JPH05303853A - Servowriting method - Google Patents

Abstract

PURPOSE:To reduce the influence of an extra pulse by changing the ON time of a write gate signal at the time of servowrting and shifting the generating position of the extra pulse of a guard band residue at every neighboring track. CONSTITUTION:Write gate signals S3 to S8 shifted at a shift register 1 are sent to an arithmetic and logic section 3, signals S9 to S12 gained by an arithmetic operation are selected in sequence by a selective signal S13 corresponsive to a track at a selector 13 and made to a write gate signal S14. The ON time of the signal S14 is changed for every track by servo data S15 at a gate 15 and a write signal is sent to a magnetic head 17 only when a signal 14 is H. Therefore, one part of the extra pulse generated at the time of writing is overwritten and erased and one part is further erased by the format operation of the magnetic head. Thus, the residual extra pulse is reduced, shifted at the generating position of the extra pulse of the neighboring track and a cross talk and a reading error are reduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a servo write method for a magnetic disk device.

[0002]

2. Description of the Related Art Generally, in a magnetic disk device, servo data is written on a disk by a servo writer before factory shipment. The servo data is written by a method called the staggered method. That is, servo data is written in a zigzag manner on both sides of the magnetic disk by using two magnetic heads existing on the front and back sides. FIG. 5 shows each signal when writing the servo data by the staggered method.

FIG. 5A shows an index signal,
There is one index signal for each track of the magnetic disk. The magnetic head select signal (FIG. 5B) is a signal indicating which of the two magnetic heads is to be selected. That is, when the magnetic head select signal is at the low voltage level L, the magnetic head H0 is selected, and when the magnetic head select signal is at the high voltage level H, the magnetic head H1 is selected. The write gate signal (FIG. 5 (c)) shows the magnetic head H only when the write gate signal is “H”.
Writing to 0 and H1 becomes possible. FIG. 5D shows servo data written by the magnetic head. Figure 6
Indicates the movement of the magnetic head H0 when writing servo data using the magnetic head H0.

In the figure, Tr indicates the track pitch, and Tw indicates the gap width of the magnetic head. When performing servo write, servo data is written while shifting the magnetic head by half the track pitch, that is, Tr / 2. Therefore, for example, when the magnetic head writes servo data at the position N5 and then moves to the position N6 to write more servo data, the shaded portion M (Tw-Tr / 2) in FIG. Area is overwritten with N
The data written at position 5 is erased.

In the magnetic disk apparatus, since the servo control is performed with this overwriting boundary as an on-track, the servo data magnetization reversal section must be connected in the seek direction. Therefore, the write gate signal (FIG. 5 (c)) is turned on / off at the timing at which the magnetization reversal units are connected. FIG. 7 is a diagram showing signals of respective parts and servo data and extra pulses written in tracks when performing servo writing. Fig.7 (a)-
(D) is the same as that shown in FIG.

As shown in FIG. 7E, the magnetic head H0
By this, servo data is written on the track K1 on the surface of the magnetic disk. Further, as shown in FIG. 7G, the track K on the back surface of the magnetic disk is moved by the magnetic head H1.
Servo data is written in 2.

By the way, the initial magnetization direction on the magnetic disk is not determined, and when servo write is performed by the above-described method, servo data is not input and when the write gate is open, the magnetic head is moved to the magnetic head. In contrast, a current flows in a fixed direction, and the direction of magnetization is determined. When the magnetization direction is opposite to the initial magnetization direction of the magnetic disk, the magnetization reversal occurs at the portion where the current starts flowing, and extra pulses (FIGS. 7F and 7H) are generated. FIG. 8 shows the extra pulse thus generated on the magnetic disk.

The extra pulse is connected in the radial direction of the magnetic disk as described above. By the way, in the magnetic disk device, the formatting process is performed by the magnetic head. In FIG. 8, J1, J2, J3, J
Reference numeral 4 shows the magnetic head 1 when the format process is performed. If you do such a format process,
Data is written in the extra pulse portion, and the extra pulse in this portion is erased. However, the extra pulse remains between the tracks (guard band part).

[0009]

As described above, when the conventional servo write method is used, a part of the extra pulse generated at the turning on / off of the write gate remains, and the data is actually read by the magnetic head. When reading, there is a problem that crosstalk occurs due to the influence of the extra pulse, and a read error may occur.

The present invention has been made in view of the above problems, and an object of the present invention is to reduce the influence of crosstalk due to an extra pulse generated during servo writing and to reduce the occurrence of read errors. To provide a method.

[0011]

In order to achieve the above-mentioned object, the present invention is a servo write method for writing servo data to a magnetic disk, wherein a write gate is provided in accordance with a radial position of the magnetic head with respect to the magnetic disk. A servo write method comprising: a step of changing an ON time of a signal; and a step of writing servo data to the magnetic disk by the magnetic head only during an ON time of the write gate signal.

[0012]

In the present invention, when servo write is performed, the on time of the write gate signal is changed according to the radial position of the magnetic head, so that the extra pulse generation positions remaining in the guard band are adjacent to each other. Since it shifts for each track, the influence of the extra pulse can be reduced.

[0013]

Embodiments of the present invention will now be described in detail with reference to the drawings.

