| 摘要 |
PURPOSE:To suppress an increase of an effective switch and an inflow of an unnecessary current, by grounding one piece of input port as a common input port through a key, and connecting it to order input port through a switch and a diode. CONSTITUTION:An input port (c) is grounded through a key 6, and connected to input ports (a), (b) through switches 5, 4 and diodes 8, 7, respectively. At the time of deciding a state of the switched 4, 5, output ports (d), (e) are set to an H level, and an input level of the input ports (a), (b) is decided. When the input port (a) is in an L level, the switch 5 is ON, and when said port is in an H level, the switch 5 is in an OFF state. By setting the output ports (a), (e) to an H level, ON and OFF of the key 6 can be decided irrespective of a state of the switches 4, 5, and also, when the key 6 is in an OFF state, a current comes not to flow to pull-up resistances 1-3.
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