| 摘要 |
PURPOSE:To realize the excellent key scanning with a simple constitution, by setting the chattering absorbing time necessary for each switch of a key switch group, and then securing the chattering time by means of a program timer. CONSTITUTION:The output of each contact of a switch group 1 is directly taken into a multiplexer MPX3 and controlled by switching then taken onto a data bus 7 as containing chattering. The output of a chattering absorbing time setting switch 8 is connected to the bus 7 via a buffer 9. Then the maximum chattering absorbing time is set for the group 1. A CPU4 applies periodically the address data of key scanning to a decoder 6 and then reads the state of each group of the group 1 through the MPX3. When detecting a change of state, the CPU4 holds the key scanning at that position and reads and corrects the set time of the switch 8. In such a way, the excellent key scanning is possible with a simple circuit. |
