RELEASED
PM7383 FREEDM-32A256
DATASHEET
PMC-2010336
ISSUE 1
FRAME ENGINE AND DATA LINK MANAGER 32A256
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 or equal to the level specified in the Starving 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 TAPI256 to retrieve XFER[3:0] + 1 blocks of data.
To prevent lockup, the channel transfer size (XFER[3:0]) 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. The
starving trigger level must always be set to a number of blocks greater than or
equal to the channel transfer size.
Table 14 – Level[3:0]/TRANS Settings
LEVEL[3:0]
Starving
Start
Start Transmission
Level (TRANS=1)
Trigger Level
Transmission
Level (TRANS=0)
0000
0001
0010
0011
0100
0101
0110
0111
2 Blocks
1 Block
1 Block
(32 bytes free)
(16 bytes free)
(16 bytes free)
3 Blocks
2 Blocks
1 Block
(48 bytes free)
(32 bytes free)
(16 bytes free)
4 Blocks
3 Blocks
2 Blocks
(64 bytes free)
(48 bytes free)
(32 bytes free)
6 Blocks
4 Blocks
3 Blocks
(96 bytes free)
(64 bytes free)
(48 bytes free)
8 Blocks
6 Blocks
4 Blocks
(128 bytes free)
(96 bytes free)
(64 bytes free)
12 Blocks
8 Blocks
6 Blocks
(192 bytes free)
(128 bytes free)
(96 bytes free)
16 Blocks
12 Blocks
8 Blocks
(256 bytes free)
(192 bytes free)
(128 bytes free)
24 Blocks
16 Blocks
12 Blocks
(384 bytes free)
(256 bytes free)
(192 bytes free)
PROPRIETARY AND CONFIDENTIAL
127
PMC [ PMC-SIERRA, INC ]
