
DATA SHEET
PM7367 FREEDM-32P32
ISSUE 2
PMC-1991499
FRAME ENGINE AND DATA LINK MANAGER
PROPRIETARY AND CONFIDENTIAL TO PMC-SIERRA, INC., AND FOR ITS CUSTOMER’S INTERNAL USE
213
FLAG[2:0]
Minimum Number of Flag/Idle Bytes
101
32 flags / 30 idle bytes
110
64 flags / 62 idle bytes
111
128 flags / 126 idle bytes
LEVEL[3:0]:
The indirect channel FIFO trigger level (LEVEL[3:0]), in concert with the
TRANS bit, 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 make DMA request for data as shown in the
following table. The channel FIFO trigger level to be written to the channel
provision RAM, in an indirect write operation, must be set up in this register
before triggering the write. LEVEL[3:0] 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 less
than or equal to 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 expedite 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.
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 make DMA request for data 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.