PM7375-SC datasheet(64/430 Pages) PMC

64 / 430 page

PM7375 LASAR-155

DATA SHEET

PMC-931127

ISSUE 6

LOCAL ATM SAR & PHYSICAL LAYER

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

9.3.3 GFC Extraction

The four GFC bits are extracted and serialized out via output RGFC/RLD if enabled

using the UNI_POTS bit in the LASAR-155 Master Configuration register. The

updating of RGFC by particular GFC bits may be disabled through an internal

thus allowing this output to be used as a XON/XOFF indication for controlled data

terminal applications. The serial link is forced low if cell delineation is lost.

9.3.4 Payload Descrambling

The self synchronous descrambler operates on the 48 byte cell payload using the

x43 + 1 polynomial. The descrambler is disabled for the duration of the header and

HEC fields, and may optionally be disabled.

9.4

Receive ATM and Adaptation Layer Cell Processor

The Receive ATM and Adaptation Layer Cell Processor (RALP) performs ATM layer

and AAL Type 5 (AAL-5) layer processing. In addition, if enabled, the RALP also

performs VC aging and non-activity termination. Please refer to the Operations

section for the ATM header fields and the AAL-5 protocol data unit structures.

9.4.1 ATM Layer Processing

ATM Layer processing includes open VC verification, cell filtering, cell copying and

CRC-10 verification. Cell filtering is the action of not passing cells to the PCI Host.

Cell copying is the action of copying cells to the Multipurpose Port. Cell filtering and

cell copying are mutually exclusive.

For every incoming cell, the RALP must verify that the VPI and VCI header fields

correspond to an open VC. Since only 128 VCs are allowed, a subset of the VPI

and VCI field bits are required to identify the VC. Selection of which VPI and VCI

bits contribute to the formation of the VPI/VCI code is programmable. If a cell

arrives and its VPI /VCI code does not identify an open VC, the cell is filtered.

Given that the incoming cell can be associated with an open VC, the RALP block

interprets the PTI fields to identify what payload is being carried. For F4 and F5

OAM cells, the CRC-10 is optionally verified using the polynomial, x10+x9+x5+x4+1.

If configured, cells can be filtered based on illegal PTI codepoints (110, 111), F5

OAM flows (100, 101), specific VPI/VCI codes (i.e. F4 OAM cells) or cells with

CRC-10 errors. Filtered cells are not passed onto the PCI Host and are

accumulated in the SAR PMON block.

PM7375-SC датащи(PDF) 64 Page - PMC-Sierra, Inc