US Patent 7299308 Data transmission apparatus and electronic control unit

An electronic control unit has two microcomputers. Each microcomputer has a data buffer storing data first to be transmitted in every 8 ms, a second data buffer storing data to be transmitted in every 16 ms, and a third data buffer storing data to be transmitted in every 16 ms and being different from the first and second data buffers. The microcomputer transfers at the transmission timing of every 8 ms data in the first data buffer to the transmitting buffer, while it transfers alternately the data in the second data buffer and the data in the third data buffer to the transmitting buffer. The microcomputer also transfers an ID that indicates content of the present transmitting data to the transmitting buffer.