PM7312 pmc-sierra, PM7312 Datasheet - Page 142

• Manufacturer Part Number: PM7312
• Description: Freedm 32a1024l Assp Telecom Standard Datasheet
• Manufacturer: pmc-sierra

Proprietary and Confidential to PMC-Sierra, Inc., and for its customers’ internal use.
Document No.: PMC-2021833, Issue 2
TRANS
The indirect transmission start bit (TRANS), in concert with the LEVEL[3:0] bits, configure
the various channel FIFO free space levels which trigger the HDLC processor to start
transmission of a HDLC packet as well as trigger the partial packet buffer to request data from
the upstream device as shown in the following table. The transmission start mode to be written
to the channel provision RAM, in an indirect write operation, must be set up in this register
before triggering the write. TRANS reflects the value written until the completion of a
subsequent indirect channel read operation.
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 upstream device 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 19 Level[3:0]/TRANS Settings
LEVEL[3:0]
0010
0011
0100
0101
0110
0111
1000
1001
1010
1011
4 Blocks
6 Blocks
8 Blocks
12 Blocks
16 Blocks
24 Blocks
32 Blocks
48 Blocks
64 Blocks
96 Blocks
Starving
Trigger Level
(64 bytes free)
(96 bytes free)
(128 bytes free)
(192 bytes free)
(256 bytes free)
(384 bytes free)
(512 bytes free)
(768 bytes free)
(1 Kbytes free)
(1.5 Kbytes free)
FREEDM 32A1024L ASSP Telecom Standard Product Data Sheet
Start Transmission
Level (TRANS=0)
Invalid
4 Blocks
(64 bytes free)
6 Blocks
(96 bytes free)
8 Blocks
(128 bytes free)
12 Blocks
(192 bytes free)
16 Blocks
(256 bytes free)
24 Blocks
(384 bytes free)
32 Blocks
(512 bytes free)
48 Blocks
(768 bytes free)
64 Blocks
(1 Kbytes free)
Start Transmission
Level (TRANS=1)
2 Blocks
(32 bytes free)
Invalid
4 Blocks
(64 bytes free)
6 Blocks
(96 bytes free)
8 Blocks
(128 bytes free)
12 Blocks
(192 bytes free)
16 Blocks
(256 bytes free)
24 Blocks
(384 bytes free)
32 Blocks
(512 bytes free)
48 Blocks
(768 bytes free)
Released
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