®
ISO
2
-CMOS ST-BUS™ FAMILY
MT8971B/72B
Digital Subscriber Interface Circuit
Digital Network Interface Circuit
Features
•
•
•
•
•
•
•
•
•
Full duplex transmission over a single twisted
pair
Selectable 80 or 160 kbit/s line rate
Adaptive echo cancellation
Up to 3km (8971B) and 4 km (8972B)
ISDN compatible (2B+D) data format
Transparent modem capability
Frame synchronization and clock extraction
MITEL ST-BUS compatible
Low power (typically 50 mW), single 5V supply
ISSUE 7
May 1995
Ordering Information
MT8971BE
22 Pin Plastic DIP
MT8972BE
22 Pin Plastic DIP
MT8972BC
22 Pin Ceramic DIP
MT8971BP
28 Pin PLCC
MT8972BP
28 Pin PLCC
-40°C to
+
85°C
Description
The MT8971B (DSIC) and MT8972B (DNIC) are
multi-function devices capable of providing high
speed, full duplex digital transmission up to 160
kbit/s over a twisted wire pair. They use adaptive
echo-cancelling techniques and transfer data in
(2B+D) format compatible to the ISDN basic rate.
Several modes of operation allow an easy interface
to digital telecommunication networks including use
as a high speed limited distance modem with data
rates up to 160 kbit/s.
Both devices function
identically but with the DSIC having a shorter
maximum loop reach specification. The generic
"DNIC" will be used to reference both devices unless
otherwise noted.
The MT8971B/72B is fabricated in Mitel’s ISO
2
-
CMOS process.
Applications
•
•
•
•
Digital subscriber lines
High speed data transmission over twisted
wires
Digital PABX line cards and telephone sets
80 or 160 kbit/s single chip modem
DSTi/Di
CDSTi/
CDi
Transmit
Interface
Prescrambler
Scrambler
Differentially
Encoded Biphase
Transmitter
Transmit
Filter &
Line Driver
L
OUT
F0/CLD
C4/TCK
F0o/RCK
MS0
MS1
MS2
RegC
Control
Register
Transmit
Timing
V
Bias
Address
Echo Canceller
Error
Signal
Echo Estimate
—
DPLL
MUX
L
OUT
DIS
Master Clock
Phase Locked
Transmit/
Clock
Receive
Timing &
Control
Sync Detect
Status
Receive
Precan
∑
+
Receive
Filter
-1
+2
L
IN
OSC2
DSTo/Do
CDSTo/
CDo
Receive
Interface
De-
Prescrambler
Descrambler
Differentially
Encoded Biphase
Receiver
OSC1
V
DD
V
SS
V
Bias
V
Ref
Figure 1 - Functional Block Diagram
9-107
MT8971B/72B
VRef
VBias
LOUT
NC
VDD
LIN
TEST
LOUT
VBias
VRef
MS2
MS1
MS0
RegC
F0/CLD
CDSTi/CDi
CDSTo/CDo
VSS
1
2
3
4
5
6
7
8
9
10
11
22
21
20
19
18
17
16
15
14
13
12
VDD
LIN
TEST
LOUT DIS
Precan
OSC1
OSC2
C4/TCK
F0o/RCK
DSTi/Di
DSTo/Do
4
3
2
1
28
27
26
•
22 PIN PDIP/CERDIP
Figure 2 - Pin Connections
Pin Description
Pin #
DIP PLCC
1
2
3
4,5,
6
7
8
2
3
4
5,7,
8
9
10
Name
L
OUT
V
Bias
V
Ref
Description
Line Out.
Transmit Signal output (Analog). Referenced to V
Bias
.
Internal Bias Voltage
output. Connect via 0.33 µF decoupling capacitor to V
DD
.
Internal Reference Voltage
output. Connect via 0.33 µF decoupling capacitor to V
DD
.
MS2-MS0
Mode Select
inputs (Digital). The logic levels present on these pins select the various
operating modes for a particular application. See Table 1 for the operating modes.
RegC
F0/CLD
Regulator Control
output (Digital). A 512 kHz clock used for switch mode power
supplies. Unused in MAS/MOD mode and should be left open circuit.
