PM7367 datasheet(49/323 Pages) PMC

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PM7367 FREEDM-32P32

DATA SHEET

PMC-1991499

ISSUE 2

FRAME ENGINE AND DATA LINK MANAGER

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

Figure 3 – Partial Packet Buffer Structure

16 bytes

Partial Packet

Buffer RAM

Block 511

Block 0

Block 1

Block 2

Block 3

Block 511

Block 0

Block 1

Block 2

Block 3

Block

Pointer RAM

Block 200

0x03

0xC8

0x01

The FIFO algorithm of the partial packet buffer processor is based on a

programmable per-channel transfer size. Instead of tracking the number of full

blocks in a channel FIFO, the processor tracks the number of transactions.

Whenever the partial packet writer fills a transfer-sized number of blocks or

writes an end-of-packet flag to the channel FIFO, a transaction is created.

Whenever the partial packet reader transmits a transfer-size number of blocks or

an end-of-packet flag to the RMAC block, a transaction is deleted. Thus, small

packets less than the transfer size will be naturally transferred to the RMAC

block without having to precisely track the number of full blocks in the channel

FIFO.

The partial packet roamer performs the transaction accounting for all channel

FIFOs. The roamer increments the transaction count when the writer signals a

new transaction and sets a per-channel flag to indicate a non-zero transaction

count. The roamer searches the flags in a round-robin fashion to decide for

which channel FIFO to request transfer by the RMAC block. The roamer informs

the partial packet reader of the channel to process. The reader transfers the

data to the RMAC until the channel transfer size is reached or an end of packet

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