JPS63187470A - Magnetic disk device - Google Patents

Abstract

PURPOSE:To avoid the disturbance in a variable frequency oscillator VFO by inputting a reference clock from an oscillator to the VFO at a period when a servo signal is detected and activating the VFO based on the output signal of a reference clock oscillator. CONSTITUTION:The reference clock oscillator 6 having a prescribed frequency and a detector 4 detecting a servo signal from a reproduced data are provided and the reference clock of the oscillator 6 is inputted to the VFO 11 at the period when the servo signal is detected by the detector 4 to activate the VFO 11 based on the output signal of the reference clock oscillator 6. Thus, the VFO 11 is controlled by the reference clock having a prescribed frequency during the tracking error detection period. Thus, the synchronization of the VFO 11 is not disturbed before and after the reproducing period of the servo signal and the clock pulse recorded on a magnetic disk is always discriminated stably to attain the magnetic recording and reproduction with high reliability.

Description

[Detailed Description of the Invention] [Field of Industrial Application] Is the present invention a magnetic disk? t21.4. The present invention relates to a magnetic disk device that controls the position of a magnetic head based on a servo signal recorded on a magnetic disk at +f.

[Prior Art] Magnetic disk devices are used for storing various types of data! ) is widely used.

In magnetic disk drives, 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 compatibility in recording and reproduction. Therefore, regarding the position of the magnetic head, a tracking servo technique is known in which the position of the magnetic head is controlled based on reproduction of a servo signal recorded on a magnetic disk.

Servo signals for tracking servo are recorded on the magnetic disk along with data. Servo signals generally have irregular waveforms.

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

Therefore, when performing tracking servo, in addition to the regular data pulse train, irregular servo signals are sent to the VF.
It will be input to O. Therefore, during the input period of the servo signal, the synchronization of the VFO is disturbed, and even when the next reproduction data pulse is input, it takes time to recover the synchronization, and the discrimination of the clock pulse becomes unstable. There is 1111.

[Means for Solving the Problems] In order to solve the above-mentioned problems, the present invention provides a variable frequency oscillator that generates a basic signal for discriminating recording clock pulses from data pulses reproduced from a magnetic disk. , a magnetic disk drive having means for controlling the position of a magnetic head based on a servo signal recorded on a magnetic disk, which is provided with a reference clock oscillator of a predetermined frequency and a detector for detecting the servo signal from reproduced data; The reference clock of the oscillator is input to the variable frequency oscillator during a period in which a servo signal is detected by the device, and the variable frequency oscillator is operated based on the output signal of the reference clock oscillator.

[Function] According to the above configuration, since the predetermined reference frequency is input to the VFO during the period in which the servo signal is input, the synchronization of the VFO is not disturbed.

[Example] Hereinafter, the present invention will be described in detail based on the example shown in the drawings.

FIG. 1 shows the configuration of the main parts of a magnetic disk device employing the present invention. In FIG.
It is rotationally driven by a rotational drive system (not shown). A magnetic head 2 comes into contact with the magnetic disk 1 via a hedra seek mechanism (not shown). The magnetic disk 2 moves in the radial direction of the magnetic disk 1 to perform recording and reproduction on a desired track on the magnetic disk 1.

The recording system is not shown here, and only the reproduction system and servo system are shown. That is, magnetic herad 2
The reproduced output signal is input to the amplifier 3, amplified by a predetermined gain, and then sent to the pulse detector 5 and the servo signal detector 4.
is input. These detectors each include a waveform shaping circuit, a frequency discrimination circuit, and the like.

The output of the servo signal detector 4 is input to one input terminal of an AND gate 7.8. A signal inverted by an inverter 9 is input to the AND gate 8 . The output of pulse detector 5 is guided to one input of AND gate 8.

