| 摘要 |
PURPOSE:To prevent the malfunction of a filter circuit consisting of a microcomputer from occurring with simple constitution. CONSTITUTION:The signal level of an input signal (a) from the interrupt input port INTO of the microcomputer 8 is read in an input signal level read-in circuit 11, and the present value X of a read in signal level is compared with a preceding value Y at a comparator 12, and a signal level coincidence counter 13 operated by receiving the coincidence signal (b) of both values X and Y outputs a count-up signal (d) when counting arrives at a prescribed number of count. An interrupt input discrimination circuit 16 outputs an interrupt permission signal (g) at a prescribed signal level 'L' by receiving the detection signal (f) of a signal level detection circuit 15. An edge detection circuit 18 detects the edge part of the trailing and leading edges of the input signal (a), and resets the signal level coincidence counter 13 at every detection of the edge part. |
