MT8926
repeating 16 bit code words of the form: 11111111
0XXXXXX0, where XXXXXX is the message content.
The PMAC will automatically append the prefix byte
11111111 to the transmit message and remove it from
the receive message. It will also indicate the
reception of a valid message. When bit-oriented
messages are not being transported, message-
oriented facility data link signals, assembled by an
external HDLC controller (i.e., MT8952), can be
passed through the PMAC to the MT8976/77 for
transmission.
The PMAC can implement an ESF payload loopback
by routing the MT8976/77 DSTo stream to the
MT8976/77 DSTi input (see Figure 6). The payload
loopback is controlled through the loopback control
word, Channel 15 of CSTi1 (see Figure 3). When the
payload loopback is disabled, data entering the
PMAC’s DSTi0 pin is transferred to the PMAC DSTo.
DSTo of the PMAC should be connected to the DSTi
pin of the MT8976/77 framer.
PMAC - Framer Interworking
The MT8926 PMAC is designed to function with the
MT8976/77 T1 framer. Figure 9 illustrates a typical
application and the connections involved in realizing
this interface. Both the PMAC and framer receive the
extracted clock and data from the T1 line interface.
This allows the MT8926 to perform B8ZS recovery
and BPV detection, as well as SF or ESF
synchronization, framing error detection, facility data
link extraction, and line loopback code detection.
Some of the CSTi1 channels that are not used to
control the MT8976/77 are used to control the
PMAC, therefore, CSTi1 will connect to both devices.
Figure 3 shows the channels of CSTi1 that carry the
MT8976/77 Per Channel Control Words, as well as
the MT8926 control data. C2i and F0i supply timing
references for both devices.
The CSTo stream of the MT8976/77 framer enters
the PMAC on CSTi0 (see Figure 4). The PMAC adds
its performance data to form the CSTo stream of the
PMAC. Figure 5 shows the channels and status bits
that the PMAC has added to CSTo. E8Ko of the
framer will also pass through the PMAC, E8Ki to
E8Ko, under control of CSTi1.
It should be noted that the PMAC will replace some
of the data of MT8976/77 Master Status Words 1 and
2. This is outlined in Tables 1 and 2.
Bit
7
6
5
4
3
2
1
0
MT8976/77 CSTo
YLALR
MIMIC
ERR
ESFYLW
MFSYNC
BPV
SLIP
SYN
MT8926 CSTo
YLALR
MIMIC
ALRM
RAI
MFSYNC
LOS
SLIP
SYN
Table1. Master Status Word 1 Data Substitution
Bit
7
6
5
4
3
2
1
0
MT8976/77 CSTo
BlAlm
FrCnt
Xst
BPVCnt
BPVCnt
CRCCNT
CRCCNT
CRCCNT
MT8926 CSTo
BlAlm
FrCnt
Xst
SEI
FSI
CSI
BSI
AIS
Table 2. Master Status Word 2 Data Substitution
The MT8926 can be programmed to either pass data
through from FDLi to FDLo and on to the MT8976/77
input TxFDL, or insert bit-oriented messages into the
FDL via the transmit bit-oriented message register,
channel 7 of CSTi1. This function is under control of
the FDLEn bit of the PMAC Control Word. See
Application section Figure 9 for FDL connections.
Channel 15 of CSTi1, the Loopback Control Word, is
used to control the line loopback code generation
and payload loopback functions of the PMAC. This is
done by internally connecting the MT8926 DSTo to
either a line loopback enable code generator, a line
loopback disable code generator, DSTi0 or DSTi1.
Figure 6 illustrates the connections required to
support these functions. The DSTo of the framer
15
MS
W1
16-18
PCWS
19
X
20-22
PCSW
23
X
24-26
PCSW
27
X
24-26
PCSW
31
MS
W2
0-2
PCSW
MT8976/77
CSTo
T1
PCSW
PSW
MSW
=
=
=
1-3
CSTi0
3
4-6
PS PCSW
W
4-6
7
X
8-10
PCSW
11
X
12-14
PCSW
7-9
10-12
13-15
16-18
19-21
22-24
Per Channel Status Word
Phase Status Word
Master Status Word
FIgure 4 - MT8926 CSTi0 (MT8976/77 CSTo) Channel Allocation Versus T1 Channels
4-7
MITEL [ MITEL NETWORKS CORPORATION ]
