| 摘要 |
PURPOSE:To prevent a key operation detecting circuit from making a misjudgement owing to the bound of a hammer by inhibiting a key touch signal and a key state signal which are outputted first from varying for a specific time from the point of time when a switch element operates by the depression of a key for the 1st time. CONSTITUTION:A rise detecting circuit 43, a fall detecting circuit 45, etc., constitute a key state detecting means 54, a fall detecting circuit 27, a counter 29, etc., constitute a key touch detecting means 55, and OR gates 25 and 41, a rise detecting circuit 49, an AND gate 51, a comparator 31, etc., constitute an inhibiting means 57. Then even if switch elements 19 and 21 are turned off temporarily and then turned on owing to the bound, the inhibiting means 57 inhibits the key touch signal and key state signal from varying for the specific time from the start of key operation. Those signals are held by the key touch detecting means 55 and key state detecting means 53 respectively. Consequently, malfunction due to the bound of a hammer is prevented. |
