DEMO KIT AVAILABLE
DS21349
3.3V T1/J1 Line Interface Unit
www.maxim-ic.com
GENERAL DESCRIPTION
FEATURES
The DS21349 is a fully integrated LIU for longhaul or short-haul T1 applications over twistedpair installations. It interfaces to two twisted-pair
lines—one pair for transmit and one pair for
receive through an appropriate network
interface. The device can be configured for
control through software or hardware mode.
Software control is accomplished over a serial
port in hardware mode; individual pin settings
allow stand-alone operation. The device provides
a precise, crystal-less jitter attenuator that can be
placed in either the transmit or receive path.
APPLICATIONS
Routers
Data Service Units (DSUs)
Channel Service Units (CSUs)
Muxes
Switches
Channel Banks
T1/E1 Test Equipment
PIN CONFIGURATION
TOP VIEW
4 3 2 1 28 27 26
5
6
7
8
9
10
11
DS21349
12 13 14 15 16 17 18
Fully Integrated Line Interface Unit (LIU)
Pin Compatible with LevelOne LXT362
Supports Both Long Haul and Short Haul
Crystal-Less Jitter Attenuator
Jitter Attenuator Programmable for Transmit
or Receive Path
Meets ANSI T1.102, T1.403, T1.408, and
AT&T 62411
Usable Receive Sensitivity of 0dB to -36dB
That Allows the Device to Operate on
0.63mm (22AWG) Cables Up to 6k Feet in
Length
Five Line Build-Out Settings for Short-Haul
Applications
Four CSU Filters from 0dB to -22.5dB
Transmit/Receive Performance Monitors
with Driver-Fail, Monitor-Open, and Lossof-Signal Outputs
Bipolar or NRZ Interface
Programmable B8ZS Encoder/Decoder
QRSS Generator/Detector
Local, Remote, and Analog Loopbacks
Generates and Detects In-Band Loop-Up and
Loop-Down Codes
Serial Interface Provides Access to Control
Registers
ORDERING INFORMATION
25
24
23
22
21
20
19
DS21349Q
TEMP
RANGE
0°C to +70°C
PINPACKAGE
28 PLCC
DS21349Q+
0°C to +70°C
28 PLCC
PART
DS21349QN
-40°C to +85°C 28 PLCC
DS21349QN+ -40°C to +85°C 28 PLCC
PLCC
+Denotes lead-free/RoHS-compliant package.
Note: Some revisions of this device may incorporate deviations from published specifications known as errata. Multiple revisions of any device
may be simultaneously available through various sales channels. For information about device errata, click here: www.maxim-ic.com/errata.
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REV: 011206
DS21349
TABLE OF CONTENTS
1.
2.
3.
4.
5.
DETAILED DESCRIPTION ................................................................................................. 4
OPERATING MODES......................................................................................................... 5
INITIALIZATION AND RESET............................................................................................ 9
REGISTER DEFINITIONS .................................................................................................. 10
TRANSMITTER................................................................................................................... 16
5.1
5.2
5.3
5.4
6.
TRANSMIT DIGITAL DATA INTERFACE ............................................................................................... 16
TRANSMIT MONITORING .................................................................................................................. 16
TRANSMIT IDLE MODE ..................................................................................................................... 16
TRANSMIT PULSE SHAPE ................................................................................................................ 16
RECEIVER .......................................................................................................................... 17
6.1
6.2
6.3
6.4
7.
8.
9.
RECEIVE EQUALIZER ....................................................................................................................... 17
RECEIVE DATA RECOVERY .............................................................................................................. 17
RECEIVE DIGITAL-DATA INTERFACE ................................................................................................. 17
RECEIVE MONITOR MODE ............................................................................................................... 17
JITTER ATTENUATION ..................................................................................................... 18
HARDWARE MODE ........................................................................................................... 18
SOFTWARE MODE ............................................................................................................ 19
9.1
10.
INTERRUPT HANDLING .................................................................................................................... 19
DIAGNOSTIC MODE OPERATION.................................................................................... 22
10.1
LOOPBACK MODES ......................................................................................................................... 22
10.1.1
10.1.2
10.1.3
10.1.4
10.1.5
10.2
Local Loopback (LLB)...................................................................................................................................22
Analog Loopback (ALB)................................................................................................................................22
Remote Loopback (RLB) ..............................................................................................................................22
Network Loopback ........................................................................................................................................23
Dual Loopback..............................................................................................................................................23
INTERNAL PATTERN GENERATION AND DETECTION .......................................................................... 24
10.2.1 Transmit Alarm-Indication Signal (TAIS) ......................................................................................................24
10.2.2 Quasirandom Signal Source (QRSS) ...........................................................................................................24
10.2.3 In-Band Network Loop-Up or Loop-Down Code Generator .........................................................................25
10.3
ERROR INSERTION AND DETECTION................................................................................................. 25
10.3.1
10.3.2
10.3.3
10.3.4
10.4
ALARM MONITORING ....................................................................................................................... 26
10.4.1
10.4.2
10.4.3
10.4.4
10.5
Bipolar Violation Insertion (INSBPV) ............................................................................................................25
Logic Error Insertion (INSLE) .......................................................................................................................25
Logic Error Detection (QPD).........................................................................................................................25
Bipolar Violation Detection (BPV).................................................................................................................25
Receive-Carrier Loss (RCL) .........................................................................................................................26
Alarm-Indication-Signal Detection (AIS) .......................................................................................................26
Driver-Fail Monitor-Open (DFMO) ................................................................................................................26
Jitter Attenuator Limit Trip (JALT).................................................................................................................26
OTHER DIAGNOSTIC REPORTS ........................................................................................................ 26
10.5.1 Receive Line-Attenuation Indication .............................................................................................................26
11.
12.
13.
13.1
NETWORK INTERFACE .................................................................................................... 27
DC CHARACTERISTICS .................................................................................................... 31
PACKAGE INFORMATION ................................................................................................ 35
28-PIN PLCC (56-G4001-001) ...................................................................................................... 35
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DS21349
LIST OF FIGURES
Figure 1-1. Block Diagram....................................................................................................................................... 4
Figure 2-1. Hardware Mode Pinout ........................................................................................................................ 6
Figure 2-2. Serial Port Mode Pinout....................................................................................................................... 6
Figure 9-1. Serial Data Port Operation for Read Access.................................................................................. 20
Figure 9-2. Serial Data Port Operation for Write Access.................................................................................. 20
Figure 10-1. Loopbacks in the DS21349 Block Diagram.................................................................................. 24
Figure 11-1. Basic Network Interface .................................................................................................................. 28
Figure 11-2. T1 Transmit Pulse Template .......................................................................................................... 29
Figure 11-3. Jitter Tolerance ................................................................................................................................. 30
Figure 11-4. Jitter Attenuation............................................................................................................................... 30
Figure 12-1. Serial Bus Read Timing (MODE1 = 1) .......................................................................................... 32
Figure 12-2. Serial Bus Write Timing (MODE1 = 1) .......................................................................................... 32
Figure 12-3. AC Characteristics for Receive Side ............................................................................................. 33
Figure 12-4. AC Characteristics for Transmit Side ............................................................................................ 34
LIST OF TABLES
Table 2-A. Operating Modes ................................................................................................................................... 5
Table 2-B. Control Pins for Hardware and Software Modes .............................................................................. 5
Table 2-C. Signal Descriptions ............................................................................................................................... 7
Table 4-A. Register Map ........................................................................................................................................ 10
Table 4-B. Register Bit Positions.......................................................................................................................... 10
Table 4-C. Jitter Attenuator Selection.................................................................................................................. 11
Table 4-D. Line Code and Interface Selection ................................................................................................... 11
Table 4-E. Line Build-Out Selection..................................................................................................................... 11
Table 4-F. Data Pattern Selection ........................................................................................................................ 12
Table 9-A. CLKE Pin Selection............................................................................................................................. 19
Table 9-B. Control and Operation Mode Selection............................................................................................ 21
Table 10-A. Diagnostic Modes.............................................................................................................................. 22
Table 11-A. Specifications for Receive Transformer......................................................................................... 27
Table 11-B. Specifications for Transmit Transformer........................................................................................ 27
Table 11-C. Transformer Turns Ratio vs. Series Resistance .......................................................................... 27
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DS21349
1. DETAILED DESCRIPTION
The DS21349 is a complete T1 line interface unit (LIU) for short-haul and long-haul applications.
