RELEASED
PM73123 AAL1GATOR-8
DATASHEET
PMC-2000097
ISSUE 2
8 LINK CES/DBCES AAL1 SAR
single DS0 with no signaling nibble and no pointer, set T_CHAN_UNSTRUCT =
1 in the QUEUE_CONFIG word of the T_QUEUE_TBL.
4) The TALP fills the rest of the cell payload with data and/or signaling
information. The T_CHAN_ALLOC table in the transmit queue table determines
which channels are dedicated to which queue. If a bit is set, the channel
represented by that bit is assigned to that queue. The TALP successively writes
the data from the marked channels into the UTOPIA interface. If the
LOOPBACK_ENABLE bit is set in the TX_CONFIG register then the cell is
written into a separate FIFO to be looped back to RALP. A queue-based
parameter, BYTES_PER_CELL, decides when enough payload bytes have been
obtained. If this number is fewer than 47, then the remaining bytes for the cell
are loaded with P_FILL_CHAR. This implies that because of the presence of the
structure pointer, the number of fill bytes will not be constant for structured data
queues.
DBCES mode requires some additional adjustments. A bitmask must be placed
at the beginning of a structure that is pointed to by a structure pointer. This
bitmask can be one to four bytes in length. Also, the active status of the
channels must be factored in. Only if a bit is set in the T_CHAN_ALLOC table
and the corresponding channel is active does the TALP write data from the
channel into the UTOPIA interface. If none of the channels is active, the cell will
be filled with the null bitmask.
5) The structure used for signaling is determined by the mode of the line and the
value of E1_WITH_T1_SIG. Normally the signaling structure will follow the mode
of the line. However, if the line is in E1 mode and E1_WITH_T1_SIG is set, then
a T1 signaling structure is used. This means that for a single DS0, signaling is
inserted after 24 data bytes instead of after 16 data bytes. If data is to be sent
from the data queue, this process continues byte-by-byte while updating pointers
and counters until one of the following occurs:
• The cell is complete.
• The last data byte for the last frame of the multiframe has been set.
6) When signaling information is to be sent, data is obtained from the signaling
locations of the multiframe, with the help of the channel allocation table
(T_CHAN_ALLOC). This process proceeds byte-by-byte until one of the following
occurs:
• The cell is complete.
• All signaling nibbles for all channels assigned to the queue have been sent.
Figure 31 shows an example of the payload generation process.
PMC-SIERRA, INC. PROPRIETARY AND CONFIDENTIAL
98
PMC [ PMC-SIERRA, INC ]
