PM7367 datasheet(228/323 Pages) PMC

228 / 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

214

The HDLC processor starts transmitting a packet when the channel FIFO free

space is less than or equal to the level specified in the appropriate Start

Transmission Level column of the following table or when an end of a packet

is stored in the channel FIFO. When the channel FIFO free space is greater

than the level specified in the Expedite Trigger Level column of the following

table and the HDLC processor is transmitting a packet and an end of a

packet is not stored in the channel FIFO, the partial packet buffer makes

expedited requests to the TMAC to retrieve XFER[2:0] + 1 blocks of data.

To prevent lockup, the channel transfer size (XFER[2:0]) can be configured to

be less than or equal to the start transmission level set by LEVEL[3:0] and

TRANS. Alternatively, the channel transfer size can be set, such that, the

total number of blocks in the logical channel FIFO minus the start

transmission level is an integer multiple of the channel transfer size.

Table 24 – Level[3:0]/TRANS Settings

LEVEL[3:0]

Expedite

Trigger Level

Start

Transmission

Level (TRANS=0)

Start Transmission

Level (TRANS=1)

0000

2 Blocks

(32 bytes free)

1 Block

(16 bytes free)

1 Block

(16 bytes free)

0001

3 Blocks

(48 bytes free)

2 Blocks

(32 bytes free)

1 Block

(16 bytes free)

0010

4 Blocks

(64 bytes free)

3 Blocks

(48 bytes free)

2 Blocks

(32 bytes free)

0011

6 Blocks

(96 bytes free)

4 Blocks

(64 bytes free)

3 Blocks

(48 bytes free)

0100

8 Blocks

(128 bytes free)

6 Blocks

(96 bytes free)

4 Blocks

(64 bytes free)

0101

12 Blocks

(192 bytes free)

8 Blocks

(128 bytes free)

6 Blocks

(96 bytes free)

0110

16 Blocks

(256 bytes free)

12 Blocks

(192 bytes free)

8 Blocks

(128 bytes free)

0111

24 Blocks

(384 bytes free)

16 Blocks

(256 bytes free)

12 Blocks

(192 bytes free)

1000

32 Blocks

(512 bytes free)

24 Blocks

(384 bytes free)

16 Blocks

(256 bytes free)

1001

48 Blocks

(768 bytes free)

32 Blocks

(512 bytes free)

24 Blocks

(384 bytes free)

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