Receive sensitivity adjusts automatically to the incoming signal and can be limited to -18dB, -26dB, or
-36dB. The device can generate the necessary DSX-1 line build-outs or CSU line build-outs of 0dB,
-7.5dB, -15dB, and -22.5dB. The on-board crystal-less jitter attenuator requires a 1.544MHz reference
clock. The jitter attenuator FIFO is selectable to either 32 bits or 128 bits in depth and can be placed in
either the transmit or receive data paths. The DS21349 has diagnostic capabilities such as loopbacks and
QRSS pattern generation and detection. The device can also generate and detect the in-band loop-up and
loop-down codes specified in AT&T 62411. The device can be configured for control using a serial
interface, or for hardware mode. The device fully meets all of the latest T1 specifications including ANSI
T1.102-1999, ANSI T1.403-1999, ANSI T1.408, and AT&T 62411.
MCLK
Figure 1-1. Block Diagram
VCO / PLL
NLOOP
4 of 35
RCLK
RPOS
RNEG
LOTC mux
In Band Loop gen.
AIS detect
QRSS Detector
In Band Loop
Code Detector
Logic Error Insert
QRSS
B8ZS Decoder
B8ZS Encoder
INT
CLKE
SCLK
SDI
SDO
CS
Serial Interface
MODE0
MODE1
Hardware Interface
Remote Loopback
Jitter Attenuator
RCL Detector
Local Loopback
Trnasmit AIS
Peak Detect
Power connections
Wave Shaping
CSU Filters
Line Drivers
TTIP
VSM
TVDD
VDD
GND
GND
TRING
Analog Loopback
RTIP
JASEL
L0
L1
L2
L3
LLB
RLB
TBL/QRSS
Filter
RRING
Clock / Data
Recovery
RCL/QPD
TCLK
TPOS
TNEG
DS21349
2. OPERATING MODES
The DS21349 has several pins with multiple functions and names according to the selected operating
mode. These operating modes are summarized in the tables below.
Table 2-A. Operating Modes
PIN
1
2
3
4
6
7
8
13
16
19
20
QRSS DISABLED
BIPOLAR
NRZ
QRSS ENABLED
BIPOLAR
NRZ
MCLK
TCLK
TPOS
TNEG
RNEG
RPOS
TDATA
INSBPV
BPV
RDATA
INSLER
INSBPV
RNEG
RPOS
BPV
RDATA
RCLK
TTIP
TRING
RTIP
RRING
Control pins are affected by serial port and hardware modes.
Table 2-B. Control Pins for Hardware and Software Modes
PIN
5
9
11
12
23
24
25
17
18
26
27
28
HARDWARE MODE
NRZ
QRSS
MODE1
MODE0
JASEL
RCL
RCL/QPD
L0
L1
L2
L3
NLOOP
RLB
NLB
LLB
ALB
TAIS
QRSS
SERIAL PORT MODE
NRZ
QRSS
MODE1
MODE0
N.C.
RCL
RCL/QPD
INT
SDI
SDO
N.C.
NLOOP
CS
SCLK
CLKE
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DS21349
4
3
2
1
28
27
26
TNEG
TPOS
TCLK
MCLK
TAIS/QRSS
LLB
RLB
Figure 2-1. Hardware Mode Pinout
5
6
7
8
9
10
11
DS21349
25
24
23
22
21
20
19
L2
L1
L0
G ND
V DD
RR ING
RTIP
RCL/QPD
TTIP
GND
TVDD
TRING
L3
NLOOP
12
13
14
15
16
17
18
M O D E1
RN EG
RPO S
RC L K
M O D E0
V SM
JA SE L
4
3
2
1
28
27
26
TNEG
TPOS
TCLK
MCLK
CLKE
SCLK
CS
Figure 2-2. Serial Port Mode Pinout
DS21349
12
13
14
15
16
17
18
5
6
7
8
9
10
11
RCL/QPD
TTIP
GND
TVDD
TRING
N/C
NLOOP
MODE1
RNEG
RPOS
RCLK
MODE0
VSM
N/C
6 of 35
25
24
23
22
21
20
19
SDO
SDI
INT
GND
VDD
RRING
RTIP
DS21349
Table 2-C. Signal Descriptions
PIN
NAME
I/O
1
MCLK
I
2
TCLK
I
TPOS
3
TDATA
I
INSLER
TNEG
4
I
INSBPV
5
MODE1
I2
RNEG
6
O
BPV
RPOS
7
O
RDATA
FUNCTION
Master Clock. A 1.544MHz clock source with TTL levels is applied at this pin. This
clock is used internally for both clock/data recovery and for jitter attenuation.1
Transmit Clock. A 1.544MHz primary clock. Used to clock data through the transmit
side formatter. Can be sourced internally by MCLK or RCLK.
Transmit Positive Data. Sampled on the falling edge of TCLK for data to be
transmitted out onto the line.
Transmit NRZ Data. Sampled on the falling edge of TCLK for data to be transmitted
onto the line.
Transmit Insert Logic Error. Rising edge on INSLER inserts a logic error into the
outbound QRSS pattern. Sampled on falling edge of TCLK.
Transmit Negative Data. Sampled on the falling edge of TCLK for data to be
transmitted out onto the line.
Transmit Insert Bipolar Violation. INSBPV is sampled on the falling edge of TCLK.
Rising edge inserts one BPV.
Mode Select 1. Connect low to select hardware mode. Connect high to select serial
port mode. See also MODE0.
Receive Negative Data. Updated on the rising edge (CCR2.0 = 0) or the falling edge
(CCR2.0 = 1) of RCLK with the bipolar data out of the line interface. Always valid
on rising edge of RCLK in hardware mode.
Receive Bipolar Violation. Transitions high for one clock cycle marking an inbound
bipolar violation. Valid on rising edge of RCLK.
Receive Positive Data. Updated on the rising edge (CCR2.0 = 0) or the falling edge
(CCR2.0 = 1) of RCLK with bipolar data out of the line interface. Always valid on
rising edge of RCLK in hardware mode.
Receive Data. RDATA is the NRZ output from the line interface. Set NRZE
(CCR1.6) to a 1 for NRZ applications. In NRZ mode, data is output on RPOS while a
received error causes a positive-going pulse synchronous with RCLK at RNEG
(Section 6).
Receive Clock. Buffered recovered clock from the line. Synchronous to MCLK in
absence of signal at RTIP and RRING.
Mode Select 0. Set high to disable all output pins (including the serial control port).
Set low for normal operation. Useful in board level testing. See also MODE1.
8
RCLK
O
9
MODE0
I2
10
VSM
I
Voltage Supply Mode. Connect high for 3.3V operation. Has 10kΩ pullup.
I2
Jitter Attenuator Select
0 = Place the jitter attenuator on the transmit side
1 = Place the jitter attenuator on the receive side
Float = Disable jitter attenuator
Not used in software mode
11
JASEL
RCL
12
13/
16
14
15
QPD
TTIP/
TRING
VSS
TVDD
Receive Carrier Loss. An output that toggles high during a receive carrier loss.
