14.7.3 Loading Messages Into Transmit Queue

Loading transmit message objects into the TXQ works similarly to loading message objects into a transmit FIFO. The application must check the CxTXQSTA register to see if there is space in the TXQ. The CxTXQUA registers should be used instead of the CxFIFOUAx registers to calculate the address to load the message and set the UINC bit (CxTXQCON[8]) to increment the head of the TXQ.

Table 14-9. Transmit Message Object (TXQ and TX FIFO)
Words	Bits	Bits 31/23/5/7	Bit 30/22/14/6	Bit 29/21/13/5	Bit 28/20/12/4	Bit 27/19/11/3	Bit 26/18/10/2	Bit 24/16/8/0
T0	31:24	—	—	SID11	EID[17:6]
	23:16	EID[12:5]
	15:8	EID[4:0]					SID[10:8]
	7:0	SID[7:0]
T1	31:24	SEQ[22:15]
	23:16	SEQ[14:7]
	15:8	SEQ[6:0]						ESI
	7:0	FDF	BRS	RTR	IDE	DLC[3:0]
T2	31:24	Transmit Buffer Data Byte 3
	23:16	Transmit Buffer Data Byte 2
	15:8	Transmit Buffer Data Byte 1
	7:0	Transmit Buffer Data Byte 0
T3	31:24	Transmit Buffer Data Byte 7
	23:16	Transmit Buffer Data Byte 6
	15:8	Transmit Buffer Data Byte 5
	7:0	Transmit Buffer Data Byte 4
Ti	31:24	Transmit Buffer Data Byte n
	23:16	Transmit Buffer Data Byte n - 1
	15:8	Transmit Buffer Data Byte n - 2
	7:0	Transmit Buffer Data Byte n - 3


bit T0.31-30	Unimplemented: Read as ‘x’
bit T0.29	SID11: In FD mode, the standard ID can be extended to 12 bit using r1.
bit T0.28-11	EID[17:0]: Extended Identifier
bit T0.10-0	SID[10:0]: Standard Identifier
bit T1.31-9	SEQ[22:0]: Sequence to keep track of transmitted messages in Transmit Event FIFO
bit T1.8	ESI: Error Status Indicator In CAN to CAN Gateway mode (CiCON.EXIGM=`1`), the transmitted ESI flag is a “logical OR” of T1.ESI and error passive state of the CAN controller; In Normal mode ESI indicates the error status. `1` = Transmitting node is error passive. `0` = Transmitting node is error active.
bit T1.7	FDF: FD Frame; distinguishes between CAN and CAN FD formats.
bit T1.6	BRS: Bit Rate Switch; selects if data bit rate is switched.
bit T1.5	RTR: Remote Transmission Request; not used in CAN FD.
bit T1.4	IDE: Identifier Extension Flag; distinguishes between the base and extended format.
bit T1.3-0	DLC[3:0]: Data Length Code