An electronic control unit includes first and second devices. A transmitter of the first device transmits data to a receiver of the second device by start-stop synchronization communication. On detecting a communication error, the second device transmits a communication stop signal to the first device, recovers the receiver, and transmits a restart signal to the first device when the receiver is recovered. Upon receipt of the communication stop signal, the first device stops the transmitter and initializes a transmission buffer, and commands the transmitter to restart transmitting the data upon receipt of the communication restart signal from the second device.