The successful data frame transmit interrupt routine is not necessary as CAN has its own mechanism to resend faulty messages, however it can be used to tell the main application when a message has been sent. When polling is used, as it is with ‘USE_CAN_POLL’ defined in the Renesas sample code, the check transmit function should be called to confirm a transmission. If CAN interrupts are used instead, that is, ‘USE_CAN_POLL’ is not defined, the interrupt service routine is automatically triggered and a message can at that time be polled for a successful transmission. With either of these methods, the user can then flag the application when the message is sent.