JP2572383B2 - Magnetic disk device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic disk drive, and more particularly to a magnetic disk drive that controls a magnetic head position based on a servo signal recorded on a magnetic disk.

2. Description of the Related Art Magnetic disk drives are widely used in various data storage fields.

In a magnetic disk device, it is very important to accurately control various conditions such as the number of rotations of the magnetic disk and the position of the magnetic head in order to maintain recording and reproduction compatibility. Therefore, with respect to the position of the magnetic head, a tracking servo technique for controlling the position of the magnetic head based on the reproduction of a servo signal recorded on a magnetic disk is known.

A servo signal for tracking servo is recorded on a magnetic disk together with data. The servo signal generally has an irregular waveform.

[Problems to be Solved by the Invention] On the other hand, when performing double-density recording in a magnetic disk device, a window for discriminating clock pulses from a reproduced data pulse train following a frequency fluctuation of reproduced data due to a rotational fluctuation of the magnetic disk. A variable frequency oscillator (hereinafter referred to as VFO) for generating a signal is used. In the conventional device, a reproduced data pulse is always input to the VFO as a control pulse, and a window signal is generated based on the data pulse.

Therefore, when performing tracking servo, irregular servo signals in addition to the regular data pulse train
Input to O. Therefore, there is a problem in that the synchronization of the VFO is disturbed during the input period of the servo signal, and it takes time until the synchronization is restored even when the next reproduced data pulse is input, and the discrimination of the clock pulse becomes unstable.

[Means for Solving the Problems] In the present invention, in order to solve the above problems,
A magnetic disk device having a variable frequency oscillator for generating a basic signal for discriminating a recording clock pulse from a data pulse reproduced from a magnetic disk, and means for controlling a magnetic head position based on a servo signal recorded on the magnetic disk In, a reference clock oscillator of a predetermined frequency, and a detector for detecting the servo signal from the reproduction data is provided, a reference clock of the oscillator is input to the variable frequency oscillator during a period in which the servo signal is detected by the detector, A configuration is employed in which the variable frequency oscillator operates based on the output signal of the reference clock oscillator.

[Operation] According to the above configuration, the predetermined reference frequency is input to the VFO during the period when the servo signal is input, so that the synchronization of the VFO is not disturbed.

EXAMPLES Hereinafter, the details of the present invention will be described based on examples shown in the drawings.

FIG. 1 shows a configuration of a main part of a magnetic disk drive employing the present invention. In the figure, reference numeral 1 denotes a magnetic disk of a predetermined system such as a hard disk or a floppy disk, which is rotationally driven by a rotational drive system (not shown). The magnetic head 2 contacts the magnetic disk 1 via a head seek mechanism (not shown). The magnetic head 2 moves in the radial direction of the magnetic disk 1 so that the magnetic disk 1
Recording and reproduction are performed on the desired track above.

Here, illustration of the recording system is omitted, and only the reproducing system and the servo system are shown. That is, the reproduction output signal of the magnetic head 2 is input to the amplifier 3, amplified by a predetermined gain, and then input to the pulse detector 5 and the servo signal detector 4. These detectors each include a waveform shaping circuit and a frequency discriminating circuit.

The output of the servo signal detector 4 is input to one input terminal of the AND gates 7, 8. The signal inverted by the inverter 9 is input to the AND gate 8. The output of the pulse detector 5 is guided to one input of an AND gate 8.
An output signal of the oscillator 6 that generates a reference clock having a predetermined frequency is led to the remaining input of the AND gate 7. The output signals of the AND gates 7 and 8 are input to the OR gate 10, and the output of the OR gate 10 is input to the VFO 11 as a control pulse. The VFO 11 is an oscillator that generates a window signal for discriminating a clock pulse based on a reproduction signal as described above, and has the same configuration as that of the related art.

The operation in the above configuration will be described. FIG. 2 shows signal waveforms on the signal lines indicated by reference numerals A to D in FIG.

The signal output from the amplifier 3 becomes regular reproduced data and an irregular servo signal as indicated by the symbol A in FIG. When the servo signal detector 4 detects the servo signal as indicated by the symbol B, it outputs a high level. This high-level signal is input to a tracking servo system (not shown) and is used to control the position of the magnetic head 2.

