MT8926
Bit
7-6
Name
YLALR
&
MIMIC
ALRM
Description
These bits (Yellow Alarm Indication and Mimic) contain information from the
MT8976/77 that is unaltered by the MT8926. See Master Status Word 1 of the
MT8976/77 data sheet.
Alarm. This bit will be set if the MT8926 detects a 1 in the F
S
bit position of the
twelfth frame of an SF superframe (alternate yellow alarm indication). ALRM will be
low when the F
S
bit is 0.
When receiving an ESF signal or if bit 3 (FSEL) of the PMAC Control Word (CSTi1
Channel 11) is low, the ALRM bit will always be low.
Remote Alarm Indication (also known as ESF Yellow Alarm). This bit is set if an
RAI code word (repeating hex FF00 pattern) is received on the ESF facility data
link. This code must be correctly detected in seven out of 10 messages. RAI will be
reset if more than three of 10 messages are in error.
When receiving an SF signal, this bit will always be low.
This bit (Multiframe Synchronization) contains information from the MT8976 that is
unaltered by the MT8926. See Master Status Word 1 of the MT8976 data sheet.
Loss of Signal. This bit will go high when the MT8926 detects 128 or more
consecutive zeros in the line signal. It will be reset after the device detects a 12.5%
ones density (48 ones in two or less frames) in the received signal.
These bits (Slip Indication and Synchronization) contain information from the
MT8976/77 that is unaltered by the MT8926. See Master Status Word 1 of the
MT8976/77 data sheet.
Table 3. Master Status Word 1 (CSTo Channel 15)
5
4
RAI
3
2
MFSYNC
LOS
1-0
SLIP
&
SYN
Bit 1
0
0
1
Bit 0
0
1
0
Description
Normal operation. The transmit data applied to DSTi0 will pass through the PMAC, and be
output on DSTo.
Payload Loopback mode. Connect as per Figure 6. The received data on DSTo of the
MT8976/77 is routed through the PMAC to the DSTi input of the MT8976/77.
Transmit Line Loopback Enable. Connect as per Figure 6. DSTo of the PMAC will be internally
connected to an SF line loopback enable code generator. That is, a repeating 00001 code is
placed in the 24 T1 channels of DSTo, so it may be transmitted by the framer.
Transmit Line Loopback Disable. Connect as per Figure 6. DSTo of the PMAC will be internally
connected to an SF line loopback disable code generator. That is, a repeating 001 code is
placed in the 24 T1 channels of DSTo, so it may be transmitted by the framer.
Table 4 - Loopback Control Word (CSTi1 Channel 15)
1
1
Note: Bits 2 to 7 of the Loopback Control Word are not used.
interrupts
from
occurring
during
system
initialization. It should be noted that when the
MT8926 is acquiring synchronization the CRC and
BPV counters may record errors.
ALRM (SF Yellow Alarm)
an ESF signal is being received or when FSel is low,
ALRM will always be low.
A low to high transition of the ALRM bit will initiate a
group one (G1) interrupt.
Remote Alarm Indication (RAI)
The MT8926 will recognize the sixth F
S
bit of an SF
superframe as an alternate Yellow Alarm indicator, if
FSel of the PMAC Control Word is high. That is,
when this F
S
bit is high/low, the ALRM bit of Master
Status Word 1 will be high/low (see Table 3). When
The PMAC will decode the bit-oriented priority
codeword 11111111 00000000 received on the FDL
as a Remote Alarm Indication (RAI or Yellow Alarm)
signal as per T1.403/408. See the section on
4-9
MITEL [ MITEL NETWORKS CORPORATION ]
