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PM7329 S/UNI-APEX-1K800
DATASHEET
PMC-2010141
ISSUE 2
ATM TRAFFIC MANAGER AND SWITCH
PROPRIETARY AND CONFIDENTIAL TO PMC-SIERRA, INC., AND FOR ITS CUSTOMERS’ INTERNAL USE
167
Table 28
- Port Count Context Record Structure
MPLWord
En (bit #)
Bits
Parameter
Description
33:32
Unused
Reserved
31
PortEn
Enables the port. When PortEn = 1, it permits cells to
be received and transmitted if the class and VCs are
setup. The PortEn should be set to zero 0 only after
the class and VC have been torn down.
If the PortEn is set to zero prior to tearing down a VC,
then incoming cells will increment either the
DiscardCnt or CLPxDiscardCnt. Cells that exist in the
queues when the port is disabled may be transmitted.
Details are listed below.
If PortEn changes from 1->0, the first cell at the head
of each class queue shall be transmitted. Any cells
remaining in the queues will not be transmitted.
Exception to this case is if the port contains a shaped
class, where the transmission of cells in the queues
will continue until there is one cell per VC remaining.
When PortEn = 0, all incoming cells to this port will be
discarded, CellRxErrICI updated, and the maskable
interrupt QCellRxErr will be sent.
For non FCQ VCs in cell discard mode, the
DiscardCnt is incremented when a cell is received.
For non FCQ VCs in EPD/PPD discard mode, the
DiscardCnt is incremented when the first cell is
received, and CLPxDiscardCnt is incremented when
subsequent cells are received.
For FCQ VCs, the CLPxDiscardCnt is incremented
when a cell is received. If a frame is in the process of
being re-assembled when PortEn = 1->0, the
CLPxDiscardCnt will be incremented by the length of
the re-assembly queue plus 1 (cell that arrived).
30:28
Unused
Reserved
0/1/2/3
27:20
PortMaxThrsh Maximum threshold for cells on a per-Port basis. 4 bit
logarithmic, 4 bit fractional encoding. A zero value will
effectively disable congestion at the Port level for this
port.