PM7382-PI datasheet(87/330 Pages) PMC

87 / 330 page

RELEASED

PM7382 FREEDM-32P256

DATA SHEET

PMC-2010333

ISSUE 3

FRAME ENGINE AND DATA LINK MANAGER 32P256

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

software programmable limit. If a channel FIFO under-runs, the HDLC processor

aborts the packet.

The configuration of the HDLC processor is accessed using indirect channel

read and write operations. When an indirect operation is performed, the

information is accessed from RAM during a null clock cycle inserted by the

TCAS256 block. Writing new provisioning data to a channel resets the channel’s

entire state vector.

8.8.2 Transmit Partial Packet Buffer Processor

The partial packet buffer processor controls the 32 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 16 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 TMAC256 block and transfers packet

data from the TMAC256 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.

PM7382-PI Datasheet(PDF) 87 Page - PMC-Sierra, Inc