JP3037250B2 - Magnetic disk drive - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic disk drive, and more particularly to a highly reliable magnetic disk drive capable of reducing read / write errors caused by off-track.

[0002]

2. Description of the Related Art Conventionally, in a magnetic disk device of a data surface servo system, a sampling time for reading position information in servo information is longer than in a magnetic disk device of a servo system using a dedicated servo surface. For this reason, off-track may not be immediately detected to stop the write operation.

[0003] When the servo surface servo method is used,
Since a head for writing data and a head for reading positioning information are common, off-track may occur due to the influence of writing at the time of reading. It is becoming clear that the same phenomenon occurs when a magnetoresistive head is used for the write head and the read head, which are different from each other.

Further, in recent years, a magnetic disk drive has become smaller and smaller.
With the increase in capacity, there is a technical trend to increase the areal recording density of a magnetic disk, and the influence of off-track becomes greater due to the increase in the track recording density in the track direction along with the linear recording density in the circumferential direction of the magnetic disk. Has been
The solution of the off-track problem has become an important issue.

Conventionally, in magnetic disk devices, data has been written by confirming the address of data using an ID. However, in order to increase the recording capacity, the ID is deleted.
Less is used. ID as before
In some cases, the ID information is read before writing, and when the off-track is large, a read error occurs when reading the ID, so that off-track writing can be prevented to some extent.

As a conventional technique for preventing off-track write, in a magnetic disk drive disclosed in Japanese Patent Application Laid-Open No. Hei 8-32149, data is read immediately before writing while accelerating parameters under a condition where a data error is likely to occur. When an error occurs, an attempt is made to avoid off-track writing by determining that off-track has occurred. However, this workaround is due to mechanical causes such as resonance during seek of the positioning positioner mechanism. Off track, and after on track determination,
There is a drawback that it cannot cope with a case where the head changes during writing to cause off-track, and cannot be used when a magnetoresistive head is used with an offset between write and read.

In the magnetic disk control device disclosed in Japanese Patent Application Laid-Open No. 2-308480, offset reading is performed when an ID error occurs during writing, and off-track is determined when reading is normally performed. Although measures to write data by writing are disclosed,
This measure is effective when the magnetic disk generates off-track due to aging, but off-track write is performed for an off-track error that occurs instantaneously. There is a drawback that the data error rate is reduced, and the method cannot be applied to an ID-less magnetic disk device.

Further, in Japanese Patent Application Laid-Open No. Hei 6-236504, in order to eliminate the influence of the noise remaining after the reading at the time of reading,
A means for off-tracking the adjacent portion and writing after DC erasure is disclosed. In this means, the error rate of the written data is improved, but the error rate is reduced by the DC erasure of the adjacent data. I do. In this case, since it is necessary to save the data of the adjacent cylinder before DC erasing, there is a drawback that the data cannot be applied when the error rate is reduced over the adjacent cylinder.

[0009]

As described above, the conventional magnetic disk drive detects an off-track error and performs a data read recovery process when data is written off-track. There is a problem of causing a decrease.

[0010] It is an object of the present invention to execute, when an off-track error is detected during a write operation, a write operation again from the address before the address of the track where the off-track is detected, and as a means for recovering data of an adjacent track. An object of the present invention is to provide a magnetic disk drive in which data in an adjacent track is read and rewritten to prevent a decrease in error rate.

[0011]

According to the present invention, there is provided a magnetic disk drive comprising a magnetic disk incorporated in a disk enclosure, a magnetic head for recording and reproducing data, and a VC for reciprocating the magnetic head in a radial direction of the magnetic disk.
M (Voice Coil Motor), a read / write circuit for performing recording / reproducing processing, a spindle motor for rotating a magnetic disk, a positioning control circuit for positioning a magnetic head, a signal modulation / demodulation circuit for modulating / demodulating a signal, A disk controller for controlling the signal modulation / demodulation circuit, and a microcomputer for controlling the disk controller, means for detecting an off-track error during execution of the write operation, and rewriting data of the track on which the off-track error is detected, Read the data of the track adjacent to the track that detected the off-track error,
Error processing means for rewriting read data.

The magnetic disk is characterized in that a positioning signal for performing positioning control is recorded.

The means for detecting the off-track error during the execution of the write operation comprises a positioning control circuit for positioning the magnetic head.

The positioning control circuit includes means for detecting an off-track direction.

The positioning control circuit sends an off-track error to the microcomputer.

The error processing means reads data from at least one address before the address of the track where the off-track error is detected to the address adjacent to the address of the track where the off-track error of the adjacent track is detected. Data is rewritten.

