Motorola MPC823e Reference Manual page 856

Communication Processor Module
Figure 16-118 illustrates an example of the RX buffer descriptor process. It shows the
resulting state of the RX buffer descriptors after they receive 10 characters, an idle period,
and five characters (one with a framing error). The example assumes that MRBLR = 8 in the
SMCx parameter RAM.
RECEIVE BD 0
E
0
STATUS
LENGTH
32-BIT BUFFER POINTER
POINTER
RECEIVE BD 1
E
0
STATUS
LENGTH
POINTER 32-BIT BUFFER POINTER
RECEIVE BD 2
E
STATUS 0
LENGTH
32-BIT BUFFER POINTER
POINTER
RECEIVE BD 3
E
1
STATUS
LENGTH
POINTER
32-BIT BUFFER POINTER
10 CHARS
CHARACTERS
RECEIVED BY UART
TIME
Figure 16-118. SMCx UART Receive Buffer Descriptor Example
16-402
ID
0
0008
ID
1
0002
IDLE TIMEOUT
OCCURRED
ID FR
1
0
0004
BYTE 4 HAS
FRAMING ERROR
XXXX
LONG IDLE PERIOD
MPC823e REFERENCE MANUAL
MRBLR = 8 BYTES FOR THIS SMC
BUFFER
BYTE 1
BYTE 2
BUFFER
ETC.
FULL
BYTE 8
BUFFER
BYTE 9
BYTE 10
EMPTY
BUFFER
BYTE 1
BYTE 2
BYTE 3
BYTE 4 ERROR!
EMPTY
BUFFER
BYTE 5
ADDITIONAL
BYTES WILL BE
RECEPTION
STORED UNLESS IDLE
STILL IN
COUNT EXPIRES
PROGRESS
(MAX_IDL)
WITH THIS
BUFFER
5 CHARS
FOURTH CHARACTER
HAS FRAMING ERROR!
8 BYTES
8 BYTES
8 BYTES
8 BYTES
PRESENT
TIME
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