is sampled “High” on the falling edge of this clock signal.
Interfacing the Receive Overhead Data Output Interface block to the Terminal Equipment (Method
2)
Figure 206 illustrates how one should interface the
Receive Overhead Data Output Interface block to the
Terminal Equipment, when using Method 2 to sample
and process the overhead bits from the Inbound E3
data stream.
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XRT72L53
THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. P1.1.8
FIGURE 206. ILLUSTRATION OF HOW TO INTERFACE THE TERMINAL EQUIPMENT TO THE RECEIVE OVERHEAD DATA
OUTPUT INTERFACE BLOCK (FOR METHOD 2).
E3_OH_In
RxOH
E3_OH_Enable_In
RxOHEnable
E3_Clk_In
RxOutClk
Rx_Start_of_Frame
RxOHFrame
Terminal Equipment
XRT72L5x E3 Framer
Method 2 Operation of the Terminal Equipment
“High”. By doing this, the Terminal Equipment will
be able to keep track of which overhead bit is
being output via the RxOH output pin. Based
upon this information, the Terminal Equipment
will be able to derive some meaning from these
overhead bits.
3. Table 91 relates the number of RxOHEnable output pulses (that have occurred since both the
RxOHFrame and the RxOHEnable pins were
both sampled “High”) to the E3 overhead bit that
is being output via the RxOH output pin.
If the Terminal Equipment intends to sample any
overhead data from the Inbound E3 data stream (via
the Receive Overhead Data Output Interface), then it
is expected to do the following.
1. Sample the state of the RxOHFrame signal (e.g.,
the Rx_Start_of_Frame input) on the falling edge
of the RxOutClk clock signal, whenever the RxOHEnable output signal is also sampled “High”.
2. Keep track of the number of times that the RxOHEnable signal has been sampled “High” since
the last time the RxOHFrame was also sampled
TABLE 91: THE RELATIONSHIP BETWEEN THE NUMBER OF RXOHENABLE OUTPUT PULSES (SINCE RXOHFRAME WAS
LAST SAMPLED "HIGH") TO THE E3 OVERHEAD BIT, THAT IS BEING OUTPUT VIA THE RXOH OUTPUT PIN
NUMBER OF RXOHENABLE OUTPUT PULSES
THE OVERHEAD BIT BEING OUTPUT BY THE
XRT72L53
0 (Clock edge is coincident with RxOHFrame being detected “High”)
FA1 Byte - Bit 7
1
FA1 Byte - Bit 6
2
FA1 Byte - Bit 5
3
FA1 Byte - Bit 4
4
FA1 Byte - Bit 3
5
FA1 Byte - Bit 2
6
FA1 Byte - Bit 1
7
FA1 Byte - Bit 0
8
FA2 Byte - Bit 7
9
FA2 Byte - Bit 6
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XRT72L53
THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
áç
PRELIMINARY
REV. P1.1.8
TABLE 91: THE RELATIONSHIP BETWEEN THE NUMBER OF RXOHENABLE OUTPUT PULSES (SINCE RXOHFRAME WAS
LAST SAMPLED "HIGH") TO THE E3 OVERHEAD BIT, THAT IS BEING OUTPUT VIA THE RXOH OUTPUT PIN
NUMBER OF RXOHENABLE OUTPUT PULSES
THE OVERHEAD BIT BEING OUTPUT BY THE
XRT72L53
10
FA2 Byte - Bit 5
11
FA2 Byte - Bit 4
12
FA2 Byte - Bit 3
13
FA2 Byte - Bit 2
14
FA2 Byte - Bit 1
15
FA2 Byte - Bit 0
16
EM Byte - Bit 7
17
EM Byte - Bit 6
18
EM Byte - Bit 5
19
EM Byte - Bit 4
20
EM Byte - Bit 3
21
EM Byte - Bit 2
22
EM Byte - Bit 1
23
EM Byte - Bit 0
24
TR Byte - Bit 7
25
TR Byte - Bit 6
26
TR Byte - Bit 5
27
TR Byte - Bit 4
28
TR Byte - Bit 3
29
TR Byte - Bit 2
30
TR Byte - Bit 1
31
TR Byte - Bit 0
32
MA Byte - Bit 7
33
MA Byte - Bit 6
34
MA Byte - Bit 5
35
MA Byte - Bit 4
36
MA Byte - Bit 3
37
MA Byte - Bit 2
38
MA Byte - Bit 1
39
MA Byte - Bit 0
40
NR Byte - Bit 7
437
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XRT72L53
THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. P1.1.8
TABLE 91: THE RELATIONSHIP BETWEEN THE NUMBER OF RXOHENABLE OUTPUT PULSES (SINCE RXOHFRAME WAS
LAST SAMPLED "HIGH") TO THE E3 OVERHEAD BIT, THAT IS BEING OUTPUT VIA THE RXOH OUTPUT PIN
NUMBER OF RXOHENABLE OUTPUT PULSES
THE OVERHEAD BIT BEING OUTPUT BY THE
XRT72L53
41
NR Byte - Bit 6
42
NR Byte - Bit 5
43
NR Byte - Bit 4
44
NR Byte - Bit 3
45
NR Byte - Bit 2
46
NR Byte - Bit 1
47
NR Byte - Bit 0
48
GC Byte - Bit 7
49
GC Byte - Bit 6
50
GC Byte - Bit 5
51
GC Byte - Bit 4
52
GC Byte - Bit 3
53
GC Byte - Bit 2
54
GC Byte - Bit 1
55
GC Byte - Bit 0
Figure 207 presents the typical behavior of the Receive Overhead Data Output Interface block, when
Method 2 is being used to sample the incoming E3
overhead bits.
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XRT72L53
THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. P1.1.8
FIGURE 207. ILLUSTRATION OF THE SIGNALS THAT ARE OUTPUT VIA THE RECEIVE OVERHEAD DATA OUTPUT INTERMETHOD 2).
FACE BLOCK (FOR
RxOutClk
RxOHEnable
Recommended
Sampling
Edges
RxOHFrame
RxOH
6.3.5
face
Payload Bit 4239
FA1, Bit 7
The Receive Payload Data Output Inter-
FA1, Bit 6
FA1, Bit 5
FA1, Bit 4
Figure 208presents a simple illustration of the Receive Payload Data Output Interface block.
439
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XRT72L53
THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. P1.1.8
FIGURE 208. A SIMPLE ILLUSTRATION OF THE RECEIVE PAYLOAD DATA OUTPUT INTERFACE BLOCK
RxOHInd
RxSer
RxNib[3:0]
RxClk
Receive
ReceivePayload
Payload
Data
Output
Data Output
Interface
Interface
From Receive E3
Framer Block
RxOutClk
RxFrame
Each of the output pins of the Receive Payload Data
Output Interface block are listed in Table 92 and described below. The exact role that each of these out-
put pins assume, for a variety of operating scenarios
are described throughout this section.
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XRT72L53
THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
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PRELIMINARY
REV. P1.1.8
TABLE 92: LISTING AND DESCRIPTION OF THE PIN ASSOCIATED WITH THE RECEIVE PAYLOAD DATA OUTPUT
INTERFACE BLOCK
SIGNAL NAME
TYPE
DESCRIPTION
RxSer
Output
Receive Serial Payload Data Output pin:
If the user opts to operate the XRT72L53 in the serial mode, then the chip will output the payload data, of the incoming E3 frames, via this pin. The XRT72L53 will output this data upon the
rising edge of RxClk.
The user is advised to design the Terminal Equipment such that it will sample this data on the
falling edge of RxClk.
NOTE: This signal is only active if the NibInt input pin is pulled "Low".
RxNib[3:0]
Output
Receive Nibble-Parallel Payload Data Output pins:
If the user opts to operate the XRT72L53 in the nibble-parallel mode, then the chip will output
the payload data, of the incoming E3 frames, via these pins. The XRT72L53 will output data
via these pins, upon the falling edge of the RxClk output pin.
The user is advised to design the Terminal Equipment such that it will sample this data upon
the rising edge of RxClk.
NOTE: These pins are only active if the NibInt input pin is pulled "High".
RxClk
Output
Receive Payload Data Output Clock pin:
The exact behavior of this signal depends upon whether the XRT72L53 is operating in the
Serial or in the Nibble-Parallel-Mode.
Serial Mode Operation
In the serial mode, this signal is a 34.368MHz clock output signal. The Receive Payload Data
Output Interface will update the data via the RxSer output pin, upon the rising edge of this
clock signal.
The user is advised to design (or configure) the Terminal Equipment to sample the data on the
RxSer pin, upon the falling edge of this clock signal.
Nibble-Parallel Mode Operation
In this Nibble-Parallel Mode, the XRT72L53 will derive this clock signal, from the RxLineClk
signal. The XRT72L53 will pulse this clock 1060 times for each Inbound E3 frame. The
Receive Payload Data Output Interface will update the data, on the RxNib[3:0] output pins
upon the falling edge of this clock signal.
The user is advised to design (or configure) the Terminal Equipment to sample the data on the
RxNib[3:0] output pins, upon the rising edge of this clock signal
RxOHInd
Output
Receive Overhead Bit Indicator Output:
This output pin will pulse "High" whenever the Receive Payload Data Output Interface outputs
an overhead bit via the RxSer output pin. The purpose of this output pin is to alert the Terminal
Equipment that the current bit, (which is now residing on the RxSer output pin), is an overhead
bit and should not be processed by the Terminal Equipment.
