PM73121ꢀAAL1gator II
Data Sheet
PMC-Sierra, Inc.
PMC-980620
,VVXHꢀꢁ
AAL1 SAR Processor
7. The CSD circuit computes the number of credits for those nine frames and adds the result to
the total.
New credits = 9 × 4 = 36
QUE_CREDITS = 36 + 12.5 = 48.5
If the queue is on a line in SDF-MF mode, the CSD makes a signaling adjustment to the
QUE_CREDITS before writing this value to memory. (If the queue is not in SDF-MF mode,
the signaling adjustment is not made and the QUE_CREDITS calculated in Step 7 is written
to memory.)
The calculation determines the number of signaling bytes in the structure, then generates an
average number of signaling bytes inserted into cells per frame, and finally multiplies this
average number by the frame differential to adjust the QUE_CREDITS.
8. The CSD converts the frame differential from units of frames to units of one-eighth of multi-
frames.
In performing this calculation, the CSD also uses the FRAME_REMAINDER value from the
QUE_CREDITS location in the T_QUEUE_TBL. This example assumes that FRAME_
REMAINDER = 1 from the previous calculation on this queue.
E1: Frame differential (in eighths of a multiframe) = (frame differential + FRAME_
REMAINDER) ÷ 2
T1: Frame differential (in eighths of a multiframe) = (frame differential + FRAME_
REMAINDER) ÷ 3
Frame differential = (9 + 1) ÷ 3 = 10, or three-eighths of a multiframe, remainder 1.
The CSD writes the remainder of this division into the FRAME_REMAINDER location for
use in the next calculation on this queue.
9. The CSD calculates the signaling credit adjustment by multiplying the frame differential
expressed in eighths of a multiframe by the number of signaling bytes in a structure.
Number of signaling bytes in the structure = 4 channels × 0.5 bytes per channel = 2 bytes
per multiframe
Signaling adjustment = three eighths × 2 = 0.75 bytes
10. Then the CSD adds the signaling credit adjustment to the total and writes the result to mem-
ory, in preparation for the next service on this queue.
QUEUE_CREDITS = 48.5 + 0.75 = 49.25 bytes
Unstructured lines use the same procedure. In the case of unstructured lines, the number of chan-
nels allocated to the queue is 32. Because there is never a pointer, the average number of credits
spent per cell is always 47.
ꢂꢅ
PMC [ PMC-SIERRA, INC ]
