JPS6344187A - Defect detection system for magnetic disk medium - Google Patents

Abstract

PURPOSE:To enable the recording of a defect existing between data tracks within a home address, by sending an offset signal to a control means to detect the defect with a data head shifted outside a normal track. CONSTITUTION:A control means 15 drives a carriage 5 using servo information for head positioning to control a servo head 4 and a data head 3 so that they follow desired tracks. While the heads 3 and 4 is kept following the desired tracks, a data pattern for detecting defects is written into or read out of a magnetic disk medium with the head 3 to detect a defect in a medium. An offset setting means 16 sends an offset signal to the control means 15 so that the head 3 is shifted by a specified value from the center of the track which follows. Then, the head 3 is offset by an offset value inputted into the means 15 from the means 16 from the center of the track which the head follows. Under such a condition, the data pattern for detecting defects is written into or read out of the magnetic disk medium with the head 3 offset to detect a defect in the medium.

Description

[Detailed Description of the Invention] [Summary] Due to manufacturing problems, magnetic disk media have defects on their surfaces. These defects are detected and recorded, and data is recorded while avoiding the defect location. If the relative position of the track and data head is misaligned due to differences in the environmental conditions during use, it will be affected by this defect. Defect detection is performed by shifting.

[Industrial application field]

The present invention relates to a magnetic disk drive, and in particular, a defect detection method for a magnetic disk medium that allows defects on a magnetic disk medium used in the '6n disk drive to be detected outside the range of a trunk. Regarding.

Due to the manufacturing process, it is difficult to produce magnetic disk media without defects on the entire surface.In order to improve yield, it is necessary to detect defects, record the defect positions, and avoid using the defect positions. ing.

That is, a magnetic disk is usually composed of a plurality of magnetic disk media, and out of a plurality of recording surfaces, one recording surface is used as a servo surface to record servo information for positioning a magnetic head to a target cylinder. Therefore, the assembled magnetic disk is based on the servo information on this servo surface.
Read/write is performed for each track on each data recording surface, and when a defect in each track is detected, the read/write is performed as a skip defect within the home address set at a certain distance from the index of the corresponding track. Areas that are not written are recorded.

By the way, when using a magnetic disk on which defects have been recorded in this manner, it is necessary that there be no inconvenience even under different environmental conditions.

[Conventional technology]

FIG. 4 is a diagram illustrating the relationship between a magnetic disk and a magnetic head.

1 is a data recording surface of the magnetic disk, 2 is a servo surface, 3 is a data head for reading/writing data, 4 is a servo head for reading servo information, 5 is a cylinder for the purpose of data head 3 and servo head 4 This is a carrier positioning position.

The magnetic disk device uses a servo head 4 to read servo information recorded on a servo surface 2, detects a target cylinder based on this servo information, controls a carriage 5, and positions the data head 3 at the target cylinder.

When detecting defects in a magnetic disk medium, the carriage 5 is driven according to the servo information on the servo surface 2, the data head 3 is sequentially positioned in each cylinder, and the write and write operations on the data recording surface 1 are performed for each data track of the same cylinder. Conduct leads.

FIG. 5 is a block diagram showing an example of a medium defect detection circuit.

A test m7 is connected to the magnetic disk device 6, and a data pattern is sent from the write data sending circuit 11 to the data head 3 via the amplifier circuit 8, and written on the track of the magnetic disk.

This data pattern uses the one with the shortest magnetization reversal interval among the data patterns written in the magnetic disk device 6.

Next, this written data pattern is read out by the data head 3, and input as an analog signal from the amplifier circuit 9 to the average level detection circuit 12 and the peak value detection circuit 13.

The average level detection circuit 12 detects the average level of the data pattern written to the trunk, and detects the average level of the data pattern written to the trunk, and
The low dark value is sent to the peak value detection circuit 13.