The XRT72L53 will update this signal, upon the rising edge of RxOHInd.
The user is advised to design (or configure) the Terminal Equipment to sample this signal
(along with the data on the RxSer output pin) on the falling edge of the RxClk signal.
NOTE: For E3 applications, this output pin is only active if the XRT72L53 is operating in the
Serial Mode. This output pin will be "Low" if the device is operating in the Nibble-Parallel Mode.
RxFrame
Output
Receive Start of Frame Output Indicator:
The exact behavior of this pin, depends upon whether the XRT72L53 has been configured to
operate in the Serial Mode or the Nibble-Parallel Mode.
Serial Mode Operation:
The Receive Section of the XRT72L53 will pulse this output pin "High" (for one bit period)
when the Receive Payload Data Output Interface block is driving the very first bit (or Nibble) of
a given E3 frame, onto the RxSer output pin.
Nibble-Parallel Mode Operation:
The Receive Section of the XRT72L53 will pulse this output pin "High" for one nibble period,
when the Receive Payload Data Output Interface is driving the very first nibble of a given E3
frame, onto the RxNib[3:0] output pins.
441
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XRT72L53
THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. P1.1.8
Operation of the Receive Payload Data Output Interface block
The XRT72L53 will output the payload data, of the incoming E3 frames, upon the rising edge of RxClk.
The Receive Payload Data Output Interface permits
the user to read out the payload data of Inbound E3
frames, via either of the following modes.
Delineation of Inbound DS3 Frames
The XRT72L53 will pulse the RxFrame output pin
"High" for one bit-period, coincident with it driving the
first bit within a given E3 frame, via the RxSer output
pin.
• Serial Mode
• Nibble-Parallel Mode
Each of these modes are described in detail, below.
6.3.5.1 Serial Mode Operation Behavior of the
XRT72L53
If the XRT72L53 has been configured to operate in
this mode, then the XRT72L53 will behave as follows.
Payload Data Output
Interfacing the XRT72L53 to the Receive Terminal
Equipment
Figure 209 presents a simple illustration as how the
user should interface the XRT72L53 to that terminal
equipment which processes Receive Direction payload data.
FIGURE 209. ILLUSTRATION OF THE RECEIVE PAYLOAD DATA OUTPUT INTERFACE BLOCK (OF THE XRT72L53
DS3/E3 FRAMER IC) BEING INTERFACED TO THE RECEIVE TERMINAL EQUIPMENT (SERIAL MODE OPERATION)
Rx_E3_Clock_In
34.368 MHz Clock Signal
34.368 MHz
Clock Source
RxClk
RxSer
E3_Data_In
RxLineClk
RxFrame
Rx_Start_of_Frame
RxOHInd
Rx_E3_OH_Ind
Terminal Equipment
(Receive Payload Section)
XRT72L5x E3 Framer
Required Operation of the Terminal Equipment
The XRT72L53 will update the data on the RxSer output pin, upon the rising edge of RxClk. Hence, the
Terminal Equipment should sample the data on the
RxSer output pin (or the E3_Data_In pin at the Terminal Equipment) upon the rising edge of RxClk. As the
Terminal Equipment samples RxSer with each rising
edge of RxClk it should also be sampling the following signals.
• RxFrame
• RxOHInd
The Need for sampling RxFrame
The XRT72L53 will pulse the RxFrame output pin
"High" coincident with it driving the very first bit of a
given E3 frame onto the RxSer output pin. If knowledge of the E3 Frame Boundaries is important for the
operation of the Terminal Equipment, then this is a
very important signal for it to sample.
The Need for sampling RxOHInd
The XRT72L53 will indicate that it is currently driving
an overhead bit onto the RxSer output pin, by pulsing
the RxOHInd output pin "High". If the Terminal Equipment samples this signal "High", then it should know
that the bit, that it is currently sampling via the RxSer
pin is an overhead bit and should not be processed.
The Behavior of the Signals between the Receive
Payload Data Output Interface block and the Terminal Equipment
The behavior of the signals between the XRT72L53
and the Terminal Equipment for E3 Serial Mode Operation is illustrated in Figure 210.
442
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XRT72L53
THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. P1.1.8
FIGURE 210. AN ILLUSTRATION OF THE BEHAVIOR OF THE SIGNALS BETWEEN THE RECEIVE PAYLOAD DATA OUTPUT INTERFACE BLOCK OF THE XRT72L53 AND THE TERMINAL EQUIPMENT
Terminal Equipment Signals
E3_Clock_In
E3_Data_In
Payload[1522]
Payload[1523]
FAS, Bit 9
FAS, Bit 8
FAS, Bit 9
FAS, Bit 8
Rx_Start_of_Frame
E3_Overhead_Ind
XRT72L5x Receive Payload Data I/F Signals
RxClk
RxSer
Payload[1532]
Payload[1533]
RxFrame
RxOH_Ind
E3 Frame Number N
E3 Frame Number N + 1
Note: RxFrame pulses high to denote
E3 Frame Boundary.
Note: FAS, A and N-Bits will not be processed by the
Transmit Payload Data Input Interface.
Note: RxOH_Ind pulses high to
denote Overhead Data
(e.g., the FAS, A and N bits).
2. Unlike Serial Mode operation, the duty cycle of
RxClk, in Nibble-Parallel Mode operation is approximately 25%.
6.3.5.2 Nibble-Parallel Mode Operation Behavior of the XRT72L53
If the XRT72L53 has been configured to operate in
the Nibble-Parallel Mode, then the XRT72L53 will behave as follows.
Delineation of Inbound DS3 Frames
Payload Data Output
The XRT72L53 will output the payload data of the incoming E3 frames, via the RxNib[3:0] output pins, upon the rising edge of RxClk.
NOTES:
1. In this case, RxClk will function as the Nibble Clock
signal between the XRT72L53 the Terminal Equipment. The XRT72L53 will pulse the RxClk output
signal "High" 1060 times, for each Inbound E3
frame.
The XRT72L53 will pulse the RxFrame output pin
"High" for one nibble-period coincident with it driving
the very first nibble, within a given Inbound E3 frame,
via the RxNib[3:0] output pins.
Interfacing the XRT72L53 the Terminal Equipment.
Figure 211 presents a simple illustration as how the
user should interface the XRT72L53 to that terminal
equipment which processes Receive Direction payload data.
443
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XRT72L53
THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. P1.1.8
FIGURE 211. ILLUSTRATION OF THE XRT72L53 DS3/E3 FRAMER IC BEING INTERFACED TO THE RECEIVE SECTION
TERMINAL EQUIPMENT (NIBBLE-MODE OPERATION)
OF THE
34.368 MHz
Clock Source
8.592 MHz Clock Signal
Rx_E3_Clock_In
RxClk
RxNib[3:0]
E3_Data_In[3:0]
RxLineClk
RxFrame
Rx_Start_of_Frame
Rx_E3_OH_Ind
RxOH_Ind
Terminal Equipment
(Receive Payload Section)
XRT72L5x E3 Framer
Required Operation of the Terminal Equipment
The XRT72L53 will update the data on the RxNib[3:0]
line, upon the rising edge of RxClk. Hence, the Terminal Equipment should sample the data on the RxNib[3:0] output pins (or the E3_Data_In[3:0] input
pins at the Terminal Equipment) upon the rising edge
of RxClk. As the Terminal Equipment samples RxSer
with each rising edge of RxClk it should also be sampling the RxFrame signal.
The Need for Sampling RxFrame
The XRT72L53 will pulse the RxFrame output pin
"High" coincident with it driving the very first nibble of
a given E3 frame, onto the RxNib[3:0] output pins. If
knowledge of the E3 Frame Boundaries is important
for the operation of the Terminal Equipment, then this
is a very important signal for it to sample.
The Behavior of the Signals between the Receive
Payload Data Output Interface block and the Terminal Equipment
The behavior of the signals between the XRT72L53
and the Terminal Equipment for E3 Nibble-Mode operation is illustrated in Figure 212.
444
XRT72L53
THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
áç
PRELIMINARY
REV. P1.1.8
FIGURE 212. ILLUSTRATION OF THE SIGNALS THAT ARE OUTPUT VIA THE RECEIVE OVERHEAD DATA OUTPUT INTERMETHOD 2).
FACE BLOCK (FOR
Terminal Equipment Signals
RxOutClk
Rx_E3_Clock_In
E3_Data_In[3:0]
Overhead Nibble [0]
Overhead Nibble [1]
Rx_Start_of_Frame
Rx_E3_OH_Ind
XRT72L5x Receive Payload Data I/F Signals
RxOutClk
RxClk
RxNib[3:0]
Overhead Nibble [0]
Overhead Nibble [1]
RxFrame
RxOH_Ind
E3 Frame Number N
E3 Frame Number N + 1
Note: RxFrame pulses high to denote
E3 Frame Boundary.
Recommended Sampling Edge of Terminal
Equipment
6.3.6 Receive Section Interrupt Processing
The Receive Section of the XRT72L53 can generate
an interrupt to the MIcrocontroller/Microprocessor for
the following reasons.