The error processing means includes means for calculating, from the address of the track in which the off-track error is detected, an address adjacent to the address of the track in which the off-track error is detected in an adjacent track in the off-track direction. And

The microcomputer has means for calculating, from the address of the track where the off-track error is detected, an address adjacent to the address of the track where the off-track error of the adjacent track in the off-track direction is detected.

The error processing means reads data of an adjacent track in the off-track direction and rewrites the read data.

The error processing means offset-reads data of an adjacent track in the off-track direction.

The error processing means offset-reads data of an adjacent track in the off-track direction under microcomputer control.

[0022]

Next, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a schematic diagram showing an embodiment of a magnetic disk drive 20 according to the present invention.

Referring to FIG. 1, the magnetic disk drive 20
Is a magnetic disk 2 built in the disk enclosure 1, a magnetic head 3 for recording and reproducing data, and a VC for reciprocatingly driving the magnetic head 3 in the radial direction of the magnetic disk 2.
M (Voice CoilMotor) 4, a read / write circuit 5 for performing recording and reproduction processing, a spindle motor (not shown) for rotating and driving the magnetic disk 2, a positioning control circuit 6 for positioning the magnetic head 3, and a signal , A disk controller 9 for controlling the signal modulation / demodulation circuit 7, and a microcomputer 8 for controlling the disk controller 9.

The microcomputer 8 controls the positioning control circuit 6 to position the magnetic head 3 at a predetermined address in response to a data write request from a higher-level device (not shown). A positioning control signal for performing positioning control is written on the magnetic disk 2. The signal is read by a magnetic head 3, and a read / write circuit 5 and a signal modulation / demodulation circuit 7 demodulate necessary signals. The positioning control circuit 6 controls the VCM 4 based on the signal,
Is positioned on the magnetic disk 3. When the predetermined positioning is completed, the positioning control circuit 6 notifies the microcomputer 8 of the completion of the positioning.

The microcomputer 8 controls the disk controller 9 to write data to the magnetic disk 2 after the positioning is completed. The disk controller 9 sends the write data to the signal modulation / demodulation circuit 7, sends the modulated signal to the read / write circuit 5, and writes the data on the magnetic disk 2 with the magnetic head 3.

If the position to be positioned deviates from a predetermined range during data writing, the positioning control circuit 6 sends an off-track error (positioning error) to the microcomputer 8. At this time, the microcomputer 8 interrupts the write operation and performs a rewrite operation.

The microcomputer 8 executes positioning control in response to a data read request from the host device in the same manner as write, and controls the disk controller 9.

A signal read from the magnetic disk 2 by the magnetic head 3 is amplified to a predetermined amplitude by the read / write circuit 5 and sent to the signal modulation / demodulation circuit 7, which sends the signal from the read / write circuit. And sends the demodulated data to the disk controller 9. When an error occurs in the demodulated signal, the disk controller 9 performs data correction or reread operation.

Next, the operation of the magnetic disk drive 20 according to an embodiment of the present invention will be described with reference to FIG.

Referring to FIG. 2, after the magnetic head 3 is positioned at a predetermined position, the microcomputer 8 performs a data write operation. At this time, if the positioning position deviates from a predetermined range during data writing, the positioning control circuit 6 sends an off-track error to the microcomputer 8. At this time, the microcomputer 8 interrupts the write operation and performs a rewrite operation.

As described above, when an off-track error is detected during a write operation, after a write retry is performed,
The address of a track adjacent to the address at which the error was detected is calculated from the address at which writing was interrupted by detecting the positioning error and the direction of the off-track at which the positioning error was detected.

Thereafter, the microcomputer 8 controls the positioning control circuit 6
And the disk controller 9 to read data from the specified number of addresses before the address of the adjacent cylinder calculated by the above calculation to the address of the adjacent cylinder calculated by the above calculation. Is temporarily stored in a buffer (not shown). Thereafter, the held data is written to the read address. At this time, if a data error occurs during reading, a predetermined read retry is performed. In this case, as will be described later, means for reading the magnetic head while offsetting it from a predetermined positioning position is effective. After the predetermined processing is completed in the above procedure, the writing ends.

Further, a detailed description will be given with reference to FIG. 3 schematically showing the recording data state of the magnetic disk device 20 according to an embodiment of the present invention. FIG. 3 shows a recording state on the surface of the magnetic disk 2 of the magnetic disk device 20 using the data surface servo method as an example.

FIG. 3A shows a normal recording state, in which servo zones used for positioning control are continuously written in the track direction, and a data zone for storing data is provided between the servo zones. is there. There is room between each track in the data zone to reduce the effect between tracks. FIG. 3A shows an ideal state when there is no fluctuation due to a positioning error.