Frame Pulse/C-Channel Load
(Digital). In DN mode a 244 ns wide negative pulse input
for the MASTER indicating the start of the active channel times of the device. Output for
the SLAVE indicating the start of the active channel times of the device. Output in MOD
mode providing a pulse indicating the start of the C-channel.
Control/Data ST-BUS In/Control/Data In
(Digital). A 2.048 Mbit/s serial control &
signalling input in DN mode. In MOD mode this is a continuous bit stream at the bit rate
selected.
Control/Data ST-BUS Out/Control/Data Out
(Digital). A 2.048 Mbit/s serial control &
signalling output in DN mode. In MOD mode this is a continuous bit stream at the bit rate
selected.
Negative Power Supply
(0V).
9
12
CDSTi/
CDi
CDSTo/
CDo
V
SS
10
13
11
12
13
14
14
15
16
17
DSTo/Do
Data ST-BUS Out/Data Out
(Digital). A 2.048 Mbit/s serial PCM/data output in DN mode.
In MOD mode this is a continuous bit stream at the bit rate selected.
DSTi/Di
Data ST-BUS In/Data In
(Digital). A 2.048 Mbit/s serial PCM/data input in DN mode. In
MOD mode this is a continuous bit stream at the bit rate selected.
F0o/RCK
Frame Pulse Out/Receive Bit Rate Clock
output (Digital). In DN mode a 244 ns wide
negative pulse indicating the end of the active channel times of the device to allow daisy
chaining. In MOD mode provides the receive bit rate clock to the system.
C4/TCK
Data Clock/Transmit Baud Rate Clock
(Digital). A 4.096 MHz TTL compatible clock
input for the MASTER and output for the SLAVE in DN mode. For MOD mode this pin
provides the transmit bit rate clock to the system.
Oscillator Output.
CMOS Output.
15
19
16
21
OSC2
9-108
CDSTi/CDi
CDSTo/CDo
VSS
DSTo/Do
DSTi/Di
F0o/RCK
NC
12
13
14
15
16
17
18
MS2
NC
MS1
MS0
RegC
F0/CLD
NC
5
6
7
8
9
10
11
25
24
23
22
21
20
19
NC
LOUT DIS
Precan
OSC1
OSC2
NC
C4/TCK
28 PIN PLCC
MT8971B/72B
Pin Description (continued)
Pin #
DIP PLCC
17
18
22
23
Name
OSC1
Precan
Description
Oscillator Input.
CMOS Input. D.C. couple signals to this pin. Refer to D.C. Electrical
Characteristics for OSC1 input requirements.
Precanceller Disable.
When held to Logic ’1’
,
the internal path from L
OUT
to the
precanceller is forced to V
Bias
thus bypassing the precanceller section. When logic ’0’, the
L
OUT
to the precanceller path is enabled and functions normally. An internal pulldown (50
kΩ) is provided on this pin.
No Connection.
Leave open circuit.
1,6,
11,
18,
20,
25
19
20
21
22
24
26
27
28
NC
L
OUT
DIS
L
OUT
Disable.
When held to logic “1”, L
OUT
is disabled (i.e., output = V
Bias
). When logic
“0”, L
OUT
functions normally. An internal pulldown (50 kΩ) is provided on this pin.
TEST
L
IN
V
DD
Test Pin.
Connect to V
SS
for normal operation.
Receive Signal
input (Analog).
Positive Power Supply
(+5V) input.
