JPH07320430A - Magnetic disk device - Google Patents

Abstract

PURPOSE:To increase the productivity of a magnetic disk device by providing a verifing means reproducing a servo signal from a magnetic disk and judging whether the servo signal satisfies specifications or not and unnecessitating the servo signal verifying of a servo track writer. CONSTITUTION:A servo mark and gray code detecting circuit 18 compares reproduced pulse signals with the prescribed bit pattern of a servo mark 10b and detects a mark 10b when they coincide with each other and fetches a code 10c in the timing of a gray code 10c and supplys them to a CPU 20. Moreover, a reproducing signal outputted by a low-pass filter 15 is supplied to a peak holding circuit 21, which performs peak holdings of respective signals A, B, C, D of the reproducing signal and an A/D converter 22 digitizes the signal and then the digital signal is supplied to the CPU 20. A digital filtering is performed and whether a positioning signal (A-B) obtained by subtracting the level of the signal B from the level of the signal A satisfies respectively a runout specification and a spike specification or not, is checked in the CPU 20.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic disk device, and more particularly to a magnetic disk device for verifying a servo signal recorded on a magnetic disk.

[0002]

2. Description of the Related Art A servo signal for tracking is previously recorded on a magnetic disk which is a recording medium of a magnetic disk device at the time of manufacturing, and during normal recording / reproduction, the servo signal is reproduced to track a magnetic head.

Conventionally, at the time of manufacturing, a servo track writer is used to write a servo signal on a magnetic disk,
After that, the servo track writer reproduces the servo signal from the magnetic disk to verify (verify) whether the servo signal is written according to the standard.

[0004]

Conventionally, a servo track writer for writing a servo signal on a magnetic disk is very expensive because it has expensive equipment such as a laser length measuring device, and the number of servo track writers is large. Is limited.

Since the servo signals recorded by the servo track writer whose number is limited are verified, verification time is required and there is a problem that the productivity of magnetic disks cannot be improved. Further, since the servo track writer needs a circuit for verification, there is a problem that the cost of the servo track writer becomes high.

The present invention has been made in view of the above points,
An object of the present invention is to provide a magnetic disk device which improves the productivity of a magnetic disk by eliminating the servo signal verification of the servo track writer and reduces the cost of the servo track writer.

[0007]

According to a first aspect of the present invention, in a magnetic disk device for recording / reproducing on a magnetic disk on which a servo signal is recorded in advance, a servo signal is reproduced from the magnetic disk to establish a standard. It has a verification means for determining whether or not it is satisfied.

According to a second aspect of the present invention, the verification means separates a positioning signal obtained from a tracking control signal of the servo signal reproduced in the on-track state into a low frequency component and a high frequency component. A filter means, a runout judging means for judging whether the runout due to the eccentricity of the magnetic disk satisfies the standard from the low frequency component, and a judgment for whether the spike due to the scratch of the magnetic disk satisfies the standard from the frequency component. And spike determination means.

According to a third aspect of the present invention, the verification means determines that the automatic gain control signal of the servo signals is standardized from the level of the tracking control signal of the servo signals reproduced in the on-track state. It has an AGC judging means for judging whether or not it is satisfied.

According to a fourth aspect of the present invention, the verification means changes the reference level for pulsing the servo mark signal and the address information signal for identifying the servo signal among the reproduced servo signals. It has a level changing means.

According to a fifth aspect of the present invention, the verification means converts a track pitch, which is a distance between adjacent tracks, from a signal level for tracking control of a servo signal reproduced in a tracking state with an offset. ,
It has a track pitch determining means for determining whether or not the track pitch satisfies the standard.

[0012]

According to the first aspect of the invention, the servo track writer for recording the servo signal on the magnetic disk is provided because it has a verifying means for reproducing the servo signal from the magnetic disk and judging whether or not the standard is satisfied. With this, there is no need to verify the servo signal recorded on the magnetic disk,
The productivity of the magnetic disk by the servo track writer is improved, it is not necessary to provide a verification circuit in the servo track writer, and the cost can be reduced.

