| 摘要 |
PURPOSE:To reduce the power consumption of a key scanning circuit by starting a key scanning job after a key input detecting means detects the input of either one of keys. CONSTITUTION:When a momentary switch 11 is pushed, the output of a key input amplifier 18 is changed to an L level from an H level. This level change is applied to a delay line 22 of a key input detecting circuit 20 as well as to an exclusive OR circuit 25. Then the output of the circuit 25 is set at an H level for the delay time of the line 22 based on the change of the output of the amplifier 18 to an L level from an H level. As a result, a set/reset type flip-flop 27 is set under a setting state (H level) and a counter 1 is started to scan the output of a decoder 2 successively to H levels from H levels. Then the push of the switch 11 is detected by checking that the amplifier 18 is set at an H level when the output of an output amplifier 4 is changed to an H level from an L level.
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