38.5.1 Transmit Message Object

Table 38-7 specifies the transmit message object used by the TXQ and the transmit FIFOs. The transmit objects contain the message ID, control bits and payload.

• SID: Standard Identifier or Base Identifier.
• EID: Extended Identifier.
• DLC: Data Length Code; specifies the number of data bytes to transmit (see 38.4.1.1 DLC Encoding).
• IDE: Identifier Extension; clearing this bit will transmit a base frame, setting this bit will transmit an extended frame.
• RTR: Remote Transmit Request; this bit is only specified in CAN 2.0 frames. Setting this bit will request a transmission of a receiving node.
• FDF: FD Format; if this bit is set, a CAN FD frame will be transmitted; otherwise, a CAN 2.0 frame will be transmitted. If Normal CAN 2.0 mode is selected, this bit is ignored and only CAN 2.0 frames are transmitted.
• BRS: Bit Rate Switch; the data phase of a CAN FD frame will be transmitted using DBR if this bit is set. If the bit is clear, the whole frame will be transmitted using NBR.
• ESI: Error State Indicator; normally, the ESI bit reflects the error status of the transmitting node. A recessive ESI bit in a CAN FD frame indicates that the transmitting node is error passive; a dominant bit shows that the transmitting node is error active. If ESIGM (C1CON[17]) = 0, this bit in the object is ignored. If ESIGM = 1, the ESI bit in the transmitted message will be transmitted recessive if the CAN FD Protocol Module is error passive, or if the ESI bit in the message object is set. A gateway application would use it to signal that the ESI bit of the transmitting node is set.
• SEQ: Sequence Number; SEQ is not transmitted on the CAN bus. It is used to keep track of the transmitted messages. SEQ is stored in the TEF message object.
• Transmit Buffer Data: Contains the payload of the message. Only the number of data bytes specified by the DLC are transmitted. Byte 0 is transmitted first, followed by 1, 2 and so on.