ISO-CMOS ST-BUSTM Family
MT8952B
HDLC Protocol Controller
Data Sheet
Features
August 2011
•
Formats data as per X.25 (CCITT) level-2
standards
•
Go-Ahead sequence generation and detection
•
Single byte address recognition
•
Microprocessor port and directly accessible
registers for flexible operation and control
Ordering Information
MT8952BE1
MT8952BP1
MT8952BPR1
MT8952BS1
28
28
28
28
Pin
Pin
Pin
Pin
PDIP*
PLCC*
PLCC*
SOIC*
Tubes
Tubes
Tape & Reel
Tubes
*Pb Free Matte Tin
-40C to +85C
•
19 byte FIFO in both send and receive paths
•
Handshake signals for multiplexing data links
•
High speed serially clocked output (2.5 Mbps)
•
Digital sets, PBXs and private packet networks
•
ST-BUS compatibility with programmable channel
selection for data and separate timeslot for
control information
•
D-channel controller for ISDN basic access
•
C-channel controller to Digital Network Interface
Circuits (typically MT8972)
•
Interprocessor communication
•
Independent watchdog timer
•
Facility to disable protocol functions
•
Low power ISO-CMOS technology
Description
The MT8952B HDLC Protocol Controller frames and
formats data packets according to X.25 (Level 2)
Recommendations from the CCITT.
Applications
•
Data link controllers and protocol generators
TEOP
C-Channel
Interface
Transmit
FIFO
Transmit
Logic
Zero
Insertion
Flag/Abort
Generator
CDSTo
D0-D7
A0-A3
Micro
Processor
R/W
CS
E
Interface
F0i
Control
Interrupt
Registers
Address
Decoder
and Status
Register
Timing
Logic
CKi
RxCEN
TxCEN
IRQ
WD
VDD
VSS
Receive
FIFO
Receive Logic
Address
Detection
Zero
Deletion
Flag/Abort/
Idle
Detection
RST
CDSTi
REOP
Figure 1 - Functional Block Diagram
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Zarlink, ZL and the Zarlink Semiconductor logo are trademarks of Zarlink Semiconductor Inc.
Copyright 1997-2011, Zarlink Semiconductor Inc. All Rights Reserved.
MT8952B
CDSTi
CDSTo
RxCEN
TxCEN
VDD
RST
F0i
4
3
2
1
28
27
26
VDD
RST
F0i
CKi
TEOP
REOP
D7
D6
D5
D4
D3
D2
D1
D0
WD
IRQ
A0
A1
A2
A3
CS
5
6
7
8
9
10
11
12
13
14
15
16
17
18
28
27
26
25
24
23
22
21
20
19
18
17
16
15
25
24
23
22
21
20
19
CKi
TEOP
REOP
D7
D6
D5
D4
E
R/W
VSS
D0
D1
D2
D3
1
2
3
4
5
6
7
8
9
10
11
12
13
14
TxCEN
RxCEN
CDSTo
CDSTi
WD
IRQ
A0
A1
A2
A3
CS
E
R/W
VSS
Data Sheet
28 PIN PLCC
28 PIN PDIP/SOIC
Figure 2 - Pin Connections
Change Summary
Changes are from the November 2005 issue to the August 2011 issue.
Page
Item
1
Ordering Information
Change Summary
Removed leaded packages as per PCN notice.
Pin Description
Pin No.
Name
Description
1
TxCEN
Transmit Clock Enable - This active LOW input enables the transmit section in the External
Timing Mode. When LOW, CDSTo is enabled and when HIGH, CDSTo is in high impedance
state. If the Protocol Controller is in the Internal Timing Mode, this input is ignored.
2
RxCEN
Receive Clock Enable - This active LOW input enables the receive section in the External
Timing Mode. When LOW, CDSTi is enabled and when HIGH, the clock to the receive
section is inhibited. If the Protocol Controller is in the Internal Timing Mode, this input is
ignored.
3
CDSTo
C and D channel Output in ST-BUS format - This is the serial formatted data output from
the transmitter in NRZ form. It is in ST-BUS format if the Protocol Controller is in Internal
Timing Mode with the data in selected timeslots (0,2,3 and 4) and the C-channel information
in timeslot No. 1. If the Protocol Controller is in External Timing Mode, the formatted data is
output on the rising edge of the clock (CKi) when TxCEN LOW. If TxCEN is HIGH, CDSTo is
in high impedance state.
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MT8952B
Data Sheet
Pin Description (continued)
Pin No.
Name
Description
4
CDSTi
C and D channel Input in ST-BUS format - This is the serial formatted data input to the
receiver in NRZ form. It must be in ST-BUS format if the Protocol Controller is in Internal
Timing Mode with the input data in selected timeslots (0,2,3 and 4) and the C-channel
information in timeslot No.1. If the Controller is in External Timing Mode, the serial input data
is sampled on the falling edge of the clock CKi when RxCEN is LOW. If RxCEN is HIGH, the
clock to receive section is inhibited.
5
WD
Watch-Dog Timer output - Normally a HIGH level output, going LOW if the Watchdog timer
times out or if the external reset (RST) is held LOW. The WD output remains LOW as long
as RST is held LOW.
6
IRQ
Interrupt Request Output (Open Drain) - This active LOW output notifies the controlling
microprocessor of an interrupt request. It goes LOW only when the bits in the Interrupt
Enable Register are programmed to acknowledge the source of the interrupt as defined in
the Interrupt Flag Register.
7-10
A0-A3
Address Bus Inputs - These bits address the various registers in the Protocol Controller.
They select the internal registers in conjunction with CS, R/W inputs and E Clock. (Refer to
Table 1.)
11
CS
12
E
13
R/W
Read/Write Control - This input controls the direction of data flow on the data bus. When
HIGH, the I/O buffer acts as an output driver and as an input buffer when LOW.
14
VSS
Ground (0 Volt).
15-22
D0-D7
Bidirectional Data Bus - These Data Bus I/O ports allow the data transfer between the
HDLC Protocol Controller and the microprocessor.
23
REOP
Receive End Of Packet (Output) - This is a HIGH going pulse that occurs for one bit
duration when a closing flag is detected on the incoming packets, or the incoming packet is
aborted, or when an invalid packet of 24 or more bits is received.
24
TEOP
Transmit End Of Packet (Output) - This is a HIGH going pulse that occurs for one bit
duration when a packet is transmitted correctly or aborted.
25
CKi
Clock Input (Bit rate clock or 2 x bit rate clock in ST-BUS format while in the Internal
Timing Mode and bit rate Clock in the External Timing Mode) - This is the clock input
used for shifting in/out the formatted packets. It can be at bit rate (C2i) or twice the bit rate
(C4i) in ST-BUS format while the Protocol Controller is in the Internal Timing Mode. Whether
the clock should be C2i (typically 2.048 MHz) or C4i (typically 4.096 MHz) is decided by the
BRCK bit in the Timing Control Register. If the Protocol Controller is in the External Timing
Mode, it is at the bit rate.
26
F0i
Frame Pulse Input - This is the frame pulse input in ST-BUS format to establish the
beginning of the frame in the Internal Timing Mode. This is also the signal clocking the
watchdog timer.
27
RST
RESET Input - This is an active LOW Schmitt Trigger input, resetting all the registers
including the transmit and receive FIFOs and the watchdog timer.
28
VDD
Supply (5 Volts).
Chip Select Input - This is an active LOW input enabling the Read or Write operation to
various registers in the Protocol Controller.
Enable Clock Input - This input activates the Address Bus and R/W input and enables data
transfers on the Data Bus.
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MT8952B
Data Sheet
Address Bits
Registers
A3
A2
A1
A0
Read
Write
0
0
0
0
FIFO Status
-
0
0
0
1
Receive Data
Transmit Data
0
0
1
0
Control
Control
0
0
1
1
Receive Address
Receive Address
0
1
0
0
C-Channel Control (Transmit)
C-Channel Control (Transmit)
0
1
0
1
Timing Control
Timing Control
0
1
1
0
Interrupt Flag
Watchdog Timer
0
1
1
1
Interrupt Enable
Interrupt Enable
1
0
0
0
General Status
-
1
0
0
1
C-Channel Status (Receive)
Table 1 - Register Addresses
-
Introduction
The MT8952B HDLC Protocol Controller handles bit oriented protocol structure and formats the data as per the
packet switching protocol defined in the X.25 (Level 2) recommendations of the CCITT. It transmits and receives the
packeted data (information or control) serially in a format shown in Figure 3, while providing the data transparency
by zero insertion and deletion. It generates and detects the flags, various link channel states and the abort
sequence. Further, it provides a cyclic redundancy check on the data packets using the CCITT defined polynomial.