O
O
—
—
QPD. Output high when QRSS detector is searching for QRSS data pattern. Output
high for one-half clock cycle on bit error. Connect to external counter to count bit
errors.
Transmit Tip and Ring. Analog line driver outputs. These pins connect through a
step-up transformer to the line (Section 5).
Ground for Transmitter Block
Positive Supply. 3.3V ±5% for the transmitter block. See also VSM pin 10.
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DS21349
PIN
NAME
I/O
17
L3
I
18
NLOOP
O
19/
20
21
22
RTIP/
RRING
VDD
VSS
23
L0
I
—
—
I/O
INT
L1
24
I
SDI
L2
25
O
SDO
RLB
I2
26
NLB
CS
27
LLB
I2
TAIS
QRSS
I2
CLKE
LBO3. LBO0 through LBO3 are used to select transmitter output pulse, and receiver
gain.
Network Loopback Active. Output high when RLB is activated by in-band loop-up
command present for 5 seconds. Output is reset when RLP is deactivated by in-band
loop-down command present for 5 seconds. Activation of remote loopback through
hardware pin 26 or control bit RLB releases the NLOOP output.
Receive Tip and Ring. Analog inputs for clock recovery circuitry. These pins connect
through a 1:1 transformer to the line (Section 6).
Positive Supply. 3.3V ±5%. See also VSM pin 10.
Signal Ground
LBO0. LBO0 through LBO3 are used to select transmitter output pulse, and receiver
gain.
INT. Used to alert the host when one or more bits are set in the status register.
LBO1. LBO0 through LBO3 are used to select transmitter output pulse, and receiver
gain.
Serial Data Input. Input for serial address and data stream. Sampled on rising of
SCLK.
LBO2. LBO0 through LBO3 are used to select transmitter output pulse, and receiver
gain.
Serial Data Output. Updated on falling edge of SCLK if CLKE is connected high.
Updated on rising edge of SCLK if CLKE is connected low. SDO is high-Z during
write cycle or when CS is high.
Remote Loopback. Used to invoke remote loopback. When held high, the transmitter
inputs are ignored and inbound data received at RTIP and RRING is routed to the
transmitter outputs, TTIP and TRING and transmitted at the inbound recovered clock
rate.
Network Loopback. Enables network loopback detection when RLB floats.
Chip Select. Must be low to read or write to the device. CS is an active-low signal.
SCLK
28
FUNCTION
Local Loopback. Used to invoke local loopback. When held high, digital inputs
TPOS and TNEG are looped back to RPOS and RNEG, through the jitter attenuator
if enabled. Floating this input invokes analog loopback. The analog output signal at
TTIP and TRING is routed to the receive inputs RTIP and RRING.
Serial Clock Input. Input clock to operate serial port. Max clock rate, 2.048MHz.
Transmit AIS. Input high forces transmitter to output unframed all ones. Unavailable
in remote loopback.
QRSS. Floating this pin enables QRSS pattern generator and detector. Input low
enables normal transmission of data.
Clock Edge Select
0 = Update RNEG/RPOS on falling edge of RCLK, SDO updated on rising edge of
SCLK.
1 = Update RNEG/RPOS on rising edge of RCLK, SDO updated on falling edge of
SCLK.
Note 1: G.703 requires an accuracy of ±50ppm for T1. TR62411 and ANSI specifications require an accuracy of ±32ppm for T1 interfaces.
Note 2: Input pins have three operating modes.
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DS21349
3. INITIALIZATION AND RESET
During power-up, all control registers are cleared, disabling the transmitter outputs. The device requires a
master clock supplied to the MCLK input pin to operate the PLL. This master clock must be independent,
free-running, and jitter free.
A reset initializes the status and state machines for the RCL, AIS, NLOOP, and QRSS blocks. Under
software control, setting the RESET bit (CR2.7) clears all registers. Allow up to 100ms for the receiver to
recover from initialization.
9 of 35
DS21349
4. REGISTER DEFINITIONS
The DS21349 contains eight registers for configuring the device and reading status. These are accessible
using the serial port. Table 4-A lists the register names and addresses.
Reading or writing to the internal registers requires writing one address/command byte prior to
transferring register data. The first bit written (LSb) of the address/command byte specifies whether the
access is a read (1) or a write (0). The next 6 bits identify the register address.
The last bit (MSb) of the address/command byte is the burst mode bit. When the burst bit is enabled (set
to 1) and a READ operation is performed, addresses 10h through 17h are read sequentially, starting at
address 10h. And when the burst bit is enabled and a WRITE operation is performed, addresses 10h
through 17h are written sequentially, starting at address 10h. Burst operation is stopped once address 17h
is read. All data transfers are initiated by driving the CS input low. All data transfers are terminated if the
CS input transitions high. Port control logic is disabled and SDO is tri-stated when CS is high.
Table 4-A. Register Map
REGISTER
Control Register 1
Control Register 2
Control Register 3
Interrupt Mask Register
Transition Status Register
Status Register
Information Register
Control Register 4
SYMBOL
CR1
CR2
CR3
IMR
TSR
SR
IR
CR4
ADDRESS
B010000
B010001
B010010
B010011
B010100
B010101
B010110
B010111
Table 4-B. Register Bit Positions
SYMBOL
CR1
CR2
CR3
IMR
TSR
SR
IR
CR4
7 (MSb)
JASEL1
RESET
JA6HZ
Z16D
Z16D
—
RL3
—
6
JASEL0
PAT1
TPD
JALT
JALT
—
RL2
—
5
4
3
2
ENCENB
UNIENB
L3
L2
PAT0
TAIS
ENLOOP
ALB
—
EQZMON20 EQZMON26
JA128
DFMO
B8ZSD
QRSS
AIS
DFMO
B8ZSD
QRSS
AIS
DFMO
—
QRSS
AIS
RL1
RL0
LUP
LDN
—
—
—
RCL2048
Note: Set unused bits to 0 for normal operation.
10 of 35
1
L1
LLB
LIRST
NLOOP
NLOOP
NLOOP
TSCD
XFMR2
0 (LSb)
L0
RLB
TAOZ
RCL
RCL
RCL
LOTC
XFMR1
DS21349
CR1 (B010000): Control Register 1
MSb
JASEL1
JASEL0
SYMBOL
JASEL1
JASEL0
ENCENB
UNIENB
L3
L2
L1
L0
ENCENB
POSITION
CR1.7
CR1.6
CR1.5
CR1.4
CR1.3
CR1.2
CR1.1
CR1.0
UNIENB
L3
L2
LSb
L0
L1
FUNCTION
Jitter attenuator select (Table 4-C)
Jitter attenuator select (Table 4-C)
B8ZS and NRZ control (Table 4-D)
BPV and NRZ control (Table 4-D)
Line build-out control (Table 4-E)
Line build-out control (Table 4-E)
Line build-out control (Table 4-E)
Line build-out control (Table 4-E)
Table 4-C. Jitter Attenuator Selection
JASEL1
JASEL0
JITTER ATTENUATOR FUNCTION
0
1
X
1
1
0
Transmit path
Receive path
Disabled
Table 4-D. Line Code and Interface Selection
UNIENB
ENCENB
LINE CODE
INTERFACE
0
1
X
0
0
1
AMI
AMI
B8ZS
Bipolar
NRZ
NRZ
Table 4-E. Line Build-Out Selection
L3
L2
L1
L0
APPLICATION
OUTPUT SIGNAL
Rx GAIN (dB)
0
0
0
0
0
0
0
0
1
1
1
1
1
1
0
0
1
1
0
0
1
1
0
0
1
1
1
1
0
1
0
1
0
1
0
1
0
1
0
0
1
1
0
0
0
0
1
1
1
1
1
1
0
1
0
1
T1 Long Haul
T1 Long Haul
T1 Long Haul
T1 Long Haul
T1 Long Haul
T1 Long Haul
T1 Long Haul
T1 Long Haul
D4 Short Haul
T1 Short Haul
T1 Short Haul
T1 Short Haul
T1 Short Haul
T1 Short Haul
0dB
-7.5dB
-15dB
-22.5dB
0dB
-7.5dB
-15dB
-22.5dB
6V
DSX-1 (0ft to 133ft)
DSX-1 (133ft to 266ft)
DSX-1 (266ft to 399ft)
DSX-1 (399ft to 533ft)
DSX-1 (533ft to 655ft)
36
36
36
36
26
26
26
26
18
18
18
18
18
18
11 of 35
DS21349
CR2 (B010001): Control Register 2
MSb
RESET
PAT1
PAT0
SYMBOL
POSITION
RESET
PAT1
PAT0
CR2.7
CR2.6
CR2.5
TAIS
CR2.4
ENLOOP
CR2.3
ALB
CR2.2
LLB
CR2.1
RLB
CR2.0
TAIS
ENLOOP
ALB
LLB
LSb
RLB
FUNCTION
Resets device states and clears all registers.
