Preliminary Information
MH89770
MH89770
High Speed
DIP
Parallel
MT8920B
(Mode 2)
SWITCH
MT8977
Telecom Bus
OUTA
D -D
Tx
0
7
DSTi
TxA
TxB
STo0
EQU
Line
Driver
STi0
DSTo
A -A
0
5
STo1
CSTi0
CSTo
CSTi1
OUTB
RxT
MT89761
CS
R/W
OE
C4i
F0i
Rx
F0i
RxA
RxB
•
•
Line
C2i
•
Driver
MMS MS1 24/32
C1.5i
RxR
+5V
RxD
•
Signalling and
Link Control
BUS
MT8920B
(Mode 1)
E8Ko
E1.5i
D -D
STo0
STi0
0
7
A -A
0
5
STo1
CLOCK
EXTRACTOR
CS
DS
R/W
C4i
F0i
•
DTACK
IRQ
•
MT8941
IACK
12.352 MHz
Osc.
1.544 MHz
CVb
MMS
+5V
F0i
C2o
F0b
16.384 MHz
Osc.
•
C4b
C8Kb
Figure 12 - Using the MH89770 in a Parallel Bus Environment
MT8976. The signals are combined to produce a
composite return to zero signal which is clocked into
the MT8976 at RxD.
and link functions may be controlled easily through
the STPA transmit RAM’s Tx0, Tx1, while status
information is read at receive RAM Rx0. In addition,
interrupts can be set up to notify the system in case
of slips, loss of sync, alarms, violations, etc.
2. Interfacing the MH89770 to a Parallel Bus
The MH89770 can be interfaced to a high speed
parallel bus or to a microprocessor using MT8920B
Parallel Access Circuit (STPA). Fig. 12 shows the
MT8977 interfaced to a parallel bus structure using
two STPA’s operating in modes 1 and 2.
3. PCM/Voice Channel Bank
The D3/D4 channel bank is one of the most widely
used pieces of equipment in the North American
network today. The D3/D4 channel converts 24
analog telephone lines into the 24 channels of a T1
serial stream. The channel bank is the interface point
between a digital switching or transmission system
and the analog telephone loop. The industry is
moving towards end-to-end digital connections
(ISDN), but the analog channel bank will still be in
use for many years to come.
The first STPA operating in mode 2 (MMS=0,
MS1=1, 24/32=0), routes data and/or voice
information between the parallel telecom bus and the
T1 or CEPT link via DSTi and DSTo. The second
STPA, operating in mode 1 (MMS=1) provides
access from the signalling and link control bus to the
MH89770 status and control channels. All signalling
4-143
MITEL [ MITEL NETWORKS CORPORATION ]
