MPC563XM Reference Manual, Rev. 1
1274
Freescale Semiconductor
Preliminary—Subject to Change Without Notice
CODE — Message Buffer Code
This 4-bit field can be accessed (read or write) by the CPU and by the Flexcan module itself, as part
of the message buffer matching and arbitration process. The encoding is shown in
and
. See
Section 28.5, “Functional Description,”
for additional information.
0
3
4
7
9
1
0
1
1
1
2
1
5
1
6
2
3
2
4
3
1
$0
CODE
S
R
R
I
D
E
R
T
R
LENGTH
TIME STAMP
$4
PRIO
ID (Standard/Extended)
ID (Extended)
$8
Data Byte 0
Data Byte 1
Data Byte 2
Data Byte 3
$
C
Data Byte 4
Data Byte 5
Data Byte 6
Data Byte 7
= Unimplemented or Re-
served
Figure 28-2. Message Buffer Structure
Table 28-4. Message Buffer Code for Rx buffers
Rx Code
BEFORE
Rx New Frame
Description
Rx Code
AFTER
Rx New Frame
Comment
0000
INACTIVE: MB is not active.
–
MB does not participate in the matching
process.
0100
EMPTY: MB is active and
empty.
0010
MB participates in the matching process. When
a frame is received successfully, the code is
automatically updated to FULL.
0010
FULL: MB is full.
0010
The act of reading the C/S word followed by
unlocking the MB does not make the code
return to EMPTY. It remains FULL. If a new
frame is written to the MB after the C/S word
was read and the MB was unlocked, the code
still remains FULL.
0110
If the MB is FULL and a new frame is
overwritten to this MB before the CPU had time
to read it, the code is automatically updated to
OVERRUN. Refer to
for details about overrun behavior.