Selects output data pattern (Table 4-F).
Selects output data pattern (Table 4-F).
0 = Transmit data normally
1 = Transmit unframed all ones
0 = Disable in-band loop-code detection
1 = Enable in-band loop-code detection
0 = Disable analog loopback
1 = Enable analog loopback
0 = Disable local loopback
1 = Enable local loopback
0 = Disable remote loopback
1 = Enable remote loopback
Table 4-F. Data Pattern Selection
PAT0
PAT1
0
0
1
1
0
1
0
1
DATA SOURCE
TPOS/TNEG
Transmit QRSS
In-band loop-up 00001
In-band loop-down 001
CR3 (B010010): Control Register 3
MSb
JA6HZ
TPD
—
SYMBOL
POSITION
JA6HZ
CR3.7
TPD
CR3.6
—
CR3.5
EQZMON20
CR3.4
EQZMON26
CR3.3
JA128
CR3.2
LIRST
CR3.1
TAOZ
CR3.0
EQZMON20
EQZMON26
JA128
LIRST
LSb
TAOZ
FUNCTION
0 = Set bandwidth of jitter attenuator to 3Hz
1 = Set bandwidth of jitter attenuator to 6Hz; not available if
JA128 = 1
0 = Enable transmitter outputs
1 = Disable transmitter outputs
—
0 = Normal receiver operation
1 = Add 20dB of resistive gain to inbound signal
0 = Normal receiver operation
1 = Add 26dB of resistive gain to inbound signal
0 = Jitter attenuator buffer depth = 32 bits
1 = Jitter attenuator buffer depth = 128 bits
0 = Normal operation
1 = Reset the receive LIU state machine
0 = Disable transmit alternate 1s and 0s
1 = Enable transmit alternate 1s and 0s
12 of 35
DS21349
IMR (B010011): Interrupt Mask Register
MSb
Z16D
JALT
DFMO
SYMBOL
POSITION
Z16D
IMR.7
JALT
IMR.6
DFMO
IMR.5
B8ZSD
IMR.4
QRSS
IMR.3
AIS
IMR.2
NLOOP
IMR.1
RCL
IMR.0
B8ZSD
QRSS
AIS
NLOOP
LSb
RCL
FUNCTION
0 = Enable 16-zero detect interrupt
1 = Disable 16-zero detect interrupt
0 = Enable jitter-attenuator limit-trip interrupt
1 = Disable jitter-attenuator limit-trip interrupt
0 = Enable driver-open interrupt
1 = Disable driver-open interrupt
0 = Enable B8ZS-detect interrupt
1 = Disable B8ZS-detect interrupt
0 = Enable QRSS interrupt
1 = Disable QRSS interrupt
0 = Enable AIS interrupt
1 = Disable AIS interrupt
0 = Enable network-loopback interrupt
1 = Disable network-loopback interrupt
0 = Enable receive carrier-loss interrupt
1 = Disable receive carrier-loss interrupt
TSR (B010100): Transition Status Register
MSb
Z16D
JALT
DFMO
B8ZSD
QRSS
AIS
NLOOP
LSb
RCL
SYMBOL
POSITION
FUNCTION
Z16D
TSR.7
JALT
TSR.6
DFMO
TSR.5
B8ZSD
TSR.4
QRSS
TSR.3
Set when the receiver detects B8ZS codewords; cleared when
IMR.4 is cleared.
Set when SR.3 changes state; cleared when IMR.3 is cleared.
AIS
TSR.2
Set when SR.2 changes state; cleared when IMR.2 is cleared.
NLOOP
TSR.1
Set when SR.1 changes state; cleared when IMR.1 is cleared.
RCL
TSR.0
Set when SR.0 changes state; cleared when IMR.0 is cleared.
Set when the receiver detects 16 consecutive 0s; cleared when
IMR.7 is cleared.
Set when the jitter attenuator FIFO reaches to within 4 bits of its
limit; cleared when IMR.6 is cleared.
Set when SR.5 changes state; cleared when IMR.5 is cleared.
13 of 35
DS21349
SR (B010101): Status Register
MSb
—
—
DFMO
SYMBOL
—
—
DFMO
—
QRSS
AIS
NLOOP
POSITION
SR.7
SR.6
SR.5
SR.4
SR.3
SR.2
SR.1
RCL
SR.0
—
QRSS
AIS
NLOOP
LSb
RCL
FUNCTION
—
—
Set when transmitter detects open circuit.
—
Set when the QRSS pattern is present at the receiver.
Set when the AIS pattern is present at the receiver.
Set when the in-band loop-up code is present at the receiver.
Set when receiver has detected consecutive s set forth by CR4.2.
Cleared when the receiver detects 14 1s in a window of 112 clock
cycles.
IR (B010110): Information Register
MSb
RL3
RL2
RL1
SYMBOL
POSITION
RL3
RL2
RL1
RL0
LUP
LDN
TSCD
LOTC
IR.7
IR.6
IR.5
IR.4
IR.3
IR.2
IR.1
IR.0
RL0
LUP
LDN
TSCD
LSb
LOTC
FUNCTION
—
—
—
—
Set when in-band loop-up code is being received.
Set when in-band loop-down code is being received.
Set when transmitter detects a short circuit.
Set when TCLK has not transitioned for approximately 5µs.
Receive Level Indication: RL0 is the LSB and RL3 is the MSB of a 4-bit nibble that is used to indicate the inbound
signal strength. Convert the binary to decimal and multiply by -2.5dB. The result indicates the approximate
attenuation seen at the receiver inputs.
14 of 35
DS21349
CR4 (B010111): Control Register 4
MSb
—
—
SYMBOL
POSITION
—
—
—
—
—
CR4.7
CR4.6
CR4.5
CR4.4
CR4.3
RCL2048
CR4.2
XFMR2
CR4.1
XFMR1
CR4.0
—
—
—
RCL2048
XFMR2
FUNCTION
—
—
—
—
—
0 = RCL threshold: 192 consecutive 0s
1 = RCL threshold: 2048 consecutive 0s
Set to 0 for use with standard transformers.
Set to 1 for use with alternate transformers (Table 11-C)
Set to 0 for use with standard transformers.
