Released
Datasheet
PM73487 QRT
PMC-Sierra, Inc.
PMC-980618
Issue 3
622 Mbps ATM Traffic Management Device
choice of whether or not to send or drop one or more of the cells is affected by the EOF informa-
tion, because one frame that is being dropped may end, and another frame that is not to be
dropped may start.
2.6.5 Transmit Recovery Algorithm
No recovery algorithm is needed for the resequencing of one algorithm since the SN is ignored.
For resequencing of two algorithms, when a cell with SN s is received, and s is neither equal to
the expected cell number e, nor equal to e + 1, then the cell is dropped. The new expected SN (for
the next cell) is set at s + 1. The next time two consecutive cells are received in ascending SN
order, the channel will have recovered its sequence. Using this algorithm, some legitimate cells
may be dropped while recovering. For example, if the next two cells are legitimate, but are
received in descending SN order, they will both be dropped.
2.6.6 Transmit Multicast Cell Background Process
The transmit multicast background process traverses the linked list for that channel and prepares a
list of pointers to cells and pointers to headers for multicast cells. This allows the dequeue process
to replicate the cell with new headers to each entry in the linked list. This is necessary because
multicast cells are bound to different destinations and need different headers.
Figure 45 shows the replication process that occurs, according to how the fields in the MC_LIST
word are set.
Multicast cell is available in the input FIFO.
Look up the NEXT_MC_HEADER_PTR entry in the
TX_CHANNEL_TABLE pointed to by the OUT_CHAN.
1
Make an entry for the cell in the output FIFO for that
SC on the indicated VO. Increment the MC_COUNT
state bit. Check REPLICATE_CELL bit.
1
0
Look up the
NEXT_MC_ADD in the
multicast control block.
Move the head pointer in
the input FIFO and clear
ENQ_PEND state bit.
1
0
Figure 45. Multicast Background Process
40
PMC [ PMC-SIERRA, INC ]
