| 摘要 |
<p>PURPOSE:To prevent a microprocessor system from runaway by monitoring the hit of a power supply through a microprocessor unit and resetting said unit at the detection of the hit. CONSTITUTION:At the ON of a power supply, a capacitor 5 is charged with +5V through a resistor 3 and the microprocessor unit 10 is reset on the basis of an input to a reset input terminal 12. At that time, a TR9 in a discharge circuit 6 is not turned on, so that no influence is exerted upon an RC circuit 2. If the power supply is turned off intermittently under said state, a voltage detecting circuit in the microprocessor unit 10 detects voltage drop on the basis of an input from an analog input terminal 13 and outputs a driving signal ''0'' from a port output terminal 11 to a TR9. When the TR9 is turned on, the charged capacitor 5 in the RC circuit 2 is discharged through the TR9, and when power supply voltage is raised instantaneously, the microprocessor unit 10 is reset because the capacitor 5 is sufficiently discharged.</p> |