• Change in Receive LOS Condition
• Change in Receive OOF Condition
• Change in Receive LOF Condition
• Change in Receive AIS Condition
• Change in Receive FERF Condition
• Change of Framing Alignment
• Change in Receive Trail Trace Buffer Message
• Detection of FEBE (Far-End Block Error) Event
• Detection of BIP-8 Error
• Detection of Framing Byte Error
• Reception of a new LAPD Message
6.3.6.1 Enabling Receive Section Interrupts
As mentioned in Section 1.6, the Interrupt Structure
within the XRT72L53 contains two hierarchical levels.
• Block Level
• Source Level
The Block Level
The Enable state of the Block level for the Receive
Section Interrupts dictates whether or not interrupts
(if enabled at the source level), are actually enabled.
The user can enable or disable these Receive Section interrupts, at the Block Level by writing the appropriate data into Bit 7 (Rx DS3/E3 Interrupt Enable)
within the Block Interrupt Enable register (Address =
0x04), as illustrated below.
• Detection of Payload Type Mismatch
445
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XRT72L53
THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. P1.1.8
BLOCK INTERRUPT ENABLE REGISTER (ADDRESS = 0X04)
BIT 7
BIT 6
BIT 5
RxDS3/E3
Interrupt
Enable
BIT 4
BIT 3
BIT 2
Not Used
BIT 1
BIT 0
TxDS3/E3
Interrupt
Enable
One-Second
Interrupt
Enable
R/W
RO
RO
RO
RO
RO
R/W
R/W
X
0
0
0
0
0
0
0
• If the XRT7300 LIU IC declares an LOS condition,
and drives the RLOS input pin (of the XRT72L53
Framer IC) “High”.
Setting this bit-field to “1” enables the Receive Section at the Block Level) for interrupt generation. Conversely, setting this bit-field to “0” disables the Receive Section for interrupt generation.
6.3.6.2 Enabling/Disabling and Servicing Interrupts
As mentioned earlier, the Receive Section of the
XRT72L53 Framer IC contains numerous interrupts.
The Enabling/Disabling and Servicing of each of
these interrupts is described below.
6.3.6.2.1 The Change in Receive LOS Condition Interrupt
If the Change in Receive LOS Condition Interrupt is
enabled, then the XRT72L53 Framer IC will generate
an interrupt in response to either of the following conditions.
1. When the XRT72L53 Framer IC declares an LOS
(Loss of Signal) Condition, and
2. When the XRT72L53 Framer IC clears the LOS
condition.
Conditions causing the XRT72L53 Framer IC to
declare an LOS Condition.
• If the XRT72L53 Framer IC detects 32 consecutive
“0”, via the RxPOS and RxNEG input pins.
Conditions causing the XRT72L53 Framer IC to
clear the LOS Condition.
• If the XRT7300 LIU IC clears the LOS condition and
drives the RLOS input pin (of the XRT72L53
Framer IC) “Low”.
• If the XRT72L53 Framer IC detects a string of 32
consecutive bits (via the RxPOS and RxNEG input
pins) that does NOT contain a string of 4 consecutive “0’s”.
Enabling and Disabling the Change in Receive
LOS Condition Interrupt
The user can enable or disable the Change in Receive LOS Condition Interrupt, by writing the appropriate value into Bit 1 (LOS Interrupt Enable), within
the RxE3 Interrupt Enable Register - 1, as indicated
below.
RXE3 INTERRUPT ENABLE REGISTER - 1 (ADDRESS = 0X12)
BIT 7
BIT 6
BIT 5
Not Used
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
COFA
Interrupt
Enable
OOF
Interrupt
Enable
LOF
Interrupt
Enable
LOS
Interrupt
Enable
AIS
Interrupt
Enable
RO
RO
RO
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
X
0
Setting this bit-field to “1” enables this interrupt. Conversely, setting this bit-field to “0” disables this interrupt.
Servicing the Change in Receive LOS Condition
Interrupt
• It will assert the Interrupt Request output pin (INT),
by driving it “Low”.
• It will set Bit 1 (LOS Interrupt Status), within the Rx
E3 Interrupt Status Register - 1 to “1”, as indicated
below.
Whenever the XRT72L53 Framer IC detects this interrupt, it will do all of the following.
446
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XRT72L53
THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. P1.1.8
RXE3 INTERRUPT STATUS REGISTER - 1 (ADDRESS = 0X14)
BIT 7
BIT 6
BIT 5
Not Used
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
COFA
Interrupt
Status
OOF
Interrupt
Status
LOF
Interrupt
Status
LOS
Interrupt
Status
AIS
Interrupt
Status
RO
RO
RO
RUR
RUR
RUR
RUR
RUR
0
0
0
0
0
0
1
0
Whenever the user’s system encounters the Change
in Receive LOS Condition Interrupt, then it should do
the following.
declares or clears the LOS defect. Hence, the
user can determine the current state of the LOS
defect by reading the state of Bit 4 (RxLOS)
within the Rx E3 Configuration and Status Register - 2, as illustrated below.
1. It should determine the current state of the LOS
condition. Recall, that this interrupt can be generated, whenever the XRT72L53 Framer IC
RXE3 CONFIGURATION & STATUS REGISTER 2 (ADDRESS = 0X11)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
Rx LOF Algo
RxLOF
RxOOF
RxLOS
RxAIS
RxPld Unstab
Rx
TMark
RxFERF
R/W
RO
RO
RO
RO
RO
RO
RO
X
X
X
X
X
X
X
X
Conditions causing the XRT72L53 Framer IC to
declare an OOF Condition.
If the LOS state is TRUE
1. It should transmit a FERF (Far-End-Receive Failure) indicator to the Remote Terminal Equipment.
The XRT72L53 Framer IC automatically supports
this action via the FERF-upon-LOS feature.
If the LOS state is FALSE
• If the Receive E3 Framer block (within the
XRT72L53 Framer IC) detects Framing Byte errors,
within four consecutive incoming E3 frames.
Conditions causing the XRT72L53 Framer IC to
clear the OOF Condition.
1. It should cease transmitting the FERF indication
to the Remote Terminal Equipment. The
XRT72L53 Framer IC automatically supports this
action via the FERF-upon-LOS feature.
6.3.6.2.2 The Change in Receive OOF Condition Interrupt
If the Change in Receive OOF Condition Interrupt is
enabled, then the XRT72L53 Framer IC will generate
an interrupt in response to either of the following conditions.
1. When the XRT72L53 Framer IC declares an OOF
(Out of Frame) Condition, and
2. When the XRT72L53 Framer IC clears the OOF
condition.
• If the Receive E3 Framer block (within the
XRT72L53 Framer IC) transitions from the FA1,
FA2 Octet Verification state to the In-Frame state
(see Figure 175).
• If the Receive E3 Framer block transitions from the
OOF Condition state to the In-Frame state (see Figure 175).
Enabling and Disabling the Change in Receive
OOF Condition Interrupt
The user can enable or disable the Change in Receive OOF Condition Interrupt, by writing the appropriate value into Bit 3 (OOF Interrupt Enable), within
447
áç
XRT72L53
THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. P1.1.8
the RxE3 Interrupt Enable Register - 1, as indicated
below.
RXE3 INTERRUPT ENABLE REGISTER - 1 (ADDRESS = 0X12)
BIT 7
BIT 6
BIT 5
Not Used
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
COFA
Interrupt
Enable
OOF
Interrupt
Enable
LOF
Interrupt
Enable
LOS
Interrupt
Enable
AIS
Interrupt
Enable
RO
RO
RO
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
X
0
• It will assert the Interrupt Request output pin (INT),
by driving it “Low”.
Setting this bit-field to “1” enables this interrupt. Conversely, setting this bit-field to “0” disables this interrupt.
• It will set Bit 3 (OOF Interrupt Status), within the Rx
E3 Interrupt Status Register - 1 to “1”, as indicated
below.
Servicing the Change in Receive OOF Condition
Interrupt
Whenever the XRT72L53 Framer IC detects this interrupt, it will do all of the following.
RXE3 INTERRUPT STATUS REGISTER - 1 (ADDRESS = 0X14)
BIT 7
BIT 6
BIT 5
Not Used
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
COFA
Interrupt
Status
OOF
Interrupt
Status
LOF
Interrupt
Status
LOS
Interrupt
Status
AIS
Interrupt
Status
RO
RO
RO
RUR
RUR
RUR
RUR
RUR
0
0
0
0
0
0
1
0
declares or clears the OOF defect. Hence, the
user can determine the current state of the LOS
defect by reading the state of Bit 5 (RxOOF)
within the Rx E3 Configuration and Status Register - 2, as illustrated below.
Whenever the user’s system encounters the Change
in Receive OOF Condition Interrupt, then it should do
the following.
1. It should determine the current state of the OOF
condition. Recall, that this interrupt can be generated, whenever the XRT72L53 Framer IC
RXE3 CONFIGURATION & STATUS REGISTER 2 (ADDRESS = 0X11)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
Rx LOF Algo
RxLOF
RxOOF
RxLOS
RxAIS
RxPld Unstab
Rx
TMark
RxFERF
R/W
RO
RO
RO
RO
RO
RO
RO
X
X
X
X
X
X
X
X
If the OOF state is TRUE
1. It should transmit a FERF (Far-End-Receive Failure) indicator to the Remote Terminal Equipment.
The XRT72L53 Framer IC automatically supports
this action via the FERF-upon-OOF feature.
