JPS60101763A - Magnetic disk recording device - Google Patents

Abstract

PURPOSE:To switch circuit resolution invariably according to the resolution of data by discriminating on the resolution of data read out by a magnetic head from the read data, and switching filters. CONSTITUTION:The data read out by the magnetic head 1 is outputted through the 1st and the 2nd LPFs 3 and 4, a differentiating circuit 5, a comparator 6, and a waveform shaping circuit 7. The 1st and the 2nd LPFs differ in frequency band, and a switching circuit 8 for short-circuit control over the LPF4 is connected to the LPF4. The waveform signal S1 from the differentiating circuit 5 is inputted to a comparator 6 and converted into a rectangular wave signal S2 which is at a level H or L about the zero level. The signal S2 is inputted to a saddle detecting circuit 9 to detect whether the saddle part in the waveform signal S1 crosses the zero level; when the saddle part does not cross the zero level, a filter switching circuit 8 is put in short-circuit control operation and when the saddle part crosses the zero level, the short-circuit state of the switching circuit 8 is reset. Consequently, invariably correct data is read out.

Description

[Detailed description of the invention] [Technical field of invention] The present invention relates to a magnetic disk recording device.

[Technical background of the invention and points therebetween] In a magnetic disk recording device, for example, a magnetic head is brought into contact with a magnetic disk, data is read from the magnetic disk, and the data is passed through first and second low-pass filters. Furthermore, the signal is outputted via a differentiating circuit and a comparator, and a second low-pass filter is short-circuited depending on the required resolution. This is because the resolution of data differs between the outer track and the inner track of the magnetic disk, so it is necessary to change the resolution of the data reading circuit accordingly.

In other words, since the resolution of the outer track is high, the resolution of the circuit is lowered through both the first and second low-pass filters to extract the data, and conversely, the resolution of the inner track is low, so the data is extracted from the track through the first and second low-pass filters. Data is extracted by increasing the resolution of the circuit through only one low-pass filter.

Conventionally, the resolution of such a data readout circuit has been switched by, for example, mounting a magnetic head and detecting the operating position of the carrier with an optical detector, or counting the operating position of the carrier with a counter. , and those that are performed when the count value reaches a certain value are known. However, in all of these methods, the resolution of the circuit is switched between the 1st and rack positions of the magnetic head, and the switching position is always fixed. Changes in resolution depending on the state are not taken into account at all, and therefore there is a problem in that filters are switched even when there is no need to switch the resolution of the circuit.

[Purpose of the Invention] This invention has been made to solve such problems, and by constantly determining the resolution of data from the data read from the magnetic head and switching filters, the circuit An object of the present invention is to provide a magnetic disk recording device that can always switch resolution in accordance with data resolution.

[Summary of the Invention] This invention rotates a magnetic disk, controls the movement of a magnetic head in the radial direction by contacting the magnetic disk, reads data from the magnetic disk, and transfers the data to a first and a second disk. In a magnetic disk drive that outputs data through a low-pass filter and further through a differentiating circuit and a comparator, a saddle detection circuit detects zero crossings at the saddle in the differentiating circuit output waveform from the signal waveform output from the comparator, and In response to the zero cross detection output from the detection circuit, the second
The low-pass filter is kept short-circuited.

Further, in the present invention, the short-circuited state of the second low-pass filter is released by a step signal to a step motor that controls the movement of the magnetic head. Furthermore, the short-circuit holding of the second low-pass filter is released by an index signal from an index detector that detects an index hole in a magnetic disk.

In other words, this invention focuses on the fact that when high-resolution data is read out by increasing the circuit resolution, a waveform section called a saddle included in the signal waveform from the differentiating circuit crosses zero, and when that zero-cross occurs, the first Both filters of the second filter are used to reduce the circuit resolution.

[Embodiments of the invention] An embodiment of the present invention will be described below with reference to the drawings.