In addition, it can generate and detect a Go Ahead sequence and recognize a single byte address in the received
frame. There is also a provision to disable the protocol functions and provide transparent access to the serial bus
through the parallel port.
Frame Format
All frames start with an opening flag and end with a closing flag as shown in Figure 3. Between these two flags, a
frame contains the data and the frame check sequence (FCS).
FLAG
DATA FIELD
FCS
FLAG
One
Byte
n Bytes
(n 2)
Two
Bytes
One
Byte
Figure 3 - Frame Format
Flag
The flag is a unique pattern of 8 bits (01111110) defining the frame boundary. The transmit section generates the
flags and appends them automatically to the frame to be transmitted. The receive section searches the incoming
packets for flags on a bit-by-bit basis and establishes frame synchronization. The flags are used only to identify and
synchronize the received frame and are not transferred to the FIFO.
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Zarlink Semiconductor Inc.
MT8952B
Data Sheet
Data
The data field refers to the Address, Control and Information fields defined in the CCITT recommendations. A valid
frame should have a data field of at least 16 bits. The first byte in the data field is the address of the frame. If RxAD
bit in the Control Register is HIGH, the incoming packet is recognized only if the address byte matches the byte
stored in the Receive Address Register or the address byte is the All-Call Address (all ONEs). The LSB of the
Receive Address Register is set LOW permanently and the comparison is done only on upper seven bits of the
received address byte. The address detection can be limited only to the upper six bits by setting HIGH both RA6/7
and RxAD bits in the Control Register.
Frame Check Sequence (FCS)
The 16 bits following the data field are the frame check sequence bits. The generator polynomial is:
G(x)=x16+x12+x5+1
The transmitter calculates the FCS on all bits of the data field and transmits after the data field and before the end
flag. The receiver performs a similar computation on all bits of the received data and FCS fields and the result is
compared with FOB8Hex. If it matches, the received data is assumed error free. The error status of the received
packet is indicated by D7 and D6 bits in the FIFO Status Register.
Zero Insertion and Deletion
The Protocol Controller, while sending either data from the FIFO or the 16 bits FCS, checks the transmission on a
bit-by-bit basis and inserts a ZERO after every sequence of five contiguous ONEs (including the last five bits of
FCS) to ensure that the flag sequence is not simulated. Similarly the receiver examines the incoming frame content
and discards any ZERO directly following the five contiguous ONEs.
Abort
The transmitter aborts a frame by sending eight consecutive ONEs. The FA bit in the Control Register along with a
write operation to the Transmit Data Register enables the transmission of abort sequence instead of the byte
written to the register. On the receive side, the ABRT bit in the General Status Register is set whenever an abort
sequence (7 or more continuous 1’s) is received. The abort sequence causes the receiver to abandon whatever it
was doing and start searching for a start flag. The FA bit in the Interrupt Status Register is set when an abort
sequence is received following a start flag and at least four data bytes (minimum for a valid frame).
Interframe Time Fill and Link Channel States
When the HDLC Protocol Controller is not sending packets, the transmitter can be in any of three states mentioned
below depending on the status of the IFTF0 and IFTF1 bits in the Control Register. These bits are also used to
disable the protocol function to provide the transparent parallel access to the serial bus through the microprocessor
port.
Idle State
The Idle state is defined as 15 or more contiguous ONEs. When the HDLC Protocol Controller is observing this
condition on the receiving channel, the Idle bit in the General Status Register is set HIGH. On the transmit side, the
Protocol Controller ends the Idle state when data is loaded into the transmit FIFO.
Interframe Time Fill State
The Protocol Controller transmits continuous flags (7EHex) in Interframe time fill state and ends this state when data
is loaded into the transmit FIFO.
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Zarlink Semiconductor Inc.
MT8952B
Data Sheet
Go Ahead State
Go Ahead is defined by the 9 bit sequence 011111110 (7FHex followed by a ZERO), and hence contiguous 7F’s
appear as Go Aheads. Once the transmitter is in ‘Go Ahead’ state, it will continue to remain so even after the data
is loaded into the FIFO. This state can only be changed by setting the IFTF bits in the Control Register to something
other than ‘GO Ahead’. The reception of this sequence is indicated by GA bit in the General Status Register and the
Protocol Controller can generate an interrupt if enabled to do so by the GA bit in the Interrupt Enable Register.
Transparent Data Transfer State
The Protocol Controller, in this state, disables the protocol functions defined earlier and provides bi-directional
access to the serial bit streams through the parallel port. Like other states, the transparent data transfer can be
selected in both timing modes.
Invalid Frames
Any frame shorter than 32 bits between the opening and closing flags (corresponding to 16 bits of data and 16 bits
FCS) is considered invalid. The Protocol Controller ignores the frame only if the frame length is less than 24 bits
between the flags. For frames of length 24 to 32 bits, it transfers the data field to FIFO and tags it as having bad
FCS in the FIFO Status Register.
Functional Description
The functional block diagram of the HDLC Protocol Controller is shown in Figure 1. It has two ports. The serial port
transmits and receives formatted data packets and the parallel port provides a microprocessor interface for access
to various registers in the Protocol Controller.
The serial port can be configured to operate in two modes depending on the IC bit in the Timing Control Register. It
can transmit/receive the packets on selected timeslots in ST- BUS format or it can, using the enable signals
(TxCEN and RxCEN), transmit/receive the packets at a bit rate equal to CKi clock input.
The microprocessor port allows parallel data transfers between the Protocol Controller and a 6800/6809 system
bus. This interface consists of Data Bus (D0-D7), Address Bus (A0-A3), E Clock, Chip Select (CS) and R/W control.
The micro-processor can read and write to the various registers in the Protocol Controller. The addresses of these
registers are given in Table 2. The IRQ is an open drain, active LOW output indicating an interrupt request to CPU.
Control and monitoring of many different interrupts that may originate from the protocol controller is implemented by
the Interrupt Flag Register (IFR) and the Interrupt Enable Register (IER). Specific events have been described that
set a bit HIGH in the Interrupt Flag Register. Such an event does not necessarily interrupt the CPU. To assert an
interrupt (pull IRQ output LOW) the bit in IER that coincides with the Interrupt Flag Register must be set HIGH. The
IRQ bit in the General Status Register is the complement of IRQ pin status. If an interrupt is asserted, this bit will be
set HIGH otherwise it will be LOW.
TEOP and REOP Outputs
The HDLC Protocol Controller provides two separate signals TEOP & REOP indicating the end of packet
transmitted and received respectively. TEOP is a HIGH going pulse for one bit duration asserted during the last bit
of the closing flag or Abort sequence of the transmit packet. REOP is also a HIGH going pulse occurring for one bit
period when a closing flag is received or an incoming packet is aborted or an invalid packet of 24 or more bits is
detected. However, REOP is not generated for invalid packets of length less than 24 bits. These ‘end of packet’
signals are useful in multiplexing several data links on to a single HDLC Protocol Controller.
Timing Modes
There are two timing modes the Protocol Controller can be run in. These timing modes refer only to the
configuration of the serial port and are not related to the microprocessor port.
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Zarlink Semiconductor Inc.
MT8952B
Data Sheet
Internal Timing Mode
The Internal Timing Mode is intended for an easy interface to various products using ST-BUS architecture,
particularly Zarlink’s Digital Network Interface Circuit (DNIC - MT8972). The data/packets are shifted in/out serially
in ST-BUS format using the timing signals F0i and C2i/C4i. In addition to framing the data, the Protocol Controller
reserves one channel (channel-1) on the ST-BUS for carrying control information (C-channel) and this timeslot can
not be used for the packetized data. While the Protocol Controller is in the Internal Timing Mode, the clock input CKi
can be either at the bit rate or at 2×bit rate depending on the BRCK bit in the Timing Control Register as shown in
Table 2.
