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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
100
11.2.2.2.1
VCI Mapping
The AAL1gator-32 supports two options for VCI to queue mapping. Eleven bits
of the VCI are always used. The eleven-bit field can be either located in the
least significant bits of the VCI or shifted up 4 bits to occupy bits 14 down to 4 of
the VCI field. The two most significant bits in the field are used to determine
which A1SP processor receives the cell.
There are two methods of detecting a cell to be redirected to the OAM queue.
The first method uses a data indicator bit in the header. The second method
uses the customary PTI field. If the data indicator is not set (VCI(8) = 0 when
SHIFT_VCI=0) or Payload Type Indicator (PTI) = 4 to 7, the cells are sent to the
OAM queue and are stored using the pointers located in the OAM receive queue
table. The head pointer is the address to the first cell received for each queue,
and is usually maintained by the microprocessor. The tail pointer is the address
of the last cell of the queue, and is maintained by the RALP. The RALP updates
the tail pointer upon each OAM cell arrival.
If the cell is a data cell ( cells received with VCI(8) = 1 when SHIFT_VCI=0 and
PTI = 0 to 3), the cell is sent to the queue with VCI(7:0). Bits 7:5 determine the
line, and bits 4:0 determine the queue. The A1SPn block ignores VCI(15:9) and
VPI(11:0). If SHIFT_VCI = 1, the interpretation of the VCI bits is shifted by four
bits.
There is also a special mode when VP_MODE_EN is set in the UI_COMN_CFG
register. When set the VPI field is used to select the A1SP and Line number.
Queue 0 is always assumed. So this mode is only available if all lines are
configured with one queue. Normally this mode can only be used if all lines are
configured in UDF-ML mode. In this mode the VCI field is used to detect an
OAM cell. If the VCI is less than or equal to 31 then the cell will go to the OAM
cell buffer.
Figure 36 shows the interpretation of the incoming cell header once the cell
arrives at the A1SP.