PM7347 datasheet(68/341 Pages) PMC

68 / 341 page

S/UNI®-JET Data Sheet

Released

Proprietary and Confidential to PMC-Sierra, Inc., and for its Customers’ Internal Use

Document ID: PMC-1990267, Issue 3

Figure 7 HCS Verification State Diagram

DETECTION

MODE

ATM DELINEATION

SYNC STATE

CORRECTION

MODE

No Errors Detected in M

(M = 1, 2, 4, or 8) consecutive cells

(Pass Last Cell)

Apparent Multi-Bit Error

(Drop Cell)

No Errors

Detected

(Pass Cell)

ALPHA

consecutive

incorrect HCS's

(To HUNT state)

DELTA

consecutive

correct HCS's

(From PRESYNC

state)

Single Bit Error

(Correct error

and pass cell)

Drop Cell

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 7). Note: 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.

10.11 RXFF Receive FIFO

The Receive FIFO (RXFF) provides FIFO management and the S/UNI-JET receive cell interface.

The receive FIFO contains four cells. The FIFO provides the cell rate decoupling function

between the transmission system physical layer and the ATM layer.

The general management functions of the RXFF are:

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