BRCK Bit
CKi Input
Output Data
Rate
0
4.096 MHz/C4i
2.048 Mbps
1
2.048 MHz/C2i
2.048 Mbps
Table 2 - Output Bit Rate In Internal Timing Mode
The Protocol Controller uses the ST-BUS timing signals F0i and C2i/C4i, and enables the transmitter and receiver
sections in the appropriate timeslots as determined by TC0-TC3 bits in the Timing Control Register.
The TxCEN and RxCEN inputs are ignored in this mode.
C-Channel Interface
This is a separate control channel (C-channel) interface relevant only in the Internal Timing Mode. The data stored
in the C-Channel Control Register is shifted out during the channel-1 timeslot of the outgoing ST-BUS (CDSTo) and
the C1EN bit in the Timing Control Register enables the transmission. The transmission of C-Channel is
independent of packet/data transmission. The data received on channel-1 of the incoming ST-BUS (CDSTi) is
shifted into the C-Channel Status Register independently and it is updated continuously.
Both the C-channel registers are accessible by the accompanying CPU through the parallel port.
External Timing Mode
In the External Timing Mode, the transmit and receive sections are enabled independently by TxCEN and RxCEN
control inputs and the formatted data packets are shifted in/out serially at a rate equal to the clock frequency on
CKi. The output is transmitted on the rising edge and the receiver samples the input on the falling edge of the clock.
The TxCEN and RxCEN controls are independent and asynchronous and have effect only after the current bit in the
packet is transmitted/received.
Although the protocol controller provides the packetized data on a limited number of channels on the ST-BUS while
operating in the Internal Timing Mode, it can packetize the data on any or all the channels of the ST-BUS if it is
operated in the External Timing Mode with appropriate enable signals on TxCEN and RxCEN.
Transparent Data Transfer
By setting the IFTF bits in the Control Register appropriately, the protocol functions can be disabled. This provides
a bidirectional access to the serial port through the microprocessor interface, with 19 byte deep FIFO in each
direction. The transparent data transfer facility functions in bytewide format and is available in both timing modes
except when the timing control bits are set for one bit/frame during the Internal Timing Mode.
The transmit data is shifted out serially on CDSTo and the operation being bytewide, only the least significant bits of
each byte loaded are transmitted, if the timing control bits are set to select 2, 6 or 7 bits/frame. When the transmit
FIFO is empty, the last byte or the portion the last byte, written to the FIFO is transmitted repeatedly. Similarly the
serial data on CDSTi is shifted in and converted to bytewide format. In case the timeslot selected is 2, 6 or 7
bits/frame, the reception involves only the most significant bits of each byte.
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Zarlink Semiconductor Inc.
MT8952B
Data Sheet
It should be noted that none of the protocol related status or interrupt bits are applicable in transparent data transfer
state. However, the FIFO related status and interrupt bits are pertinent and carry the same meaning as they do
while performing the protocol functions.
Watchdog Timer
This is a fixed eleven stage binary counter with F0i as the input and WD as the output from the last stage. This
counter can be reset either by the external input (RST) or by writing XXX0 1010 to the Watchdog Timer Register.
The WD output is normally HIGH and if the Watchdog Timer Register is not written within 210 cycles of F0i input
after it is reset, the WD output will go LOW for a period of 210 cycles of F0i. Even though the F0i input is not
required for formatting data in the External Timing Mode, it is necessary for the operation of the watchdog timer.
Order of Bit Transmission/Reception
The Least Significant Bit (LSB) corresponding to D0 on the data bus is transmitted first on the serial output
(CDSTo). On the receiving side, the first bit received on the serial input (CDSTi) is considered as the LSB and
placed on D0 of the data bus.
Registers
There are several registers in the HDLC Protocol Controller accessible to the associated micro-processor via the
data bus. The addresses of these registers are given in Table 1 and their functional details are given below.
FIFO Status Register (Read)
This register (Figure 4) indicates the status of transmit and receive FIFOs and the received byte as described
below.
D7
D6
D5
Rx Byte
Status
D4
D3
Rx FIFO
Status
D2
Tx FIFO
Status
D1
D0
LOW
LOW
Figure 4 - FIFO Status Register
Rx Byte Status: These two bits (D7 and D6) indicate the status of the received byte ready to be read from the
receive FIFO. The status is encoded as shown in Table 3.
Rx Byte
Status Bits
Status
D7
D6
0
0
Packet Byte
0
1
First Byte
1
0
Last Byte (Good FCS)
1
1
Last Byte (Bad FCS)
Table 3 - Received Byte Status
Rx FIFO Status: These bits (D5 and D4) indicate the status of receive FIFO as given by Table 4. The Rx FIFO
status bits are not updated immediately after an access of the Rx FIFO (a read from the microprocessor port, or a
write from the serial port), to avoid the existence of unrecoverable error conditions.
When in external timing mode, the MT8952B must receive two falling edges of the clock signal at the CKi input
before the Rx FIFO status bits will be updated. When in internal 2.048 MHz timing mode, the MT8952B must
receive two falling edges of the C2i clock before the Rx FIFO status bits will be updated. When in internal
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Zarlink Semiconductor Inc.
MT8952B
Data Sheet
4.096 MHz timing mode, the MT8952B must receive four falling edges of the C4i clock before the Rx FIFO
status bit will be updated (see the section on Receive Operation - Normal Packets).
Rx FIFO
Status Bits
Status
D5
D4
0
0
Rx FIFO Empty
0
1
Less than or equal to 14 bytes
1
0
Rx FIFO Full
1
1
Greater than or equal to 15 bytes
Table 4 - Receive FIFO Status
Tx FIFO Status: These two bits (D3 and D2) indicate the status of transmit FIFO as shown in Table 5.
Tx FIFO
Status Bits
Status
D3
D2
0
0
Tx FIFO Full
0
1
Greater than or equal to 5 bytes
1
0
Tx FIFO Empty
1
1
Less than or equal to 4 bytes
Table 5 - Transmit FIFO Status
The Tx FIFO status bits are updated in the same manner as the Rx FIFO bits, except that in external timing mode,
and in internal 2.048 Mbps timing mode, the Tx FIFO status bits are updated after two falling edges of the CKi or the
C2i signal (see the section on Transmit Operation - Normal Packets).
Receive Data Register (Read)
Reading the Receive Data Register (Figure 5) puts the first byte from the receive FIFO on the data bus. The first bit
of the data received on the serial input (CDSTi) is considered to be the LSB and is available on D0 of the data bus.
D7
D6
D5
D4
D3
D2
D1
D0
RD7
RD6
RD5
RD4
RD3
RD2
RD1
RD0
Figure 5 - Receive Data Register
Transmit Data Register (Write)
Writing to Transmit Data Register (Figure 6) puts the data present on the data bus into the transmit FIFO. The LSB
(D0) is transmitted first.
D7
D6
D5
D4
D3
D2
D1
D0
TD7
TD6
TD5
TD4
TD3
TD2
TD1
TD0
Figure 6 - Transmit Data Register
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Zarlink Semiconductor Inc.
MT8952B
Data Sheet
Control Register (Read/Write)
The Control Register (Figure 7) is used for general purpose control of the HDLC Protocol Controller. The bits
contained in this register and their functions are described below.
D7
D6
D5
D4
D3
D2
TxEN RxEN RxAD RA6/7 IFTF1 IFTF0
D1
D0
FA
EOP
Figure 7 - Control Register
TxEN -Transmit Enable: When set HIGH, this bit enables the transmitter and when LOW, disables it setting the
serial output (CDSTo) to high impedance state. If the transmitter is disabled during the transmission of a packet
using this bit, the Protocol Controller will wait until the completion of the packet and closing flag is transmitted or the
packet is aborted before setting the output (CDSTo) to high impedance state.
Thus TxEN bit controls the
transmission packet by packet unlike TxCEN input (pin 1) which controls it bit-by-bit. However, if the Protocol
Controller is in transparent data transfer state, the transmission will be stopped within two bit periods (maximum)
and set the output to high impedance state.
RxEN - Receive Enable: This bit enables the receiver when set HIGH and disables it when LOW. If this bit goes
LOW during the reception of the packet, the receiver can only be disabled after the current packet and its closing
flag are received or an abort is detected. Thus RxEN bit controls the receiver section packet by packet unlike
RxCEN input (pin 2) which controls it bit-by-bit. However, if the Protocol Controller is in transparent data transfer
state, the receiver will be disabled immediately.
