| 摘要 |
When using membrane key pads, it is often desirable to provide the user with a sense that contact has been made. In this regard, there is disclosed a 1 KHz 4-bit counter which is normally held at a count just beyond the place where "ones" appear in the third bit position. When it is desired to provide an audio click, the processor resets the counter to zero and then releases the counter. The "ones" in the third bit position, which occur in four consecutive counts, control the application of the 1 KHz frequency to the mechanical sounder. By connecting the fourth bit position to the synchronous reset input, the counter stops incrementing after the four consecutive "ones" and waits for the next reset by the processor.
|