In FIG. 1, reference numeral 1 denotes a magnetic head, which is placed on a carrier and whose movement in the radial direction of the magnetic disk is controlled by a step motor. The data read by the magnetic head 1 is sent to a read amplifier 2;
First low-pass filter 3, second low-pass filter 4
, a differentiating circuit 5, a comparator 6, and a waveform shaping circuit 7 in order. The first low-pass filter 4
and the second low-pass filter 4 have different frequency bands. A filter switching circuit 8 for short-circuiting the low-pass filter 4 is connected in parallel to the second low-pass filter 4 . The waveform signal S1 from the differentiating circuit 5 is input to the comparator 6 to generate a rectangular wave signal s in which a signal above the zero level is a high level and a signal below the zero level is a low level.
2, the rectangular wave signal S2 is input to the saddle detection circuit 9, and the saddle detection circuit 9 converts the waveform signal s1 into
It is detected whether the saddle portion S1- included in the saddle portion S1- crosses zero or not, and when the saddle portion S1' does not cross zero, the filter switching circuit 8 is short-circuited and the saddle portion 81'
When the zero cross occurs, the short-circuited state of the filter switching circuit 8 is released.

The saddle detection circuit 9 is constructed as shown in FIG. That is, the rectangular wave signal S2 from the comparator 6 is input to one input terminal of the exclusive OR gate 91, and the exclusive OR gates 1 to 1 through the differentiating circuit 92 are input.
91 is input to the other input terminal. The output S3 of the exclusive OR gate 91 is input to a one-shot multivibrator 93 and also to one input terminal of an AND gate 94. The multivibrator 93 outputs a pulse signal S4 having a time width shorter than the width between pulses n of the recording/reproducing signal in response to the fall of the output S3 of the exclusive OR gate 91, and outputs the pulse signal S4 to the AND gate 94. is input to the other input end of the . The output S5 of the AND gate 94 is connected to the T of the Noritsubu flop 95.
It is being input to the input terminal. A reset signal from an initial reset circuit 96 and a step signal ST for driving a step motor for controlling the movement of the magnetic head are input to the reset terminal of the flip 70 knob 95. The flip-flop 95 is set when a high level signal is input to its D input terminal and outputs a high level signal from its Q output terminal, and in this state, when a step signal is input to its reset terminal, it is reset and outputs a Q output terminal. Set the output to low level. Further, when a low level signal is input to the Q output terminal, the reset state is maintained and a low level signal is continued to be output from the Q output terminal.

The filter switching circuit 8 short-circuits the second low-pass filter 4 when a low-level signal is input from the saddle detection circuit 9, and short-circuits the second low-pass filter 4 when a high-level signal is input from the saddle detection circuit 9. This is to release the short circuit of the low-pass filter 4.

In the embodiment of the present invention configured as described above, if the resolution of the data read by the magnetic head is low and the saddle portion 81' of the waveform signal 81 output from the differentiating circuit 5 does not cross zero, each portion The output is as shown in FIG. 't, that is, the output S2 of the comparator 6 has a time width synchronized with the original frequency of the waveform signal $1, and therefore the AND output 1 of the output JS3 of the exclusive OR gate 91 and the output S4 of the multivibrator 93 is The output of 94 maintains a low level state. At this time, the flip-flop 95 maintains the reset state, so the output from its Q output terminal becomes low level, and the filter switching circuit 8 short-circuits the second low-pass filter 4 to improve circuit resolution.

The resolution of the data read out in this state is high, and as shown in FIG.
When 1- becomes zero cross J゛, comparator 6
The rectangular wave signal S2 from 1 to 2 also changes as shown in FIG.
The AND gate 94 output S5, that is, the AND gate 94 output S5, becomes a high level at the zero cross point of the saddle section, and the flip-flop 95 is set by this, and the output from the flip-flop 95 becomes Becomes a high level.

As a result, the filter switching circuit 8 releases the short-circuited state of the second low-pass filter 4, and data is outputted via both the first and second low-pass filters 3.4, and the circuit resolution is low. It can be suppressed. In this manner, the saddle portion 81' of the waveform signal S1 from the differentiating circuit 5 will no longer cross zero, and the data resolution will be appropriately controlled.

