PM73121ꢀAAL1gator II
Data Sheet
PMC-Sierra, Inc.
PMC-980620
,VVXHꢀꢁ
AAL1 SAR Processor
dropped and the POINTER_SEARCH sticky bit is set. The DROPPED_CELL counter is also
incremented. If the underrun condition persists, the microprocessor should set the conditioned bits
to derive both the data and the signaling from the conditioned areas.
Refer to line items 5 and 6 in Figure 47 on page 64 that show how a start up after an underrun
occurs.
3.6.3 Pointer Processing
When an incoming cell has a cell pointer, the cell pointer is checked against the local pointer
value maintained by the RALP. A single pointer mismatch causes no corrective actions. The
pointer is ignored and the cell is used as if it contained valid data. If two consecutive pointer mis-
matches occur, then the RALP forces an underrun condition that causes the receiver to realign to
the next incoming pointer. The proper R_COND_DATA and signaling from multiframe 0 are
played out until the new pointer is found and one CDVT worth of time has passed. The PTR_
MISMATCH sticky bit is set when the pointer mismatch occurs. The FORCED_UNDERRUN
sticky bit is set each time a cell is received and dropped during the forced underrun condition.
Then, the underrun and pointer search bits are set, as described previously in section 3.6.2
“Underrun” on page 60.
If the received cell is potentially bad as determined by SN processing, but should contain a
pointer, the pointer is not checked against the local pointer. However, in this situation, and when
cells are inserted, if the next received pointer mismatches, then a PTR_MISMATCH error is
reported and a forced underrun occurs. By not waiting for the second pointer mismatch in these
situations where bit integrity may have been lost, a quicker detection and recovery will result.
When a PTR_MISMATCH error occurs, the R_POINTER_REFRAMES counter is incremented.
Also, when a single pointer mismatch occurs, signaling information will not be updated until a
valid pointer is received to prevent corruption of the signaling information.
Parity checking is also performed on pointers if R_CHK_PARITY is set in R_MP_CONFIG. If a
parity error is detected the PTR_PARITY_ERR sticky bit will be set and the R_PTR_PAR_ERR
counter will increment. If two consecutive pointer parity errors occur, then the RALP forces an
underrun condition and resynchronizes. This resynchronization will cause R_POINTER_
REFRAMES to increment.
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PMC [ PMC-SIERRA, INC ]
