PM4341AT1XC
DATA SHEET
PMC-900602
ISSUE 7
T1 FRAMER/TRANSCEIVER
When the elastic store is being used, if the average frequency of the incoming
data is greater than the average frequency of the backplane clock, the write
pointer will catch up to the read pointer and the buffer will be filled. Under this
condition a controlled slip will occur when the read pointer crosses the next
frame boundary. The following frame of PCM data will be deleted.
If the average frequency of the incoming data is less than the average frequency
of the backplane clock, the read pointer will catch up to the write pointer and the
buffer will be empty. Under this condition a controlled slip will occur when the
read pointer crosses the next frame boundary. The last frame which was read
will be repeated.
A slip operation is always performed on a frame boundary.
To allow for the extraction of signalling information in the PCM data channels,
superframe identification is also passed through the ELST.
For payload conditioning, the ELST inserts a programmable idle code into all
channels when the FRMR is out of frame synchronization. This code is set to all
1's when the ELST is reset.
8.13 Signalling Extractor (SIGX)
The Signalling Extraction function is provided by the SIGX block.This block
provides signalling bit extraction from a PCM stream for ESF, SF, and SLC®96
framing formats, and serializes the bits into a 1.544 Mbit/s serial stream channel-
aligned to the outgoing PCM data stream. The signalling data stream contains
the A,B,C,D bits in the lower 4 channel bit locations (bits 5,6,7,8) in ESF framing
format; in SF and SLC®96 formats the A and B bits are repeated in locations C
and D (i.e. the signalling stream contains the bits ABAB for each channel). This
signalling data stream is compatible with the Basic Transmitter XBAS block. The
SIGX also provides user control over signalling freezing and provides control
over channel data inversion, signalling bit fixing and signalling debounce on a
per-channel basis.The block contains three superframes worth of signal
buffering to ensure that there is a greater than 95% probability that the signalling
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 signalling debounce
enabled, the per-channel signalling state must be in the same state for 2
superframes before appearing on the serial output stream.
The SIGX provides one superframe of signal freezing on the occurrence of slips.
When a slip event occurs, the SIGX freezes the output signalling for the entire
superframe in which the slip occurred; the signaling is unfrozen when the next
slip-free superframe occurs.
PROPRIETARY AND CONFIDENTIAL TO PMC-SIERRA, INC., AND FOR ITS CUSTOMERS’ INTERNAL USE
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PMC [ PMC-SIERRA, INC ]