If the OOF state is FALSE
1. It should cease transmitting the FERF indication
to the Remote Terminal Equipment. The
XRT72L53 Framer IC automatically supports this
action via the FERF-upon-OOF feature.
6.3.6.2.3 The Change in Receive LOF Condition Interrupt
If the Change in Receive LOF Condition Interrupt is
enabled, then the XRT72L53 Framer IC will generate
an interrupt in response to either of the following conditions.
448
áç
XRT72L53
THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. P1.1.8
1. When the XRT72L53 Framer IC declares an LOF
(Out of Frame) Condition, and
2. When the XRT72L53 Framer IC clears the LOF
condition.
Conditions causing the XRT72L53 Framer IC to
declare an LOF Condition.
• If the Receive E3 Framer block (within the
XRT72L53 Framer IC) detects Framing Byte errors,
within four consecutive incoming E3 frames and is
not able to transition back into the In-Frame state
within 1 or 3ms.
Conditions causing the XRT72L53 Framer IC to
clear the LOF Condition.
• If the Receive E3 Framer block transitions from the
OOF Condition state to the LOF Condition state
(see Figure 175).
• If the Receive E3 Framer block transitions back into
the In-Frame state.
Enabling and Disabling the Change in Receive
LOF Condition Interrupt
The user can enable or disable the Change in Receive LOF Condition Interrupt, by writing the appropriate value into Bit 3 (LOF Interrupt Enable), within the
RxE3 Interrupt Enable Register - 1, as indicated below.
RXE3 INTERRUPT ENABLE REGISTER - 1 (ADDRESS = 0X12)
BIT 7
BIT 6
BIT 5
Not Used
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
COFA
Interrupt
Enable
OOF
Interrupt
Enable
LOF
Interrupt
Enable
LOS
Interrupt
Enable
AIS
Interrupt
Enable
RO
RO
RO
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
X
0
Setting this bit-field to “1” enables this interrupt. Conversely, setting this bit-field to “0” disables this interrupt.
Servicing the Change in Receive LOF Condition
Interrupt
• It will assert the Interrupt Request output pin (INT),
by driving it “Low”.
• It will set Bit 6 (LOF Interrupt Status), within the Rx
E3 Interrupt Status Register - 1 to “1”, as indicated
below.
Whenever the XRT72L53 Framer IC detects this interrupt, it will do all of the following.
RXE3 CONFIGURATION & STATUS REGISTER 2 (ADDRESS = 0X11)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
Rx LOF Algo
RxLOF
RxOOF
RxLOS
RxAIS
RxPld Unstab
Rx
TMark
RxFERF
R/W
RO
RO
RO
RO
RO
RO
RO
X
X
X
X
X
X
X
X
6.3.6.2.4 The Change of Framing Alignment
(COFA) Interrupt
If the Change of Framing Alignment Interrupt is enabled then the XRT72L53 Framer IC will generate an
interrupt any time the Receive E3 Framer block detects an abrupt change of framing alignment.
NOTE: This interrupt is typically accompanied with the
Change in Receive OOF Condition interrupt as well.
Conditions causing the XRT72L53 Framer IC to
generate this interrupt.
If the XRT72L53 Framer detects receives at least four
consecutive E3 frames, within its Framing Alignment
bytes in Error, then the XRT72L53 Framer IC will de-
clare an OOF condition. However, while the
XRT72L53 Framer IC is operating in the OOF condition, it will still rely on the old framing alignment for E3
payload data extraction, etc.
However, if the Receive E3 Framer had to change
alignment, in order to re-acquire frame synchronization, then this interrupt will occur.
Enabling and Disabling the Change of Framing
Alignment Interrupt
The user can enable or disable the Change of Framing Alignment Interrupt by writing the appropriate value into Bit 4 (COFA Interrupt
449
áç
XRT72L53
THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. P1.1.8
RXE3 INTERRUPT ENABLE REGISTER - 1 (ADDRESS = 0X12)
BIT 7
BIT 6
BIT 5
Not Used
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
COFA
Interrupt
Enable
OOF
Interrupt
Enable
LOF
Interrupt
Enable
LOS
Interrupt
Enable
AIS
Interrupt
Enable
RO
RO
RO
R/W
R/W
R/W
R/W
R/W
0
0
0
X
0
0
0
0
• It will assert the Interrupt Request output pin (INT)
by driving it “Low”.
Writing a “1” into this bit-field enables the Change of
Framing Alignment Interrupt. Conversely, writing a “0”
into this bit-field disables the Change of Framing
Alignment Interrupt.
• It will set Bit 4 (COFA Interrupt Status), within the
Rx E3 Interrupt Status Register -2, to “1”, as indicated below.
Servicing the Change of Framing Alignment Interrupt
Whenever the XRT72L53 Framer IC generates this
interrupt, it will do the following.
RXE3 INTERRUPT STATUS REGISTER - 1 (ADDRESS = 0X14)
BIT 7
BIT 6
BIT 5
Not Used
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
COFA
Interrupt
Status
OOF
Interrupt
Status
LOF
Interrupt
Status
LOS
Interrupt
Status
AIS
Interrupt
Status
RO
RO
RO
RUR
RUR
RUR
RUR
RUR
0
0
0
1
0
0
0
0
6.3.6.2.5 The Change in Receive AIS Condition
Interrupt
If the Change in Receive AIS Condition Interrupt is
enabled, then the XRT72L53 Framer IC will generate
an interrupt in response to either of the following conditions.
1. When the XRT72L53 Framer IC declares an AIS
(Loss of Signal) Condition, and
2. When the XRT72L53 Framer IC clears the AIS
condition.
Conditions causing the XRT72L53 Framer IC to
declare an AIS Condition.
• If the XRT72L53 Framer IC detects 7 or less “0”
within 2 consecutive E3 frames.
Conditions causing the XRT72L53 Framer IC to
clear the AIS Condition.
• If the XRT72L53 Framer IC detects 2 consecutive
E3 frames that each contain 8 or more “0’s”.
Enabling and Disabling the Change in Receive
AIS Condition Interrupt
The user can enable or disable the Change in Receive LOS Condition Interrupt, by writing the appropriate value into Bit 0 (AIS Interrupt Enable), within
the RxE3 Interrupt Enable Register - 1, as indicated
below.
RXE3 INTERRUPT ENABLE REGISTER - 1 (ADDRESS = 0X12)
BIT 7
BIT 6
BIT 5
Not Used
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
COFA
Interrupt
Enable
OOF
Interrupt
Enable
LOF
Interrupt
Enable
LOS
Interrupt
Enable
AIS
Interrupt
Enable
RO
RO
RO
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
X
0
Setting this bit-field to “1” enables this interrupt. Conversely, setting this bit-field to “0” disables this inter-
rupt.
450
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XRT72L53
THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. P1.1.8
Servicing the Change in Receive AIS Condition
Interrupt
• It will assert the Interrupt Request output pin (INT),
by driving it “Low”.
Whenever the XRT72L53 Framer IC detects this interrupt, it will do all of the following.
• It will set Bit 0 (AIS Interrupt Status), within the Rx
E3 Interrupt Status Register - 1 to “1”, as indicated
below.
RXE3 INTERRUPT STATUS REGISTER - 1 (ADDRESS = 0X14)
BIT 7
BIT 6
BIT 5
Not Used
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
COFA
Interrupt
Status
OOF
Interrupt
Status
LOF
Interrupt
Status
LOS
Interrupt
Status
AIS
Interrupt
Status
RO
RO
RO
RUR
RUR
RUR
RUR
RUR
0
0
0
0
0
0
1
0
declares or clears the AIS defect. Hence, the
user can determine the current state of the AIS
defect by reading the state of Bit 4 (RxAIS) within
the Rx E3 Configuration and Status Register - 2,
as illustrated below.
Whenever the user’s system encounters the Change
in Receive AIS Condition Interrupt, then it should do
the following.
1. It should determine the current state of the AIS
condition. Recall, that this interrupt can be generated, whenever the XRT72L53 Framer IC
RXE3 CONFIGURATION & STATUS REGISTER 2 (ADDRESS = 0X11)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
Rx LOF Algo
RxLOF
RxOOF
RxLOS
RxAIS
RxPld Unstab
Rx
TMark
RxFERF
R/W
RO
RO
RO
RO
RO
RO
RO
X
X
X
X
X
X
X
X
If the AIS Condition is TRUE
1. It should begin transmitting the FERF indication
to the Remote Terminal Equipment. The
XRT72L53 Framer IC automatically supports this
action via the FERF-upon-AIS feature.
If the AIS Condition is FALSE
2. It should cease transmitting the FERF indication
to the Remote Terminal Equipment. The
XRT72L53 Framer IC automatically supports this
action via the FERF-upon-AIS feature.
6.3.6.2.6 The Change in Trail Trace Buffer Message Interrupt
If the Change in Trail Trace Buffer Message Interrupt
has been enabled, then the XRT72L53 Framer IC will
generate an interrupt any time the Receive E3 Framer
block receives a different Trail Trace Buffer message,
then it has previously read in.
Enabling and Disabling the Change in Trail Trace
Buffer Message Interrupt.
The user can enable or disable the Change in Trail
Trace Buffer Message interrupt by writing the appropriate value into Bit 6 (TTB Change Interrupt Enable)
within the Rx E3 Interrupt Enable Register - 2, as indicated below.
