| 摘要 |
PURPOSE:To inspect the key input of a keyboard device by only a keyboard itself by comparing an address code outputted from an ROM stored with address codes of respective keys with the address code of an input key. CONSTITUTION:A control circuit 19 sets the eight-bit value of a counter to zero. This count value is used as a scan signal; the high-order four bits are inputted to a decoder 5 and the low-order four bits are inputted to one input terminal of a comparator 6. The address code of the input key is detected on the basis of the scan signal and inputted to a latch 10. This address code is compared by a comparator 11 with address codes outputted from the ROM12 stored with address codes of respective codes, and when a coincident code is found, a buzzer 18 sounds to indicate that the key input is performed correctly. If a key is inputted wrongly, the comparator detects dissidence and an LED15 turns on. |
