MPC5604B/C Microcontroller Reference Manual, Rev. 8
430 Freescale Semiconductor
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 Section 22.4.6, “Matching
process for details about overrun behavior.
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 22.4.6,
“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
Note that for Tx MBs (see Tabl e 22-6), the BUSY bit should be ignored upon read, except when AEN bit is set in
the MCR.
Table 22-6. 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.
Table 22-5. Message buffer code for Rx buffers (continued)
Rx code
BEFORE
Rx new frame
Description
Rx code
AFTER
Rx new frame
Comment
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