Set to 1 for use with alternate transformers (Table 11-C)
15 of 35
LSb
XFMR1
DS21349
5. TRANSMITTER
5.1
Transmit Digital Data Interface
Data is clocked into the device at the TCLK rate. In bipolar mode, TPOS and TNEG are the data inputs;
in NRZ mode, TDATA is the data input. Input data can pass through either the jitter attenuator or the
B8ZS encoder or both. In software mode, setting ENCENB enables B8ZS encoding. In hardware mode,
floating the MODE1 pin enables B8ZS encoding. With B8ZS encoding enabled, the L0 through L3 inputs
determine the coding and is listed in Table 4-E. TCLK supplies input synchronization. See Section 12 for
the TCLK and MCLK timing requirements.
5.2
Transmit Monitoring
In software mode, the DFMO bit in the status register is set when an open circuit in the transmitter path is
detected. A transition on this bit can provide an interrupt, and a transition sets the DFMO bit in the
transition status register. Setting CDFMO in the interrupt mask register, leaving a 1 in that bit location
masks the interrupt.
5.3
Transmit Idle Mode
Transmit idle mode allows multiple transceivers to be connected to a single line for redundant
applications. When TCLK is not present, transmit idle mode becomes active, and TTIP and TRING
change to high-impedance state. Remote loopback, dual loopback, TAIS, or detection of network loop-up
code in the receive direction temporarily disable the high-impedance state.
5.4
Transmit Pulse Shape
As shown in Table 4-E, line build-out control inputs (L0 through L3) determine the transmit pulse shape.
In software mode, these control inputs are located in control register 1; in hardware mode, these control
inputs are the L0 through L3 pins.
Shaped pulses meeting the various T1, DS1, and DSX-1 specifications are applied to the AMI line driver
for transmission onto the line at TTIP and TRING. The transceiver produces DSX-1 pulses for short-haul
T1 applications (settings from 0dB to 6dB of cable) and DS1 pulses for long-haul T1 applications
(settings from 0dB to -22.5dB). Refer to Table 4-E for pulse mask specifications.
16 of 35
DS21349
6. RECEIVER
A 1:1 transformer provides the interface between the twisted pair and receiver inputs RTIP and RRING.
Recovered data is output at RPOS and RNEG (or RDATA in NRZ mode), and the recovered clock is
output at RCLK. See Section 12 for receiver timing specifications.
6.1
Receive Equalizer
The receiver can apply up to 36dB of gain. Control of the equalizer is accomplished by the L0 through L3
control inputs. These control signals are detailed in Table 4-E and determine the maximum gain that is
applied. In software mode, these control signals are in Control Register 1; in hardware mode, these
control inputs are the L0 through L3 pins. With L0 low, up to 36dB of gain can be applied; when L0 is
high, 26dB can be applied in the gain limit to provide better noise immunity in shorter loop operations.
6.2
Receive Data Recovery
The clock and data recovery engine provides input jitter tolerance that exceeds the requirements of AT&T
62411. Inbound signal is filtered, equalized, and over-sampled 16 times. Then it is applied to the B8ZS
decoder if enabled.
6.3
Receive Digital-Data Interface
Recovered data is routed to the RCL monitor. In software mode, data also goes through the alarm
indication signal (AIS) monitor. The jitter attenuator can be enabled or disabled in the receive path or
transmit path. Received data can be routed to the B8ZS decoder or bypassed. Finally, the device can send
the digital data to the framer as either bipolar or NRZ data.
6.4
Receive Monitor Mode
The receive equalizer can be used in monitor-mode applications. Monitor-mode applications require
20dB of resistive attenuation of the signal, plus an allowance for cable attenuation (less than 20dB). In
software mode, setting CR3.4 (EQZMON20) enables the device to operate in monitor-mode applications
that require 20dB of resistive attenuation of the signal. Setting CR3.3 (EQZMON26) enables the device
to operate in monitor-mode applications that require 26dB of resistve attenuation. Setting both CR3.3 and
CR3.4 enables the device to operate in monitor-mode applications that require 32dB of resistive
attenuation. The monitor mode feature is not available in hardware mode.
17 of 35
DS21349
7. JITTER ATTENUATION
The jitter attenuator only requires a jitter-free clock at 1.544MHz applied to the MCLK input. In
hardware mode, the jitter attenuator is a 32-bit FIFO buffer. Pulling the JASEL pin high places the jitter
attenuator in the receive path. Pulling the JASEL pin low places the jitter attenuator in the transmit path,
floating the JASEL pin disables the jitter attenuator. In software mode, clearing CR1.6 (JASEL0) disables
the jitter attenuator, setting CR1.6 enables the jitter attenuator. If enabled, clearing CR1.7 (JASEL1)
places the jitter attenuator in the transmit path, setting CR1.7 places the jitter attenuator in the receive
path. The jitter attenuator FIFO is 32 bits in length if CR3.2 (JA128) is cleared, 128 bits if set. The device
clocks data in the jitter attenuator using TCLK if placed in the transmit path, and RCLK if placed in the
receive path. Data is clocked out of the jitter attenuator using the dejittered clock produced by the internal
PLL. When the jitter attenuator is within two bits of overflowing or underflowing, the jitter attenuator
will adjust the output clock by one-eighth of a clock cycle. The jitter attenuator adds an average delay of
16 bits if the buffer depth is 32 bits in length, 64 bits if the buffer depth is 128 bits in length. In the event
of an RCL condition, if the jitter attenuator is in the receive path then RCLK is derived from MCLK.
Transition Status register bit TSR.6 (JALT) indicates that the jitter attenuator has adjusted the output
clock. This bit is latched, when set it remains set until the software reads the bit. The JALT can also
produce a hardware interrupt.
8. HARDWARE MODE
The DS21349 operates in hardware mode when the MODE1 pin is pulled low or floated. In hardware
mode, configuration of the device is under control of various input pins. RPOS, RNEG, and RDATA are
valid on the rising edge of RCLK only. Some functions such as INT, clock edge select, and some
diagnostic modes are not available.
18 of 35
DS21349
9. SOFTWARE MODE
The DS21349 operates in software mode when the MODE1 pin is pulled high. In software mode, a
microprocessor controls the device and reads its status through the serial port, which provides access to
the internal registers. The host processor can completely configure the device as well as get diagnostics
and status reports through the serial port. In NRZ mode, bipolar violation insertions and logic error
insertions are controlled by the BPV and INSLER pins. Similarly, the recovered clock, data, and BPV
detection are available only at output pins. All other mode settings and diagnostic information are
available through the serial port. Figure 9-1 and Figure 9-2 show the serial port data structure. The
registers are accessible through a 16-bit word composed of an 8-bit command and address byte and a
subsequent 8-bit data byte. Software mode allows control of the output timing. The CLKE pin determines
when SDO is valid relative to SCLK and when receive data is valid relative to RCLK.
9.1
Interrupt Handling
In software mode, the DS21349 provides a latched interrupt output pin. When enabled, a change in any of
the status register bits generates an interrupt. When an interrupt occurs, the INT output pin is driven low.
The INT output pin structure is an open-drain only. Each device that shares the INT line requires an
external pullup resistor. The interrupt is cleared when the interrupt condition no longer exists, and a 1 is
written to the appropriate bit in the interrupt mask register. Leaving a 1 in any of the bits in the interrupt
mask register masks that interrupt. Clearing that bit re-enables the interrupt.
