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RELEASED
PM73122 AAL1GATOR-32
DATASHEET
PMC-1981419
ISSUE 7
32 LINK CES/DBCES AAL1 SAR PROCESSOR
PROPRIETARY AND CONFIDENTIAL TO PMC-SIERRA, INC., AND FOR ITS CUSTOMERS’ INTERNAL USE
68
Figure 7 Source Priority Servicing Example
Priority 1
Priority 2
Priority 3
Priority 4
Priority 5
A1SP0
A1SP1
A1SP2
A1SP3
LOOPB
Priority 1
Priority 2
Priority 3
Priority 4
Priority 5
A1SP1
A1SP2
A1SP3
LOOPB
A1SP0
Priority 1
Priority 2
Priority 3
Priority 4
Priority 5
A1SP1
A1SP3
LOOPB
A1SP0
A1SP2
Initial Order
Order after
A1SP0 has sent
a cell
Order after
A1SP1 does not
have a cell to
send but A1SP2
has sent a cell
Time 0
Time 1
Time 2
When an A1SP is operated in high-speed mode, its companion A1SP within the
dual A1SP is left idle. If the remaining two A1SPs are not in high speed mode, it
is advantageous to provide the high-speed A1SP with more opportunities to be
serviced with a higher priority than the low-speed A1SPs. To support this, the
initial value of priority list can be programmed to be different than the default and
allow, for example, two entries of the five slots for the high-speed A1SP and no
entry for the idle A1SP. Thus, giving the high-speed A1SP 2/5 of the available
bandwidth. The initial order is loaded via the UI_Src_Poll_List register When
the Utopia interface is not enabled (UI_EN=0 in the UI_COMN_CFG register),
the value in the UI_Src_Poll_List register is loaded into the priority table as its
initial value. During operation, the initial entries will be transferred among the
priority list but the same number of entries for a particular A1SP will continue to
exist indefinitely until a reset event occurs.
If the SRC_INTF FIFO has room for a cell, the UMUX polls the current highest
priority A1SP block (or Loopback FIFO) to determine if it has a cell. If so, a cell
is read from the selected A1SP block and transferred into the SRC_INTF FIFO.
If the highest priority source does not have a cell, the next lowest priority A1SP
FIFO is examined and the process continues until all sources in the list are
polled. Each A1SP block has an 8-cell FIFO.
In the sink direction, the UMUX waits until the SNK_INTF FIFO has a cell to
send. Once the SNK_INTF FIFO has a cell to send, the UMUX polls the A1SP
associated with the cell for availability. Once the A1SP has room for the cell, the
UMUX reads the cell out of the SNK_INTF FIFO and places it in the A1SP FIFO.