| 摘要 |
<p>PURPOSE:To execute key scanning only when a key is depressed by setting a CPU output port to be a logical value '1' in a normal state and outputting the logical value '1' to the CPU output port only when the key is pushed on. CONSTITUTION:The the CPU output port 10, the logical value '1' is inputted in a normal state and a key scanning signal is inputted when a push-on switch 12ij is depressed. A CPU input port 11 outputs a key detection signal. A contact point is closed by depressing the push-on switch 12ij. When the push-on switch is depressed and the CPU output port is the logical value '1', the logical value '1' is outputted to a corresponding CPU input port 11. When either of the CPU output port 10 and the CPU input 11 is the logical value '1', depressing is detected. Only at this time, the key scanning signal is sent to the CPU output port 10 and the detection signal on the CPU input port 11 is simultaneously read so as to execute the key scanning. Thus, the bad influence of the key scanning signal is prevented and power economization is also attained.</p> |
