| 摘要 |
PURPOSE:To avoid such a case where a microprocessor is occupied for control for keyboard by stopping the key scan by the strobe signal that detected the push of a key. CONSTITUTION:When a key on a keyboard matrix 1 is pushed, only the output of the row containing said pushed key of the matrix 1 is set at a low level. While only the output corresponding to said row is set at a high level for a keyboard decoder 2. Than the output or an OR circuit 3 is set at a high level and turned into a strobe signal to be applied to an upper device. At the same time, the output of an AND circuit is set at a low level by an inverter 4. Thus the counting action of a counter 6 is stopped and the output of a scan decoder 7 is held at a low level. Therefore only the column containing a pushed key on the matrix 1 is set at a low level. Then all circuits are stopped in said state. When an operator releases the pushed key, the outputs of the matrix 1 are all set at high levels and the output of the circuit 3 is set at a low level. Then a circuit 5 is opened for restart of the scan of the matrix 1.
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