RxAD - Receive Address Detect: This bit when set HIGH, enables the address detection for the received packets.
This causes the receiver to recognize only those packets having a unique address as programmed in the Receive
Address Register or if the address byte is the All-Call address (all ONEs). The address comparison is done only on
seven bits (compatible to the first byte of the address field defined in LAPD-CCITT) and an All-Call is defined as all
ONEs in upper seven bits of the received address field. If RxAD is LOW, the address detection is disabled and
every valid packet is recognized.
RA6/7 - Receive Address Six/Seven bits: This bit, when set HIGH, limits the address detection only to the upper
six bits of the received address byte (last 6 bits of received address field) and when LOW, allows the address
comparison on seven bits. An "all call", in this case is defined as all ONEs in the upper six bits only. RA6/7 is
ignored if the address detection is disabled (RxAD=0).
IFTF0 and IFTF1 - Interframe Time Fill: Setting these bits according to the table below (Table 6) causes the
transmitter to be in one of the active or idle states or allows the Protocol Controller to be in the transparent data
transfer state.
IFTF Bits
Result
IFTF1
IFTF0
0
0
Idle State (All ONEs)
0
1
Interframe Time Fill state
(Continuous Flags)
1
0
Transparent Data Transfer
1
1
Go Ahead state (Continuous
7FHEX)
Table 6 - Interframe Time Fill Bits
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Zarlink Semiconductor Inc.
MT8952B
Data Sheet
FA - Frame Abort: When set HIGH, this bit’tags’ the next byte written to the transmit FIFO and causes an abort
sequence (eight ONEs) to be transmitted when it reaches the bottom of the FIFO. The abort sequence will be
transmitted instead of the byte that was tagged. The FA bit is cleared to ZERO upon writing the data to the transmit
FIFO. As a result, a ‘read’ of this register bit will not reflect the last data written to it.
EOP - End Of Packet: Writing a ONE to this bit ‘tags’ the next byte written to the transmit FIFO to indicate that it is
the last data byte of the packet. This bit is cleared to ZERO upon writing the data to the transmit FIFO. As a result,
a read of this register bit will not indicate the last data written to it.
Receive Address Register (Read/Write)
D7
D6
D5
D4
D3
D2
D1
D0
RA7
RA6
RA5
RA4
RA3
RA2
RA1
RA0
Figure 8 - Receive Address Register
The data in this register (Figure 8) defines the unique address for the HDLC Protocol Controller. If address
recognition is enabled using the RxAD and RA6/7 bits in the Control Register, an incoming packet is recognized
only if its address byte (seven or six most significant bits) matches the corresponding bits in this register or if the
address is an "all-call". The LSB of the Receiver Address Register is set LOW permanently and the address
comparison is done only on remaining bits of the register.
C-Channel Control Register (Read/Write)
D7
D6
D5
D4
D3
D2
D1
D0
CT7
CT6
CT5
CT4
CT3
CT2
CT1
CT0
Figure 9 - C-Channel Control Register
The data written to this register (Figure 9) is transmitted on channel-1 slot of the outgoing ST-BUS (CDSTo), when
enabled by C1EN bit in the Timing Control Register. This feature can only be used when the HDLC Protocol
Controller is in the Internal Timing Mode.
Timing Control Register (Read/Write)
The Timing Control Register (Figure 10) controls the timing mode and other related operations and provides a
software reset to the Protocol Controller. The various bits in this register are described below:
D7
D6
RST
IC
D5
D4
C1EN BRCK
D3
D2
D1
D0
TC3
TC2
TC1
TC0
Figure 10 - Timing Control Register
RST - Reset: When this bit is set HIGH, all the registers in the HDLC Protocol Controller are reset and the data in
the FIFOs is lost. This is equivalent to the external reset with the exception that the RST bit does not affect itself or
the Watchdog Timer Register and WD output. The RST bit must be “cleared” (written as a logic “0”) twice before the
MT8952B will be removed from its reset state (see section on RESET operation).
IC - Internal Control: When this bit is cleared to ZERO, the Protocol Controller is in the External Timing Mode.
The transmit and receive sections are enabled by the inputs TxCEN and RxCEN respectively, and F0i is used only
for the watchdog timer operation. When this bit is a ONE, the Protocol Controller is in the Internal Timing Mode. The
transmit and receive sections are enabled by the internally generated timings derived from the inputs CKi and F0i.
The F0i input defines the beginning of a frame (Figure 24) and the transmitter and receiver sections are enabled in
the timeslots as determined by the bits TCO-TC3. The inputs TxCEN and RxCEN are ignored in this mode.
11
Zarlink Semiconductor Inc.
MT8952B
Data Sheet
C1EN - Channel-1 Enable: When HIGH, it enables the transmission of C-channel information on channel-1 timeslot of the outgoing ST-BUS (CDSTo) and when LOW, puts CDSTo into high impedance state during that period.
However, the C-channel information is received independently and the C-channel Status Register is updated
continuously. Note that C1EN has relevance only during the Internal Timing Mode.
BRCK- Bit Rate Clock: This bit is used during the Internal Timing Mode to select the clock rate and ignored if the
Protocol Controller is in the External Timing Mode. It should be set HIGH if the input clock (CKi) is at the bit rate
(C2i) and should be LOW for the clock input at 2 x bit rate (C4i). In both cases, the clock should be properly
phase related to F0i as shown in Figure 25.
TC0-TC3 - Timing Control Bits: In the Internal Timing Mode the transmitter and the receiver sections are enabled
during the times defined by the Timing Control Bits TC0-TC3 (Table 7). This applies only to the ST-BUS channels 0,
2, 3 and 4 carrying the packets or transparent data (channel-1 pertains to C-channel information). The output
CDSTo is put during the remaining time intervals not enabled by these bits.
Timing Control Bits
TC3
TC2
TC1
TC0
X
X
0
1
X
X
X
X
X
0
0
0
0
0
1
1
1
1
0
0
1
1
1
0
0
1
1
0
1
0
0
1
0
1
0
1
ST-BUS
Channel
Number
0
0
0
0
2
3
4
2 and 3
2, 3 and 4
Bits
/Frame
1
2
6
7
8
8
8
16
24
X : Don’t Care
Table 7 - Timing Control Bits
Interrupt Flag Register (Read)
Reading the Interrupt Flag Register puts the interrupt status bits on the data bus. This register is reset when it is
read and a particular bit will not be set until its particular condition occurs again. The functional details of each bit
are provided in Figure 11.
D7
D6
D5
D4
GA
EOPD
Tx
DONE
FA
D3
D2
Tx
Tx
4/19 URUN
FULL
D1
D0
Rx
15/19
FULL
Rx
OFLW
Figure 11 - Interrupt Flag Register
GA - Go Ahead: This bit when set HIGH, indicates the detection of ‘go ahead’ sequence on the incoming data
stream (CDSTi).
EOPD - End of Packet Detect: A HIGH on this bit confirms the reception of an ‘end of packet’ flag, an abort
sequence or an invalid packet of 24 or more bits on the incoming data stream (CDSTi).
Tx DONE - Transmitter Done: This bit, when HIGH, indicates that the packet transmission is complete and the
Transmit FIFO is empty. The falling edge of TEOP output causes this interrupt status bit to be set HIGH if the FIFO
is empty.
FA - Frame Abort: This bit is set HIGH to indicate that a frame abort has been detected on the incoming data
stream.
12
Zarlink Semiconductor Inc.
MT8952B
Data Sheet
Tx 4/19 FULL - Transmit FIFO 4/19 full: This bit if set HIGH, indicates that the transmit FIFO has only 4 bytes
remaining in it and another 15 bytes could be loaded. This bit has significance only when the transmit FIFO is being
depleted and not when it is getting loaded.
Tx URUN - Transmit FIFO underrun: This bit when HIGH, identifies that the transmit FIFO is empty without the
Protocol Controller being given the ‘end of packet’ indication. This indicates that the transmit FIFO has underrun
and the Protocol Controller will transmit an abort sequence automatically. Tx DONE will be set 8 bit times after Tx
URUN is set.