The peak value detection circuit 13 compares the dark value with each of the peak values of the analog signal, and if there is a peak value lower than the dark value, it determines the distance from the servo head 4 to the index created by the index creation circuit IO. , the length of time that the analog signal was lower than the dark value is recorded in the file 14.

The defective data recorded in this file 14 is recorded on each track in the format shown in FIG. 5 when the magnetic disk device 6 is shipped.

FIG. 6 is a diagram illustrating an example of medium defect position recording.

For each data trunk, from the position where the index is detected, following the gap ■ where "O" is recorded, a synchronization signal ■ is recorded, and the cylinder number ■ and head number ■ for this data track are recorded. .

Subsequently, after the gap (2) in which "0#" is recorded, defect data (2) is recorded in which data indicating the medium defect position based on the distance from the index and its length is recorded.

Subsequently, a gap (2) in which "0" is recorded, an address mark (2) in which nothing is recorded, and a gap (2) in which "O#" is recorded are recorded, and the same contents as (1) to (2) are recorded in [phase].

FIG. 7 is a diagram illustrating a conventional defect detection method.

For data, D3 is writing and reading each data track 00. Therefore, defects existing in each data track within the readable range of the data node 3 can be detected.

For example, in FIG. 7, data tracks ■, ■.

The range indicated by ■ is the readable range of the data head 3, and the defect @ existing in the data track @ is the data head 3's readable range.
It can be detected by However, the data node 3
Defects (2) that exist outside the readable range cannot be detected.

[Problem that the invention aims to solve]

As mentioned above, conventionally it is possible to detect defect 0 within the range in which the data node 3 can read, but it is not possible to detect defects [phases] that exist between each data track. is not recorded as a skip defect.

Therefore, if the relative position between the data nodal 3 and the data track deviates during medium defect detection and during use due to thermal expansion of the magnetic disk medium or the arm that attaches the data head 3 to the carriage 5, for example, as shown in FIG. If the position of the node 3 shifts toward the data track ■ as shown in 3a, the defect ■ is not recorded in the home address, so the position of the node 3 shifts to the data track 0 being tracked. The problem is that this is where the data is recorded and is affected by this defect.

In view of these problems, it is an object of the present invention to make it possible to also detect defects @ and record them in the home address.

[Means for solving problems]

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

A servo track is recorded on the servo surface 2 shown in FIG. 4, and the servo head 4 reads servo information from this servo track and sends it to the control means 15.

The control means 15 detects the deviation from the center of the track followed by the servo head 4 from this servo information, and drives the carriage 5 so that this deviation is eliminated.
and move the data head 3.

Therefore, when the gutter 4 is accurately following a servo track consisting of one of the servo tracks, the gutter 3 is directed to the data track attached to the carriage 5, for example, the data track forming the same cylinder as the servo trunk. Follow the data track @ in Figure 7.

Here, as explained in FIG. 5 according to the instructions from the tester 7,
The data head 3 writes and reads the data track 7, detects the defect (2), and records it in the home address as explained in FIG.

The tester 7 instructs the offset setting means 16 to send an offset signal, and the control means 15 controls the offset setting means 16.
Since the carriage 5 is driven based on the offset I sent out by the servo head 4, the servo head 4 deviates from the center of the servo track it is following.

Therefore, the data head 3 is also shifted from the center of the data track 7. In this state, the data head 3 is caused to write and read again to detect defects and record them in the home address.

Next, by changing the polarity of the offset signal, the servo head 4 is shifted from the center of the servo track to the opposite side, and the data head 3 detects the defect in the same manner as described above.

[Effect]

The offset setting means 16 sends an offset signal to the control means 15 in response to an instruction from the tester 7 to set the data head 3.
The tester 7 can write a data pattern on the medium outside the normal track range, and detect media defects by using this data pattern. and can be recorded in the home address.

〔Example〕

FIG. 2 is a block diagram of a circuit showing an embodiment of the present invention.
FIG. 3 is a diagram illustrating the operation of FIG. 2.

