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FlexCAN Module
MPC5644A Microcontroller Reference Manual, Rev. 6
1400
Freescale Semiconductor
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
Section 32.5.5, Matching process
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
), the BUSY bit should be ignored upon read, except when MCR[AEN] is set.
Table 32-6. Message Buffer Code for Tx buffers
RT
R
Initial
Tx
code
Code after
successful
transmissio
n
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 MCR[AEN] 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 32-5. Message Buffer Code for Rx buffers
Rx Code
BEFORE
Rx New Frame
Description
Rx Code
AFTER
Rx New Frame
Comment
Summary of Contents for MPC5644A
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