According to another aspect of the invention, there is provided filter means for separating the positioning signal obtained from the tracking control signal of the servo signals reproduced in the on-track state into a low frequency component and a high frequency component. A runout determining means for determining whether the runout due to the eccentricity of the magnetic disk satisfies the standard from the low frequency component, and a spike determining means for determining whether the spike due to the scratch of the magnetic disk satisfies the standard from the frequency component. Therefore, it is possible to determine whether or not the positioning signal satisfies the specifications of the runout and the spike.

According to the third aspect of the invention, the automatic gain control signal of the servo signals satisfies the standard from the level of the tracking control signal of the servo signals reproduced in the on-track state. Since it has the AGC judging means for judging whether or not it is possible to judge whether the signal for automatic gain control satisfies the standard.

According to another aspect of the present invention, there is provided reference level changing means for changing the reference level for pulsing the servo mark signal and the address information signal for identifying the servo signal among the reproduced servo signals. Therefore, it is possible to determine whether the servo mark signal and the address information satisfy the standard by changing the reference level and reading the servo mark signal and the address information.

According to the fifth aspect of the invention, the track pitch, which is the distance between adjacent tracks, is converted from the signal level for tracking control of the servo signal reproduced in the tracking state with an offset, and the track pitch is converted. Has a track pitch determining means for determining whether or not satisfies the standard, it is possible to determine whether or not the track pitch satisfies the standard.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS First, a magnetic disk will be described. A servo signal is previously written on the magnetic disk by a servo track writer. This magnetic disk is a data surface servo system, and each cylinder is provided with a servo signal area in which servo signals are recorded at, for example, 72 locations per disk rotation, and a data area for recording and reproducing data is provided subsequent to the servo signal area. It is provided. As shown in FIG. 2, the servo signal is a read / write recovery 10a, which is a gap for absorbing a read / write difference, a servo mark 10b having a predetermined bit pattern for identifying the servo signal, and a cylinder number. And a gray code 10c recording address information such as a sector number, an AGC field 10d for automatic gain control (AGC),
It is composed of A, B, C, and D signals 10e for tracking, and a pad 10f in which the tal data is recorded.

FIG. 1 is a block diagram of an embodiment of the magnetic disk device of the present invention. In the figure, reference numeral 11 denotes a magnetic disk, and a magnetic head 12 reads and reproduces a recorded signal from the magnetic disk 11. Only the servo signal is read during servo signal verification in the manufacturing process, but during normal use after shipment, the servo signal and data are read by the magnetic head 12, and write data is supplied from a recording circuit (not shown) to the magnetic head 12 Is written on the magnetic disk 11.

The reproduced signal read by the magnetic head 12 is amplified by the preamplifier 13 and supplied to the AGC amplifier 14, where the gain is adjusted and amplified. AGC amplifier 1
The reproduction signal output from 4 is supplied to the pulse shaping circuit 16 after the unnecessary high frequency component is removed by the low-pass filter 15.
Here, the pulse waveform is shaped by being compared with the reference level. The reproduction pulse signal output from the pulse shaping circuit 16 is supplied from a terminal 17 to a demodulation circuit (not shown), and the servo mark and gray code detection circuit 18 is also provided.
Is supplied to.

Servo mark and gray code detection circuit 1
Reference numeral 8 compares the reproduction pulse signal with a predetermined bit pattern of the servo mark 10b, and detects the servo mark 10b when both match. With the detection timing of the servo mark 10b as a reference, the gray code 10c,
A at the position reproduction timing with the A, B, C, D signals 10e
The gain of the GC amplifier 14 is maintained and the AGC field 1
A gain holding control signal for updating the gain of the AGC amplifier 14 at 0d is supplied to the AGC amplifier 14. Further, the gray code 10c is captured at the reproduction timing of the gray code 10c and supplied to the CPU 20.

