PM7367 datasheet(82/323 Pages) PMC

82 / 323 page

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

block. Writing new provisioning data to a channel resets the channel's entire

state vector.

8.7.2 Transmit Partial Packet Buffer Processor

The partial packet buffer processor controls the 8 Kbyte partial packet RAM

which is divided into 16 byte blocks. A block pointer RAM is used to chain the

partial packet blocks into circular channel FIFO buffers. Thus, non-contiguous

sections of RAM can be allocated in the partial packet buffer RAM to create a

channel FIFO Figure 15 shows an example of three blocks (blocks 1, 3, and 200)

linked together to form a 48 byte channel FIFO. The three pointer values would

be written sequentially using indirect block write accesses. When a channel is

provisioned with this FIFO, the state machine can be initialised to point to any

one of the three blocks.

The partial packet buffer processor is divided into three sections: reader, writer

and roamer. The roamer is a time-sliced state machine which tracks each

channel's FIFO buffer free space and signals the writer to service a particular

channel. The writer requests data from the TMAC block and transfers packet

data from the TMAC to the associated channel FIFO. The reader is a time-sliced

state machine, which transfers the HDLC information from a channel FIFO to the

HDLC processor when the HDLC processor requests it. If a buffer under-run

occurs for a channel, the reader informs the HDLC processor and purges the

rest of the packet.

PM7367 датащи(PDF) 82 Page - PMC-Sierra, Inc