RXE3 INTERRUPT ENABLE REGISTER - 2 (ADDRESS = 0X13)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
Not Used
TTB
Change
Interrupt
Enable
Not Used
FEBE
Interrupt
Enable
FERF
Interrupt
Enable
BIP-8
Error Interrupt
Enable
Framing
Byte Error
Interrupt
Enable
RxPld
Mis
Interrupt
Enable
RO
R/W
RO
R/W
R/W
R/W
R/W
R/W
0
0
0
0
X
0
0
0
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áç
XRT72L53
THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. P1.1.8
Writing a “1” into this bit-field enables the Change in
Trail Trace Buffer Message Interrupt. Conversely, writing a “0” into this bit-field disables the Change in Trail
Trace Buffer Message Interrupt.
Whenever the XRT72L53 Framer IC generates this
interrupt, it will do the following.
Servicing the Change in Trail Trace Buffer Message Interrupt
• It will set Bit 6 (TTB Change Interrupt Status),
within the Rx E3 Interrupt Status Register - 2, as
indicated below.
• It will assert the Interrupt Request output pin (INT)
by driving it “Low”.
RXE3 INTERRUPT STATUS REGISTER - 2 (ADDRESS = 0X15)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
Not Used
TTB
Change
Interrupt
Status
Not Used
FEBE
Interrupt
Status
FERF
Interrupt
Status
BIP-8
Error Interrupt
Status
Framing
Byte Error
Interrupt
Status
RxPld
Mis
Interrupt
Status
RO
RUR
RO
RUR
RUR
RUR
RUR
RUR
0
1
0
0
0
0
0
0
Conditions causing the XRT72L53 Framer IC to
declare an FERF Condition.
• It will write the contents of this newly received Trail
Trace Buffer Message, into the RxTTB-0 (located at
0x1C) through RxTTB-15 (located at 0x2B) registers.
Whenever the Terminal Equipment encounters the
Change in Trail Trace Buffer Message Interrupt, then
it should read out the contents of the 16 RxTTB registers.
6.3.6.2.7 The Change in Receive FERF Condition Interrupt
If the Change in Receive FERF Condition Interrupt is
enabled, then the XRT72L53 Framer IC will generate
an interrupt in response to either of the following conditions.
1. When the XRT72L53 Framer IC declares a FERF
(Far-End Receive Failure) Condition, and
2. When the XRT72L53 Framer IC clears the FERF
condition.
• If the XRT72L53 Framer IC begins receiving E3
frames which have the FERF bit (within the MA
byte, set to “1”).
Conditions causing the XRT72L53 Framer IC to
clear the AIS Condition.
• If the XRT72L53 Framer IC begins receiving E3
frames that do NOT have the FERF bit set to “1”.
Enabling and Disabling the Change in Receive
AIS Condition Interrupt
The user can enable or disable the Change in Receive FERF Condition Interrupt, by writing the appropriate value into Bit 3 (FERF Interrupt Enable), within
the RxE3 Interrupt Enable Register - 2, as indicated
below.
RXE3 INTERRUPT ENABLE REGISTER - 2 (ADDRESS = 0X13)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
Not Used
TTB
Change
Interrupt
Enable
Not Used
FEBE
Interrupt
Enable
FERF
Interrupt
Enable
BIP-8
Error Interrupt
Enable
Framing
Byte Error
Interrupt
Enable
RxPld
Mis
Interrupt
Enable
RO
R/W
RO
R/W
R/W
R/W
R/W
R/W
0
0
0
0
X
0
0
0
Setting this bit-field to “1” enables this interrupt. Conversely, setting this bit-field to “0” disables this interrupt.
Servicing the Change in Receive FERF Condition
Interrupt
Whenever the XRT72L53 Framer IC detects this interrupt, it will do all of the following.
• It will assert the Interrupt Request output pin (INT),
by driving it “Low”.It will set Bit 3 (FERF Interrupt
452
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XRT72L53
THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. P1.1.8
Status), within the Rx E3 Interrupt Status Register 2 to “1”, as indicated below
RXE3 INTERRUPT STATUS REGISTER - 2 (ADDRESS = 0X15)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
Not Used
TTB
Change
Interrupt
Status
Not Used
FEBE
Interrupt
Status
FERF
Interrupt
Status
BIP-8
Error Interrupt
Status
Framing
Byte Error
Interrupt
Status
RxPld
Mis
Interrupt
Status
RO
RUR
RO
RUR
RUR
RUR
RUR
RUR
0
0
0
0
1
0
0
0
declares or clears the FERF defect. Hence, the
user can determine the current state of the LOS
defect by reading the state of Bit 0 (RxFERF)
within the Rx E3 Configuration and Status Register - 2, as illustrated below.
Whenever the user’s system encounters the Change
in Receive FERF Condition Interrupt, then it should
do the following.
1. It should determine the current state of the FERF
condition. Recall, that this interrupt can be generated, whenever the XRT72L53 Framer IC
RXE3 CONFIGURATION & STATUS REGISTER 2 (ADDRESS = 0X11)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
Rx LOF Algo
RxLOF
RxOOF
RxLOS
RxAIS
RxPld Unstab
Rx
TMark
RxFERF
R/W
RO
RO
RO
RO
RO
RO
RO
X
X
X
X
X
X
X
X
6.3.6.2.8 The Detection of FEBE (Far-EndBlock Error) Event Interrupt
If the Detection of FEBE Event Interrupt is enabled,
then the XRT72L53 Framer IC will generate an interrupt, anytime the Receive E3 Framer block has received an E3 frame with the FEBE bit-field (within the
MA byte) set to “1”.
Enabling and Disabling the Detection of FEBE
Event Interrupt
The user can enable or disable the Detection of
FEBE Event’ interrupt by writing the appropriate value
into Bit 4 (FEBE Interrupt Enable) within the Rx E3 Interrupt Enable Register - 2, as indicated below.
RXE3 INTERRUPT ENABLE REGISTER - 2 (ADDRESS = 0X13)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
Not Used
TTB
Change
Interrupt
Enable
Not Used
FEBE
Interrupt
Enable
FERF
Interrupt
Enable
BIP-8
Error Interrupt
Enable
Framing
Byte Error
Interrupt
Enable
RxPld
Mis
Interrupt
Enable
RO
R/W
RO
R/W
R/W
R/W
R/W
R/W
0
0
0
X
X
0
0
0
Setting this bit-field to “1” enables this interrupt. Conversely, setting this bit-field to “0” disables this interrupt.
Servicing the Detection of the FEBE Event Interrupt
Whenever the XRT72L53 Framer IC detects this interrupt, it will do the following.
• It will assert the Interrupt Request output pin (INT),
by driving it “High”.It will set the Bit 4 (FEBE Interrupt Status), within the RxE3 Interrupt Status Register - 2 as indicated below.
453
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XRT72L53
THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. P1.1.8
RXE3 INTERRUPT STATUS REGISTER - 2 (ADDRESS = 0X15)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
Not Used
TTB
Change
Interrupt
Status
Not Used
FEBE
Interrupt
Status
FERF
Interrupt
Status
BIP-8
Error Interrupt
Status
Framing
Byte Error
Interrupt
Status
RxPld
Mis
Interrupt
Status
RO
RUR
RO
RUR
RUR
RUR
RUR
RUR
0
0
0
1
0
0
0
0
If the Detection of BIP-8 Error Interrupt is enabled,
then the XRT72L53 Framer IC will generate an interrupt, anytime the Receive E3 Framer block has detected an error in the EM (Error Monitoring) byte,
within an incoming E3 frame.
Whenever the Terminal Equipment encounters the
Detection of FEBE Event Interrupt, it should do the
following.
• It should read the contents of the PMON FEBE
Event Count Registers (located at Addresses 0x56
and 0x57) in order to determine the number of
FEBE Events that have been received by the
XRT72L53 Framer IC.
6.3.6.2.9
Enabling and Disabling the Detection of FEBE
Event Interrupt
The user can enable or disable the Detection of BIP-8
Error’ interrupt by writing the appropriate value into
Bit 2 (BIP-8 Interrupt Enable) within the Rx E3 Interrupt Enable Register - 2, as indicated below.
The Detection of BIP-8 Error Interrupt
RXE3 INTERRUPT ENABLE REGISTER - 2 (ADDRESS = 0X13)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
Not Used
TTB
Change
Interrupt
Enable
Not Used
FEBE
Interrupt
Enable
FERF
Interrupt
Enable
BIP-8
Error
Interrupt
Enable
Framing
Byte Error
Interrupt
Enable
RxPld
Mis
Interrupt
Enable
RO
R/W
RO
R/W
R/W
R/W
R/W
R/W
0
0
0
X
X
0
0
0
• It will assert the Interrupt Request output pin (INT),
by driving it “High”.
Setting this bit-field to “1” enables this interrupt. Conversely, setting this bit-field to “0” disables this interrupt.
• It will set the Bit 2 (BIP-8 Interrupt Status), within
the RxE3 Interrupt Status Register - 2 as indicated
below.
Servicing the Detection of the BIP-8 Error Interrupt
Whenever the XRT72L53 Framer IC detects this interrupt, it will do the following.
