RM0017 Datasheet, PDF (423/904 Pages) STMicroelectronics – The SPC560Bx and SPC560Cx is a new family

FlexCAN
RM0017
Rx code
BEFORE
Rx new frame
Table 205. Message buffer code for Rx buffers
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
0110
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.
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
0110
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.
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
0110
An EMPTY buffer was written with a new frame
(XY was 01).
A FULL/OVERRUN buffer was overwritten (XY
was 11).
1. Note that for Tx MBs (see Table 206), the BUSY bit should be ignored upon read, except when AEN bit is set in the MCR.
RTR
X
X
0
Initial Tx
code
1000
1001
1100
Table 206. Message buffer code for Tx buffers
Code after
successful
transmission
Description
–
–
1000
INACTIVE: MB does not participate in the arbitration process.
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.
Transmit data frame unconditionally once. After transmission, the
MB automatically returns to the INACTIVE state.
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