MPC563XM Reference Manual, Rev. 1
Freescale Semiconductor
1275
Preliminary—Subject to Change Without Notice
0110
OVERRUN: a frame was
overwritten into a full buffer.
0010
If the code indicates OVERRUN but the CPU
reads the C/S word and then unlocks the MB,
when a new frame is written to the MB the code
returns to FULL.
0110
If the code already indicates OVERRUN, and
yet another new frame must be written, the MB
will be overwritten again, and the code will
remain OVERRUN. Refer to
for details about overrun
behavior.
0XY1
1
BUSY: Flexcan is updating the
contents of the MB. The CPU
must not access the MB.
0010
An EMPTY buffer was written with a new frame
(XY was 01).
0110
A FULL/OVERRUN buffer was overwritten (XY
was 11).
1
Note that for Tx MBs (see
), the BUSY bit should be ignored upon read, except when AEN bit is set
in the MCR register.
Table 28-5. Message Buffer Code for Tx buffers
RTR
Initial Tx
code
Code after
successful
transmission
Description
X
1000
–
INACTIVE: MB does not participate in the arbitration process.
X
1001
–
ABORT: MB was configured as Tx and CPU aborted the
transmission. This code is only valid when AEN bit in MCR is
asserted. MB does not participate in the arbitration process.
0
1100
1000
Transmit data frame unconditionally once. After transmission, the
MB automatically returns to the INACTIVE state.
1
1100
0100
Transmit remote frame unconditionally once. After transmission,
the MB automatically becomes an Rx MB with the same ID.
0
1010
1010
Transmit a data frame whenever a remote request frame with the
same ID is received. This MB participates simultaneously in both
the matching and arbitration processes. The matching process
compares the ID of the incoming remote request frame with the ID
of the MB. If a match occurs this MB is allowed to participate in the
current arbitration process and the Code field is automatically
updated to ‘1110’ to allow the MB to participate in future arbitration
runs. When the frame is eventually transmitted successfully, the
Code automatically returns to ‘1010’ to restart the process again.
0
1110
1010
This is an intermediate code that is automatically written to the MB
by the MBM as a result of match to a remote request frame. The
data frame will be transmitted unconditionally once and then the
code will automatically return to ‘1010’. The CPU can also write
this code with the same effect.
Table 28-4. Message Buffer Code for Rx buffers
Rx Code
BEFORE
Rx New Frame
Description
Rx Code
AFTER
Rx New Frame
Comment