The servo head 4 follows a servo track consisting of a servo surface 2 (FIG. 4) indicating the position of the target cylinder on the magnetic disk, successively outputs the servo information recorded on the servo track, and outputs the servo information recorded on the servo track to the positioning signal generation circuit 17. The signal is sent to the head position detection circuit 18.

The positioning signal generation circuit 17 generates a reference signal indicating the center position of the servo track from the servo information, and sends it to the position error detection circuit 20. Further, the head position detection circuit 18 creates a position signal for the servo head 4 from the servo information, and sends it to the position error detection circuit 20.

The position error detection circuit 20 determines the difference between the reference signal sent out by the positioning signal creation circuit 17 and the position signal sent out by the head position detection circuit 18, and drives the carriage drive circuit 21 to adjust the carriage so that the difference is eliminated. Control 5.

The tester 7 uses the data head 3 to write and read data patterns as explained in FIG. 5, and if there is a defect, it records it in a file. Therefore, as explained in FIG. 6, this defect can be recorded in the home address.

Next, the testing machine 7 gives the offset setting circuit 19 a polarity that indicates the direction of shift and instructs it to send an offset signal, and the offset setting circuit 19 adjusts the head/nod position just as if the position of the servo head 4 had shifted. An offset/offset signal is added to the position signal sent by the detection circuit 18 and sent to the position error detection circuit 20.

The position error detection circuit 20 determines that there is an error in the position of the servo head 4 by the offset amount of this offset signal, and sends a signal to the carriage drive circuit 21 to move the carriage 5.

Therefore, the data head 3 moves as much as the carriage 5 moves.
Offset from the normal data track center, for example, moving from the center of data track 0 toward the adjacent data trunk 0 or 0, as shown in FIG. 338 or 3b.

Here, the tester 7 causes the node 3 to write and read the data pattern, and if there is a defect, it records it in a file. Therefore, this defect can be recorded in the home address. Therefore, defects @ or [phase], which could not be detected conventionally, can be recorded in the home address.

〔Effect of the invention〕

As explained above, since the present invention makes it possible to detect defects adjacent to a track, it is possible to record all defects within the range where the data head may shift within the home address.

[Brief explanation of drawings]

Fig. 1 is a block diagram of the principle of the present invention, Fig. 2 is a block diagram of a circuit showing an embodiment of the present invention, Fig. 3 is a diagram explaining the operation of the second leap, and Fig. 4 is a magnetic disk. 5 is a diagram illustrating an example of a medium defect detection circuit, FIG. 6 is a diagram illustrating an example of medium defect position recording, and FIG. 7 is a conventional It is a figure explaining a defect detection method. In the figure, 1 is a data surface, 2 is a servo surface, 3 is a data head, 4 is a servo head, 5 is a carriage, 6
is a magnetic disk device, 7 is a testing machine, 8.9 is an amplifier circuit, IO is an index creation circuit, 11 is a write data sending circuit, 12 is an average level detection circuit, 13 is a peak value detection circuit, 14 is a file, 15 is Control means, 16 is offset setting means, 17 is a positioning signal generation circuit, 18 is a head position detection circuit, 19 is an offset setting circuit. figure

Claims (1)

[Claims] Control means (15) for controlling the head to follow a desired track using servo information for head positioning.
), the control means (15) causes the head to follow each track, and the head writes a data pattern for defect detection onto the magnetic disk medium and reads the data pattern. an offset setting means (16) for detecting a defect in the track and sending an offset signal to the control means (15) so that the track is shifted by a predetermined amount from the center of the track being followed; The control means (
15) The head is offset from the center of the track being followed by the offset amount input in step 15), and in the offset state, the head writes a defect detection data pattern onto the magnetic disk medium and reads the data pattern. A method for detecting defects in a magnetic disk medium, which is characterized in that defects in the medium are detected by detecting defects in the medium.