F0
C4
DSTi
AA A
AAAAA
AAAAA
AA
AAAAA
AA
AAAAA
B1
7
AA
AAAAA
AA
AAAAA
AA
AAAAA
AAAA
A A
AAAAAA
A AA
AAAAA
A AA
AAAAA
A A
AAAAAA
B1
7
A AA
AAAAA
A AA
AAAAA
A AA
AAAAA
B1
6
B1
5
B1
4
B1
3
B1
2
B1
1
AAAAAAAAAAAAAAAAAAAAAAAA AAAAAAAAAAAAAAAAA
AAAA
AAAAAAAAAAAAAAAAAAAAAAAA AAAAAAAAAAAAAAAAA
AAAA
AAAA
B1
0
AAAAAAAAAAAAAAAAAAAAAAAA AAAAAAAAAAAAAAAAA
B1
7
AAAAAAAAAAAAAAAAAAAAAAAA AAAAAAAAAAAAAAAAA
AAAA
AAAAAAAAAAAAAAAAAAAAAAAA AAAAAAAAAAAAAAAAA
AAAA
AAAAAAAAAAAAAAAAAAAAAAAA AAAAAAAAAAAAAAAAA
AAAA
AAAAAAAAAAAAAAAAAAAAAAAA AAAAAAAAAAAAAAAA
AAAA
AAAAAAAAAAAAAAAAAAAAAAAA AAAAAAAAAAAAAAAA
AAAA
AAAAAAAAAAAAAAAAAAAAAAAA AAAAAAAAAAAAAAAA
AAAA
AAAA
B1
0
AAAAAAAAAAAAAAAAAAAAAAAA AAAAAAAAAAAAAAAA
B1
7
AAAAAAAAAAAAAAAAAAAAAAAA AAAAAAAAAAAAAAAA
AAAA
AAAAAAAAAAAAAAAAAAAAAAAA AAAAAAAAAAAAAAAA
AAAA
AAAAAAAAAAAAAAAAAAAAAAAA AAAAAAAAAAAAAAAA
AAAA
DSTo
B1
6
B1
5
B1
4
B1
3
B1
2
B1
1
F0o
Channel Time 0
Figure 3 - DV Port - 80 kbit/s (Modes 2, 3, 6)
F0
C4
DSTi
A A
AAAAA
AAAAA
A
AAAAA
A
AAAAA
B1
7
B1
6
B1
5
B1
4
A
AAAAA
A
AAAAA
A
AAAAA
AAAA
A A
AAAAA
AAAAA
A
AAAAA
A
AAAAA
B1 B1 B1 B1
A
AAAAA
7
6
5
4
A
AAAAA
A
AAAAA
A
AAAA
AAAAAAAA AAA
AAAA
AAAAAAAAA AAAA
AAAA
AAAAAAAA AAA
AAAA
AAAAAAAAA AAAA
AAAA
AAAAAAA
AAAA
B1
3
B1
2
B1
1
B1
0
AAAAAAAA AAA
B2
7
B2
6
B2
5
B2
4
B2
3
B2
2
B2
1
B2
0
AAAAAAAAA AAAA
B1
7
AAAAAAAA AAA
AAAA
AAAAAAAAA AAAA
AAAA
AAAAAAAA AAA
AAAA
AAAAAAAAA AAAA
AAAA
AAAAAAAA
AAAA
AAAAAAAAA AAAA
AAAA
AAAAAAAA AAA
AAAA
AAAAAAAAA AAAAA
AAAA
AAAAAAAA AAA
AAAA
AAAA
AAAAAAAA AAA
B2 B2 B2 B2 B2 B2 B2 B2
AAAAAAAAA AAAAA
AAAAAAA
AAAAAAAAA AAAAA
AAAA
B1
B1
3
B1
2
B1
1
B1
0
AAAAAAAA
AAAAAAA
AAAA
7
6
5
4
3
2
1
0
AAAAAAAAA AAAAA
7
AAAAAAAA AAA
AAAA
AAAAAAAAA AAAAA
AAAA
AAAAAAAA
AAAA
AAAAAAAAA AAAAA
AAAAAAAAA
AAAAAAAA
AAAA
DSTo
F0o
Channel Time 0
Channel Time 16
Figure 4 - DV Port - 160 kbit/s (Modes 2, 3, 6)
9-109
MT8971B/72B
Functional Description
The MT8971B/72B is a device which has been
designed primarily as an interface for the Integrated
Services Digital Network (ISDN). However, it may be
used in practically any application that requires high
speed data transmission over two wires, including
smart telephone sets, workstations, data terminals
and computers.
