RELEASED
PM73123 AAL1GATOR-8
DATASHEET
PMC-2000097
ISSUE 2
8 LINK CES/DBCES AAL1 SAR
Figure 36 Robust SN Algorithm
Invalid
Start
Out of
sequence,
discard stored,
Valid SN,
discard stored
Invalid
discard
stored
OUT OF
SYNC
Out of sequence
Discard stored
Out of sequence
discard stored
seq
accept
stored
In
Out of seq/ accept stored
In seq -1+1/accept stored
In seq/insert cells
Invalid SN/accept
seq
-1/ discard
In
SYNC
Out
Of SEQ
In seq -1+1/accept stored
Invalid
In seq –1/discard stored
If the cell is stored, the RALP then transfers the cell to the external memory
using the R_CHAN_ALLOC fields in the R_QUEUE_TBL. If a cell is accepted,
the wr_ptr for the RFTC is advanced to make the cell available to the RFTC. . 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-8
also provides protection from buffer overrun and pointer misalignment.
Note that during an underrun, the RALP ‘Robust’ sequence number processing
state machine freezes in its current state. For example, if the state machine is in
PMC-SIERRA, INC. PROPRIETARY AND CONFIDENTIAL
114
PMC [ PMC-SIERRA, INC ]