The reproduction signal output from the low-pass filter 15 is fed back to the AGC amplifier 14 for automatic gain control, and further supplied to the peak hold circuit 21. The peak hold circuit 21 uses the reproduced signal A,
Peak holding of each of the B, C, and D signals is performed, and the hold level is supplied to the A / D converter 22. The A / D converter 22 digitizes the hold levels of the A, B, C, and D signals and supplies them to the CPU 20. Meanwhile D
The / A converter 23 converts the digital data supplied from the CPU 20 into an analog signal to generate a reference level, and supplies this to the pulse shaping circuit 16.

The CPU 20 controls the rotation servo of the spindle motor for rotating the magnetic disk 11 and the magnetic head 1.
The servo control of the voice coil motor for moving 2 is performed, and the operation of the entire magnetic disk device is controlled according to the command supplied from the host device.

FIG. 3 shows a flowchart of the servo signal verification process executed by the CPU 20. This process is performed for each cylinder of the magnetic disk 11. First, step S10
Then, the digital data for setting the reference level of the pulse shaping circuit 16 to 50% is supplied to the D / A converter 23. Here, the reference level of 50% is a median value when the minimum value of the reproduction signal output from the low-pass filter 15 is 0% and the maximum value is 100%.

In the next step S20, A, B, C, D supplied from the A / D converter 22 in the on-track state.
The peak level of each signal is captured and written in the work area in the CPU 20. The level acquisition of each of the A, B, C, and D signals is performed for one track, that is, for one rotation of the magnetic disk.

Here, the A, B, C, and D signals are, for example, the A signal level and the B signal level in the state where the tracks are on-track to the tracks n, n + 1, and n + 2, as shown in FIG. The positioning signal A-B is zero, and the difference CD between the C signal level and the D signal level is zero at the track boundary positions of the tracks n, n + 1, and n + 2.

Next, in steps S30 and S40, digital filtering is performed to check whether the positioning signals A-B obtained by subtracting the B signal level from the A signal level satisfy the runout standard and the spike standard. To do. Here, the positioning signal AB should be zero in the on-track state, but the positioning signal AB is deviated from zero due to the inclusion of the runout or the spike. The runout is caused by the eccentricity of the magnetic disk 11, and is a low frequency component whose frequency is 100 Hz or less when the rotation speed of the magnetic disk 11 is 4500 rpm, for example. The spike is a high frequency component having a frequency of 100 Hz or higher, which is generated due to a scratch or the like on the magnetic disk 11. Therefore, for example, the runout is taken out by a low-pass filter having a cutoff frequency of 180 Hz, and the cutoff frequency 18
A 0 Hz high pass filter can remove the spikes.

FIG. 5 shows a flowchart of the digital filtering process executed in steps S30 and S40, respectively. Here, filtering is performed using the difference equation represented by the following equation.

[0028] _{W n = X n -b1 · W} n-1 -b2 · W n-2 ··· (1) Y n = a0 · W n + a1 · W n-1 + a2 · W n-2 ··· (2) Coefficients b1, b2, a0, a1, in the equations (1) and (2)
By changing a2, the filter characteristic, that is, the high-pass filter or the low-pass filter, and the cutoff frequency can be changed.

In step S41 of FIG. 4, YMAX corresponding to the maximum value of Y _n , W1 corresponding to W _n-1 and W2 corresponding to W _n-2 are reset to zero. Then step S4
In step 2, the steps are repeated up to 72 times, which is the number of servo signal areas for one rotation of the disk. In step S43, POSA which is the level of the A signal and POSB which is the level of the B signal are read from the work area, and X corresponding to the level of the positioning signals AB is calculated.

At step S44, the expressions (1) and (2) are reproduced.
Is calculated and Y is calculated in the next step S45. _nOf Y corresponding to
It is determined whether the logarithmic value is greater than or equal to the absolute value of YMAX, and | Y |
> | YMAX |
The YMAX is updated and the process returns to step S42.

As a result, when the processing of FIG. 4 is completed, Y
The maximum value of runout or spike is stored in MAX. Here, for example, ± 1.2 μm from the on-track position
When a track shift occurs and the track shifts to an adjacent track to perform off-track, the maximum value of the runout stored in YMAX is ± 3. If it is within the range of 6 μm, it is determined that the runout standard is satisfied, and if it is outside this range, it is determined that it is out of the standard. Also,
In step S40, it is determined that the spike standard is satisfied if the track deviation is within the range of ± 0.66 μm,
If it is outside this range, it is determined to be out of standard.

