PM73121AAL1gator II
PMC-Sierra, Inc.
L
PMC-980620
,VVXH
AAL1 SAR Processor
Data Sheet
35235,(7$5<$1'&21),'(17,$/7230&6,(55$,1&$1')25,76&86720(56,17(51$/86(
If the cell is accepted, the RALP then transfers the cell to the external memory using the R_
CHAN_ALLOC fields in the R_QUEUE_TBL. Figure 32 shows this receive cell process. If a
valid cell is not received in time, the queue may enter an underrun condition.
The CDVT value allows the receiver to be configured to store a variable amount of data for that
queue before data is emitted. This storage permits the cells to arrive with variable delays without
causing errors on the line outputs. This CDVT value is used when the first cell is received after an
underrun. The AAL1gator II also provides protection from buffer overrun and pointer misalign-
ment.
The RALP reads the ATM cell from the RUTOPIA FIFO, verifies the header, and determines the
Figure 33.
Receive Cell Processing
Wait for a cell in the
receive UTOPIA FIFO.
Is the cell a
data cell
No
Check CRC-10 and place
cell in OAM queue.
Yes
Is SNP
correct
Correct SN/SNP as specified
in ITU-T Recommendation
I.363.1 (refer to
Appendix B
“References” on page 203
).
Able to correct
Is SN
correct
No
Yes
Place data and signaling in
appropriate timeslots and
update write pointers.
Accept/drop cell as specified
in ITU-T Recommendation
I.363.1 “Fast SN Algorithm”
(refer to
Appendix B
“References” on page 203
).
Drop
Accept
Unable to correct
No