GD32A50x User Manual
601
For transmission (Tx mailbox), if this bit is set to '1' (recessive), and the bus
transmits this bit as ‘0’ (dominant), then it means an arbitration loss. If this bit is set
to '0' (dominant), and the bus transmits this bit as '1' (recessive), it is treated as a
bit error. If the value configured matches the value transmitted, it is considered a
successful bit transmission.
For reception (Rx mailbox), it will be stored with the value received on the CAN bus.
0: In Tx mailbox, the current mailbox has a data frame to be transmitted. In Rx
mailbox, it may be considered in matching process.
1: In Tx mailbox, it means the current mailbox has a remote request frame to be
transmitted. In Rx mailbox, incoming remote request frames may be stored.
Note:
When configured as CAN FD frames, the RTR bit must be negated. This bit
must be considered in classical frames only.
19:16
DLC[3:0]
Data length code in bytes
This bit field is the length (in bytes) of the Rx or Tx payload.
For reception (Rx mailbox), no need to write this bit field, they are written by the
CAN module with the DLC field of the received frame.
For transmission (Tx mailbox), this bit field is written by the CPU with value of the
frame to be transmitted. When RTR is 1, the frame to be transmitted is a remote
request frame and does not include the data field, regardless of the DLC field.
15:0
TIMESTAMP[15:0]
Free-Running counter timestamp
This bit field is a copy of the free running counter, captured for Tx and Rx frames at
the time when the beginning of the ID field appears on the CAN bus.
Table 23-2. Data bytes for DLC
DLC
Data size in bytes
i (0 ≤ i ≤ 8)
i (0 ≤ i ≤ 8)
9
12
10
16
11
20
12
24
13
32
14
48
15
64
Table 23-3.
Mailbox Rx CODE
CODE Meaning
CODE
after
reception
Servi
ced
(1)
RRFR
MS
(2)
Description
0b0000
INACTIV
E
-
-
-
Mailbox does not participate in the matching process.
0b0100 EMPTY
FULL
-
-
When a frame is received successfully (after the Move-
in
process), the CODE field is automatically updated to