PM7345 datasheet(71/306 Pages) PMC

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PM7345 S/UNI-PDH

DATA SHEET

PMC-931011

ISSUE 6

SATURN USER-NETWORK INTERFACE

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

The SPLT block generates a stuff length pattern of 18, 19 or 20 octets determined

by the phase alignment of the start of the G.751 E3 frame and the start of the E3

PLCP frame. The stuff length may be incremented or decremented by one

depending on the value of the C13/CADD input.

The C13/CADD input can be provisioned to loop time the PLCP transmit frame to an

externally applied 8 kHz reference.

The Zn, growth octets are set to 00H. The Zn octets may be inserted from an

external device via the path overhead stream input, TPOH.

9.16 TXCP Transmit Cell Processor

The Transmit Cell Processor (TXCP) Block integrates circuitry to support ATM cell

payload scrambling, header check sequence (HCS) generation, and idle/unassigned

cell generation.

The TXCP scrambles the cell payload field using the self synchronizing scrambler

with polynomial x43 + 1. The header portion of the cells is not scrambled. Note that

cell payload scrambling is optional in the S/UNI-PDH, and is required by ITU-T

Recommendation I.432. The ATM Forum DS3 UNI specification requires that cell

payloads are unscrambled for the DS3 physical layer interface (however discussions

are ongoing to make scrambling a requirement in the future).

The HCS is generated using the polynomial, x8 + x2 + x + 1. The coset polynomial

x6 + x4 + x2 + 1 is added (modulo 2) to the calculated HCS octet as required by the

ATM Forum UNI specification, and ITU-T Recommendation I.432. The resultant

octet optionally overwrites the HCS octet in the transmit cell. When the transmit

FIFO is empty, the TXCP inserts idle/unassigned cells. The idle/unassigned cell

header is fully programmable using five internal registers. Similarly, the 48 octet

information field is programmed with an 8 bit repeating pattern using an internal

9.17 TXFF Transmit FIFO

The Transmit FIFO (TXFF) provides FIFO management and the S/UNI-PDH

transmit cell interface. The transmit FIFO contains four cells. The FIFO depth may

be programmed to four, three, two, or one cells. The FIFO provides the cell rate

decoupling function between the transmission system physical layer and the ATM

layer.

PM7345 Datasheet(PDF) 71 Page - PMC-Sierra, Inc