SPRUHM9H October 2014 – May 2024 TMS320F28075 , TMS320F28075-Q1 , TMS320F28076
If the shift register of the CAN Core is ready for loading and if there is no data transfer between the IFx registers and Message RAM, the MsgVal bits in the Message Valid register and the TxRqst bits in the transmission request register are evaluated. The valid message object with the highest priority pending transmission request is loaded into the shift register by the message handler and the transmission is started. The message object's NewDat bit is reset.
After a successful transmission and if no new data was written to the message object (NewDat = 0) since the start of the transmission, the TxRqst bit is reset. If TxIE is set, IntPnd is set after a successful transmission. If the CAN has lost the arbitration or if an error occurred during the transmission, the message is retransmitted as soon as the CAN bus is free again. If meanwhile the transmission of a message with higher priority has been requested, the messages are transmitted in the order of the priority.
If automatic retransmission mode is disabled by setting the DAR bit in the CAN control register, the behavior of bits TxRqst and NewDat in the Message Control register of the Interface register set is as follows:
When a transmission failed (lost arbitration or error) bit NewDat remains set. To restart the transmission, the application has to set TxRqst again.
Received remote frames do not require a receive object for storage. The remote frames automatically trigger the transmission of a data frame, if the RmtEn bit is set in the matching Transmit Object.