PM6341 E1XC
DATA SHEET
PMC-910419
ISSUE 8
E1 FRAMER/TRANSCEIVER
additionally, if all the bits in timeslot 16 are logic 0 for 1 or 2 (selectable) CAS
multiframes. Loss of CAS multiframe alignment is also declared if frame
alignment has been lost.
9.4.5 Alarm Integration
The Alarm Integrator Block monitors the OOF and the AIS indications, verifying
that each condition has persisted for 104 ms (±6 ms) before indicating the alarm
condition. The alarm is removed when the condition has been absent for 104 ms
(±6 ms).
The AIS alarm algorithm accumulates the occurrences of AISD (AIS detection).
AISD is defined as an unframed pattern with less than 3 zeros in two consecutive
frame times (512 bits). The Alarm Integrator Block counts the occurrences of
AISD over a 4 ms interval and indicates a valid AIS presence when 13 or more
AISD indications (of a possible 16) have been received. Each interval with a
valid AIS presence indication increments an interval counter which declares AIS
Alarm when 25 valid intervals have been accumulated. An interval with no valid
AIS presence indication decrements the interval counter; the AIS Alarm
declaration is removed when the counter reaches 0. This algorithm provides a
99.8% probability of declaring an AIS Alarm within 104 ms in the presence of a
-3
10 mean bit error rate.
The TS16 AIS alarm algorithm accumulates the occurrences of T16AISD (TS16
AIS detection). T16AISD is defined as two consecutive all ones time slot 16
bytes while out of signalling multiframe. Each interval with a valid TS16 AIS
presence indication increments an interval counter which declares TS16 AIS
Alarm when 22 valid intervals have been accumulated. An interval with no valid
TS16 AIS presence indication decrements the interval counter; the TS16 AIS
Alarm declaration is removed when the counter reaches 0. This algorithm
provides a 99.1% probability of declaring an TS16 AIS Alarm within 3.1 ms after
-3
loss of signalling multiframe detection in the presence of a 10 mean bit error
rate.
The red alarm algorithm monitors occurrences of OOF over a 4 ms interval,
indicating a valid OOF interval when one or more OOF indications occurred
during the interval, and indicating a valid in frame (INF) interval when no OOF
indication occurred for the entire interval. Each interval with a valid OOF
indication increments an interval counter which declares RED Alarm when 25
valid intervals have been accumulated. An interval with valid INF indication
decrements the interval counter; the RED Alarm declaration is removed when the
counter reaches 0. This algorithm biases OOF occurrences, leading to
declaration of red alarm when intermittent loss of frame alignment occurs.
PROPRIETARY AND CONFIDENTIAL TO PMC-SIERRA, INC., AND FOR ITS CUSTOMERS’ INTERNAL USE
49
PMC [ PMC-SIERRA, INC ]
