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Communication Processor Module
MOTOROLA
MPC823 USER’S MANUAL
16-305
SCC2
COMMUNICATION
16
PROCESSOR
MODULE
CR—CRC Error indication bits
This bit indicates that this frame contains a CRC error. The received CRC bytes are always
written to the receive buffer.
OV—Overrun
This bit indicates that a receiver overrun has occurred during buffer reception.
CD—Carrier Detect Lost
This bit indicates when the CD pin is negated during buffer reception.
DATA LENGTH
This field represents the number of octets that the communication processor module writes
into this buffer descriptor data buffer. The communication processor module only writes it
once as the buffer is closed. The actual amount of memory allocated for this buffer should
be greater than or equal to MRBLR.
RX DATA BUFFER POINTER
This field always point to the first location of the associated data buffer and must be divisible
by four, unless the RFW bit in the GSMR_H is set to 8 bits wide, even or odd. The buffer can
reside in internal or external memory.
16.9.21.10 SCC2 TRANSPARENT TRANSMIT BUFFER DESCRIPTOR. Data is sent to
the communication processor module for transmission on an SCC2 channel by arranging it
in buffers referenced by the channel’s transmit (TX) buffer descriptor table. Using the buffer
descriptors, the communication processor module confirms transmission or indicates error
conditions so that the processor knows the buffers have been serviced. You must prepare
the status and control bits before transmission, but they are set by the communication
processor module after the buffer has been transmitted.
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
OFFSET + 0
R
RES
WI
L
TC
CM
RESERVED
UN
CT
OFFSET + 2
DATA LENGTH
OFFSET + 4
TX DATA BUFFER POINTER
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. You should clear all the status bits before submitting the buffer
descriptor to the communication processor module. For example, the parity error
bit is only set when a parity error occurs.