| 摘要 |
<p>PURPOSE:To obtain a power supply voltage detection circuit with high reliability and low power consumption by incorporating a flag detecting the stop of oscillation of an oscillation circuit generating a driving clock in a micro computer loading CPU and peripheral hardware on the same chip. CONSTITUTION:A time constant circuit consisting of a resistance 10 and a capacitor 11, and an RS flip flop (F/F) 13 are provided for the micro computer 2 loading CPU 3, peripheral hardware 4 and a clock oscillation circuit 5 on the same chip. The time constant of the time constant circuit is set to be considerably longer than the period of the clock. The output of the time constant circuit is raised by the supply of a power source 1 and F/F 13 is set. Then, the oscillation circuit 5 starts oscillation, CPU 3 is operated and F/F 13 is reset. A clock pulse clears the time constant circuit through a rise edge detection circuit 9. CPU 3 reads the output of F/F 13 and judges a system to be no power abnormality when F/F 13 is reset as it is.</p> |
