Communications system of two-wire line enhancing fail-safe performance

摘要

Five ECUs control vehicle devices using CAN protocol. Each of ECUs is provided with a resistor and a switch for activating the resistor. A first and fifth ECUs are arranged on the leftmost and rightmost ends. Resistors of the first and fifth ECUs are used as terminating resistors to a two-wire communications line. When the two-wire communications line is broken, the first ECU sends a test signal while other ECUs excluding the fifth ECU turn on the switches from right to left. When the test signal can be received, a broken point is located on the right side of ECU that turns on its switch at that time. Thereafter ECUs on the left side of the broken point conduct communication.