Table 9-A. CLKE Pin Selection
CLKE PIN
OUTPUT
OUTPUT UPDATED ON
RPOS
LOW
RNEG
Falling RCLK
RDATA
SDO
Rising SCLK
RPOS
HIGH
RNEG
Rising RCLK
RDATA
SDO
Falling SCLK
19 of 35
DS21349
Figure 9-1. Serial Data Port Operation for Read Access
Read Access CLKE = 0
SCLK
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
D0
D1
D2
D3
D4
D5
D6
16
CS
SDI
A1
1
A2
A3
A4
A5
B
0
(lsb)
(msb)
SDO
D7
(lsb)
(msb)
Read Access CLKE = 1
1
SCLK
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
CS
SDI
1
A1
A2
A3
A4
A5
0
(lsb)
B
(msb)
SDO
D1
D0
D2
D3
D4
D5
D6
D7
(lsb)
(msb)
Figure 9-2. Serial Data Port Operation for Write Access
SCLK
1
2
3
4
5
6
0
A1
A2
A3
A4
A5
7
8
9
10
11
12
13
14
15
16
CS
SDI
(lsb)
0
B
DO
(msb)
(lsb)
WRITE ACCESS ENABLED
SDO
20 of 35
D1
D2
D3
D4
D5
D6
D7
(msb)
DS21349
Table 9-B. Control and Operation Mode Selection
MODE1
MODE0
Low
Low
Low
High
High
High
Open
Open
Open
Low
High
Open
Low
High
Open
Low
High
Open
HARDWARE SOFTWARE NRZ BIPOLAR AMI B8ZS
On
On
On
Off
Off
Off
On
On
On
Off
Off
Off
On
On
On
Off
Off
Off
Off
Off
On
X
X
X
On
On
On
21 of 35
On
On
Off
X
X
X
Off
Off
Off
Off
Off
On
X
X
X
Off
Off
Off
Off
Off
Off
X
X
X
On
On
On
OUTPUTS
DISABLED
No
Yes
No
No
Yes
No
No
Yes
No
DS21349
10. DIAGNOSTIC MODE OPERATION
The DS21349 offers several diagnostic modes as listed in Table 10-A. Various diagnostic modes are only
available in software mode. In hardware mode, the diagnostic modes are selected by a combination of pin
settings. In software mode, the diagnostic modes are selected by setting appropriate bits in the diagnostic
control register.
Table 10-A. Diagnostic Modes
AVAILABILITY
HARDWARE SOFTWARE
Local Loopback (LLB)
Yes
Yes
Analog Loopback (ALB)
Yes
Yes
Remote Loopback (RLB)
Yes
Yes
In-Band Network Loopback (NLB)
Yes
Yes
Dual Loopback (DLOOP)
Yes
Yes
Internal Data Pattern Generation and Detection
Transmit AIS (TAIS)
Yes
Yes
Quasirandom Signal Source (QRSS)
Yes
Yes
In-Band Loop-Up/Down Code Generator
No
Yes
Error Insertion and Detection
Bipolar Violation Insertion (INSBPV)
Yes
Yes
Logic Error Insertion (INSLER)
Yes
Yes
Bipolar Violation Detection (BPV)
Yes
Yes
Logic Error Detection, QRSS (QPD)
Yes
Yes
Alarm Condition Monitoring
Receive Carrier Loss (RCL) Monitoring
Yes
Yes
Receive Alarm Indication Signal (AIS) Monitoring
No
Yes
Transmit Driver Failure Monitoring (DFMO)
No
Yes
Jitter Attenuator Limit Trip (JALT)
No
Yes
Other Diagnostic Reports
Receive Line Attenuation Indicator (LATN)
No
Yes
DIAGNOSTIC MODE
SOFTWARE MODE
MASKABLE
No
No
No
Yes
No
No
Yes
No
No
No
No
No
Yes
Yes
Yes
Yes
No
10.1 Loopback Modes
10.1.1 Local Loopback (LLB)
When local loopback is enabled (set LLB in CR2, or pull the LLB pin high), inbound data at the receiver
inputs are ignored. TCLK and TPOS/TNEG pass through the jitter attenuator if enabled and are output at
RCLK and RPOS/RNEG. The transmit path is unaffected by LLB, and will continue to transmit data
normally (or AIS if TAIS is enabled).
10.1.2 Analog Loopback (ALB)
When analog loopback (ALB) is enabled (set ALB in CR2, or float the LLB pin), the receiver input pins
are disconnected from the clock and data recovery circuit and replaced by TTIP and TRING. This tests
the entire device including the jitter attenuator, transmitter, and receiver circuits.
10.1.3 Remote Loopback (RLB)
When remote loopback (RLB) is enabled (set RLB in CR2, or pull RLB pin high), inbound data at the
receiver inputs is looped back to the transmitter path. Data passes through the jitter attenuator if enabled.
The B8ZS encoder and decoder are not included in the loopback path. The receive path continues to
operate normally.
22 of 35
DS21349
10.1.4 Network Loopback
When ENLOOP is enabled (set ENLOOP in CR2, or float the ENLOOP pin), the in-band loop code
detector is enabled. The receiver detects the in-band loop code patterns (00001 = loop up and
001 = loop down) present in the inbound data. The detectors detect both framed and unframed loop codes.
When the loop-up pattern is detected and present for 5 seconds, the device invokes remote loopback.
ENLOOP is dropped when:
1) The in-band loop-down pattern is present for 5 seconds.
2) RLB is activated.
3) ALB is activated.
10.1.5 Dual Loopback
Dual loopback is the simultaneous enabling of RLB and LLB. If the jitter attenuator is enabled and, when
both loopback paths are enabled, the jitter attenuator is placed in the local loopback path.
23 of 35
DS21349
MCLK
Figure 10-1. Loopbacks in the DS21349 Block Diagram
VCO/PLL
NLOOP
AIS Detector
RCLK
RPOS
RNEG
LOTC mux
QRSS Detector
In-Band Loop Gen.
In-Band Loop
Code Detector
QRSS
B8ZS Decoder
B8ZS Encoder
Logic Error Insert
Remote Loopback
Jitter Attenuator
Local Loopback
RCL Detector
Filter
Clock / Data
Recovery
Transmit AIS
TTIP
Wave Shaping
TRING
Line Drivers
RTIP
CSU Filters
RRING
Peak Detect
RCL/QPD
TCLK
TPOS
TNEG
10.2 Internal Pattern Generation and Detection
10.2.1 Transmit Alarm-Indication Signal (TAIS)
When TAIS is enabled (set TAIS in CR2, or pulling the TAIS pin high), the transmitter inputs
TPOS/TNEG and TDATA are ignored and the devices transmits unframed all ones at the transmitter
outputs at the TCLK frequency. If TCLK is not present, then the device uses MCLK to transmit. Both
TAIS and LLB can be enabled at the same time. The transmitter input data is looped back to the receiver
outputs through the jitter attenuator if enabled and the unframed all ones pattern is transmitted at TTIP
and TRING.
10.2.2 Quasirandom Signal Source (QRSS)
The QRSS data pattern is described in AT&T 62411. The pattern is represented by the polynomial 220- 1
with the additional requirement that no more than 14 consecutive 0s be present in the pattern. When
QRSS is enabled (PAT0 = 0 and PAT1 = 1 in CR2 or float the QRSS pin), the data at the transmitter
inputs TPOS/TNEG or TDATA is ignored and replaced by the output of the QRSS pattern generator. In
addition, logic errors can be inserted into the data pattern with a rising edge on the INSLER input pin. If
no logic errors are to be inserted, then the INSLER pin must remain low. If the logic error occurs on the
same clock cycle as a 1 that has been inserted to suppress 15 0s, then the logic error is delayed until the
next clock cycle. The logic error insertion is available in both NRZ and bipolar data modes. Enabling the
QRSS pattern also enables the QRSS detector in the receiver. Pattern synchronization occurs when there
are no errors in 64 bits. When synchronized, the QPD output pin goes low. Once synchronized, an error
in the pattern causes the QPD output to go high for one-half RCLK cycle. In software mode, the level on
the CLKE pin determines the relationship between QPD and RCLK. When CLKE is low, QPD is high
when RCLK is high. When CLKE is high, QPD is high when RCLK is low. The QPD output can be used
to trigger an external bit error counter. When RCL is active or the receiver is not synchronized to the
QRSS pattern, then QPD maintains an output high.
