| 摘要 |
PURPOSE:To prevent the uncontrollable run of CPU by resetting CPU and disconnecting backup RAM from CPU when battery voltage becomes equal to or below the predetermined level, and clearing data in the backup RAM when an ignition switch is at the OFF position. CONSTITUTION:When power supply voltage fed from a battery 1 to a microcomputer 4 via a regulator 3 becomes equal to or below the predetermined voltage, the reset signal of CPU is outputted. A reset release signal is outputted when the voltage restores to or becomes above the predetermined voltage. In outputting the reset signal, RAM with backup function 6 is disconnected from CPU and when an ignition switch is at the OFF position, the memory data of RAM 6 is cleared. When the voltage of the battery 1 drops, the uncontrollable run of CPU is prevented preliminarily and the backup RAM 6 is disconnected therefrom for protecting stored data. Furthermore, the previous data is cleared at a re-start and it is ensured to prevent erroneous control operation.
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