Abstract: Five electronic control units (ECU) 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 this time. Thereafter ECUs on the left side of the broken point conduct communication.

Abstract: In a control information rewriting system, a rewriting device for vehicle ECUs and a control center are provided. A function f necessary for the rewriting device to access the ECUs is stored the control center. When data communication is carried out by way of a telephone line network, the control center acquires ID information from the rewriting device and acquires a telephone number of the call origin. When the association relationship between this ID and telephone number matches an association relationship stored in the database, the control center determines the rewriting device to be a legitimate one. Only when the control center determines that the rewriting device is a legitimate one, it transmits the function f to the rewriting device to enable rewriting of control information of the ECUs.

Abstract: 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.

Abstract: A fail-safe system used in integrated control of a vehicle includes structural-element control portions. Preset priority degrees are given to the structural-element control portions, respectively. A manager control portion stores one or more substitute programs designed to implement functions of ones among the structural-element control portions which are necessary for travel of the vehicle. A downloading device operates for, when one of the structural-element control portions which is necessary for travel of the vehicle fails, selecting one from non-failed ones of the structural-element control portions as a download destination in accordance with the priority degrees and downloading the substitute program corresponding to the failed structural-element control portion into the selected download-destination structural-element control portion. The selected download-destination structural-element control portion is lower in priority degree than the failed structural-element control portion.

Abstract: A fail-safe system used in integrated control of a vehicle includes structural-element control portions. Preset priority degrees are given to the structural-element control portions, respectively. A manager control portion stores one or more substitute programs designed to implement functions of ones among the structural-element control portions which are necessary for travel of the vehicle. A downloading device operates for, when one of the structural-element control portions which is necessary for travel of the vehicle fails, selecting one from non-failed ones of the structural-element control portions as a download destination in accordance with the priority degrees and downloading the substitute program corresponding to the failed structural-element control portion into the selected download-destination structural-element control portion. The selected download-destination structural-element control portion is lower in priority degree than the failed structural-element control portion.

Abstract: In a control information rewriting system, a rewriting device for vehicle-ECUs and a control center are provided. A function f necessary for the rewriting device to access the ECUs is stored the control center. When data communication is carried out by way of a telephone line network, the control center acquires ID information from the rewriting device and acquires a telephone number of the call origin. When the association relationship between this ID and telephone number matches an association relationship stored in the database, the control center determines the rewriting device to be a legitimate one. Only when the control center determines that the rewriting device is a legitimate one, it transmits the function f to the rewriting device to enable rewriting of control information of the ECUs.

Abstract: A power voltage generator is supplied with the power voltage applied directly and via an ignition switch from a battery. The power voltage generator always supplies a power source to a computer equipped with a back-up memory and supplies to a comparator a power voltage signal from the power voltage generator when the ignition switch is turned on. The comparator compares a predetermined voltage signal with the power voltage signal from the power voltage generator. When the power voltage signal is higher than the reference voltage signal, the comparator issues a command to execute the program to a computer. The computer issues a write command to enable the back-up memory when it is judged that the increased voltage is stabilized, to thereby set up a write enable mode. If the power voltage signal drops when the ignition switch is turned off, this condition is detected using the output signal of the comparator. And it is judged whether or not the command to the back-up memory is being executed.