PM73121ꢀAAL1gator II
Data Sheet
PMC-Sierra, Inc.
PMC-980620
,VVXHꢀꢁ
AAL1 SAR Processor
•
•
The determination on whether or not the inserted cell should contain a pointer is based on
the pointer generation rules defined by ITU-T Recommendation I.363.1. A pointer will be
assumed if the queue is structured and the following conditions are met:
•
The SN is even AND there has been no other pointer in the group of eight cells so far
AND (the sequence number = 6 OR the structure ends within the current inserted cell
or next cell).
If the queue is in SDF-MF mode and the inserted cell should contain signaling data, the
number of payload bytes is adjusted but no signaling information is written to the
signaling buffer. Therefore, the old signaling information will be played out.
NOTE: In SDF-FR mode, the CES specification states that if the queue contains data for
only one DS0, no pointer is used. If a queue is configured in this manner, set R_
CHAN_UNSTRUCT in the R_MAX_BUF word (refer to “R_MAX_BUF Word
Format” on page 157).
•
The value of the payload data depends on the value of INSERT_DATA in R_SN_
CONFIG (refer to “R_SN_CONFIG Word Format” on page 160). The default is to load
the value of 0xFF. Other options are to use conditioned data as defined by R_CONDQ_
DATA, old data, or pseudorandom data. If old data is chosen, no data will be written and
the old data in the receive buffer will be used. The receive buffer write pointer will be
adjusted to the correct location. If the pseudorandom data option is chosen, the data played
out will be the value of R_CONDQ_DATA with the MSB replaced by the current value of
18
7
the pseudorandom number generator x + x + 1.
NOTES: • All DS0s within the replaced cell will use the same algorithm. To minimize the
overhead of generating the inserted cells, use the old data option whenever possi-
ble. The old data option still needs to do internal processing on a byte-by-byte
basis, but since it does not have to write any data, it is about twice as fast as the
other options.
• The “Fast SN Algorithm” will, under certain situations, allow bad cells to pass
through. When this occurs the cells are marked as potentially bad. Any cells
marked as bad will not have pointer verification done on them and any signaling
data or SRTS information they contain will not be written. However, if these cells
should contain pointers or signaling data, adjustments are made to the amount of
payload data written so bit integrity is maintained.
• The pseudorandom option is not available for UDF-HS mode.
The RALP will maintain bit integrity if there is no more than one consecutive errored cells, or if
there are up to six lost cells and the queue does not underrun. To maximize the tolerance of the
RALP to errored cells, the R_CDVT and R_MAX_BUF values should be increased a little to
ꢃꢇ
PMC [ PMC-SIERRA, INC ]
