RELEASED
PM4354 COMET-QUAD
DATASHEET
PMC-1990315
ISSUE 6
FOUR CHANNEL COMBINED E1/T1/J1
TRANSCEIVER / FRAMER
PROPRIETARY AND CONFIDENTIAL TO PMC-SIERRA, INC. AND FOR ITS CUSTOMERS’ INTERNAL USE
47
When the backplane receive timing is recovered from the receive data the elastic store can be
bypassed to eliminate the one frame delay. In this configuration (the Clock Master backplane
receive modes), the elastic store is used to synchronize the backplane receive frames to the
transmit line clock so that per-DS0 loopbacks may be enabled.
To allow for the extraction of signaling information in the data channels, superframe identification
is also passed through the ELST.
For payload conditioning, the ELST may optionally insert a programmable idle code into all
channels when the framer is out of frame synchronization. This code is set to all 1’s when the
ELST is reset.
9.10 Signaling Extractor (SIGX)
The Signaling Extraction (SIGX) block provides channel associated signaling (CAS) extraction
from an E1 signaling multi-frame or from ESF or SF T1 formats. It selectively debounces the bits,
and serializes the results onto the BRSIG[x] or CASBRD outputs. Debouncing is performed on
individual signaling bits. This BRSIG[x] (CASBRD) output is channel aligned with BRPCM[x]
(MVBRD) output, and the signaling bits are repeated for the entire multiframe/superframe,
allowing downstream logic to reinsert signaling into any frame, as determined by system timing.
The signaling data stream contains the A,B,C,D bits in the lower 4 channel bit locations (bits 5, 6,
7 and 8) in T1 ESF or E1 framing formats; in T1 SF format the A and B bits are repeated in
locations C and D (i.e. the signaling stream contains the bits ABAB for each channel).
The SIGX block contains three superframes worth of signal buffering to ensure that there is a
greater than 95% probability that the signaling bits are frozen in the correct state for a 50% ones
density out of frame condition, as specified in TR-TSY-000170 and BELL PUB 43801. With
signaling debounce enabled, the per-channel signaling state must be in the same state for 2
superframes before appearing on the serial output stream.
The SIGX block provides one superframe or signaling-multiframe of signal freezing on the
occurrence of slips. When a slip event occurs, the SIGX freezes the output signaling for the entire
superframe in which the slip occurred; the signaling is unfrozen when the next slip-free
superframe occurs.
The SIGX also provides control over timeslot signaling bit fixing, data inversion and signaling
debounce on a per-timeslot basis.
The SIGX block also provides an interrupt to indicate a change of signaling state on a per channel
basis.
9.11 Performance Monitor Counters (T1/E1-PMON)
The Performance Monitor Counters function is provided by the PMON block. The block
accumulates CRC error events, Frame Synchronization bit error events, and Out Of Frame
events, or optionally, Change of Frame Alignment (COFA) events with saturating counters over