Motorola MPC823e - Page 856

Communication Processor Module
16-402 MPC823e REFERENCE MANUAL MOTOROLA
SMC
COMMUNICATION
16
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.
Figure 16-118. SMCx UART Receive Buffer Descriptor Example
MRBLR = 8 BYTES FOR THIS SMC
BUFFER
BYTE 1
BYTE 2
BYTE 8
ETC.
8 BYTES
LONG IDLE PERIOD
FOURTH CHARACTER
HAS FRAMING ERROR!
5 CHARS10 CHARS
CHARACTERS
RECEIVED BY UART
TIME
BUFFER
BYTE 9
BYTE 10
8 BYTES
BUFFER
BYTE 1
BYTE 2
8 BYTES
BYTE 4 HAS
FRAMING ERROR
BUFFER
FULL
BYTE 3
BYTE 4 ERROR!
E
LENGTH
32-BIT BUFFER POINTER
RECEIVE BD 0
STATUS
0008
POINTER
0
E
LENGTH
32-BIT BUFFER POINTER
RECEIVE BD 1
STATUS
0002
POINTER
0
1
ID
0
ID
E
LENGTH
32-BIT BUFFER POINTER
RECEIVE BD 2
STATUS
0004
POINTER
0
ID
0
FR
1
E
LENGTH
32-BIT BUFFER POINTER
RECEIVE BD 3
STATUS
XXXX
POINTER
1
BUFFER
BYTE 5
8 BYTES
RECEPTION
STILL IN
PROGRESS
WITH THIS
BUFFER
PRESENT
TIME
IDLE TIMEOUT
OCCURRED
EMPTY
EMPTY
ADDITIONAL
BYTES WILL BE
STORED UNLESS IDLE
COUNT EXPIRES
(MAX_IDL)