PM5347 datasheet(70/302 Pages) PMC

70 / 302 page

PM5347 S/UNI-PLUS

DATA SHEET

PMC-941033

ISSUE 6

SATURN USER NETWORK INTERFACE PLUS

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

Figure 5

- Cell Delineation State Diagram

HUNT

PRESYNC

SYNC

correct HCS

(byte by byte)

DELTA

consecutive

correct HCS's

(cell by cell)

Incorrect HCS

(cell by cell)

ALPHA

consecutive

incorrect HCS's

(cell by cell)

The values of ALPHA and DELTA determine the robustness of the delineation

process. ALPHA determines the robustness against false misalignments due to

bit errors. DELTA determines the robustness against false delineation in the

synchronization process. ALPHA is chosen to be 7 and DELTA is chosen to be

6. These values result in an average time to delineation of 100.98 µs and 33.66

µs for the STS-1 and STS-3c rates, respectively.

Descrambler

The self synchronous descrambler operates on the 48 byte cell payload only.

The circuitry descrambles the information field using the x43 + 1 polynomial. The

descrambler is disabled for the duration of the header and HCS fields and may

optionally be disabled for the payload.

Cell Filter and HCS Verification

Cells are filtered (or dropped) based on HCS errors and/or a cell header pattern.

Cell filtering is optional and is enabled through the RACP registers. Cells are

passed to the receive FIFO while the cell delineation state machine is in the

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