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Communication Processor Module
DATA LENGTH
This field represents the number of octets the communication processor module writes into
this buffer descriptor data buffer. It is written by the communication processor module once
the buffer descriptor is closed. When this buffer descriptor is the last buffer descriptor in the
frame (L = 1), the data length contains the total number of frame octets, including 2 or 4
bytes for CRC. The actual amount of memory allocated for this buffer must be greater than
or equal to the MRBLR.
RX DATA BUFFER POINTER
This field points to the first location of the associated data buffer. It resides in internal or
external memory and must be divisible by four.
16.9.16.10 SCCx HDLC TRANSMIT BUFFER DESCRIPTOR.Data is sent to the SCCx
HDLC controller for transmission on an SCCx channel by arranging it in buffers referenced
by the channel's TX buffer descriptor table. Using the transmit (TX) buffer descriptors, the
communication processor module confirms transmission and indicates error conditions so
that the core knows the buffers have been serviced.
0
1
2
R
RES
W
OFFSET + 0
OFFSET + 2
OFFSET + 4
OFFSET + 6
NOTE:
You are only responsible for initializing the items in bold.
Note: The communication processor module sets all the status bits in this buffer
descriptor, but you must clear them before submitting the buffer descriptor to the
communication processor module.
R—Ready
0 = The data buffer associated with this buffer descriptor is not ready for transmission.
You are free to manipulate this buffer descriptor or its associated data buffer. The
communication processor module clears this bit after the buffer has been
transmitted or an error condition is encountered.
1 = The data buffer, which you have prepared, has not been transmitted or is currently
being transmitted. You cannot write any fields of this buffer descriptor once this bit
is set.
Bits 1 and 7–13—Reserved
These bits are reserved and must be set to 0.
16-248
3
4
5
6
7
I
L
TC
CM
DATA LENGTH
TX DATA BUFFER POINTER
MPC823e REFERENCE MANUAL
8
9
10
11
12
RESERVED
13
14
15
UN
CT
MOTOROLA
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