| 摘要 |
A key scanning apparatus includes display control circuit for receiving display data and for generating a display control signal which includes display timing periods for driving a display and key scan timing periods for scanning a key matrix. The display timing periods and the key scan timing periods appear in the display control signal in a time sharing manner. The key scanning apparatus also includes a key scan control circuit for outputting a key scan signal to scan the key matrix on the basis of the display control signal and selector for selectively applying either one of the display control signal and the key scan signal to data transfer lines. When the selector outputs the display control signal to the data transfer lines, transfer display data is transferred, and when the selector outputs the key scan signal to the transfer lines, key scan data is transferred. An interrupt control circuit is also provided which generates and outputs a key scan interrupt request signal to the CPU and a key data hold circuit is also provided which receives and holds key data from the key matrix in synchronism with the key scan signal, applies the held data to the CPU, and generates a key scan inhibit signal to inhibit the succeeding key scan operation until the held key data is read by the CPU.
|
