PM7344 S/UNI-MPH
DATA SHEET
PMC-950449
ISSUE 6
MULTI-PHY USER NETWORK INTERFACE
FIFODP[1] FIFODP[0] FIFO DEPTH
0
0
1
1
0
1
0
1
4 cells
3 cells
2 cells
1 cell
Note that FIFODP[1:0] only affects when TCA is asserted. All four cells of the
FIFO may be filled before an overflow is declared.
It is not recommended that the FIFO depth be set to 1 cell. If a cell write is
initiated only when TCA is asserted to logic 1, half the bandwidth is lost to
idle/unassigned cells. For minimum latency and maximum throughput, set
the FIFO depth to 2 cells.
HCSADD:
The HCSADD bit enables the addition of the coset polynomial x6 + x4 + x2 + 1
to the HCS octet before transmission as required by the ATM Forum UNI
specification. When a logic 1 is written to HCSADD, the coset polynomial is
added to the HCS. When a logic 0 is written to HCSADD, the calculated HCS
value is inserted, unmodified into the transmit cell. HCSINS must be set to
logic 1 for HCSADD to have any effect.
HCSDQDB:
The HCSDQDB bit controls the cell header octets included in the HCS
calculation. When a logic 1 is written to HCSDQDB, header octets two, three,
and four are used in the HCS calculation as required by the IEEE-802.6
DQDB specification. When a logic 0 is written to HCSDQDB, all four header
octets are used in the HCS calculation as required by the ATM Forum UNI
specification, and the ITU-T Recommendation I.432.
HCSINS:
The HCSINS bit controls the insertion of the calculated header check
sequence (HCS) in the transmit stream. When a logic 1 is written to
HCSINS, the calculated HCS overwrites the HCS placeholder octet position
in the cell that is read from the transmit FIFO. When a logic 0 is written to
HCSINS, the value passed through the FIFO in the HCS placeholder octet
position is inserted unmodified in the transmit cell. The HCS value is
calculated and inserted externally when HCSINS is a logic 0.
PROPRIETARY AND CONFIDENTIAL TO PMC-SIERRA, INC., AND FOR ITS CUSTOMERS’ INTERNAL USE
207
PMC [ PMC-SIERRA, INC ]
