PM7344 datasheet(73/293 Pages) PMC

73 / 293 page

PM7344 S/UNI-MPH

DATA SHEET

PMC-950449

ISSUE 6

MULTI-PHY USER NETWORK INTERFACE

PROPRIETARY AND CONFIDENTIAL TO PMC-SIERRA, INC., AND FOR ITS CUSTOMERS’ INTERNAL USE

RXCP configuration/control registers. More precisely, filtering is performed when

filtering is enabled or when HCS errors are found when HCS checking is

enabled. Otherwise, all cells are passed on regardless of any error conditions.

Cells are dropped if the HCS pattern is invalid or if the filtering 'Match Pattern'

and 'Match Mask' registers are programmed with a certain blocking pattern. Idle

cells are not automatically filtered. If they are required to be filtered, then that

filtering criterion (i.e. the cell header pattern) must be programmed through the

Idle/Unassigned Cell Pattern and Mask registers. For ATM cells,

Idle/Unassigned cells are identified by the standardized header pattern of 'H00,

'H00, 'H00 and 'H01 in the first 4 octets followed by the valid HCS octet.

While the cell delineation state machine is in the SYNC state, the HCS

verification circuit implements the state machine shown in figure 10.

In normal operation, the HCS verification state machine remains in the

'Correction' state. Incoming cells containing no HCS errors are passed to the

receive FIFO. Incoming single-bit errors are optionally corrected, and the

resulting cell is passed to the FIFO. Upon detection of a single-bit error or a

multi-bit error, the state machine transitions to the 'Detection' state.

A programmable hysteresis is provided when dropping cells based on HCS

errors. When a cell with an HCS error is detected, the RXCP can be

programmed to continue to discard cells until m (where m = 1, 2, 4, 8) cells are

received with correct HCS. The mth cell is not discarded (see Figure 16). Note

that the dropping of cells due to HCS errors only occurs while the cell delineation

state machine is in the SYNC state (see Figure 15).

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