Rx15/19 FULL - Receive FIFO 15/19 full: This bit when HIGH, confirms that the receive FIFO has 15 bytes in it
and it can receive four more bytes.
Rx OFLW - Receive FIFO overflow: This bit when set HIGH, indicates that the receive FIFO is full and a ‘write’
occurred indicating an overflow. The byte causing this and all the subsequent bytes written while the FIFO is in this
state are lost. The receiver begins to search for a new start flag.
Watchdog Timer Register (Write)
The Watchdog Timer Register operates in conjunction with the Watchdog Timer and the WD output. Writing the
code of XXX0 1010 in the register resets the WD timer. If the register is not re-written within 210 cycles of F0i after
resetting the timer, the WD output goes LOW. This register serves the sole purpose of resetting the timer and hence
relevant only if it is written with the above data.
Interrupt Enable Register (Read/Write)
This register enables/disables the interrupts as specified in the Interrupt Flag Register (IFR). Setting HIGH the
appropriate bits in this register (IER) enables the associated interrupt source. However, the masked bits in the IFR
are still valid but they do not cause the IRQ output to go LOW. The description of the bits enabling the various
interrupts is identical to those of the Interrupt Flag Register.
General Status Register (Read)
This register (Figure 12) contains the general status information on the Protocol Controller.
D7
D6
Rx
Tx
OFLW URUN
D5
D4
D3
D2
D1
D0
GA
ABRT
IRQ
IDLE
LOW
HIGH
Figure 12 - General Status Register
Rx OFLW - Receive FIFO overflow: This bit, if set HIGH, indicates that the receive FIFO has overflowed. The byte
causing this and all the subsequent bytes written while the FIFO is in this state are lost. Note that this bit is the
same as the Rx OFLW bit in Interrupt Flag Register (IFR) and can only be cleared by reading the IFR.
Tx URUN - Transmit FIFO Underrun: When HIGH, this bit indicates that the transmit FIFO has underrun. Under
this condition the packet being transmitted is aborted. This bit is the same as the Tx URUN bit in the Interrupt Flag
Register (IFR) and can only be cleared when the IFR is read.
GA - Go Ahead: This bit is set HIGH if a ‘go ahead’ is received on the incoming data stream and is cleared when
the Interrupt Flag Register is read. This bit is the same as the GA bit in the IFR.
ABRT - Abort: The reception of contiguous seven ONEs on incoming data, sets this bit HIGH and reading the
General Status Register, clears it.
IRQ - Interrupt Request: This bit refers to the status of the interrupt request output from the Protocol Controller. If
HIGH, it indicates that the IRQ (pin 6) output is LOW and vice versa.
IDLE - Idle Channel: This bit, if set HIGH, identifies that the receiver is detecting an idle channel at its input
(minimum 15 ONEs).
13
Zarlink Semiconductor Inc.
MT8952B
Data Sheet
C-Channel Status Register (Read)
D7
D6
D5
D4
D3
D2
D1
D0
CR7
CR6
CR5
CR4
CR3
CR2
CR1
CR0
Figure 13 - C-Channel Status Register
The C-Channel Register (Figure 13) continuously stores the data received during the channel-1 timeslot of the
incoming ST-BUS (CDSTi) during the Internal Timing Mode of the Protocol Controller.
Reset
When the MT8952B is reset by a low going pulse on the RST pin or by setting (logic high) the RST bit in the Timing
Control Register, the device is put into the following state:
a. All bits in the Timing Control Register are cleared (logic 0) by an external reset. An internal reset clears all
bits except the RST bit.
b. All bits in the Interrupt Enable Register are cleared (logic 0).
c. All bits in the Control Register are cleared (logic 0).
d. All bits in the Interrupt Register are cleared (logic 0).
e. All bits in the General Status Register are cleared (logic 0) except for the two least significant bits.
f. Receive and Transmit Registers are cleared and the FIFO Status Register reflects their state accordingly.
g. The WD output is reset low by an external reset but is not affected by an internal reset.
h. The Transmitter and the Receiver are disabled.
Transmit Operation
After a reset, which the external circuitry should provide upon power up, the transmit section is disabled. Before
enabling this section, the timing should be set up. On reset, the serial port is set to External Timing Mode. In case
this is not desired, the Timing Control Register should be written to with the appropriate data. Once in the correct
timing mode, the Transmit Enable (TxEN) bit in the Control Register can be set. Now that the transmitter is enabled
it will be in the Idle channel state. If any other channel state or the transparent data transfer facility is required, the
IFTF bits in the Control Register should be set accordingly.
Normal Packets
To start a packet, the data is written into the transmit FIFO starting with the address field. All the data must be
written to the FIFO in a bytewide manner. When the data is detected in the transmit FIFO, the protocol controller will
proceed in one of the following ways:
If the transmitter is in idle state, the present byte of eight ONEs being transmitted is completed and then followed
by a start flag and subsequently the data in the transmit FIFO is transmitted.
If the transmitter is in the interframe time fill state, the flag presently being transmitted is finished and then another
start flag is transmitted before transmitting the data from the transmit FIFO.
If the transmitter is in go ahead state, it continues to be in that state even after the data is loaded into the FIFO. Only
when the IFTF bits are set to choose something other than go ahead will the data be transmitted.
If the transmitter is in transparent data transfer state, the protocol functions are disabled and the data in the transmit
FIFO is transmitted on CDSTo.
14
Zarlink Semiconductor Inc.
MT8952B
Data Sheet
To indicate that the particular byte is the last byte of the packet, the EOP bit in the Control Register must be set
before the last byte is written into the transmit FIFO. The EOP bit is cleared automatically when the data byte is
written to the FIFO. After the transmission of the last byte in the packet, the frame check sequence (16 bits) is sent
followed by a closing flag. If there is any more data in the transmit FIFO, another flag is transmitted followed by the
new data. In case of no data in the FIFO, the transmitter assumes the selected link channel state. During the
transmission of either the data or the frame check sequence, the Protocol Controller checks the transmitted
information on a bit by bit basis and inserts a ZERO after every sequence of five consecutive ONEs.
Transmit FIFO Full
When the Transmit FIFO is full, this state is indicated by the Transmit FIFO status bits in the FIFO Status Register.
These bits do not change state for two bit periods after an access of the FIFO from either the serial port or the
microprocessor port. The bit period is determined by the CKi signal frequency. If the bus cycle of the controlling
microprocessor is much shorter than the bit period, the Transmit FIFO status bits may not be updated in time for the
next microprocessor read of the FIFO Status Register.
To make sure that the microprocessor does not overwrite the Tx FIFO, if over four bytes of information have been
written to the Tx FIFO, the microprocessor should wait for a 4/19 FULL interrupt before writing to the Tx FIFO again.
When a 4/19 FULL interrupt has been received, a maximum of 15 bytes should be written to the Tx FIFO, then
transfer of information to the Tx FIFO should stop and the 4/19 FULL interrupt should be waited for once more. The
FIFO may be allowed to empty if no more information is to be sent at the moment. This procedure should keep
software independent of the frequency of the CKi signal.
Transmit Underrun
A transmit underrun occurs when the last byte loaded into the transmit FIFO was not ‘flagged’ with the ‘end of
packet’ (EOP) bit and there are no more bytes in the FIFO. In such a situation, the Protocol Controller transmits the
abort sequence (eight ONEs) and moves to the selected link channel state.
Abort Transmission
If it is desired to abort the packet currently being loaded into the transmit FIFO, the next byte written to the FIFO
should be ‘flagged’ to cause this to happen. The FA bit of the Control Register must be set HIGH, before writing the
next byte into the FIFO. This bit is cleared automatically once the byte is written to the FIFO. When the ‘flagged’
byte reaches the bottom of the FIFO, a frame abort sequence is sent instead of the byte and the transmitter
operation returns to normal.
Go Ahead Transmission
By setting the IFTF bits in the Control Register appropriately the transmitter can be made to send the Go Ahead
sequences when the Protocol Controller is not sending the packets. Since the go ahead is defined as 011111110,
contiguous 7FHex’ s appear as go aheads. As long as the IFTF bits are set to choose go aheads, the transmitter will
send them even if data is subsequently loaded into the FIFO. Only when the IFTF bits are set to select something
other than go aheads, will the data be transmitted.
