STANDARD PRODUCT
PM4328 TECT3
DATASHEET
PMC-2011596
ISSUE 1
HIGH DENSITY T1/E1 FRAMER
AND M13 MULTIPLEXER
optionally set to either halt searching for CRC multiframe altogether, or may
continue searching for CRC multiframe alignment using the established basic
frame alignment. In either case, no further adjustments are made to the basic
frame alignment, and no offline searches for basic frame alignment occur once
CRC-to-non-CRC interworking is declared: it is assumed that the established
basic frame alignment at this point is correct.
AIS Detection
When an unframed all-ones receive data stream is received, an AIS defect is
indicated by setting the AISD bit to logic 1 when fewer than three zero bits are
received in 512 consecutive bits or, optionally, in each of two consecutive periods
of 512 bits. The AISD bit is reset to logic 0 when three or more zeros in 512
consecutive bits or in each of two consecutive periods of 512 bits. Finding frame
alignment will also cause the AISD bit to be set to logic 0.
Signaling Frame Alignment
Once the basic frame alignment has been found, the E1-FRMR searches for
Channel Associated Signaling (CAS) multiframe alignment using the following
G.732 compliant algorithm: signaling multiframe alignment is declared when at
least one non-zero time slot 16 bit is observed to precede a time slot 16
containing the correct CAS alignment pattern, namely four zeros (“0000”) in the
first four bit positions of timeslot 16.
Once signaling multiframe alignment has been found, the E1-FRMR sets the
OOSMFV bit of the E1-FRMR Framing Status register to logic 0, and monitors
the signaling multiframe alignment signal, indicating errors occurring in the 4-bit
pattern, and indicating the debounced value of the Remote Signaling Multiframe
Alarm bit (bit 6 of timeslot 16 of frame 0 of the multiframe). Using debounce, the
Remote Signaling Multiframe Alarm bit has < 0.00001% probability of being
-3
falsely indicated in the presence of a 10 bit error rate.
The block declares loss of CAS multiframe alignment if two consecutive CAS
multiframe alignment signals have been received in error, or additionally, if all the
bits in time slot 16 are logic 0 for 1 or 2 (selectable) CAS multiframes. Loss of
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
PROPRIETARY AND CONFIDENTIAL
61
PMC [ PMC-SIERRA, INC ]