Returning to FIG. 3, step S50 will be described.
Then, it is checked whether the AGC field 10d satisfies the standard. Here, it is determined whether the A signal level and the B signal level of each servo signal are below a predetermined level (for example, about 2V). If the AGC field 10d is normally recorded, the level of each of the A signal and the B signal is, for example, about 1 V due to the gain updated in this AGC field. But AGC field 10
d has an abnormality such as missing, and the playback level is 60%
When the AGC amplifier 14 is lowered to a certain extent, the gain of the AGC amplifier 14 is increased and the levels of the A signal and the B signal exceed predetermined levels. Utilizing this, when the A signal and B signal levels exceed a predetermined value, there is missing in the AGC field 10d, and it is determined that the standard is not met.

Next, in step S60, it is checked whether the C signal and the D signal satisfy the standard. On-track even track (track n, n + 2 in Figure 4)
Since the C signal level is low and the D signal level is high, the sum of the A signal level and the B signal level is used as a reference level, and when the C signal level is 0.35 times or more of the reference level, there is a problem such as a well. Then, if the D signal level is, for example, 0.65 times or less of the reference level, it is determined that there is an abnormality such as missing, and it is determined to be out of standard.

Since the C signal level is high and the D signal level is low in the odd-numbered tracks (track n + 1 in FIG. 4) in the on-track state, if the C signal level is less than 0.65 times the reference level, there is an abnormality such as missing. And D
When the signal level is 0.35 times the reference level or more, it is determined to be out of the standard because there is an abnormality such as springing out.

Next, in steps S70 to S90, it is checked whether the spacing standard is satisfied. In step S70, tracking is performed by offsetting +1/4 track by using C signal and D signal, and
Each of the signal level and the B signal level is fetched, the absolute value of the positioning signals A-B is calculated and stored in the work area. Further, in step S80, the C signal and the D signal are used to obtain -1.
/ 4 track offset is performed for tracking, the A signal level and the B signal level of each servo signal are taken in, and the absolute value of the positioning signals AB is calculated and stored in the work area.

After that, in step S90, the added value of the absolute values of the positioning signals AB obtained in steps S70 and S80 of each servo signal is converted into a distance. This conversion is performed by multiplying by a predetermined coefficient, and it is compared whether or not the converted distance is within the reference range of the 1/2 track width. When the added value is out of the reference range, it is determined to be out of the standard.

In steps S100 to S130, it is checked whether the servo mark 10b and the gray code 10c satisfy the standard. In step S100, the reference level of the pulse shaping circuit 16 is set to (5
Digital data of 0 + X)% (X is, for example, 10) is supplied to the D / A converter 23. Step S110
Then, in this state, servo mark 10b or gray code 1
If 0c cannot be detected by the servo mark and gray code detection circuit 16, it is determined to be nonstandard.

In step S120, the reference level of the pulse shaping circuit 16 is set to (50-X)% (X
Supplies the digital data of 10) to the D / A converter 23. In step S130, if the servo mark 10b or the gray code 10c cannot be detected by the servo mark and gray code detection circuit 16 in this state, it is determined to be nonstandard.

As described above, since the servo signal is verified in the magnetic disk device, it is not necessary to verify the servo signal in the servo track writer. For this reason, the time required for verifying the servo signal in the servo track writer becomes unnecessary, and the productivity of the magnetic disk is greatly improved. Further, since it is not necessary to provide a circuit for verifying the servo track writer, the cost thereof can be reduced.

On the other hand, in the magnetic disk device, the servo signal is verified by the software in the CPU 20, and the peak hold circuit, the A / D converter and the D / A converter are used for the original servo control (speed control, position control). However, the cost of the magnetic disk device is not increased at all.

In the above embodiment, the magnetic disk of the data surface servo system has been described as an example, but the present invention can be applied to the magnetic disk of the servo surface servo system in which one of the plurality of magnetic disks is the servo surface. The invention is not limited to the above embodiment.

