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Communication Processor Module
CD—Carrier Detect Lost
This bit indicates that the carrier detect signal is negated during frame reception.
DATA LENGTH
This field represents the number of octets the communication processor module writes into
this buffer descriptor data buffer once the buffer descriptor is closed. When this buffer
descriptor is the last one in the frame, DATA LENGTH contains the total number of frame
octets. The actual amount of memory allocated for this buffer must be greater than or equal
to the contents of the MRBLR.
Note: If the received frame has a length that is an exact multiple of the MRBLR, the
buffer descriptor with the L bit set does not actually have any characters in it and
the DATA LENGTH field contains a value equal to the sum of the DATA
LENGTH fields of the other buffer descriptors in the frame.
RX DATA BUFFER POINTER
This field always points to the first location of the associated data buffer and can reside in
internal or external memory.
16.9.19.12.3 SCCx ASYNC HDLC Transmit Buffer Descriptor. Data is sent to the SCCx
ASYNC HDLC controller for transmission on an SCCx channel by arranging it in buffers
referenced by the channel transmit (TX) buffer descriptor table. Using the buffer descriptors,
the SCCx ASYNC HDLC controller confirms transmission or indicates error conditions so
that the core will know 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.
16-282
3
4
5
6
7
I
L
RES
CM
DATA LENGTH
TX DATA BUFFER POINTER
MPC823e REFERENCE MANUAL
8
9
10
11
12
RES
13
14
15
CT
MOTOROLA
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