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Communication Processor Module
0
1
2
E
RES
W
OFFSET + 0
OFFSET + 2
OFFSET + 4
OFFSET + 6
NOTE:
You are only responsible for initializing the items in bold.
E—Empty
0 = The data buffer associated with this RX buffer descriptor has been filled with data
or reception has been aborted because of an error condition. The core is free to
examine or write to any fields of this RX buffer descriptor. The communication
processor module does not use this buffer descriptor as long as the E bit is zero.
1 = The data buffer associated with this buffer descriptor is empty or is currently
receiving data. This RX buffer descriptor and its associated receive buffer are
owned by the communication processor module. Once the E bit is set, the core
must not write any fields of this RX buffer descriptor.
Bits 1, 7, and 9—Reserved
These bits are reserved and must be set to 0.
W—Wrap (Final Buffer Descriptor in Table)
0 = This is not the last buffer descriptor in the RX buffer descriptor table.
1 = This is the last buffer descriptor in the RX buffer descriptor table. After this buffer
is used, the communication processor module receives incoming data into the first
buffer descriptor that RBASE points to in the table. The number of RX buffer
descriptors in this table is programmable and determined only by the W bit and
overall space constraints of the dual-port RAM.
I—Interrupt
0 = The RXB bit is not set after this buffer is used, but RXF operation remains
unaffected.
1 = The RXB or RXF bit in the SCCE–HDLC register is set when the SCCx HDLC
controller uses this buffer. These two bits can cause interrupts if they are enabled.
L—Last in Frame
This bit is set by the SCCx HDLC controller when this buffer is the last one in a frame. This
implies the reception of a closing flag or reception of an error, in which case one or more of
the CD, OV, AB, and LG bits are set. The SCCx HDLC controller writes the number of frame
octets to the DATA LENGTH field.
0 = This buffer is not the last one in a frame.
1 = This buffer is the last one in a frame.
16-246
3
4
5
6
7
I
L
F
CM
RES
DATA LENGTH
RX DATA BUFFER POINTER
MPC823e REFERENCE MANUAL
8
9
10
11
12
DE
RES
LG
NO
AB
13
14
15
CR
OV
CD
MOTOROLA
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