| 摘要 |
PURPOSE:To prevent an error which is caused by influence of an external noise, etc., by counting the number of depressed keys by a status signal showing a depressed or released state of a key, and comparing this count value with a count value of the key which has been depressed. CONSTITUTION:A controlling circuit 3 retrieves a depressed or released stage of a key of a keyboard 7, and stores its state as a status signal at the storing position of a memory 5 corresponding to the key. At the same time, the number of depressed key is counted by a counter 4, and also a code signal CDS is outputted to the outside in accordance with said count value and the signal STS. An error detecting circuit 6 reads out the signal STS in order, and makes a counter 10 count the number of depressed keys. A comparing circuit 11 compares both count values of the counters 4 and 10, and outputs an error signal ERS to the circuit 3 in the event of dissidence of both the count values. When the signal ERS is given, the circuit 3 checks an output of the signal CDS. In this way, it is possible to prevent an output of an error code signal, which is caused by influence of an external noise, etc. |
