STANDARD PRODUCT
PM4351 COMET
DATA SHEET
PMC-1970624
ISSUE 10
COMBINED E1/T1 TRANSCEIVER
CAS multiframe alignment is also declared if basic frame alignment has been
lost.
National Bit Extraction
The E1-FRMR extracts and assembles the submultiframe-aligned National bit
codewords Sa4[1:4] , Sa5[1:4] , Sa6[1:4] , Sa7[1:4] and Sa8[1:4]. The
corresponding register values are updated upon generation of the CRC
submultiframe interrupt.
This E1-FRMR also detects the V5.2 link ID signal, which is defined as the
condition where 2 out of 3 Sa7 bits are zeroes. Upon reception of this Link ID
signal, the V52LINKV bit of the E1-FRMR Framing Status register is set to
logic 1. This bit is cleared to logic 0 when 2 out of 3 Sa7 bits are ones.
Alarm Integration
The OOF and the AIS defects are integrated, 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).
The E1-FRMR counts the occurrences of AISD over a 4 ms interval and
indicates a valid AIS is present 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
-3
AIS Alarm within 104 ms 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
46
PMC [ PMC-SIERRA, INC ]
