ST STM32F40 Series Reference Manual page 695

Controller area network (bxCAN)
CAN TX mailbox identifier register (CAN_TIxR) (x=0..2)
Address offsets: 0x180, 0x190, 0x1A0
Reset value: 0xXXXX XXXX (except bit 0, TXRQ = 0)
All TX registers are write protected when the mailbox is pending transmission (TMEx reset).
This register also implements the TX request control (bit 0) - reset value 0.
31 30 29
rw rw rw
15 14 13
rw rw rw
Bits 31:21 STID[10:0]/EXID[28:18]
Bit 20:3 EXID[17:0]: Extended identifier
Bit 2 IDE
Bit 1 RTR
Bit 0 TXRQ
695/1422
28 27 26 25
STID[10:0]/EXID[28:18]
rw rw rw rw
12 11 10 9
EXID[12:0]
rw rw rw rw
:
Standard identifier or extended identifier
The standard identifier or the MSBs of the extended identifier (depending on the IDE bit
value).
The LSBs of the extended identifier.
:
Identifier extension
This bit defines the identifier type of message in the mailbox.
0: Standard identifier.
1: Extended identifier.
:
Remote transmission request
0: Data frame
1: Remote frame
:
Transmit mailbox request
Set by software to request the transmission for the corresponding mailbox.
Cleared by hardware when the mailbox becomes empty.
Doc ID 018909 Rev 4
24 23 22 21
rw rw rw rw
8 7 6 5
rw rw rw rw
20 19 18 17
EXID[17:13]
rw rw rw rw
4 3 2 1
IDE RTR
rw rw rw rw
RM0090
16
rw
0
TXRQ
rw