PM73121ꢀAAL1gator II
Data Sheet
PMC-Sierra, Inc.
PMC-980620
,VVXHꢀꢁ
AAL1 SAR Processor
by the microprocessor. The tail pointer is the address of the last cell of the queue, and is main-
tained by the RALP. The RALP updates the tail pointer upon each OAM cell arrival. Figure 31
shows the interpretation of the incoming cell header.
11
11
10
10
9
9
8
7
7
6
5
4
4
3
2
1
0
0
VPI
Ignored
SHIFT_VCI = 0
SHIFT_VCI = 1
15
14
13
12
Ignored
8
6
5
3
2
1
VCI
Data
Line
Queue MOD 32
11
10
9
8
8
7
6
5
4
3
2
1
0
VPI
Ignored
15
14
Ignored
13
12
Data
11
10
9
7
6
5
4
3
2
1
0
VCI
Ignored
Line
Queue MOD 32
Figure 31. Cell Header Interpretation
If SHIFT_VCI = 0, cells received with VCI(8) = 1 and PTI = 0 to 3 are interpreted as data cells
and are sent to the queue with VCI(7:0). Bits 7:5 determine the line, and bits 4:0 determine the
queue. The receiver ignores VCI(15:9) and VPI(11:0). If SHIFT_VCI = 1, the interpretation of
the VCI bits is shifted by four bits.
When the cell is a data cell, the RALP verifies the SN CRC. If the SN CRC does not verify, the
RALP attempts to correct it as specified in ITU-T Recommendation I.363.1 and increments the
R_INCORRECT_SNP counter (refer to “R_INCORRECT_SNP Word Format” on page 158). If
the RALP cannot correct the cell, it identifies the cell as invalid.
If the DISABLE_SN bit (refer to “DISABLE_SN” on page 160) has not been set for this queue,
then sequence number processing is done in accordance with the “Fast SN Algorithm” described
in ITU-T Recommendation I.363.1. Based on the value of the current SN and SNP and the previ-
ous SN and SNP, the RALP either accepts the current cell, drops the current cell, or accepts the
current cell and inserts cells. Inserted cells have the following properties:
•
If the queue is in an unstructured mode or if the queue is in structured mode and the
inserted cell should not contain a pointer, each inserted cell contains the number of
payload bytes as determined by R_BYTES_CELL in R_MP_CONFIG (refer to “R_MP_
CONFIG Word Format” on page 155).
•
•
If the queue is in a structured mode and the inserted cell should contain a pointer and R_
BYTES_CELL is equal to 47, then the inserted cell contains 46 payload bytes.
If the queue is in a structured mode and the inserted cell should contain a pointer and R_
BYTES_CELL is less than 47, then the inserted cell contains R_BYTES_CELL payload
bytes.
ꢃꢆ
PMC [ PMC-SIERRA, INC ]
