| 摘要 |
<p>PURPOSE:To check a reset signal by a microcomputer system itself by checking the reset signal by the rise of a pulse signal and its pulse width. CONSTITUTION:When a power supply VCC for the microcomputer is turned on at a time t1, the microcomputer is held at the L level which is the reset state up to a prescribed time t2 by a built-in power ON reset circuit and the reset state is released, so that the VCC is turned on and the microcomputer is turned to the operatable state. Simultaneously, a reset signal RST is inputted to a terminal B of an one-shot multivibrator 1. The vibrator 1 outputs a pulse having pulse width T (t2-t3) for a terminal Q on the basis of time constants R, C. The output is inputted to a discriminating circuit 2, which discriminates the switching from the L level to the H level of the reset signal by checking the rise of the pulse from L to H and the pulse width T. Consequently, the reset signal generated at the ON of a power supply can be tested by the system itself.</p> |
