MT9079 Datasheet, PDF (43/54 Pages) Mitel Networks Corporation – CMOS ST-BUS™ FAMILY Advanced Controller for E1

MT9079
Common Channel Signalling Interface
The MT9079 Transparent Mode
Figure 14 shows how to interface DSTi and DSTo
time slot 16 to the MC68302 for the control of
Common Channel Signalling (CCS) data. As can be
seen in the timing diagram, the MT8980D CSTo
signal must be programmed to go high during the bit
position just before time slot 16 (i.e., time slot 15, bit
0). This will enable the NMSI1 pins for one time slot
(eight C2 cycles) when the NMSI1 port is operated in
PCM mode. The STo stream of the MT8980D must
also be programmed to be high impedance during
time slot 16. C2 is used to clock data into and out of
the NMSI1 port.
It should be noted that the DS signal of the MC68302
must be inverted to interface to the MT8980D. Also,
DTACK must be connected to the MT8980D DTA and
pulled-up with a 909 ohms resistor.
Figure 15 illustrates an application in which the
MT9079 transparent mode can be used. That is, a
digital cross-connect multiplexer that switches
complete PCM 30 trunks and does not require time
slot switching. It should be noted that any MT9079
devices that transport time slot switched data must
operate in termination mode otherwise, the CRC-4
remainder will be in error.
In transparent mode the complete PCM 30 data
stream will pass through the MT9079 except for the
data link (S_a4 of the NFAS - 4kbit/sec. maintenance
channel). The CRC-4 remainder will not be
generated by the transmit section of the MT9079, but
the CRC-4 remainder bits received on DSTi will be
modified to reflect the new data link bits. This has the
advantage that any CRC-4 errors that occur on the
To Line
Interface
Digital Cross-Connect Matrix
MT9079
TxA
DSTo
TxB
DSTi
MT8980D
STi0
STo0
Switch 0,0
MT8980D
Switch 0,M
MT9079
DSTo
TxA
DSTi
TxB
C4i/C2i
C4
C4
C4i/C2i
RxA
RxB
E2i
TxMF
RxMF
m+1 Frame
Delay
RxMF
TxMF
RxA
RxB
E2i
To Line
Interface
To Data Link
Controller
MT8980D
Switch n,0
MT8980D
Switch n,M
To Data Link
Controller
Figure 15 - PCM-30 (E1) Trunk Cross-Connect using the MT9079 Transparent Mode
MT9079
DSTi
DSTo
C4i/C2i
TxA
TxB
RxA
RxB
E2i
C2 C4
Manchester Encoder
CLKi Tx+
NRZ
Datai Tx-
Transmit Fibre Interface
Tx+
Tx-
Transmit Fibre
Manchester Decoder
NRZ _Data0
CODEi
RxCLK
Receive Fibre Interface
RxData
Receive Fibre
Figure 16 - MT9079 Fibre Interface Circuit
4-279