| 摘要 |
PURPOSE:To eliminate malfunction due to differences in threshold voltage and operating voltage, and control a resetting circuit even by the stop of a clock signal by generating a control signal through AND operation between the output of a source voltage drop detecting circuit and an external clock. CONSTITUTION:An AND gate 24 outputs the clock signal when the output of the source voltage drop detecting circuit 9 decreases below the threshold voltage. A counter 26 outputs a unit step signal a set time of T seconds later to a monostable multivibrator 27 by said clock signal, and the monostable multivibrator 27 outputs one pulse, An FF28 receives it and its output Q resets the reset R of a multivibrator 29. The multivibrator 29 sends out a specific output signal when input pulse width is larger than pulse width set by the multivibrator 29 by the clock signal outputted by the AND gate 24. Then, a microprocessor 23 decreases the output to a low level when necessary. Namely, the counter 26 is controlled by the AND gate 24, so malfunction due to power source variation is prevented. |
