JP2944821B2 - Servo write method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[0002]

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

FIG. 5A shows an index signal.
One index signal exists for one round of one 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. 5C) is used only when the write gate signal is "H".
0 and H1 can be written. FIG. 5D shows servo data written by the magnetic head. FIG.
Indicates the movement of the magnetic head H0 when writing servo data using the magnetic head H0, for example.

In FIG. 1, Tr indicates a track pitch, and Tw indicates a gap width of a magnetic head. When performing servo writing, servo data is written while the magnetic head is shifted by half the track pitch, that is, Tr / 2. For this reason, for example, when the magnetic head writes servo data at the position N5 and then moves to the position N6 to further write the servo data, the hatched portion M (Tw-Tr / 2) shown in FIG. The region is overwritten by N
The data written at the position 5 is erased.

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

As shown in FIG. 7E, the magnetic head H0
As a result, servo data is written to the track K1 on the surface of the magnetic disk. Also, as shown in FIG. 7 (g), the track K on the back surface of the magnetic disk is
2 is written with servo data.

By the way, the initial magnetization direction on the magnetic disk is not determined. When servo writing is performed by the above-described method, no servo data is input, and when the write gate is open, the magnetic head On the other hand, a current flows in a certain direction, and the direction of magnetization is determined. If this magnetization direction is opposite to the initial magnetization direction of the magnetic disk, magnetization reversal occurs at a portion where current starts to flow, and extra pulses (FIGS. 7 (f) and 7 (h)) are generated. FIG. 8 shows extra pulses generated on the magnetic disk in this manner.

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

[0009]

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

The present invention has been made in view of such a problem, and an object of the present invention is to reduce the influence of crosstalk due to extra pulses generated at the time of servo writing and reduce the occurrence of read errors. It is to provide a method.

[0011]

In order to achieve the above-mentioned object, the present invention provides 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 a magnetic head with respect to the magnetic disk. A servo write method comprising: changing a signal on-time; and writing servo data to the magnetic disk by the magnetic head only during a time when the write gate signal is on.

[0012]

According to the present invention, when performing servo writing, the on-time of the write gate signal is changed in accordance with the radial position of the magnetic head. Since the shift is performed for each track, the influence of the extra pulse can be reduced.

[0013]

Embodiments of the present invention will be described below 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 performing a servo write method according to one 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 inputted, and which shifts the write gate signal in synchronization with the clock signal. That is, the shift register 1 outputs the write gate signal S1
Are shifted to output signals S3 to S8. The logical operation unit 3 includes OR gates 5 and 7 and AND gates 9 and 1
1 and performs a logical operation to generate signals S9 to S12.
Is output (FIG. 2). The selector 13 converts the signal S9 to the signal S12 based on the select signal S13 corresponding to the track.
Are sequentially selected as the write gate signal S14 and the gate 1
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 units, servo data written on a track, and extra pulses when performing a servo write.

FIG. 3A shows an index signal,
One index signal exists for one rotation of the magnetic disk. Magnetic head select signal (FIG. 3B)
Is a signal indicating which one 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
Is satisfied, the magnetic head H1 is selected.

Write gate signal S14 (FIG. 3C)
Can write to the magnetic heads H0 and H1 only when this write gate signal is "H". In this 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 via the gate 15 as part of the write signal.

As shown in FIG. 3E, the magnetic head H0
As a result, servo data is written to the track K3 on the surface of the magnetic disk. Also, as shown in FIG. 3G, the track K on the back surface of the magnetic disk is
4 is written with servo data.

By the way, the initial magnetization direction on the magnetic disk is not determined, and when servo writing is performed by the above-described method, no servo data is input and when the write gate is open, the magnetic head is Thus, a current flows in a certain direction, and the direction of magnetization is determined. If the direction of this magnetization is opposite to the initial magnetization direction of the magnetic disk, 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 signals (S9 to S12) and the extra pulses generated on the track.

When writing servo data, the magnetic head is moved like Q1 to Q8 to write servo data. For example, when writing servo data while 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". , An extra pulse is generated at the position indicated by A1 in the figure. When writing servo data while the magnetic head is at Q2, an extra pulse is generated at the position indicated by A2 in the figure because the write gate signal is S10. 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 extra pulse B1 of the extra pulse A1 is overwritten at the time of servo data, so that the extra pulse of the B1 portion is erased. You. Similarly, the extra pulses from B2 to B8 are also erased.

Next, a formatting process is performed by a magnetic head. In the figure, R1 to R4 indicate the position of the magnetic head when the formatting process is performed. A part of the extra pulse is erased by this format processing. That is, among the extra pulses in A1, C1
Parts are erased. The portion C2 of the extra pulse at A2 is erased. Similarly, from C3 to C
The extra pulses in the eight parts are erased.

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

As described above, in this embodiment, the number of residual extra pulses is reduced, and the position where extra pulses are generated in an adjacent track is shifted. 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, according to the present invention, the influence of crosstalk due to extra pulses generated at the time of servo writing is reduced, and the occurrence of read errors is reduced.

[Brief description of the drawings]

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

FIG. 2 is a waveform diagram of a signal of each unit in FIG. 1;

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

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

FIG. 5 is a diagram showing signals at the time of servo writing in a conventional example.

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

FIG. 7 is a diagram showing signals of respective parts, servo data written on a track, and extra pulses when performing servo writing 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)

(57) [Claims] 1. A servo write method for writing servo data to a magnetic disk, wherein the on-time of a write gate signal is changed in accordance with a radial position of a magnetic head with respect to the magnetic disk; Writing servo data to the magnetic disk by the magnetic head only during the period of time.