| 摘要 |
PURPOSE:To prevent a fault holding FF from being reset during an MPU runaway by providing an FF which mades a reset output instruction signal from an MPU (microprocessor unit) effective or ineffective, and resetting a fault detection state only when the reset output instruction signal is made effective. CONSTITUTION:A circuit which resets a fault holding FF10 for storing a fault detection signal IS on the basis of a reset output instruction RO from an MPU4 is provided with an FF8 for making a reset output instruction from the MPU4 effective or ineffective. Then, a reset signal SR outputted by an OR circuit 3 which inputs signals from a reset switch 1 and a starting resetting circuit 2 resets the MPU4 to an initial state and also sets the FF8. An AND gate 9 is opened by the set output of this FF8 to supply the reset output instruction signal RO, outputted in the middle of an initial program of the MPU4, to the FF10, which is set. Therefore, a danger that the fault holding FF is reset during a runaway of the MPU is eliminated. |