C-Channel Transmission
By setting the C1EN bit in the Timing Control Register HIGH, the information loaded in the C-Channel Control
Register can be transmitted over channel-1 timeslot of the outgoing ST-BUS (CDSTo). This is available only during
the Internal Timing Mode of the Protocol Controller.
Transparent Data Transfer
The IFTF bits in the Control Register can be set to provide transparent data transfer disabling the protocol
functions. The transmitter no longer generates the Flag, GA, Abort and Idle sequences nor does it insert the zeros
and calculate the FCS. It operates in both timing modes in bytewide manner and transmits data serially on CDSTo.
If the Protocol Controller is in the Internal Timing Mode and the Timing Control bits are set to select 2, 6 or 7
15
Zarlink Semiconductor Inc.
MT8952B
Data Sheet
bits/frame, the corresponding least significant bits of every byte loaded into the transmit FIFO are only transmitted.
The transparent data transfer facility is not available when the Timing Control bits are set for 1 bit/frame. In case the
FIFO is empty, the last byte or the portion of the last byte, written to the FIFO is transmitted repeatedly. Note that
the transparent data transfer can be disabled immediately in software (unlike during the transmission of packets)
using TxEN bit in the Control Register.
The operation of the transmitter is similar in the External Timing Mode.
Receive Operation
After a reset on power up, the receive section is disabled. Timing set up considerations are similar to that of the
transmit section. Address detection is also disabled when a reset occurs. If address detection is required, the
Receiver Address Register is loaded with the desired address and the RxAD bit in the Control Register is set HIGH.
The receive section can then be enabled by RxEN bit in the Control Register.
Normal Packets
After initialization as explained above, the serial data starts to be clocked in and the receiver checks for the idle
channel and flags. If an idle channel is detected, the ‘Idle’ bit in the General Status Register is set HIGH. Once a
flag is detected, the receiver synchronizes itself in a bytewide manner to the incoming data stream. The receiver
keeps resynchronizing to the flags until an incoming packet appears. The incoming packet is examined on a bit-bybit basis, inserted zeros are deleted, the FCS is calculated and the data bytes are written into the receive FIFO.
However, the FCS and other control characters like the flag, abort etc., never appear in the FIFO. If the address
detection is enabled, the first byte following the flag is compared to the byte in the Receive Address Register and to
All-Call address. If a match is not found, the entire packet is ignored and nothing is written to the FIFO. If the
incoming address byte is valid, the packet is received in normal fashion. All the bytes written to the receive FIFO
are flagged with two status bits. The status bits are found in the FIFO status register and indicate whether the byte
to be read from the FIFO is the first byte of the packet, the middle of the packet, the last byte of the packet with
good FCS or the last byte of the packet with bad FCS. This status indication is valid for the byte to be read from the
receive FIFO.
The incoming data is always written to the FIFO in a bytewide manner. However, in the event of data sent not being
a multiple of eight bits, the software associated with the receiver should be able to pick the data bits from the MSB
positions of the last byte in the received data written to the FIFO. The Protocol Controller does not provide any
indication as to how many bits this might be.
Receive FIFO Empty
When the Receive FIFO is empty, this state is indicated by the Receive FIFO status bits in the FIFO Status
Register. As with the Tx FIFO status bits (see Transmit FIFO Full Section), these bits are not updated for two bit
periods after any access of the Receive FIFO. If the controlling microprocessor’s bus cycle is much shorter than a
bit period on the serial port, then the status bits may not be updated to indicate there is no information left in the Rx
FIFO before the microprocessor has returned to read the Rx FIFO again. The result is an underflow condition that is
only evident by redundant bytes in the received message.
To avoid a Rx FIFO underflow, reading information from the Rx FIFO should be approached in two ways. The first
approach is to be used when the MT8952B indicates (via interrupt) that the Rx FIFO is 15/19 FULL. The controlling
microprocessor should then immediately read 14 bytes from the Rx FIFO. This will avoid emptying the FIFO. The
second approach is to be used when an End of Packet interrupt is signalled by the MT8952B. The controlling
microprocessor should then empty the Rx FIFO until the Rx Byte Status bits in the FIFO Status Register indicate
that the byte about to be read is the last byte. These bits are “tag“ bits whose state was determined before the End
of Packet condition was indicated, therefore their state is valid.
16
Zarlink Semiconductor Inc.
MT8952B
Data Sheet
Invalid Packets
If there are less than 24 data bits between the opening and closing flags, the packet is considered invalid and the
data never enters the receive FIFO. This is true even with data and the abort sequence, the total of which is less
than 24 bits. The data packets that are at least 24 bits but less than 32 bits long are also invalid, but not ignored.
They are clocked into the receive FIFO and tagged as having bad FCS.
Frame Abort
When a frame abort is received the appropriate bits in the Interrupt Flag and Status Registers are set. The last byte
of the packet that was aborted is written to the FIFO with a status of ‘packet byte’ tagged to it. The CPU determines
which packet in the FIFO was aborted, if there is more than one packet in the FIFO, by the absence of ‘last byte’
status on any of the bytes.
Idle Channel
While receiving the idle channel, the idle bit in the general status register remains set.
Go Ahead
The occurrence of this sequence can be used to generate an interrupt as described earlier. The receive circuitry will
not recognize a frame abort followed by a flag as go ahead.
C-Channel Reception
The information contained in channel-1 of the incoming ST-BUS (CDSTi) is shifted into the C-Channel Status
Register during the Internal Timing Mode.
Transparent Data Transfer
By setting the IFTF bits in the Control Register to select the transparent data transfer, the receive section can be
made to disable the protocol functions like Flag/Abort/GA/Idle detection, zero deletion, CRC calculation and
address comparison. The received data is shifted in from CDSTi and written to receive FIFO in bytewide format. If
the Protocol Controller is in the Internal Timing Mode and the Timing Control bits are set to 2, 6 or 7 bits/frame, the
respective MSBs of each byte are only to be read from the data bus. The transparent data transfer facility is not
available when the Timing Control bits are set to one bit/frame. The receive section can be disabled in software
immediately using the RxEN bit in the Control Register.
The operation of the receiver is similar in the External Timing Mode.
Receive Overflow
Receive overflow occurs when the receive section attempts to load a byte to an already full receive FIFO. This
status can be used to generate the interrupt as described earlier.
Typical Connection
A typical connection to the HDLC Protocol Controller is shown in Figure 14. The parallel port interfaces with
6800/6809 type processors. The bits A0-A3 are the addresses of various registers in the Protocol Controller. The
microprocessor can read and write to these registers treating them as memory locations.
The serial port transmits/receives the packetized data. It can be connected to a digital transmission medium or to a
digital network interface circuit. The TEOP and REOP are the ‘end of packet’ signals on transmit and receive
direction respectively. F0i and CKi are the timing signals with CKi accepting either the bit rate clock or 2 x bit rate
clock in the internal timing mode. TxCEN and RxCEN are the enable inputs in the External Timing Mode.
17
Zarlink Semiconductor Inc.
MT8952B
Data Sheet
WD is the output of the watchdog timer. It goes LOW when the timer times out or if the RST input is held LOW. This
output can be used to reset the associated microprocessor. The RST is an active LOW input which resets the
entire circuitry.
TIMING AND CONTROL
CKi
F0i
RST
CDSTo
D0-D7
PARALLEL
INTERFACING
WITH 6809
TYPE
PROCESSORS
R/W
TEOP
MT8952B
SERIAL PORT
TxCEN
CS
WITH
HDLC Protocol
E
FORMATTED
Controller
A0-A3
CDSTi
DATA
REOP
WD
RxCEN
IRQ
VDD
VSS
Figure 14 - Typical Connection Diagram
Applications
The MT8952B has a number of applications for transferring data or control information over a digital channel while
providing built-in error detection capability. In combination with the MT8972 (the Digital Network Interface Circuit), it
can be used to transmit digital data over a twisted wire pair.
The block schematic of one such application is shown in Figures 15 and 16. They refer to the primary and
secondary ends of a voice/data communication link using the Digital Network Interface Circuits (DNIC). Each end is
associated with one DNIC which interfaces twisted wire pair to the digital data rate up to 160kbps (2B+D, framing
signal and housekeeping information).
18
Zarlink Semiconductor Inc.
