RELEASED
PM73123 AAL1GATOR-8
DATASHEET
PMC-2000097
ISSUE 2
8 LINK CES/DBCES AAL1 SAR
3) After servicing all the queues for that frame, the CSD circuit advances to the
next active line located in the line queue. If there are no active lines, the CSD
circuit returns to the idle state to wait for the next line to request service.
Figure 30 shows how the CSD assigns credits to determine in which frames cells
should be sent.
Figure 30 Frame Advance FIFO Operation
Frame Boundaries
TFTC
CSD
RL_DATA(0
FR_ADVANCE_FIFO
The CSD reads
frame
advances and
determines
Set
NEXT_
SERV
RL_FSYNC(0)
The TFTC sees
frame advance
records this in the
FR_ADVANCE_FIFO
cells to be sent
RL_DATA(1
RL_FSYNC(1)
The following is an example of the calculations the CSD circuit performs. This
example assumes a structured line with four channels allocated to one queue in
non-DBCES mode.
1) The TFTC writes Line 3 and Frame 4 to the FR_ADVANCE_FIFO.
2) The CSD circuit determines the queue for which a cell is ready by finding a
set bit in the Transmit Calendar. In this example, it is queue number 100.
3) The CSD circuit reads the number of credits for queue number 100. The
number of credits is always greater than 47 because it is ready for service. In
this example, QUE_CREDITS = 59.375.
4) The CSD circuit subtracts AVG_SUB_VALU, the average number of credits
spent per cell. (Remember: For structured lines, the average number of
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