PM7346 datasheet(91/419 Pages) PMC

91 / 419 page

PM7346 S/UNI-QJET

DATASHEET

PMC-960835

ISSUE 6

SATURN QUAD USER NETWORK INTERFACE FOR J2, E3, T3

PMC-SIERRA, INC. PROPRIETARY AND CONFIDENTIAL TO PMC-SIERRA INC., AND ITS CUSTOMERS’ INTERNAL USE 70

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 can be blocked if the HCS pattern is

invalid or if the filtering 'Match Pattern' and 'Match Mask' registers are

programmed with a certain blocking pattern. ATM Idle cells are filtered by

default. For ATM cells, Null cells (Idle 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 11.

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 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-50 can be

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

received with a correct HCS. The mth cell is not discarded (see Figure 11). Note

that the dropping of cells due to HCS errors only occurs while the ATMF is in the

SYNC state.

Cell delineation can optionally be disabled, allowing the RXCP-50 to pass all

data bytes it receives.

PM7346 Datasheet(PDF) 91 Page - PMC-Sierra, Inc