RXE3 INTERRUPT STATUS REGISTER - 2 (ADDRESS = 0X15)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
Not Used
TTB
Change
Interrupt
Status
Not Used
FEBE
Interrupt
Status
FERF
Interrupt
Status
BIP-8
Error
Interrupt
Status
Framing
Byte Error
Interrupt
Status
RxPld
Mis
Interrupt
Status
RO
RUR
RO
RUR
RUR
RUR
RUR
RUR
0
0
0
0
0
1
0
0
Whenever the Terminal Equipment encounters the
Detection of BIP-8 Error Interrupt, it should do the fol-
lowing.
454
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XRT72L53
THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. P1.1.8
• It should read the contents of the PMON Parity
Error Event Count Registers (located at Addresses
0x54 and 0x55) in order to determine the number of
BIP-8 Errors that have been received by the
XRT72L53 Framer IC.
received an E3 frame with an incorrect Framing Byte
(e.g., FA1 or FA2) value.
Enabling and Disabling the Detection of FEBE
Event Interrupt
The user can enable or disable the Detection of
Framing Byte Error’ interrupt by writing the appropriate value into Bit 1 (Framing Byte Error Interrupt Enable) within the Rx E3 Interrupt Enable Register - 2,
as indicated below.
6.3.6.2.10 The Detection of Framing Byte Error
Interrupt
If the Detection of Framing Byte Error Interrupt is enabled, then the XRT72L53 Framer IC will generate an
interrupt, anytime the Receive E3 Framer block has
RXE3 INTERRUPT ENABLE REGISTER - 2 (ADDRESS = 0X13)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
Not Used
TTB
Change
Interrupt
Enable
Not Used
FEBE
Interrupt
Enable
FERF
Interrupt
Enable
BIP-8
Error Interrupt
Enable
Framing
Byte Error
Interrupt
Enable
RxPld
Mis
Interrupt
Enable
RO
R/W
RO
R/W
R/W
R/W
R/W
R/W
0
0
0
X
X
0
0
0
• It will assert the Interrupt Request output pin (INT),
by driving it “High”.
Setting this bit-field to “1” enables this interrupt. Conversely, setting this bit-field to “0” disables this interrupt.
• It will set the Bit 4 (Framing Byte Error Interrupt Status), within the RxE3 Interrupt Status Register - 2
as indicated below.
Servicing the Detection of Framing Byte Error Interrupt
Whenever the XRT72L53 Framer IC detects this interrupt, it will do the following.
RXE3 INTERRUPT STATUS REGISTER - 2 (ADDRESS = 0X15)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
Not Used
TTB
Change
Interrupt
Status
Not Used
FEBE
Interrupt
Status
FERF
Interrupt
Status
BIP-8
Error Interrupt
Status
Framing
Byte Error
Interrupt
Status
RxPld
Mis
Interrupt
Status
RO
RUR
RO
RUR
RUR
RUR
RUR
RUR
0
0
0
1
0
0
0
0
Whenever the Terminal Equipment encounters the
Detection of Framing Byte Error Interrupt, it should do
the following.
contents a Payload Type value that is different from
the expected Payload Type value.
• It should read the contents of the PMON Framing
Bit/Byte Error Count Registers (located at
Addresses 0x52 and 0x53) in order to determine
the number of Framing Byte errors that have been
received by the XRT72L53 Framer IC.
During system configuration, the user is expected to
specify the Payload Type value that is expected of the
Receive E3 Framer to receive (within each E3 frame),
by writing this value into the RxPLDExp[2:0] bit-fields
within the Rx E3 Configuration & Status Register - 1,
as indicated below.
Conditions causing this interrupt to be generated.
6.3.6.2.11 The Detection of Payload Type Mismatch Interrupt
If the Detection of Payload Type Mismatch Interrupt is
enabled, then the XRT72L53 Framer IC will generate
an interrupt, anytime the Receive E3 Framer block receives a MA byte (within an incoming E3 frame) that
As long as the Receive E3 Framer block receives E3
frames that contains this Payload Type value, no interrupt will be generated. However, the instant that it
receives an E3 frame, that contains a different Pay-
455
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XRT72L53
THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. P1.1.8
load Type value, then the XRT72L53 Framer IC will
generate this interrupt.
RXE3 CONFIGURATION & STATUS REGISTER 1 (ADDRESS = 0X10)
BIT 7
BIT 6
BIT 5
RxPLDType[2:0]
BIT 4
BIT 3
RxFERF
Algo
RxTMark
Algo
BIT 2
BIT 1
BIT 0
RxPLDExp[2:0]
RO
RO
RO
RO
RO
R/W
R/W
R/W
0
0
0
0
0
0
0
0
Enabling and Disabling the Detection of Payload
Type Mismatch Interrupt.
The user can enable or disable the Detection of Payload Type Mismatch Interrupt by writing the appropri-
ate data into Bit 0 (RxPld Mis Interrupt Enable), within
the Rx E3 Interrupt Enable Register - 2, as indicated
below.
RXE3 INTERRUPT ENABLE REGISTER - 2 (ADDRESS = 0X13)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
Not Used
TTB
Change
Interrupt
Enable
Not Used
FEBE
Interrupt
Enable
FERF
Interrupt
Enable
BIP-8
Error Interrupt
Enable
Framing
Byte Error
Interrupt
Enable
RxPld
Mis
Interrupt
Enable
RO
R/W
RO
R/W
R/W
R/W
R/W
R/W
0
0
0
X
X
0
0
X
Setting this bit-field to “1 enables the Detection of
Payload Type Mismatch Interrupt. Conversely, setting
this bit-field to “0” disables the Detection of Payload
Type Mismatch Interrupt.
Whenever the XRT72L53 Framer IC generates this
interrupt, it will do the following.
Servicing the Detection of Payload Type Mismatch Interrupt
• It will set Bit 0 (RxPld Mis Interrupt Status), within
the Rx E3 Interrupt Enable Register -2 to “1”, as
indicated below.
• It will assert the Interrupt Request output pin (INT)
by driving it “Low”.
RXE3 INTERRUPT STATUS REGISTER - 2 (ADDRESS = 0X15)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
Not Used
TTB
Change
Interrupt
Status
Not Used
FEBE
Interrupt
Status
FERF
Interrupt
Status
BIP-8
Error Interrupt
Status
Framing
Byte Error
Interrupt
Status
RxPld
Mis
Interrupt
Status
RO
RUR
RO
RUR
RUR
RUR
RUR
RUR
0
0
0
1
0
0
0
0
6.3.6.2.12 The Receive LAPD Message Interrupt
If the Receive LAPD Message Interrupt is enabled,
then the XRT72L53 Framer IC will generate an interrupt anytime the Receive HDLC Controller block has
received a new LAPD Message frame from the Remote Terminal Equipment, and has stored the contents of this message into the Receive LAPD Message buffer.
Enabling/Disabling the Receive LAPD Message
Interrupt
The user can enable or disable the Receive LAPD
Message Interrupt by writing the appropriate data into
Bit 1 (RxLAPD Interrupt Enable) within the Rx E3
LAPD Control Register, as indicated below.
456
áç
XRT72L53
THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. P1.1.8
RXE3 LAPD CONTROL REGISTER (ADDRESS = 0X18)
BIT 7
BIT 6
BIT 5
BIT 4
Not Used
BIT 3
BIT 2
BIT 1
BIT 0
DL from NR
RxLAPD
Enable
RxLAPD
Interrupt
Enable
RxLAPD
Interrupt
Status
RO
RO
RO
RO
R/W
R/W
R/W
RUR
0
0
0
0
0
0
0
X
Writing a “1” into this bit-field enables the Receive
LAPD Message Interrupt. Conversely, writing a “0” into this bit-field disables the Receive LAPD Message
Interrupt.
Servicing the Receive LAPD Message Interrupt
• It will assert the Interrupt Request output pin (INT),
by driving it “Low”.
• It will set Bit 0 (RxLAPD Interrupt Status), within the
Rx E3 LAPD Control register to “1”, as indicated
below.
Whenever the XRT72L53 Framer IC generates this
interrupt, it will do the following.
RXE3 LAPD CONTROL REGISTER (ADDRESS = 0X18)
BIT 7
BIT 6
BIT 5
BIT 4
Not Used
BIT 3
BIT 2
BIT 1
BIT 0
DL from NR
RxLAPD
Enable
RxLAPD
Interrupt
Enable
RxLAPD
Interrupt
Status
RO
RO
RO
RO
R/W
R/W
R/W
RUR
0
0
0
0
0
0
1
1
• It will write the contents of the newly Received
LAPD Message into the Receive LAPD Message
buffer (located at 0xDE through 0x135).
out the contents of the Receive LAPD Message buffer, and respond accordingly.
Whenever the Terminal Equipment encounters the
Receive LAPD Message Interrupt, then it should read
457
áç
XRT72L53
THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. 1.1.8
7.0 DIAGNOSTIC OPERATION OF THE
XRT72L53 FRAMER
The XRT72L53 DS3/E3 Framer IC permits the user to
command it to operate in the Framer Local Loop-back
Mode. When the user does this than the data will be
as follows.
1. Data will enter the XRT72L53 Framer IC via both
the Transmit Payload Data Input Interface and the
Transmit Overhead Data Input Interface blocks.
2. This data will be processed through the Transmit
DS3/E3 Framer block and the Transmit DS3/E3
LIU Interface block.
3. This Transmit Output data will be internally
looped-back into the Receive Path via the
Receive LIU Interface block.
