![](http://datasheet.mmic.net.cn/330000/PM73121_datasheet_16444365/PM73121_64.png)
PM73121AAL1gator II
PMC-Sierra, Inc.
L
PMC-980620
,VVXH
AAL1 SAR Processor
Data Sheet
35235,(7$5<$1'&21),'(17,$/7230&6,(55$,1&$1')25,76&86720(56,17(51$/86(
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.
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.
Figure 31.
Cell Header Interpretation
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
Queue MOD 32
Line
Ignored
Ignored
VCI
Data
11
10
9
8
7
6
Ignored
5
4
3
2
1
0
11
10
9
8
7
6
5
4
3
2
1
0
Ignored
15
14
13
12
11
10
9
8
7
6
Line
5
4
3
2
1
0
Ignored
Queue MOD 32
SHIFT_VCI = 0
VPI
VCI
SHIFT_VCI = 1
VPI
Data