PURPOSE: To reduce the number of parts by using a light emitting diode for input as well as display operation.
CONSTITUTION: In case of display operation, a transistor TR1 is turned on. A current from a power source V1 is led to the transistor TR1 of an output port from an input/output terminal through the circuit consisting of a light emitting diode 4, a resistance R2, a power source V2, resistances R1 and R2. Then, the diode 4 emits light and is operated as a display device. When the optical output is projected to the diode 4, the operating point of the diode 4 is set. The current flowing to the diode 4 flows to the power source V2, the resistance R1, the diode 4, and the power source V1 and the voltage change is outputted to the input/output terminal of a microcomputer 1. Thus, the number of parts is reduced.
YAMADA MASAAKI
INOUE MASAAKI
MORI HIROSHI
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