4. This data will then be processed through the
Receive DS3/E3 Framer block and will ultimately
arrive at both the Receive Payload Data Output
Interface and Receive Overhead Data Output
Interface blocks, where this data will be output to
the terminal equipment.
The Framer Local Loop-back Path is also illustrated
below in Figure 213 .
FIGURE 213. ILLUSTRATION OF THE FRAMER LOCAL LOOP-BACK PATH, WITHIN THE XRT72L53 DS3/E3 FRAMER
IC
Framer Local Loop-back Path
TxOHFrame
TxOHEnable
TxOH
TxOHClk
TxOHIns
TxOHInd
TxSer
TxNib[3:0]
TxInClk
TxNibClk
TxFrame
MOTO
D[7:0]
A[8:0]
IntB*
CSB*
RdB_DS
WrB_RW
Rdy_Dtck
Reset*
ALE_AS
RxSer
RxNib[3:0]
RxOutClk
RxNibClk
RxFrame
RxOHFrame
RxOH
RxOHClk
RxOHEnable
Transmit Overhead
Input
Interface Block
Transmit
Payload Data
Input
Interface Block
TxPOS
Transmit DS3/E3
Framer Block
Transmit LIU
Interface
Block
TxNEG
TxLineClk
Microprocessor
Interface
Tx LAPD Buffer/
Controller
Rx LAPD Buffer/
Controller
Receive Payload
Data Output
Interface Block
RxPOS
Receive DS3/E3
Framer Block
Receive LIU
Interface
Block
RxNEG
RxLineClk
Receive Overhead
Output
Interface Block
458
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XRT72L53
THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. 1.1.8
The user can configure the XRT72L53 into the Framer Local-Loop-back Mode by writing a “1” into bit-field
7 (Local Loop-back) within the Framer Operating
Mode Register, as illustrated below.
FRAMER OPERATING MODE REGISTER (ADDRESS = 0X00)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
Local Loopback
DS3/E3*
Internal
LOS
Enable
RESET
Interrupt
Enable Reset
Frame Format
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
1
X
X
0
X
X
X
X
TimRefSel[1:0]
2. The XRT72L53 DS3/E3 Framer IC cannot be configured to operate in the Framer Local Loop-back
Mode, if it is configured to operate in Modes 1 or
Mode 4 (Loop-Timing Modes). The user must configure the XRT72L53 Framer to operate in one of
the Local-Timing modes.
NOTES:
1. When the XRT72L53 DS3/E3 Framer IC is operating in the Framer Local-Loop-back Mode, no data
will be output via the TxPOS and TxNEG output
pins.
459
áç
XRT72L53
THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. 1.1.8
8.0 HIGH SPEED HDLC CONTROLLER MODE
OF OPERATION
Each channel, within the XRT72L53 device can be
configured to operate in the High-Speed HDLC Controller Mode. Whenever a given channel is configured
to operate in this mode then the following will happen.
1. The Transmit Section of the channel will be configured to accept outbound data (from the user’s
Terminal Equipment) via an 8-bit wide input interface labeled TxHDLCDat_n[7:0]. The Transmit
Section of the channel will then encapsulate all
data, that it receives via TxHDLCDat_n[7:0].
2. The Transmit Section of the channel will then
encapsulate all data, that it receives via the
TxHDLCDat_n[7:0] interface, into HDLC frames.
These HDLC frames are variable-length packets
and are transported to the remote terminal equipment via the outbound DS3 or E3 payload data
bits.
3. As the Transmit Section accepts and processes
data from the user’s terminal equipment, then it
will perform all of the necessary “0” stuffing into
the outbound HDLC frame, in order to prevent the
user-supplied data from mimicking either the flag
sequence octet (0x7E) or the ABORT sequence.
4. The Transmit Section can also be configured to
compute and append either a 16-bit or 32-bit
CRC value to the end of this “0” stuffed user’s
data, as a trailer.
5. Whenever the Transmit Section has no user data
to send to the remote terminal equipment (via
HDLC frames) then it will transmit a continuous
stream of flag sequence octets (0x7E) via the
DS3 or E3 payload bits.
6. The Receive Section of the channel will be configured to receive and extract out these HDLC
frames via the inbound DS3/E3 data stream. The
Receive Section will then output the contents of
these received HDLC frames in a byte-wide manner via the RxHDLCDat_n[7:0] output pins.
7. If the Receive Section of the channel is only
receiving a stream of flag sequences (0x7E) then
it will terminate this data stream and will not output any data via the RxHDLCDat_n[7:0] output
pins.
8. As the Receive Section of the channel receives
these HDLC frames, it will also do the following.
• Compute and verify the 16-bit or 32-bit CRC value
(which has been appended to the HDLC frame, as
a trailer).
• Perform the necessary “0” un-stuffing in order to
restore the original content of the user-supplied
data.
8.1 CONFIGURING THE CHANNEL TO OPERATE IN THE
HIGH SPEED HDLC CONTROLLER MODE
The user can configure a given channel to operate in
the High Speed HDLC Controller Mode by writing the
appropriate data into the Channel’s HDLC Control
Register.
The address location of the HDLC Control register,
for each of the three channels (within the XRT72L53
device) is listed below in Table 93 .
TABLE 93: ADDRESS LOCATIONS OF EACH OF THE
HDLC CONTROL REGISTERS WITHIN THE
XRT72L53 DEVICE .
CHANNEL NUMBER
ADDRESS LOCATION
0
0x82
1
0x282
2
0x482
The user can configure a given channel to operate in
the High-Speed HDLC Controller Mode by setting bit
6 (HDLC ON), within the appropriate HDLC Control
Register to “1”, as depicted below.
HDLC CONTROL REGISTER (ADDRESS = 0X82)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
Framer
By-Pass
HDLC
ON
CRC-32
Select
Reserved
HDLC
Loop-Back
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
1
0
0
0
0
0
0
8.2 OPERATING THE HIGH SPEED HDLC CONTROLLER
Once the user has configured a given channel to operate in the High-Speed HDLC Controller Mode, then
both the Transmit and Receive HDLC Controller
BIT 2
BIT 1
BIT 0
Reserved
blocks, within the appropriate channel will be active.
The next few sections describe how to use the Transmit and Receive HDLC Controller blocks, within a given channel.
460
XRT72L53
THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. 1.1.8
8.2.1 Operating the Transmit HDLC Controller
Block
Once the user has configured a given channel to operate in the High-Speed HDLC Controller mode, then
certain pins (which have multiple functions) will be
configured to support operation of the Transmit and
Receive HDLC Controller blocks.
áç
The Transmit HDLC Controller block, within each
channel consists of the following pins.
• Snd_Msg_n
• Snd_FCS_n
• TxHDLCClk_n
• TxHDLCDat_n[7:0]
Each of these pins are described below in Table 94 .
461
áç
XRT72L53
THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. 1.1.8
TABLE 94: DESCRIPTION OF EACH OF THE TRANSMIT HDLC CONTROLLER PINS
PIN NAME
TYPE
Snd_Msg_n
I
DESCRIPTION
Send Message Command:
This input pin permits the user to command the Transmit HDLC Controller block to
begin sampling and latching the data, which is being applied to the TxHDLCDat_n[7:0]
input pins.
If the user pulls this input pin "High", then the Transmit HDLC Controller block will
begin to sample and latch the data (which is applied to the TxHDLCDat_n[7:0] input
pins), upon the rising edge of TxHDLCClk_n. Each byte of this sampled data will ultimately be encapsulated into an outbound HDLC Frame.
If the user pulls this input pin "Low", then the Transmit HDLC Controller block will NOT
sample and latch data (which is residing on the TxHDLCDat_n[7:0] input pins. As a
consequence, no outbound HDLC Frames will be generated, and the Transmit HDLC
Controller block will simply generate a constant stream of Flag Sequence octets
(0x7E).
Snd_FCS_n
I
Send Frame Check Sequence Command:
The user’s terminal equipment is expected to control both this input pin, along with the
Snd_Msg_n input pin, during the construction and transmission of each outbound
HDLC frame.
This input pin permits the user to command the Transmit HDLC Controller block to
compute and insert the compute FCS (Frame-Check Sequence) value into the backend of the outbound HDLC frame, as a trailer.
If the user has configured the Transmit HDLC Controller to compute and insert a CRC16 value into the outbound HDLC frame, then the terminal equipment is expected to
pull this input pin "High" for two periods of TxHDLCClk_n.
Conversely, if the user has configured the Transmit HDLC Controller to compute and
insert a CRC-32 value into the outbound HDLC frame, then the terminal equipment is
expected to pull this input pin "High" for four periods of TxHDLCClk_n.
TxHDLCClk_n
O
Transmit HDLC Controller Clock Output signal:
This output signal functions as the demand clock for the Transmit HDLC Controller.
When the user pulls the Snd_Msg_n input pin "High", then the Transmit HDLC Controller block will begin to sample and latch the contents of the TxHDLCDat_n[7:0] upon
the rising edge of this clock signal. As a consequence, the user is advised to design/
configure their terminal equipment circuitry to output data (onto the
TxHDLCDat_n[7:0] bus), upon the falling edge of this clock signal.
Since the Transmit HDLC Controller block is sampling and latching 8-bits of data at a
given time, it may be presumed that the frequency of the TxHDLCClk_n output signal
is either 34.368MHz/8 or 44.736MHz/8. In general, this presumption is true. However,
because the Transmit HDLC Controller is also performing “0” stuffing of the user data
that it receives from the Terminal Equipment, the frequency of this signal may be
slower.
