PM73121ꢀAAL1gator II
Data Sheet
PMC-Sierra, Inc.
PMC-980620
,VVXHꢀꢁ
AAL1 SAR Processor
until it recognizes the attention bit is no longer set. Failure to observe this requirement can result
in loss of attention requests. All parameters must be set up before CMD_REG_ATTN is asserted.
7.11 Activating a New Queue on an Active Line
Before a new queue on an active line can be activated, all transmit queue table structures must be
properly set up. Refer to section 7.6.8 “T_QUEUE_TBL” on page 134. The proper bit in the T_
ADD_QUEUE table is then set, followed by an assertion of the CSD_ATTN bit.
NOTES:
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Only bits for new queues in the T_ADD_QUEUE table should be set when the CSD_
ATTN bit is set. If bits are left set from previous add queue operations, the cell genera-
tion process will be corrupted.
•
•
Before reactivating a previously active queue, be sure to reinitialize all the registers in
the queue table for that queue.
If backpressure on the transmit UTOPIA port is severe enough to prevent the TALP
from building cells when they are scheduled, the CSD_ATTN bit will not clear until
the TALP has a chance to build those cells. Under this condition, the CSD_ATTN bit
may not clear until the backpressure stops. Note that a VC is not considered to be
started until the CSD clears the CSD_ATTN bit.
In UDF-HS mode, the CSD_ATTN bit is not used. Simply being in UDF-HS mode and not in
software reset and having the TX_ACTIVE bit set for queue 0 will activate the queue.
7.12 Making Changes to an Active Queue
Before reconfiguration, a queue should be deactivated by clearing the ACTIVE bit in the transmit
queue table (refer to section 7.6.8 “T_QUEUE_TBL” on page 134). The queue will not be
deactivated until the next entry in the calendar is encountered. The time for the next calendar
entry to be encountered is:
(FRAMES_PER_CELL + 1) × the frame rate
NOTES:
•
•
The frame rate is typically 125 µs. Refer to “FRAMES_PER_CELL” on page 136.
Before reactivating a previously active queue, be sure to reinitialize all the registers in
the queue table for that queue.
ꢀꢅꢆ
PMC [ PMC-SIERRA, INC ]