FIG. 1 is a block diagram showing a configuration of a main part of a servo writer for carrying out a servo write method according to an embodiment of the present invention. FIG. 2 is a waveform diagram of the signals S3 to S12.

The shift register 1 is a shift register to which a write gate signal S1 having a waveform as shown in FIG. 5C and a clock signal are input and which shifts the write gate signal in synchronization with this clock signal. That is, the shift gate 1 outputs the write gate signal S1.
The signals S3 to S8 that are shifted are output. The logical operation unit 3 includes OR gates 5 and 7 and AND gates 9 and 1
1 and performs a logical operation to output signals S9 to S12.
Is output (FIG. 2). The selector 13 selects the signal S9 to the signal S12 according to the select signal S13 corresponding to the track.
Are sequentially selected to form the gate 1 as the write gate signal S14.
Send to 5. The gate 15 sends a write signal to the magnetic head 17 only when the write gate signal S14 is "H". FIG. 3 is a diagram showing signals of respective parts and servo data and extra pulses written in a track when servo writing is performed.

FIG. 3A shows the index signal,
There is one index signal for each rotation of the magnetic disk. Magnetic head select signal (Fig. 3 (b))
Is a signal indicating which of the two magnetic heads is to be selected. That is, when the magnetic head select signal is at the low voltage level L, the magnetic head H0
Is selected and the magnetic head select signal is at the high voltage level H.
, The magnetic head H1 is selected.

Write gate signal S14 (FIG. 3 (c))
Can write in the magnetic heads H0 and H1 only when the write gate signal is "H". Then, in the present embodiment, the ON time of the write gate signal S14 is changed for each track. Servo data S15
Is sent to the magnetic head 17 as part of the write signal via the gate 15.

As shown in FIG. 3 (e), the magnetic head H0
By this, servo data is written in the track K3 on the surface of the magnetic disk. Further, as shown in FIG. 3G, the track K on the back surface of the magnetic disk is moved by the magnetic head H1.
Servo data is written in 4.

By the way, the initial magnetization direction on the magnetic disk has not been determined, and when servo write is performed by the above-mentioned method, servo data is not input and when the write gate is open, the magnetic head is Current flows in a fixed direction, and the direction of magnetization is determined. When the magnetization direction is opposite to the initial magnetization direction of the magnetic disk, the magnetization reversal occurs at the portion where the current starts to flow, and extra pulses (FIGS. 3F and 3H) are generated. FIG. 4 shows the write gate signal (S9 to S12) and the extra pulse generated on the track.

When writing servo data, the magnetic head is moved from Q1 to Q8 and the servo data is written. For example, when writing servo data when the magnetic head is at Q1, the write gate signal is S9, so when the write gate signal S9 changes from “L” to “H” and from “H” to “L”. Then, an extra pulse is generated at the position indicated by A1 in the figure. Further, when the servo data is written when the magnetic head is at Q2, the write gate signal is S10, so an extra pulse is generated at the position indicated by A2 in the figure. When the magnetic head moves from Q1 to Q8 in this way, extra pulses are generated at positions A1 to A8.

When the magnetic head moves from Q1 to Q2 and writes servo data, the B1 portion of the extra pulse indicated by A1 is overwritten during the servo data, so the extra pulse in the B1 portion is erased. It Similarly, the extra pulses from B2 to B8 are also erased.

Next, the magnetic head performs a format process. In the figure, R1 to R4 indicate the positions of the magnetic head when the format process is performed. A part of the extra pulse is erased by this formatting process. That is, C1 of the extra pulses in A1
The part is erased. The C2 portion of the extra pulse in A2 is erased. Similarly, from C3 to C
The extra pulse in part 8 is erased.

Therefore, when the format process is performed,
Extra pulses indicated by D1 to D8 in the figure remain in the guard band. The extra pulses indicated by D1 to D8 are not connected on the magnetic disk, and the amount thereof is small.

As described above, in the present embodiment, the residual extra pulse is reduced and the extra pulse generation position of the adjacent track is displaced. Therefore, at the time of reading, the magnetic head is less affected by the crosstalk due to the extra pulse, and the reading error is reduced.

[0025]

As described above in detail, according to the present invention, the influence of the crosstalk due to the extra pulse generated during the servo write is reduced, and the occurrence of read error is reduced.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a main part of a servo writer for carrying out the present invention.

FIG. 2 is a waveform diagram of signals at various parts in FIG.

FIG. 3 is a diagram showing signals of respective parts and servo data and extra pulses written in a track when performing a servo write.

FIG. 4 is a diagram showing write gate signals (S9 to S12) and an extra pulse generated on a track.

FIG. 5 is a diagram showing each signal during servo write in a conventional example.

FIG. 6 is a diagram showing movement of a magnetic head when performing servo write.

FIG. 7 is a diagram showing signals of respective parts and servo data and extra pulses written in a track when servo writing is performed in a conventional example.

FIG. 8 is a diagram showing a write gate signal and an extra pulse generated on a track in a conventional example.

[Explanation of symbols]

 1 ... shift register 3 logic circuit 13 selector 15 gate 17 magnetic head

Claims (1)

[Claims] 1. A servo write method for writing servo data to a magnetic disk, the step of changing the ON time of a write gate signal according to the radial position of a magnetic head with respect to the magnetic disk; A step of writing servo data to the magnetic disk by the magnetic head only during the time of.