24 of 35
DS21349
In software mode, the device can generate an interrupt to indicate that the QRSS pattern synchronization
has been declared or lost. Clearing the QRSS bit in the interrupt mask register enables the interrupt. Use
the QPD output to increment an external bit error counter and use the interrupt to reset the counter. The
QRSS bit in the status register is set when the QRSS pattern is detected and cleared when pattern is lost
(more than 6 bit errors in a window of 64 bits). The QRSS bit in the transition status register indicates
that the QRSS status has changed since the last QRSS interrupt clear command.
10.2.3 In-Band Network Loop-Up or Loop-Down Code Generator
In-band network loop-up or loop-down transmission is available in software mode only. The loop-up
code is transmitted when PAT0 = 1 and PAT1 = 0 in CR2. Logic errors and bipolar violations can still be
inserted when loop codes are being transmitted.
10.3 Error Insertion and Detection
10.3.1 Bipolar Violation Insertion (INSBPV)
INSBPV is available in NRZ mode. Sampling occurs on the falling edge of TCLK. A rising edge on the
NSBPV pin inserts a BPV on the next available mark, except in the following conditions:
1) If the BPV would violate a B8ZS codeword.
2) When LLB and TAIS are both active. In this case, the BPV is looped back to the BPV pin and the line
driver transmits all ones with no violation.
3) When RLB is active.
4) When NLOOP is active.
BPVs can be inserted in both NRZ and bipolar data modes when the DS21349 is configured to transmit
internally generated data patterns (QRSS or in-band loop codes).
10.3.2 Logic Error Insertion (INSLE)
When transmitting QRSS or in-band loop codes, a logic error is inserted into the outbound data pattern on
a rising edge of the INSLER pin. Remember, when transmitting the QRSS pattern, logic error insertion is
inhibited if the error would replace a 1 with a 0 and result in a string of 15 or more consecutive 0s.
10.3.3 Logic Error Detection (QPD)
After QRSS pattern synchronization, logic errors are reported at the QPD output pin. If a logic error
occurs, the QPD pin goes high for one-half RCLK cycle. In software mode, the CLKE pin determines the
phase relationship between QPD and RCLK. When CLKE is low, QPD is high when RCLK is high.
When CLKE is high, QPD is high when RCLK is low. To count logic errors, use the QPD output to
increment an external error counter. A continuous output high indicates loss of synchronization to the
QRSS pattern or receive-carrier loss.
10.3.4 Bipolar Violation Detection (BPV)
When the B8ZS encoders and decoders are disabled or when configured for NRZ mode, bipolar
violations are reported at the BPV output pin. BPV goes high for a full clock cycle to indicate a bipolar
violation. When the B8ZS encoders and decoders are enabled, BPVs that are not part of codewords are
not reported.
25 of 35
DS21349
10.4 Alarm Monitoring
10.4.1 Receive-Carrier Loss (RCL)
The receiver counts inbound 0s and declares RCL when the counter reaches 192. This applies to hardware
mode and software mode if the RCL2048 bit is cleared in CR4. In software mode, setting the RCL2048
bit changes the RCL counter to declare receive-carrier loss after 2048 consecutive 0s. Once set, the RCL
bit will remain set until the receiver detects a 12.5% density of 1s in a sliding window of 112 bits,
provided that there are no more than 98 consecutive 0s in that 112-bit window. When RCL is active,
RCLK is replaced by MCLK. RCL is indicated by an output high on the RCL pin and with a 1 in SR.0.
10.4.2 Alarm-Indication-Signal Detection (AIS)
AIS detection is only available in software mode. The receiver declares receipt of AIS when fewer than
six 0s are detected in 4632 bits (3ms). AIS is cleared when three or more 0s are received in 4632 bits. The
AIS bit in the status register (SR.2) indicates the presence of AIS. When the AIS status bit changes, the
AIS bit in the transition status register (TSR.2) is set. A change in the AIS status will generate an
interrupt if the AIS interrupt mask bit (IMR.2) bit is cleared.
10.4.3 Driver-Fail Monitor-Open (DFMO)
The DFMO bit is set in the status register when the transmitter outputs detect an open circuit. DFMO can
generate an interrupt if the DFMO interrupt mask bit (IMR.5) is cleared. This is not supported in
hardware mode.
10.4.4 Jitter Attenuator Limit Trip (JALT)
If the incoming jitter exceeds either 120 UIp-p (buffer depth is 128 bits) or 28 UIp-p (buffer depth is 32
bits), then the DS21349 will divide the internal nominal 24.704MHz (T1) clock by either 15 or 17 instead
of the normal 16 to keep the buffer from overflowing. When the device divides by either 15 or 17, it also
sets the jitter attenuator limit trip (JALT) bit in information register 1 (IR1).
10.5 Other Diagnostic Reports
10.5.1 Receive Line-Attenuation Indication
The device reports the approximate inbound signal strength in the status register (IR). The four most
significant bits indicate the signal strength in approximately 2.5dB increments.
26 of 35
DS21349
11. NETWORK INTERFACE
Transformer specifications are listed in Table 11-A and Table 11-B. Table 11-C illustrates the series
resistance necessary for the basic interface and is associated with different transformer turns ratios.
Smaller turns ratios result in lower power-supply requirements. However, series resistance provides
added protection from potentially damaging voltages that can occur during lightning strikes. A basic
network interface is illustrated in Figure 11-1. For a complete discussion of network interface design,
refer to Application Note 324: T1/E1 Network Interface Design.
Table 11-A. Specifications for Receive Transformer
SPECIFICATION
RECOMMENDED VALUE
Turns Ratio (all applications)
Primary Inductance
Leakage Inductance
Interwinding Capacitance
Receive Transformer DC Resistance
Primary (Device Side)
Secondary
1:1 ±2%
600µH minimum
1.0µH maximum
40pF maximum
2Ω maximum
2Ω maximum
Table 11-B. Specifications for Transmit Transformer
SPECIFICATION
Turns Ratio, 3.3V
Primary Inductance
Leakage Inductance
Interwinding Capacitance
Transmit Transformer DC Resistance
Primary (Device Side)
Secondary
RECOMMENDED VALUE
1:3 ±2%
600µH minimum
1.0µH maximum
40pF maximum
1.0Ω maximum
2.0Ω maximum
Table 11-C. Transformer Turns Ratio vs. Series Resistance
XFMR1
(CR4.0)
XFMR2
(CR4.1)
OPERATING
VOLTAGE
(V)
APPLICATION
N
Rt (Ω)
0
0
3.3
Long/Short
D4
1:3
0
0
1
3.3
Long/Short
1
0
3.3
Long/Short
1
1
3.3
Long/Short
1:2
1:3
1:2.5
1:3
1:2
1:3
0
3
0
1
0
3
27 of 35
DS21349
Figure 11-1. Basic Network Interface
+VDD
C
Rt
TTIP
TRANSMIT
LINE
VDD (21)
VSS (22)
TRING
Rt
N:1
(larger winding
toward the network)
VDD (15)
VSS (14)
0.1µF
0.01µF
10µF
0.1µF
10µF
DS21349
RTIP
RECEIVE
LINE
RRING
1:1
Rr
Rr
0.1µF
Note 1: All resistor values are ±1%.
