PXD10RM Datasheet, PDF (678/1332 Pages) Freescale Semiconductor, Inc – PXD10 Microcontroller

Table 18-5. Message Buffer Code for Rx Buffers (continued)
Rx Code
BEFORE
Rx New Frame
Description
Rx Code
AFTER
Rx New Frame
Comment
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 18.4.5, 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 18.4.5,
Matching process for details about overrun
behavior.
0XY1¹
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 18-6), the BUSY bit should be ignored upon read, except when AEN bit is set in}
the MCR register.
RTR
X
X
0
1
Initial Tx
code
1000
1001
1100
1100
Table 18-6. Message Buffer Code for Tx Buffers
Code after
successful
transmission
Description
–
–
1000
0100
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.
Transmit remote frame unconditionally once. After transmission,
the MB automatically becomes an Rx MB with the same ID.
18-8
PXD10 Microcontroller Reference Manual, Rev. 1
Preliminary—Subject to Change Without Notice
Freescale Semiconductor