To quickly detect the rotating angle information in the restarting of a power supply by providing a memory for storing the previous rotating angle information when the power supply is turned off.
When an ignition switch 6 is OFF, OFF signal is inputted to a microcomputer 4 through an input circuit 7 to lay an output port P01 in low level, and the transistor 12 of a power consumption switching circuit 8 is laid in OFF state. In this OFF state, the microcomputer 4 controls a transmission type photo-interrupter group 5 to power consumption reducing mode. A nonvolatile memory 3 stores the rotating angle information outputted from the microcomputer 4 while a power source +B is supplied. Namely, the nonvolatile memory 3 stores the previous rotating angle information when the power source +B is OFF, and regenerates it when the power supply is restarted. According to this, the rotating angle and rotating direction of a steering can be detected even after the stoppage of an engine or the replacement of a battery.
KURIHARA KATSUMITSU
MIIKE KOJI
NISHIMOTO SUSUMU
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