STANDARD PRODUCT
PM4351 COMET
DATA SHEET
PMC-1970624
ISSUE 10
COMBINED E1/T1 TRANSCEIVER
As a programming option, the data stream bit and timeslot alignment relative to
BRFP can be modified for Concentration Highway Interface (CHI) applications.
When configured for a multiplexed backplane, the two or four sets of PCM and
signaling streams are byte-interleaved into a 4.096 Mbit/s or 8.192 Mbit/s serial
stream.
9.30 Backplane Transmit Interface (BTIF)
The Backplane Transmit Interface allows data to be taken from a backplane in
either a 1.544 Mbit/s, 2.048 Mbit/s, 4.096 Mbit/s, 8.192 Mbit/s or sub-rate NxDS0
serial stream.
When configured to receive a 1.544 Mbit/s data rate stream, the input data
stream on the BTPCM pin to is expected to contain 24 channel bytes of data
followed by a single bit location for the framing bit or optional parity over the
previous 24 channels. The BTSIG input pin must contain 24 bytes of signaling
nibble data located in the least significant nibble of each byte followed by a
single bit position for the framing bit or optional parity over the previous frame.
The framing alignment indication on the BTFP input must indicate the framing bit
position of the 193-bit frame (or, optionally, the framing bit position of the first
frame of the superframe).
In T1 mode, when configured to provide a 2.048 Mbit/s data rate, the block
expects serial PCM data on the BTPCM pin to contain three channel bytes of
data followed by one unused byte. The signaling on the BTSIG pin must be
aligned to the least significant nibble of the associated channel on BTPCM. The
frame alignment indication is expected on the BTFP pin, going to high during the
first bit of the unused byte, indicating the next data byte is the first channel of the
frame. Alternatively, the PCM and signaling can be arranged in 24 contiguous
timeslots, starting at the timeslot indicated by the BTFP pulse.
In E1 mode, the 2.048 Mbit/s data stream consumes all timeslots of BRPCM.
The BTSIG input presents 30 bytes of signaling nibble data located in the least
significant nibble of each timeslot. The framing alignment indication on the
BTFP pin can be configured to indicate the first bit of each 256-bit frame or the
first bit of the first frame of the CRC multiframe and signaling multiframes.
BTCLK can be configured as an output, in which case, BTCLK is generated from
TCLKO. When configured for NxDS0 operation, no output clock edges are
generated during the framing bit positions and idle channels.
BTFP can be configured as an output, in which case, the COMET dictates the
frame alignment.
PROPRIETARY AND CONFIDENTIAL
64
PMC [ PMC-SIERRA, INC ]
