38.5.5 Requesting Transmission of Message in Transmit Queue

After a message is loaded into the TXQ, the message is ready for transmission. The application initiates the transmission of all messages in the queue by setting TXREQ (CxTXQCON[9]). When all messages have been transmitted, TXREQ will be cleared. The application can request transmission of the TXQ and multiple FIFOs simultaneously. The TXQ or FIFO of the CxTXQCON register with the highest priority will start transmitting first. Messages in the TXQ will be transmitted based on their ID. The message with the highest priority ID and the lowest ID value will be transmitted first.

Messages can be loaded into the TXQ while the TXQ is transmitting messages. Since TXREQ is cleared by the TXQ automatically after the TXQ empties, UINC and TXREQ of the CxTXQCON register must be set at the same time after appending a message. This ensures that all messages in the TXQ are transmitted, including the appended messages.