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.
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 of the NFAS - 4kbit/sec. maintenance
a4
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
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.
Digital Cross-Connect Matrix
MT8980D
MT8980D
MT9079
MT9079
STi0
STo0
DSTo
TxA
DSTo
DSTi
TxA
TxB
TxB
DSTi
Switch 0,0
Switch 0,M
To Line
Interface
To Line
Interface
C4i/C2i
C4i/C2i
C4
C4
RxA
RxB
RxA
RxB
E2i
m+1 Frame
Delay
E2i
TxMF
RxMF
RxMF
TxMF
MT8980D
MT8980D
To Data Link
Controller
To Data Link
Controller
Switch n,0
Switch n,M
Figure 15 - PCM-30 (E1) Trunk Cross-Connect using the MT9079 Transparent Mode
C4
C2
MT9079
Manchester Encoder
Transmit Fibre Interface
DSTi
DSTo
CLKi
Tx+
Tx+
C4i/C2i
Transmit Fibre
Receive Fibre
NRZ
NRZ
TxA
TxB
Datai
Tx-
Tx-
Manchester Decoder
Receive Fibre Interface
Data0
RxA
RxB
E2i
CODEi
RxCLK
RxData
Figure 16 - MT9079 Fibre Interface Circuit
4-279
MITEL [ MITEL NETWORKS CORPORATION ]