The remaining inputs of the AND gate 7 are led to the output signal of the oscillator 6 which generates a reference clock of a predetermined frequency. The output signal of AND gate 7.8 is input to OR gate 10, and the output of OR gate 10 is input to VFOII as a control pulse. The VFOII is an oscillator that generates a window signal for discriminating clock pulses based on reproduction zero time as described above, and has the same configuration as the conventional one.

The operation in the above configuration will be explained.

FIG. 2 shows a signal waveform on the 0 line indicated by symbols A-D in FIG.

The signal outputted from the amplifier 3 consists of regular reproduction data and irregular servo signals, as indicated by reference numeral A in FIG. When the servo signal detector 4 detects a servo signal as indicated by 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 helad 2.

On the other hand, the pulse detector 5 outputs a rectangular wave pulse like the second light C by a waveform detector using a comparator or the like.As shown in the figure, during the data reproduction period, the output of the pulse detector 5 is Although the pulse train is regular, it becomes an irregular pulse train when the servo signal is reproduced. Conventionally, this irregular pulse train was input directly to VFOII.

VFO synchronization is disrupted.

However, in this embodiment, the output of the servo signal detector 4 switches the control signal input to the VFOII via the AND gate 7.8.

That is, when the output of the servo signal detector 4 rises to the /\I level, the AND gate 7, which had been closed until then, opens, and the AND gate 8 closes via the inverter 9. As a result, a clock of a predetermined frequency output from the reference clock oscillator is input to the VFOII via the AND gate 7 and the OR gate 10.

When the servo signal switches to reproduction data, the output of the servo signal detector 4 becomes low level and the AND gate 7.8
The state of
is input.

Therefore, the input to the VFO indicated by the symbol in FIG. 2 becomes almost regular throughout the data reproduction period and the servo signal reproduction period, and as in the past, the synchronization of the window signal is disrupted due to the influence of the servo signal, and recording and reproduction operations are interrupted. The problem of stability disappears.

Therefore, the clock pulses recorded on the magnetic disk l can be stably discriminated, data can be reproduced with high precision at all times, and the position of the magnetic head can be accurately controlled using the tracking servo signal. .

In addition to the above embodiments, 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 this 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, servo signal detection is possible when the servo signal is composed of multiple signal blocks arranged temporally shifted, or when the servo signal includes a no-signal portion. Even when the output of the device 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 done.

[Effects of the Invention] As is clear from the above description, according to the present invention, a variable frequency oscillator that generates a basic signal for discriminating a recording clock pulse from a data pulse reproduced from a magnetic disk, and a A magnetic disk drive having means for controlling a magnetic head position based on a recorded servo signal, comprising a reference clock oscillator of a predetermined frequency and a detector for detecting the servo signal from reproduced data,
The reference clock of the oscillator is input to the variable frequency oscillator during the period in which the servo signal is detected by the detector, and the variable frequency oscillator is operated based on the output signal of the reference clock oscillator. During the tracking error detection period, the nf variable frequency oscillator is controlled by the reference clock having a predetermined frequency, so that the synchronization of the variable frequency oscillator is not disrupted before and after the servo signal reproduction period, and recording is always stably performed on the magnetic disk. This has an excellent effect in that it is possible to stably discriminate the generated clock pulses and to perform highly reliable magnetic recording and reproducing.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of the main parts of a magnetic disk drive employing the present invention, and FIG. 2 is a timing chart showing signal waveforms of each part in FIG. 1...Magnetic disk 2...Magnetic head 3...
Amplifier 4... Servo signal detector 5... Pulse detector 6... Reference clock oscillator 7.8...
・AND gate lO...OR gate 11...VFO

Claims (1)

[Claims] A magnetic disk device having a variable frequency oscillator that generates a basic signal for distinguishing 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. A reference clock oscillator with a predetermined frequency and a detector for detecting the servo signal from reproduced data are provided, and the 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 magnetic disk drive characterized in that the variable frequency oscillator is operated based on an output signal of a reference clock oscillator.