GD32A50x User Manual
599
including:
Tx arbitration:
-
Find out the frame with the highest priority.
Rx matching:
-
Compare the frame data received in the Rx shift buffer (an internal mailbox
descriptor) with the fields in Rx mailbox or Rx FIFO according to the configured
matching order.
Mailbox System Controller:
-
Manage RAM space selection for reception and transmission, control the mailbox
CODE, control the Rx FIFO pointer, and control the access requirement from the
APB bus to the RAM space.
The messages are stored in an
embedded RAM dedicated to the CAN module. The
dedicated RAM base address is module base address.
Shift in/out:
-
Tranmit data between the selected mailbox / Rx FIFO descriptor and the Tx or Rx
shift buffer.
CAN registers
The CAN registers is responsible for the CAN module communication with the APB bus.
23.3.1.
Mailbox descriptor
The mailbox descriptor shown in
Table 23-1. Mailbox descriptor with 64 byte payload
be used for both extended (29-bit identifier) and standard (11-bit identifier) frames. Each
mailbox is formed by 16, 24, 40, or 72 bytes, depending on the data bytes allocation for the
message payload: 8, 16, 32, or 64 data bytes, respectively. The memory area from offset
0x80 to 0x27F is used by the mailboxes.
Table 23-1.
Mailbox descriptor with 64 byte payload
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
MDES0
FD
F
BR
S
ESI
Res
erv
ed
CODE[3:0]
Res
erv
ed
SR
R
IDE
RT
R
DLC[3:0]
TIMESTAMP[15:0]
MDES1
PRIO[2:0]
ID_STD[10:0]
ID_EXD[17:0]
MDES2
DATA_0[7:0]
DATA_1[7:0]
DATA_2[7:0]
DATA_3[7:0]
...
…
…
…
…
MDES17
DATA_60[7:0]
DATA_61[7:0]
DATA_62[7:0]
DATA_63[7:0]
MDES0: Mailbox descriptor word 0
Address offset: 0x80
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
FDF
BRS
ESI
Reserved
CODE[3:0]
Reserved
SRR
IDE
RTR
DLC[3:0]
rw
rw
rw
rw
rw
rw
rw
rw
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0