MH89770 Datasheet, PDF (22/36 Pages) Mitel Networks Corporation – T1/ESF Framer & Interface Preliminary Information

MH89770
Preliminary Information
5. Digital Access Cross Connect System
(DACS)
The Digital Access Cross Connect System (DACS) is
a T1 switch with 127 T1 lines as input and output
plus one T1 line that is reserved for test and
maintenance purposes. A DACS is capable of
switching any input channel on any T1 trunk to any
output channel on any T1 trunk.
There are four main blocks in Figure 15, the T1
interfaces, the switch matrix, the control matrix, and
the clock generator. The digital trunk interface is
made up of the MH89770 plus the additional
components required to interface to the transmission
line. The MH89770 handles all of the required
transmit and receive data formatting, and converts
the 1.544 MHz serial stream into ST-BUS format so
that it can be routed through the MT8980
synchronous switch matrix.
The switch matrix can be built so that the maximum
throughput delay is 1 frame +2 channels. The switch
matrix will not only route data channels to their
destination, but it will also route the received
signalling bits through to the destination channel.
This is necessary because the receiving MH89770
decodes the T1 stream, and the transmitting
MH89770 has to reconstruct the outgoing T1 stream.
In other words, there is no multiframe integrity
between received data and transmitted data. The
total throughput delay is one frame plus ten ST-BUS
channels for the MH89770 receiver, 2.5 ST-BUS
channels for the MH89770 transmitter, and one
frame plus two ST-BUS channels for the switch
matrix for a total of 2.5 frames worst case.
Switch
Matrix
MT8980
STo0
STi0
F0i
STo7
C4i
STi7
MT8980
M
I
C
R
O
Control
Matrix
STo0
STi0
STo1
STo2
F0i
STo7
C4i
STi7
C1.5i
MT8941
DPLL #1
CVb
Clock
Generator
F0i
C12i
12.352
AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA
MHz Osc.
DPLL #2
F0i
F0b
C8Kb
C4i
C4b
16.384
C2i
C20
C16i
MHz Osc.
•••••••
MH89770
DSTi
DSTo
CSTi0
CSTo
CSTi1
OUTA
OUTB
RxT
RxR
C2i
F0i
C1.5i
E8Ko
••••••
MH89770
DSTi
DSTo
OUTA
CSTi0
CSTo
CSTi1
OUTB
RxT
RxR
C2i
F0i
C1.5i
E8Ko
T1 Interfaces
4-146
Figure 15 - Digital Access Cross Connect System (DACS)
Equal-
izer
Equal-
izer