[0042]

As described above, according to the first aspect of the present invention, since the servo means is reproduced from the magnetic disk to determine whether or not the standard is satisfied, the magnetic disk is provided with the servo signal. With a servo track writer that records a signal, it is not necessary to verify the servo signal recorded on the magnetic disk, the productivity of the magnetic disk by the servo track writer is improved, and it is not necessary to provide a verification circuit in the servo track writer. Cost can be reduced.

According to the second aspect of the invention, the filter for separating the positioning signal obtained from the tracking control signal of the servo signals reproduced in the on-track state into a low frequency component and a high frequency component. Means for determining whether a runout due to eccentricity of the magnetic disk satisfies the standard from the low frequency component, and a spike for determining whether a spike due to scratches on the magnetic disk satisfies the standard from the frequency component Since it has a determining means, it is possible to determine whether the positioning signal meets the specifications of the runout and the spike.

According to the third aspect of the invention, from the level of the tracking control signal of the servo signals reproduced in the on-track state, the automatic gain control signal of the servo signals is Since the automatic gain control signal has the AGC determining means for determining whether or not the standard is satisfied, it can be determined whether or not the automatic gain control signal satisfies the standard.

According to the present invention, the reference level for varying the reference level for pulsing the servo mark signal and the address information signal for identifying the servo signal among the reproduced servo signals. Since the variable unit is provided, it is possible to determine whether the servo mark signal and the address information satisfy the standard by changing the reference level and reading the servo mark signal and the address information.

According to the fifth aspect of the present invention, the track pitch, which is the distance between adjacent tracks, is converted from the signal level for tracking control of the servo signal reproduced in the tracking state with an offset, and the track pitch is converted. Since it has a track pitch determining means for determining whether the pitch meets the standard, it is possible to determine whether the track pitch meets the standard, which is extremely useful in practice.

[Brief description of drawings]

FIG. 1 is a block diagram of a device of the present invention.

FIG. 2 is a diagram for explaining a servo signal.

FIG. 3 is a flowchart of a servo signal verification process.

FIG. 4 is a diagram for explaining a positioning signal.

FIG. 5 is a flowchart of a digital filtering process.

[Explanation of symbols]

 11 magnetic disk 12 magnetic head 13 preamplifier 14 AGC amplifier 15 low-pass filter 16 pulse shaping circuit 18 servo mark and gray code detection circuit 20 CPU 21 peak hold circuit 22 A / D converter 23 D / A converter

Claims (5)

[Claims] 1. A magnetic disk device for recording / reproducing on / from a magnetic disk on which servo signals are recorded in advance, comprising a verification means for reproducing servo signals from the magnetic disk and determining whether or not the standard is satisfied. And a magnetic disk device. 2. The filter means for separating a positioning signal obtained from a tracking control signal of a servo signal reproduced in an on-track state into a low frequency component and a high frequency component, and the low frequency component. A runout determining means for determining whether the runout due to the eccentricity of the magnetic disk satisfies the standard from the component, and a spike determining means for determining whether the spike due to the scratch of the magnetic disk satisfies the standard from the frequency component. The magnetic disk drive according to claim 1, wherein 3. The verification means determines whether or not the automatic gain control signal of the servo signals satisfies the standard from the level of the tracking control signal of the servo signals reproduced in the on-track state. 2. The magnetic disk device according to claim 1, further comprising an AGC determining means for performing the operation. 4. The verification means includes a reference level changing means for changing a reference level for pulsing a servo mark signal for identifying a servo signal and a address information signal for identifying a servo signal among reproduced servo signals. The magnetic disk drive according to claim 1, wherein the magnetic disk drive is a magnetic disk drive. 5. The verification means converts a track pitch, which is a distance between adjacent tracks, from a signal level for tracking control of a servo signal reproduced in a tracking state with an offset, and the track pitch is a standard. 2. The magnetic disk device according to claim 1, further comprising a track pitch determining means for determining whether or not the condition is satisfied.