| 摘要 |
An output port open control device ( 65 ) allows a port (P 3 ) which outputs PWM signals of a Cos+ side to be in a high impedance state in a period in which respective PWM signals of Cos+ and Cos- supplied to a S-phase coil ( 22 ) of a stepping motor ( 2 ) are in a ground level, induced voltage corresponding to a magnetic flux variation caused in accordance with rotation of a magnet rotor ( 23 ) is generated in the S-phase coil ( 22 ), a voltage comparator ( 72 ) compares the induced voltage with a previously set threshold value and outputs presence or absence of the induced voltage, and a zero-reset judging device ( 66 ) determines that a pointer ( 4 ) is in the middle of rotation when the induced voltage is detected, and determines that the pointer ( 4 ) is in contact with a stopper mechanism ( 5 ) when it is not detected.
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