TxHDLCDat_n[7:0]
I
Transmit HDLC Controller - Input Data Bus:
These eight input pins function as the byte-wide input interface to the Transmit HDLC
Controller. If the user pulls the Snd_Msg_n input pin "High", then the Transmit HDLC
Controller block will begin to sample and latch the contents of this data bus, into the
Transmit HDLC Controller circuitry (upon the rising edge of TxHDLCClk_n). All data
that is sampled, via this byte-wide interface will ultimately be encapsulated into an outbound HDLC Controller.
If the user pulls the Snd_Msg_n input pin "Low", then the Transmit HDLC Controller
block will ignore the data that is being applied to this data bus.
Whenever the user wishes to transmit data via the
Transmit HDLC Controller block, then he/she should
pull the Snd_Msg_n input pin "High". Once the
Snd_Msg_n pin is pulled high, then the Transmit
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THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. 1.1.8
figures the Transmit HDLC Controller to begin its insertion of either the CRC-16 or CRC-32 value into the
back-end of the outbound HDLC Controller.
HDLC Controller block will begin to sample the data
on the TxHDLCDat_n[7:0] input pins, upon the rising
edge of the TxHDLCClk_n clock output signal. Each
byte of data that is sampled and latched into the
Transmit HDLC Controller block will be encapsulated
into an outbound HDLC frame.
Selecting either CRC-16 or CRC-32
After the last byte of data has been latched into the
Transmit HDLC Controller block, then the user must
pull the Snd_FCS_n input pin "High" for either two or
four TxHDLCClk_n clock periods.
If the user has configured the Transmit HDLC Controller block to append a 16-bit CRC value (from here
on, referred to as CRC-16); then the user must pull
and hold the Snd_FCS_n input pin "High" for two (2)
TxHDLCClk_n clock periods. Conversely, if the user
has configured the Transmit HDLC Controller block to
append a 32 bit CRC value (from here on, referred to
as CRC-32); then the user must pull and hold the
Snd_FCS_n input pin "High" for (4) TxHDLCClk_n
periods. Pulling the Snd_FCS_n input pin "High" con-
The user can configure the Transmit HDLC Controller
block (within Channel n) to append either a CRC-16
or CRC-32 value to the user-data within the outbound
HDLC frame, by writing the appropriate value into Bit
5 (CRC-32 Select). Setting this bit-field "High" configures the Transmit HDLC Controller block to append a
CRC-32 value to the user data, within the outbound
HDLC frame. Conversely, setting this bit-field "Low"
configures the Transmit HDLC Controller block to append a CRC-16 value to the user data, within the outbound HDLC frame.
A simple illustration of the resulting outbound HDLC
Frame (when CRC-32 Select, is invoked) is presented
below in Figure 214 .
FIGURE 214. A SIMPLE ILLUSTRATION OF AN OUTBOUND HDLC FRAME, AS ASSEMBLED BY THE TRANSMIT HDLC
CONTROLLER, WHEN CRC-32 IS SELECTED.
CRC-32
Trailer
User Supplied Data
HDLC Frame
Similarly, a simple illustration of the resulting outbound HDLC Frame (when CRC-16 is selected) is
presented below in Figure 215 .
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THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. 1.1.8
FIGURE 215. A SIMPLE ILLUSTRATION OF AN OUTBOUND HDLC FRAME, AS ASSEMBLED BY THE TRANSMIT HDLC
CONTROLLER, WHEN CRC-16 IS SELECTED.
CRC-16
Trailer
User Supplied Data
HDLC Frame
Once the outbound HDLC frame has been formed,
then it will be transmitted to the remote terminal
equipment via payload bits of the outbound DS3 or
E3 frames.
8.2.2 Operating the Receive HDLC Controller
Block
The Receive HDLC Controller block, within each
channel consists of the following pins.
If the user’s terminal equipment does not supply any
more data (which needs to be encapsulated into the
outbound HDLC frame and transmitted to the remote
terminal equipment), then the Transmit HDLC Controller block will begin transmitting a constant stream
of flag sequence octets (0x7E). These flag sequence
octets will also be transmitted to the remote terminal
equipment via the payload bits of the outbound DS3
or E3 frames.
• RxIdle_n
• Val_FCS_n
• RxHDLCClk_n
• RxHDLCDat_n[7:0]
Each of these output pins are described below in
Table 95 .
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REV. 1.1.8
TABLE 95: DESCRIPTION OF EACH OF THE RECEIVE HDLC CONTROLLER PINS
PIN NAME
TYPE
RxIdle_n
O
DESCRIPTION
Receive Idle (Flag Sequence) Indicator Signal
The combination of the RxIdle_n and Val_FCS_n output signals are used to convey
information about data that is being received via the Receive HDLC Controller block.
If RxIdle_n = “High”
The Receive HDLC Controller block will pulse this output pin "High" anytime the flag
sequence is present on the RxHDLCDat_n[7:0] output data bus.
If RxIdle_n and Val_FCS_n are both "High"
The Receive HDLC Controller block has received a complete HDLC frame, and has
determined that the FCS value (within this HDLC frame) is valid.
If RxIdle_n is "High" and Val_FCS_n is "Low"
The Receive HDLC Controller block has received a complete HDLC frame, and has
determined that the FCS value (within this HDLC frame) is invalid.
If RxIdle_n is "Low" and Val_FCS_n is "High"
The Receive HDLC Controller block has received an ABORT sequence.
Val_FCS_n
O
Valid FCS Indicator Signal
Please see description above.
RxHDLCClk_n
O
Receive HDLC Controller Clock Output signal:
The Receive HDLC Controller block outputs data (via the RxHDLCDat_n[7:0] output
pins) upon the rising edge of this clock signal. As a consequence, the user is advised
to configure/design his/her terminal equipment circuitry to sample the contents of the
RxHDLCDat_n[7:0] output pins, upon the falling edge of this clock signal.
RxHDLCDat_n[7:0]
I
Receive HDLC Controller - Output Data Bus:
The Receive HDLC Controller block outputs data (via these output pins) upon the rising edge of the RxHDLCClk_n clock signal. As a consequence, the user is advised to
configure/design his/her terminal equipment circuitry to sample the contents of this
data bus, upon the falling edge of this clock signal.
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REV. P1.1.8
ORDERING INFORMATION
PART NUMBER
PACKAGE TYPE
OPERATING TEMPERATURE RANGE
XRT72L53
27x27 mm 272 Ball PBGA
-40°C to +85°C
PACKAGE DIMENSIONS
272 Ball Plastic Ball Grid Array
(27 mm x 27 mm, PBGA)
Note: Control Dimension is the millimeters column
SYMBOL
A
A1
A2
A3
D
D1
D2
b
e
α
β
aaa
INCHES
MIN
MAX
0.067
0.106
0.020
0.028
0.008
0.028
0.039
0.051
1.055
1.071
0.950 BSC
0.937
0.953
0.024
0.035
0.0500 BSC
0.008
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MILLIMETERS
MIN
MAX
1.70
2.70
0.50
0.70
0.20
0.70
1.00
1.30
26.80
27.20
24.13 BSC
23.80
24.20
0.60
0.90
1.27 BSC
0.20
XRT72L53
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THREE CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
PRELIMINARY
REV. P1.1.8
REVISION HISTORY
Package changed from 292 pins to 272 pins. Changed from advanced to preliminary.
Added electrical characteristics.
Made edits to register description section 2.
Corrected pin names and timing diagrams.
Added sections
Rev 1.1.6 -- Made corrections to figures 37, 38, 39, 65, 75, 102, 120, 130, 161, 163, 178 and 188.
Rev 1.1.7 -- Added missing No Connect Pins to Pin Descriptions -- K1, K2, L2, L4, M2, M4, N2, P1, P4, R1,
R2, T2, T4, U1, U2, U7, U16, U18, V2, V3, V4, V5, V8, V9, V10, V11, V12, V13, V14, V15, V18, V19, W7,
W14, W17, W18, Y1, Y2, Y3, Y5, Y6, Y8, Y9, Y11, Y12, Y13, Y16, Y17, Y20
Rev. 1.1.8 Corrected spelling errors.
NOTICE
EXAR Corporation reserves the right to make changes to the products contained in this publication in order
to improve design, performance or reliability. EXAR Corporation assumes no responsibility for the use of
any circuits described herein, conveys no license under any patent or other right, and makes no representation that the circuits are free of patent infringement. Charts and schedules contained here in are only for
illustration purposes and may vary depending upon a user’s specific application. While the information in
this publication has been carefully checked; no responsibility, however, is assumed for inaccuracies.
EXAR Corporation does not recommend the use of any of its products in life support applications where
the failure or malfunction of the product can reasonably be expected to cause failure of the life support system or to significantly affect its safety or effectiveness. Products are not authorized for use in such applications unless EXAR Corporation receives, in writing, assurances to its satisfaction that: (a) the risk of injury
or damage has been minimized; (b) the user assumes all such risks; (c) potential liability of EXAR Corporation is adequately protected under the circumstances.
Copyright 2001 EXAR Corporation
Datasheet May 2001.
Reproduction, in part or whole, without the prior written consent of EXAR Corporation is prohibited.
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