In the ISDN, the DNIC is ideal for providing the
interface at the U reference point. The device
supports the 2B+D channel format (two 64 kbit/s B-
channels and one 16 kbit/s D-channel) over two
wires as recommended by the CCITT. The line data
is converted to and from the ST-BUS format on the
system side of the network to allow for easy
interfacing with other components such as the S-
interface device in an NT1 arrangement, or to digital
PABX components.
Smart telephone sets with data and voice capability
can be easily implemented using the MT8971B/72B
as a line interface. The device’s high bandwidth and
long loop length capability allows its use in a wide
variety of sets. This can be extended to provide full
data and voice capability to the private subscriber by
the installation of equipment in both the home and
central office or remote concentration equipment.
Within the subscriber equipment the MT8971B/72B
would terminate the line and encode/ decode the
data and voice for transmission while additional
electronics could provide interfaces for a standard
telephone set and any number of data ports
supporting standard data rates for such things as
computer communications and telemetry for remote
meter reading. Digital workstations with a high
degree of networking capability can be designed
using the DNIC for the line interface, offering up to
160 kbit/s data transmission over existing telephone
lines. The MT8971B/72B could also be valuable
within existing computer networks for connecting a
large number of terminals to a computer or for
intercomputer links. The highest data rates existing
for terminal to computer links is 19.2 kbit/s over
conventional analog modems. With the DNIC, this
can be increased up to 160 kbit/s at a very low cost
per line for terminal to computer links and in many
cases this bandwidth would be sufficient for
computer to computer links.
Figure 1 shows the block diagram of the MT8971B/
72B. The DNIC provides a bidirectional interface
between the DV (data/voice) port and a full duplex
line operating at 80 or 160 kbit/s over a single pair of
twisted wires. The DNIC has three serial ports. The
DV port (DSTi/Di, DSTo/Do), the CD (control/data)
port (CDSTi/CDi, CDSTo/CDo) and a line port (L
IN
,
9-110
L
OUT
). The data on the line is made up of information
from the DV and CD ports. The DNIC must combine
information received from both the DV and CD ports
and put it onto the line. At the same time, the data
received from the line must be split into the various
channels and directed to the proper ports. The
usable data rates are 72 and 144 kbit/s as required
for the basic rate interface in ISDN. Full duplex
transmission is made possible through on board
adaptive echo cancellation.
The DNIC has various modes of operation which are
selected through the mode select pins MS0-2. The
two major modes of operation are the MODEM
(MOD) and DIGITAL NETWORK (DN) modes. MOD
mode is a transparent 80 or 160 kbit/s modem. In
DN mode the line carries the B and D channels
formatted for the ISDN at either 80 or 160 kbit/s. In
the DN mode the DV and CD ports are standard ST-
BUS and in MOD mode they are transparent serial
data streams at 80 or 160 kbit/s. Other modes
include: MASTER (MAS) or SLAVE (SLV) mode,
where the timebase and frame synchronization are
provided externally or are extracted from the line and
DUAL or SINGLE (SINGL) port modes, where both
the DV and CD ports are active or where the CD port
is inactive and all information is passed through the
DV port. For a detailed description of the modes see
“Operating Modes” section.
In DIGITAL NETWORK (DN) mode there are three
channels transferred by the DV and CD ports. They
are the B, C and D channels. The B1 and B2
channels each have a bandwidth of 64 kbit/s and are
used for carrying PCM encoded voice or data. These
channels are always transmitted and received
through the DV port (Figures 3, 4, 5, 6). The C-
channel, having a bandwidth of 64 kbit/s, provides a
means for the system to control the DNIC and for the
DNIC to pass status information back to the system.
The C-channel has a Housekeeping (HK) bit which is
the only bit of the C-channel transmitted and
received on the line. The 2B+D channel bits and the
HK bit are double-buffered. The D-channel can be
transmitted or received on the line with either an 8,
16 or 64 kbit/s bandwidth depending on the DNIC’s
mode of operation. Both the HK bit and the D-
channel can be used for end-to-end signalling or low
speed data transfer. In DUAL port mode the C and D
channels are accessed via the CD port (Figure 7)
while in SINGL port mode they are transferred
through the DV port (Figures 5, 6) along with the B1
and B2 channels.
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