On the other hand, the pulse detector 5 outputs a short-wave pulse as shown in FIG. 2 by a waveform detector using a comparator or the like. As shown in the figure, the output of the pulse detector 5 has regularity during the data reproduction period, but has an irregular pulse train during reproduction of the servo signal. Conventionally, the irregular pulse train is directly input to the VFO 11, so that the synchronization of the VFO is disturbed.

However, in this embodiment, the control signal input to the VFO 11 via the AND gates 7 and 8 is switched by the output of the servo signal detector 4.

That is, when the output of the servo signal detector 4 rises to the high level, the AND gate 7 which has been closed until then is output.
Is opened, and the AND gate 8 is closed via the inverter 9. As a result, a clock of a predetermined frequency output from the reference clock oscillator via the AND gate 7 and the OR gate 10 is input to the VFO 11.

When the servo signal is switched to the reproduction data, the output of the servo signal detector 4 becomes low level and the AND gates 7, 8
Is inverted, and the output signal of the pulse detector 5 is input to the VFO 11 via the AND gate 8 and the OR gate 10.

Therefore, the input of the VFO indicated by the symbol D in FIG. 2 becomes substantially regular throughout the data reproduction period and the servo signal reproduction period, and the synchronization of the window signal is disturbed by the influence of the servo signal as in the prior art, and the recording / reproduction operation is not performed. The problem of stability is eliminated. Therefore, the clock pulse recorded on the magnetic disk 1 can be stably discriminated, data can always be reproduced with high accuracy, and the position of the magnetic head can be accurately controlled using the tracking servo signal. .

In addition to the above embodiment, a one-shot multivibrator may be added to the output terminal of the servo signal detector 4, and a signal may be output to the gate via the multivibrator. In this case, the pulse width generated by the one-shot multivibrator is set so as not to be shorter than the duration of the servo signal, and pulse generation is started at the rising edge of the output signal of the servo signal detector 4. According to such a configuration, when a servo signal is arranged in a time-shifted manner, is composed of a plurality of signal blocks, or includes a non-signal portion in a servo signal, the servo signal detection is performed. Even when the output of the detector 4 cannot be maintained at a high level as shown in FIG. 2, the outputs of the pulse detector 5 and the reference clock oscillator 6 can be switched stably, and the same effect as above can be obtained. Can be.

[Effects of the Invention] As is apparent from the above description, according to the present invention, a variable frequency oscillator for generating a basic signal for discriminating a recording clock pulse from a data pulse reproduced from a magnetic disk, and recording on a magnetic disk In a magnetic disk drive having means for controlling the position of the magnetic head based on the servo signal obtained, a reference clock oscillator of a predetermined frequency and a detector for detecting the servo signal from reproduced data are provided,
In the period in which the servo signal is detected by the detector, the reference clock of the oscillator is input to the variable frequency oscillator, and the variable frequency oscillator is operated based on the output signal of the reference clock oscillator. During the tracking error detection period, the variable frequency oscillator is controlled by a reference clock having a predetermined frequency. Therefore, before and after the servo signal reproduction period, the synchronization of the variable frequency oscillator is not disturbed and the data is always stably recorded on the magnetic disk. Clock pulse can be discriminated stably, and there is an excellent effect that highly reliable magnetic recording and reproduction can be performed.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a main part of a magnetic disk drive employing the present invention, and FIG. 2 is a timing chart showing signal waveforms of respective parts in FIG. DESCRIPTION OF SYMBOLS 1 ... Magnetic disk 2, ... Magnetic head 3 ... Amplifier, 4 ... Servo signal detector 5 ... Pulse detector, 6 ... Reference clock oscillator 7, 8 ... AND gate, 10 ... OR gate 11 ... … VFO

Claims (1)

(57) [Claims] A variable frequency oscillator for generating a basic signal for discriminating a recording clock pulse from a data pulse reproduced from a magnetic disk; and means for controlling a position of a magnetic head based on a servo signal recorded on the magnetic disk. A reference clock oscillator of a predetermined frequency, and a detector for detecting the servo signal from the reproduced data, wherein the reference clock of the oscillator is set to the variable frequency during a period in which the servo signal is detected by the detector. A magnetic disk drive, wherein the variable frequency oscillator is operated based on an output signal of a reference clock oscillator input to an oscillator.