PM7347 datasheet(191/341 Pages) PMC

191 / 341 page

S/UNI®-JET Data Sheet

Released

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

191

Document ID: PMC-1990267, Issue 3

Bit

Type

Function

Default

Bit 7

R/W

DDSCR

Bit 6

R/W

HDSCR

Bit 5

Unused

Bit 4

Unused

Bit 3

Unused

Bit 2

R/W

HCSADD

Bit 1

R/W

HCSDQDB

Bit 0

R/W

DISCOR

The DISCOR bit controls the HCS error correction algorithm. When DISCOR is a logic zero,

the error correction algorithm is enabled, and single-bit errors detected in the cell header are

corrected. When DISCOR is a logic one, the error correction algorithm is disabled, and any

error detected in the cell header is treated as an uncorrectable HCS error.

HCSDQDB

The HCSDQDB bit enables HCS checking for either ATM type cells or DQDB type cells.

When logic zero, ATM type cells are processed by checking all four octets in the header for

HCS validation. When logic one, DQDB cells are processed by checking only three of the

header octets (octets 2, 3 and 4) for HCS validation.

HCSADD

The HCSADD bit controls the addition of the coset polynomial, x6+x4+x2+1, to the HCS

octet prior to comparison. When HCSADD is a logic one, the polynomial is added, and the

resulting HCS is compared. When HCSADD is a logic zero, the polynomial is not added, and

the unmodified HCS is compared.

HDSCR

HDSCR enables the self-synchronous x43 + 1 descrambler to continue running through the

bytes which should contain the ATM cell headers. When HDSCR is set to logic zero, the

descrambling polynomial will function only over the ATM payload bytes. When HDSCR is

set to logic one, the descrambling polynomial will function over all bytes, including the five

ATM header bytes. This function is available for use with PPP packets and flags which are

scrambled at the source to prevent the generation of "killer" sequences.

PM7347 Datasheet(PDF) 191 Page - PMC-Sierra, Inc

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