At this time, when the saddle section no longer crosses zero, the output S5 of the AND gate 94 becomes low level, but the flip 70 knob 95 maintains the output at high level. Thereafter, when a step signal for moving the magnetic head is input, the flip-flop 95 is reset, and the second low-pass filter 4 is again short-circuited by the filter switching circuit 8.

In this way, the resolution of the read data is checked to decide whether to short-circuit the second low-pass filter 4 to increase the circuit resolution or to remove the short-circuit and lower the circuit resolution. The circuit resolution can be switched and controlled according to the resolution state, and the correct data can always be read without erroneously reading data due to zero crosses in the saddle section.

Next, another embodiment of the invention will be described with reference to the drawings.

Note that the same parts as in the above embodiment are given the same reference numerals, and detailed explanations will be omitted.

As shown in FIG. 5, this is done by converting the reset control of the flip-flop 95 into a step signal and obtaining it from the index detector 97 that detects the index hole of the magnetic disk.In this way, the magnetic disk rotates once. Although the flip-flop 95 is reset each time, the same effects as in the previous embodiment can be obtained.

[Effects of the Invention] As detailed above, according to the present invention, the resolution of the data read from the magnetic head is always determined from the data and the filter is switched, so that the circuit resolution can always be switched based on the data. can be performed according to the resolution of
It is possible to provide a magnetic disk recording device that can always read correct data.

[Brief explanation of the drawing]

Figures 1 to 4 show an embodiment of the present invention. Figure 1 is a block diagram, Figure 2 is a specific circuit diagram of the saddle detection circuit, and Figure 3 is a diagram showing a case where the saddle section does not cross zero. FIG. 4 is an output waveform diagram of each part when the saddle crosses zero, and FIG. 5 is a specific circuit diagram of a saddle detection circuit showing another embodiment of the present invention. DESCRIPTION OF SYMBOLS 1... Magnetic head, 3... First low-pass filter, 4... Second low-pass filter, 5... Differential circuit, 6... Comparator, 8... Filter switching circuit,
9...Saddle detection circuit. Applicant's agent Patent attorney Takehiko Suzue

Claims (3)

[Claims] (1) Rotating the magnetic disk and controlling the movement in the radial direction by bringing the magnetic head into contact with the magnetic disk,
In the magnetic disk device that reads data from the magnetic disk, passes the data through first and second low-pass filters, and further outputs the data through a differentiation circuit and a comparator, the difference is calculated from the signal waveform output from the comparator. The present invention is characterized by providing a saddle detection circuit that detects a zero-crossing of the saddle portion in a circuit output waveform, and a filter switching circuit that maintains the second low-pass filter short-circuited in response to the zero-crossing detection output from the saddle detection circuit. magnetic disk recording device. (2) While rotating the magnetic disk, the magnetic head is brought into contact with the magnetic disk, and its movement is controlled in the radial direction by a step motor, data is read from the magnetic disk, and the data is passed through the first and second low-pass filters. a saddle detection circuit that detects a zero cross of a saddle portion in the differential circuit output waveform from a signal waveform output from the comparator; and a filter switching circuit that maintains the second low-pass filter short-circuited in response to a zero-cross detection output of the filter and releases the short-circuit of the second low-pass filter in response to a step signal that drives the step motor. A magnetic disk recording device characterized by: (3) Rotating the magnetic disk and controlling the movement in the radial direction by bringing the magnetic head into contact with the magnetic disk;
In the magnetic disk device that reads data from the magnetic disk, passes the data through first and second low-pass filters, and further outputs the data through a differentiation circuit and a comparator, index detection detects an index hole in the magnetic disk. a saddle detection circuit that detects a zero cross of the saddle section in the output waveform of the differentiating circuit from the signal waveform output from the comparator, and a second low-pass filter in response to the zero cross detection output from the saddle detection circuit. A magnetic disk recording device comprising: a filter switching circuit that maintains a short circuit and releases the short circuit of the second low-pass filter in response to an index signal from the index detector.