AT32F425
Series Reference Manual
2022.03.30
Page 326
Ver 2.01
Filter match number
14 filter banks have different filtering effects dependent on the bit width mode. For example, 32-bit
identifier mask mode contains the filters numbered n while 16-bit identifier list mode contains the filters
numbered n, n+1, n+2 and n+3. When a frame of message passes through the filter number N, the
number N is stored in the RFFMN[7: 0] bit in the CAN_RFCx register. The distribution of the filter number
does not take into account the activation state of the filter banks.
Filter
bank
FIFO0
Active
Filter
number
Filter
bank
FIFO1
Active
Filter
number
0
CAN_F0FB1[31: 0]-ID
Yes
0
3
CAN_F3FB1[15: 0]-ID
Yes
0
CAN_F0FB2[31: 0]-ID
1
CAN_F3FB1[31:16]-ID
1
1
CAN_F1FB1[15: 0]-ID
Yes
2
CAN_F3FB2[15
:
0]-ID
2
CAN_F1FB1[31: 16]-ID
3
CAN_F3FB2[31:16]-ID
3
CAN_F1FB2[15: 0]-ID
4
4
CAN_F4FB1[31:0]-ID
Yes
4
CAN_F1FB2[31: 16]-ID
5
CAN_F4FB2[31:0]-
Mask
2
CAN_F2FB1[31: 0]-ID
Yes
6
5
CAN_F5FB1[15:0]-ID
No
5
CAN_F2FB2[31: 0]-Mask
CAN_F5FB1[31:16]-
Mask
6
CAN_F6FB1[15: 0]-ID
No
7
CAN_F5FB2[15:0]-ID
6
CAN_F6FB1[31:16]-Mask
CAN_F5FB2[31:16]-
Mask
CAN_F6FB2[15:0]-ID
8
7
CAN_F7FB1[15:0]-ID
No
7
CAN_F6FB2[31:16]-Mask
CAN_F7FB1[31:16]-ID
8
9
CAN_F9FB1[31:0]-ID
No
9
CAN_F7FB2[15:0]-ID
9
CAN_F9FB2[31:0]-ID
10
CAN_F7FB2[31:16]-ID
10
10
CAN_F10FB1[15:0]-ID
Yes
11
8
CAN_F8FB1[31:0]-ID
Yes
11
CAN_F10FB1[31:16]-
Mask
CAN_F8FB2[31:0]-
Mask
CAN_F10FB2[15:0]-ID
12
11
CAN_F11FB1[31:0]-ID
Yes
12
CAN_F10FB2[31:16]-
Mask
CAN_F11FB2[31:0]-ID
13
12
CAN_F12FB1[15:0]-ID
No
13
13
CAN_F13FB1[15:0]-ID
Yes
14
CAN_F12FB1[31:16]-ID
14
CAN_F13FB1[31:16]-
ID
15
CAN_F12FB2[15:0]-ID
15
CAN_F13FB2[15:0]-ID
16
CAN_F12FB2[31: 16]-ID
16
CAN_F13FB2[31:16]-
ID
17
Priority rules
When the CAN controller receives a frame of message, the message may pass through several filters.
In this case, the filter match number stored in the receive mailbox is determined according to the
following priority rules:
A 32-bit filter has priority over a 16-bit filter
For filters with identical bit width, the identifier list mode has priority over the identifier mask mode
For filter with identical bit width and identifier mode, the lower number has priority over the higher
number.
Filter configuration
The CAN filters ar configured by setting the FCS bit in the CAN_FCTRL register.
Identifier mask mode or identifier list mode can be selected by setting the FMSELx bit in the
CAN_FMCFG register.
The filter bit width can be configured as two 16 bits or one 32 bits by setting the FBWSELx bit in
the CAN_FBWCFG register.