| 摘要 |
PURPOSE:To prevent a key input by normal operation from being locked out by confirming whether or not there are plural keys pressed even in rows where pressed keys are present when there are plural keys depressed in a column. CONSTITUTION:A microprocessor 1 connects with a decoder 3 through selector lines 4 and key switches are connected to intersections of return lines 5 from outputs of the decoder 3 and scan lines to inputs of the microprocessor 1 to form a key matrix 2. The microprocessor 1 selects an optional return line 5 to read the scan line 6, thereby knowing the depression state of the key switch. Then it is confirmed whether or not there are >=2 keys pressed on the return line 5 and when so, it is further confirmed whether or not there are >=2 keys depressed even on scanning lines 6 where the depressed keys are present; when so, the depression processing of said key switches it not performed.
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