MT8952B
Data Sheet
D0-D7
R/W
M
I
C
R
O
P
R
O
C
E
S
S
O
R
DSTi
CDSTo
CS
MT8972
MT8952B
CDSTi
E
A0-A3
DSTo
HDLC PROTOCOL
DIGITAL
TO
TWISTED
WIRE PAIR
NETWORK
CONTROLLER
C4
WD
INTERFACE
(160 kbits/sec)
CIRCUIT
RST
F0
IRQ
CKi
F0i
MS0
0
MS1
0
MS2
0
B-CHANNELS (2 X 64 kbits/sec Max)
Network Interface
Primary Terminal End
Network
Figure 15 - HDLC Protocol Controller at the Primary End of the Link
D0-D7
R/W
M
I
C
R
O
P
R
O
C
E
S
S
O
R
E
A0-A3
CDSTo
DSTi
CDSTi
DSTo
MT8952B
CS
HDLC PROTOCOL
MT8972
DIGITAL
TO
TWISTED
WIRE PAIR
NETWORK
CONTROLLER
C4
WD
INTERFACE
(160 kbits/sec)
CIRCUIT
RST
F0
IRQ
F0i
CKi
MS0
0
MS1
0
MS2
1
B-CHANNELS (2 X 64 kbits/sec Max)
Network Interface
Secondary Terminal End
Network
Figure 16 - HDLC Protocol Controller at the Secondary End of the Link
19
Zarlink Semiconductor Inc.
MT8952B
Data Sheet
Primary End of the Link
The MT8952B is operating in the internal timing mode with the C-channel transceiver action enabled. The
processor loads the data or control information (D Channel) in the transmit FIFO which is packetized in HDLC
format and shifted out serially during the selected channels of the outgoing ST-BUS (CDSTo). The channels and
the number of bits per frame (frame period=125sec) can be selected by TC0-TC3 bits in the Timing Control
Register. Since channel 1 is reserved for the C-channel information and channels 2 and 3 carry B-channels (64
kbps each), the D-channel information can only be sent on channel-0. Similarly the incoming packets on CDSTi are
loaded into receive FIFO after the removal of all overhead bits and checked for any errors. The microprocessor will
then read the data from the receive FIFO.
The DNIC (MT8972) is selected to operate in single port, master mode with the digital network (DN) option enabled.
The B-channels, B1 and B2, are shown connected directly to the DNIC. Hence, these should be in ST-BUS format
enabled at the appropriate timeslot (channels 2 and 3). It can be the outputs of voice codecs (MT896X) providing
voice communication or data codecs (MT8950) for communication between RS232-C type terminals. It is possible
to use the HDLC protocol on B1 and B2 channels to provide the error detection.
This can be done by using a separate MT8952B enabled appropriately to shift out the formatted data during
channels 2 and 3 or by multiplexing the same MT8952B between B- and D- channels.
Secondary End of the Link
At the secondary end of the communication link, a similar procedure is adopted to transmit/receive the data and
control information.
The MT8952B operates in the Internal Timing Mode as at the primary end, but the DNIC (MT8972) is selected to
operate in single port, slave mode with the digital network capability enabled.
The other functions and procedures are similar to those at the primary end.
The timing signals like CKi (C2i or C4i) and F0i are provided externally at the primary end and at the secondary
end, they are derived from the received data.
Although this application describes the communication between two stations over a dedicated link, it can
be modified to serve a switched communication path by additional control functions and a call set-up procedure
many of which can be achieved in software.
20
Zarlink Semiconductor Inc.
MT8952B
Data Sheet
Absolute Maximum Ratings*
Parameter
Symbol
Min.
Max.
Units
VDD
-0.3
7.0
V
VSS-0.3
VDD+0.3
V
1
Supply voltage
2
Voltage on any pin (other than supply pins)
VI
3
Current on any pin (other than supply pins)
II / IO
25
mA
4
DC Supply or ground current
IDD / ISS
50
mA
5
Storage temperature
150
C
0.6
W
TST
-65
6 Package power dissipation
Plastic
PD
* Exceeding these values may cause permanent damage. Functional operation under these conditions is not implied.
Recommended Operating Conditions - Voltages are with respect to ground (VSS) unless otherwise stated.
Characteristics
Sym.
Min.
Typ.‡
Max.
Units
5.0
5.25
V
Test Conditions
1
Supply Voltage
VDD
4.75
2
Input HIGH voltage
VIH
2.4
VDD
V
For a Noise Margin of 400
mV
3
Input LOW voltage
VIL
VSS
0.4
V
For a Noise Margin of 400
mV
4
Frequency of operation
fCL
5.0
MHz
When clock input is at twice
the bit rate.
5 Operating temperature
TA
-40
25
85
C
‡ Typical figures are at 25C and are for design aid only: not guaranteed and not subject to production testing.
DC Electrical Characteristics - Voltages are with respect to ground (VSS) unless otherwise stated.
VDD=5V5%, VSS=0V, TA=-40 to 85C.
Characteristics
Sym.
Min.
Typ.‡
Max.
Units
Test Conditions
1
Supply Current (Quiescent)
IDD
1
10
A
Outputs unloaded and
clock input (CKi) grounded
2
Supply current (Operational)
IDD
0.4
1.0
mA
*See below
3
Input HIGH voltage
VIH
4
Input LOW voltage
VIL
0.8
V
Input leakage current
IIZ
10
A
Input capacitance
Cin
10
pF
HIGH switching point for
Schmitt Trigger (RST) input
VT+
4.0
V
LOW switching point for
Schmitt Trigger (RST) input
VT-
1.0
V
Hysteresis on Schmitt Trigger
(RST) input
VH
0.5
V
5
6
7
8
9
I
N
P
U
T
2.0
V
21
Zarlink Semiconductor Inc.
MT8952B
Data Sheet
DC Electrical Characteristics - Voltages are with respect to ground (VSS) unless otherwise stated.
VDD=5V5%, VSS=0V, TA=-40 to 85C.
Sym.
Min.
Typ.‡
Output HIGH current (on all
the outputs except IRQ)
IOH
-5
-16
mA
VOH=2.4 V
Output LOW current (on all
the outputs including IRQ)
IOL
5
10
mA
VOL=0.4 V
Characteristics
10
11
O
U
T
P
U
T
Max.
Units
Test Conditions
15
pF
Output capacitance
Co
Typical figures are at 25C and are for design aid only: not guaranteed and not subject to production testing.
12
‡
* Outputs unloaded. Input pins 12 and 25 clocked at 2048 kHz. All other inputs at VSS.
AC Electrical Characteristics† - Microprocessor Interface - (Figures 17 and 18)
Voltages are with respect to ground (VSS) unless otherwise stated.
Characteristics
Sym.
Min.
Typ.‡
Max.
Units
1
Delay between CS and E clock
tCSE
0
ns
2
Cycle time
tCYC
205
ns
3
E Clock pulse width HIGH
tEWH
145
ns
4
E Clock pulse width LOW
tEWL
60
ns
5
Read/Write setup time
tRWS
20
ns
6
Read/Write hold time
tRWH
10
ns
7
Address setup time
tAS
20
ns
8
Address hold time
tAH
60
ns
9
Data setup time (write)
tDSW
35
ns
10
Data hold time (write)
tDHW
10
ns
11
E clock to valid data delay
tDZL
tDZH
12
Data hold time (read)
tDLZ
tDHZ
145
10
60
Test Conditions
ns
Test load circuit 1 (Fig. 26)
CL=200pF
ns
Test load circuit 3 (Fig. 26)
† Timing is over recommended temperature & power supply voltages (VDD=5V5%, VSS=0V, TA=–40 to 85C).
‡ Typical figures are at 25C and are for design aid only: not guaranteed and not subject to production testing.
22
Zarlink Semiconductor Inc.
MT8952B
Data Sheet
CS
E clock initiates and
terminates the write cycle
tCSE
tEWH
E
tEWL
tf
tr
tCYC
CS
CS initiates and
terminates the write cycle
tCSE
E
tRWH
tRWS
R/W
tAS
tAH
A0-A3
tDSW
tDHW
D0-D7
NOTE: The write cycle can be initiated either by the falling edge of CS or the rising edge of E clock whichever occurs last. Similarly
the cycle can be terminated by CS (rising edge) or E clock (falling edge) whichever occurs first. The timing relations are to be
referenced from the active edge initiating or terminating the cycle
Figure 17 - Timing Information for MPU Write
23
Zarlink Semiconductor Inc.