Note 2: The Rr resistors should be 50Ω each for T1 lines.
Note 3: C = 1µF if using a 1:2 transformer; C = 2µF if using a 1:3 transformer.
28 of 35
MCLK
1.544MHz
DS21349
Figure 11-2. T1 Transmit Pulse Template
1.2
MAXIMUM CURVE
UI
Time Amp.
1.1
1.0
-0.77
-0.39
-0.27
-0.27
-0.12
0.00
0.27
0.35
0.93
1.16
0.9
0.8
NORMALIZED AMPLITUDE
0.7
0.6
-500
-255
-175
-175
-75
0
175
225
600
750
0.05
0.05
0.80
1.15
1.15
1.05
1.05
-0.07
0.05
0.05
0.5
MINIMUM CURVE
UI
Time Amp.
-0.77
-0.23
-0.23
-0.15
0.00
0.15
0.23
0.23
0.46
0.66
0.93
1.16
-500
-150
-150
-100
0
100
150
150
300
430
600
750
-0.05
-0.05
0.50
0.95
0.95
0.90
0.50
-0.45
-0.45
-0.20
-0.05
-0.05
0.4
0.3
0.2
0.1
0
-0.1
-0.2
-0.3
T1.102/87, T1.403,
CB 119 (Oct. 79), &
I.431 Template
-0.4
-0.5
-500 -400 -300
-200 -100
0
100
200
TIME (ns)
29 of 35
300
400
500
600
700
DS21349
Figure 11-3. Jitter Tolerance
UNIT INTERVALS (UIp-p)
1k
100
DS21349
TOLERANCE
TR 62411 (DEC. 90)
10
1
0.1
1
10
100
1k
10k
100k
FREQUENCY (Hz)
Figure 11-4. Jitter Attenuation
-20dB
C
ve
ur
A
T1
TR 62411 (Dec. 90)
Prohibited Area
-40dB
rve
Cu
JITTER ATTENUATION (dB)
0dB
B
-60dB
1
10
100
1K
FREQUENCY (Hz)
30 of 35
10K
100K
DS21349
12. DC CHARACTERISTICS
ABSOLUTE MAXIMUM RATINGS
Voltage Range on Any Pin Relative to Ground
Operating Temperature Range for DS21349QN
Storage Temperature Range
Soldering Temperature
-1.0V to +6.0V
-40°C to +85°C
-55°C to +125°C
See IPC/JEDEC J-STD-020 Specification
Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only,
and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is
not implied. Exposure to the absolute maximum rating conditions for extended periods may affect device reliability.
RECOMMENDED DC OPERATING CONDITIONS
(TA = -40°C to +85°C)
PARAMETER
Logic 1
Logic 0
Supply for 3.3V Operation (Note 1)
SYMBOL
MIN
TYP
MAX
UNITS
VIH
VIL
VDD
2.0
-0.3
3.135
3.3
5.5
+0.8
3.465
V
V
V
SYMBOL
MIN
TYP
MAX
UNITS
CAPACITANCE
(TA = +25°C)
PARAMETER
Input Capacitance
Output Capacitance
CIN
COUT
5
7
pF
pF
DC CHARACTERISTICS
(VDD = 3.3V ±5%, TA = -40°C to +85°C.)
PARAMETER
Input Leakage (Note 2)
Output Leakage (Note 3)
Output Current (2.4V)
Output Current (0.4V)
Power Dissipation at 3.3V (Notes 4, 5)
SYMBOL
MIN
IIL
ILO
IOH
IOL
PDD
-1.0
Note 1: Applies to VDD.
Note 2: 0V < VIN < VDD.
Note 3: Applied to INT when tri-stated
Note 4: TCLK = MCLK = 1.544MHz.
Note 5: Power dissipation for an all-ones data density.
31 of 35
TYP
-1.0
+4.0
300
MAX
UNITS
+1.0
1.0
µA
µA
mA
mA
mW
DS21349
AC CHARACTERISTICS: SERIAL PORT (MODE1 = 1)
(VDD = 3.3V ±5%, TA = -40°C to +85°C.) (Figure 12-1 and Figure 12-2)
PARAMETER
Setup Time CS to SCLK
Setup Time SDI to SCLK
Hold Time SCLK to SDI
SCLK High/Low Time
SCLK Rise/Fall Time
SCLK to CS Inactive
CS Inactive Time
SCLK to SDO Valid
SCLK to SDO Tri-State
CS Inactive or SCLK to SDO Tri-State
SYMBOL
MIN
tCSS
tSSS
tSSH
tSLH
tSRF
tLSC
tCM
tSSV
tSSH
tCSH
50
50
50
200
TYP
MAX
50
50
250
75
100
100
Figure 12-1. Serial Bus Read Timing (MODE1 = 1)
CLKE = 0
CS
tLSC
SCLK
SDO
tCSH
tSSV
HIGH-Z
LSB
HIGH-Z
MSB
CLKE = 1
CS
tLSC
SCLK
tCSH
tSSV
HIGH-Z
SDO
HIGH-Z
MSB
LSB
Figure 12-2. Serial Bus Write Timing (MODE1 = 1)
tCM
CS
SCLK
tSSS
SDI
tSRF
tCSS
tLSC
tSLH
tSSH
LSB
MSB
LSB
Control Byte
MSB
Data Byte
32 of 35
UNITS
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
DS21349
AC CHARACTERISTICS: RECEIVE SIDE
(VDD = 3.3V ±5%, TA = -40°C to +85°C.) (Figure 12-3)
PARAMETER
SYMBOL
RCLK Period
MIN
tCP
RCLK Pulse Width (Note 7)
Delay RCLK to RPOS, RNEG Valid
ns
ns
150
ns
50
Note 6: Jitter attenuator enabled in the receive path.
Note 7: Jitter attenuator disabled or enabled in the transmit path.
Figure 12-3. AC Characteristics for Receive Side
tDD
tCH
RCLK
tCP
RPOS
RNEG
IN SOFTWARE MODE:
CLKE = 1
RPOS
RNEG
IN SOFTWARE AND
HARDWARE MODE:
CLKE = 0
33 of 35
UNITS
200
tDD
tDD
MAX
648
tCH
tCL
tCH
tCL
RCLK Pulse Width (Note 6)
TYP
tCL
ns
DS21349
AC CHARACTERISTICS: TRANSMIT SIDE
(VDD = 3.3V ±5%, TA = -40°C to +85°C.) (Figure 12-4)
PARAMETER
SYMBOL
MIN
TYP
MAX
TCLK Period
tCP
TCLK Pulse Width
tCH
tCL
75
ns
TPOS/TNEG Setup to TCLK Falling or Rising
tSU
20
ns
TPOS/TNEG Hold from TCLK Falling or Rising
tHD
20
ns
TCLK Rise and Fall Times
648
UNITS
t R, t F
25
Figure 12-4. AC Characteristics for Transmit Side
tCP
tCH
tCL
tR
TCLK
TPOS
TNEG
tSU
tHD
34 of 35
ns
tF
ns
DS21349
13. PACKAGE INFORMATION
(The package drawing(s) in this data sheet may not reflect the most current specifications. The package number provided for
each package is a link to the latest package outline information.)
13.1 28-Pin PLCC (56-G4001-001)
35 of 35
Maxim/Dallas Semiconductor cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim/Dallas Semiconductor product.
No circuit patent licenses are implied. Maxim/Dallas Semiconductor reserves the right to change the circuitry and specifications without notice at any time.
Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600
© 2006 Maxim Integrated Products • Printed USA
The Maxim logo is a registered trademark of Maxim Integrated Products, Inc. The Dallas logo is a registered trademark of Dallas Semiconductor.
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