| 摘要 |
PURPOSE:To output an index pulse of an FDD of 3.5 inch size having no index hole by providing a logical circuit for outputting a signal only once, while a rotor of a spindle motor executes one rotation. CONSTITUTION:Each output signal from a phase detecting use Hall element 1 and a speed detecting use generator is waveform-shaped by the first and the second comparing circuits, respectively, a differentiating circuit 5 differentiates an output signal of the first comparing circuit, also a signal of such a pulse width as an output signal of the second comparing circuit and its logic coincide or do not coincide only once while a rotor of a spindle motor executes one rotation is outputted, and in accordance with each logic of this signal and the output signal of the second comparing circuit, a logical circuit outputs a signal only once while the rotor executes one rotation. That is to say, at a time t4 when the time has elapsed by a period T of the rotor from a time t1, both a pulse of a signal (b) from the differentiating circuit 5 and a pulse of a signal (c) from a comparator 7 appear, therefore, a signal (d) is outputted again from an AND circuit 8, and also a signal (e) is outputted from a monostable multivibrator 9. |