MT8952B
Data Sheet
CS
E clock initiates and
terminates the read cycle
tCSE
tEWH
E
tEWL
tr
tf
tCYC
CS
CS initiates and
terminates the read cycle
tCSE
E
tRWH
tRWS
R/W
tAS
tAH
A0-A3
tDLZ
tDHZ
tDZL
tDZH
D0-D7
High Impedance
VALID DATA
High Impedance
NOTE: The read cycle can be initiated either by the falling edge of CS or the rising edge of E clock whichever occurs last. Similarly
the cycle can be terminated by CS (rising edge) or E clock (falling edge) whichever occurs first. The timing relations are to be
referenced from the active edge initiating or terminating the cycle.
Figure 18 - Timing Information for MPU Read
E
tIRQR
IRQ
Figure 19 - Interrupt Request Release Time
24
Zarlink Semiconductor Inc.
MT8952B
Data Sheet
F0i
tWDLH
tWDHL
WD
Figure 20 - Watchdog Timer Input and Output
AC Electrical Characteristics† - Serial Port, RESET, WD Timer and IRQ Release Time (Figures 19, 20, 21 and
22). Voltages are with respect to ground (VSS) unless otherwise stated.
Characteristics
Min.
Typ.‡
Max.
Units
Test Conditions
1
Interrupt request release time
tIRQR
120
ns
Test load circuit 2 (Fig.26)
2
WD output delay HIGH to LOW
tWDHL
135
ns
Test load circuit 1 (Fig.26)
3
WD output delay LOW to HIGH
tWDLH
135
ns
Test load circuit 1 (Fig.26)
4
TEOP/REOP output delay
tEOPD
110
ns
Test load circuit 1 (Fig.26)
5
TEOP/REOP output hold time
tEOPH
110
ns
Test load circuit 1 (Fig.26)
6
CDSTo delay from CKi
tSTOD
125
ns
Test load circuit 1 (Fig.26)
7
CDSTi setup time
tSTiS
20
ns
8
CDSTi hold time
tSTiH
65
ns
100
ns
Timing is over recommended temperature & power supply voltages (VDD=5V5%, VSS=0V, TA=–40 to 85C).
Typical figures are at 25C and are for design aid only: not guaranteed and not subject to production testing.
9
†
‡
Sym.
RESET pulse width
tRST
tRST
RST
Figure 21 - RESET Timing
25
Zarlink Semiconductor Inc.
MT8952B
Data Sheet
Flag or Idle Sequence
End Flag or Abort Sequence
CKi
tSTOD
CDSTo
tEOPH
tEOPD
TEOP
tSTiS
tSTiH
CDSTi
tEOPD
tEOPH
REOP
Figure 22 - Serial Port Input and REOP, Output and TEOP
Note: The frequency of the clock input CKi is assumed to be at the output bit rate. However, it can be at twice the bit rate in the Internal
Timing Mode.
AC Electrical Characteristics† - Serial Port in External Timing Mode - (Figure 23)
Voltages are with respect to ground (VSS) unless otherwise stated.
Typ.‡
Characteristics
Sym.
Min.
1
Clock period on CKi pin
tCEX
400
2
CKi transition time
3
TxCEN/RxCEN setup time
tCENS
60
ns
4
TxCEN/RxCEN hold time
tCENH
40
ns
5
CDSTi setup time
tSTiS
20
ns
6
CDSTi hold time
tSTiH
65
ns
7
8
Max.
Units
Test Conditions
ns
20
tT
ns
CDSTo delay
tSToZL
tSToZH
125
CDSTo disable time
tSToLZ
tSToHZ
85
ns
Test load circuit 1 (Fig. 26)
CL=150pF
ns
Test load circuit 3 (Fig. 26)
† Timing is over recommended temperature & power supply voltages (VDD=5V5%, VSS=0V, TA=–40 to 85C).
‡ Typical figures are at 25C and are for design aid only: not guaranteed and not subject to production testing.
26
Zarlink Semiconductor Inc.
MT8952B
Data Sheet
tCEX
CKi
tT
tCENH
TxCEN/
RxCEN
tCENS
tSTiH
tSTiS
CDSTi
VALID DATA
tSToHZ
tSToLZ
tSToZL
tSToZH
CDSTo
HIGH
IMPEDANCE
HIGH IMPEDANCE
Figure 23 - Serial Port Inputs and Outputs in External Timing Mode
Note: The frequency of the clock input (CKi) should be at the output bit rate in the External Timing Mode.
F0i
125 sec
ST-BUS
Channel
31
Channel
0
Channel
1
Channel
2
Least
Significant
Bit
(D0 on the Data
Bus)
Channel
29
••••••••
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Channel
30
Bit 2
Bit 1
Channel
31
Bit 0
3.9 sec
Channel
0
Most
Significant
Bit
(D7 on the Data
Bus)
Figure 24 - ST-BUS Format
AC Electrical Characteristics† - Serial Port in Internal Timing Mode - (Figure 25)
Voltages are with respect to ground (VSS) unless otherwise stated.
Characteristics
Sym.
Min.
Typ.‡
Max.
Units
Test Conditions
1
Frame Pulse (F0i) width
tF0iW
50
ns
2
Frame Pulse (F0i) setup time
tF0iS
30
ns
See note 3.
3
Frame Pulse (F0i) hold time
tF0iH
20
ns
See note 3.
ns
Test load circuit 1 (Fig. 26)
4
5
CDSTo delay from clock input
CDSTi setup time
tSToZL
tSToZH
tSTiS
125
20
ns
27
Zarlink Semiconductor Inc.
MT8952B
Data Sheet
AC Electrical Characteristics† - Serial Port in Internal Timing Mode - (Figure 25)
Voltages are with respect to ground (VSS) unless otherwise stated.
Characteristics
Sym.
Min.
Typ.‡
Max.
Units
6
CDSTi hold time
tSTiH
65
ns
7
C2i clock period
tC2i
400
ns
Test Conditions
tC4i
200
ns
8 C4i clock period
† Timing is over recommended temperature & power supply voltages (VDD=5V5%, VSS=0V, TA=–40 to 85C).
‡ Typical figures are at 25C and are for design aid only: not guaranteed and not subject to production testing.
tF0iW
F0i
tC4i
tF0iH
CKi
(C4i)
tC2i
tF0iS
CKi
(C2i)
tSToZL
tSToZH
CDSTo
Ch. 0
Bit 7
HIGH IMPEDANCE
Ch. 0
Bit 5
tSTiH
tSTiS
Ch. 31
Bit 0
CDSTi
Ch. 0
Bit 6
Ch. 0
Bit 7
Ch. 0
Bit 6
Ch. 0
Bit 5
Figure 25 - Serial Port Input and Output in ST-BUS Format (Internal Timing Mode)
Note:
1. Channels 0 to 4 can only be active on CDSTi and CDSTo in the Internal Timing Mode.
2. Clock input CKi can be either of the ST-BUS clocks C2i (2.048MHz) or C4i (4.096 MHz) in the Internal Timing Mode.
3. The Frame Pulse set up and hold time measurements are to be referenced from the falling edge of C4i or the rising edge of C2i depending on
the clock selected.
VDD
VDD
From
output
under test
CL
Test
point
CL= 200 pF for
measurements
on Data Bus
150 pF for
measurements
on CDSTo
50 pF for
others
Test load circuit- 1
RL=1k
From
output
under test
Test
point
From
output
under test
Test
point
A
RL=1k
S1
CL
B
VSS
CL
Test load circuit- 2
Test load circuit - 3
Note: S1 is in position A
when measuring tPLZ
and in position B when
measuring tPHZ. See
note below.
Figure 26 - Test Load Circuits
Note: Active Low to High impedance times are measured from the disabling signal edge to the time when Vout has increased by 0.5 volts. Active High to
High impedance times are measured from the disabling signal edge to the time when Vout has decreased by 0.5 volts.
28
Zarlink Semiconductor Inc.
Package Code
c Zarlink Semiconductor 2005. All rights reserved.
ISSUE
ACN
DATE
APPRD.
Previous package codes
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