FIG. 3B shows a case where the data is written off-track, and the servo zone 1 of the track N + 1 is written.
Shows a state where data is written from the left side of the track and is off-track in the track N direction. In the servo zone 1, since the positioning error was equal to or smaller than the reference value, data was continuously written between the servo zone 1 and the servo zone 2. In the servo zone 2, the writing was interrupted because the positioning error exceeded the reference value. Is shown. At this time, the data between the servo zone 1 and the servo zone 2 on the track N + 1 is written at a position shifted from the position where the data should be actually written. In this state, the data error rate deteriorates. Therefore, rewriting is usually performed.

FIG. 3C shows the state after the rewriting has been performed. The error rate of the data part for which the write retry has been performed is recovered. Normally, this ends normally, but in this case, the track N +
Since data off-track from 1 remains, the error rate of this part of the data is reduced. Therefore, the data area is rewritten. Here, in order to rewrite the data, first, the written data is read. Usually, the error rate is reduced due to off-track writing. Therefore, when a read error occurs, as shown in FIG. 3C, the read head is offset and read as recovery means. The error rate is good in the track N + 1 direction because the influence of the adjacent cylinder is small. When a magnetoresistive head is used as a read head, the read head is particularly effective because it is usually smaller than the write track width. FIG. 3D shows a state when the track N is rewritten. FIG.
As is apparent from FIG. 3D, the state is equivalent to the ideal state in the case where there is no variation due to the positioning error shown in FIG. 3A, and there is an effect that the reduction of the error rate can be completely prevented. .

For reference, when the above-described read error recovery means is not implemented, a case may be considered in which off-track writing is performed from track N-1. This state is shown in FIG. In this case, data is off-track written from both sides of the adjacent cylinder,
Reducing the error rate significantly can be seen in FIG.
It is clear from (e).

As described above, as apparent from FIG. 3D, when an off-track error is detected during execution of the write operation, the write operation is performed again from the address before the address of the track where the off-track is detected. In addition, as a means for recovering data of an adjacent track, by reading data of an adjacent track and performing rewriting, it is possible to obtain a magnetic disk device in which a decrease in an error rate is prevented.

In one embodiment of the present invention described above,
If an error retry occurs when an off-track error is detected, re-writing is performed after reading the data of the adjacent track.If it is clear that the data is continuously written in advance and the adjacent track is overwritten, Needless to say, even if this processing is not performed, the same effect can be obtained.

[0041]

The first effect is that the data recovery processing which is expected to be affected by the off-track immediately after the occurrence of the off-track error is performed, so that the error rate can be prevented from lowering and the data cannot be read. This has the effect of improving the situation.

The second effect is that the influence of the error rate on the positioning error can be reduced, so that the track pitch can be reduced by the effect and the storage capacity of the magnetic disk device can be increased.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing one embodiment of a magnetic disk drive of the present invention.

FIG. 2 is a diagram showing an operation flow of an embodiment of the magnetic disk drive of the present invention.

FIG. 3A is a diagram showing a normal recording state of the magnetic disk drive of the present invention. FIG. 3B is a diagram showing a recording data state at the time of off-track write of the magnetic disk device of the present invention. FIG. 3C is a diagram showing a state of recording data after a write retry of the magnetic disk device of the present invention. FIG. 3D is a diagram showing a recording data state when a track adjacent to the off-track track of the magnetic disk device of the present invention is rewritten. FIG. 3E is a reference diagram showing a recording data state in the case where the center track is not rewritten when both of the adjacent tracks are off-track write.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Disk enclosure 2 Magnetic disk 3 Magnetic head 4 VCM 5 Read / write circuit 6 Positioning control circuit 7 Signal modulation / demodulation circuit 8 Microcomputer 9 Disk controller 20 Magnetic disk device

Claims (11)

(57) [Claims] 1. A magnetic disk incorporated in a disk enclosure, a magnetic head for recording and reproducing data, and a VCM (Voice Coil Motor) for reciprocating the magnetic head in a radial direction of the magnetic disk.
A read / write circuit for performing recording / reproducing processing, a spindle motor for rotatingly driving the magnetic disk, a positioning control circuit for positioning the magnetic head, a signal modulation / demodulation circuit for modulating / demodulating a signal, and controlling the signal modulation / demodulation circuit Means for detecting an off-track error during execution of a write operation, rewriting data of the track on which the off-track error has been detected, and detecting the off-track error. An error processing means for reading data on a track adjacent to the detected track and rewriting the read data; 2. The magnetic disk drive according to claim 1, wherein a positioning signal for performing positioning control is recorded on the magnetic disk. 3. The means for detecting an off-track error during execution of a write operation comprises the positioning control circuit for positioning the magnetic head.
The magnetic disk device according to the above. 4. The magnetic disk drive according to claim 1, wherein said positioning control circuit includes means for detecting an off-track direction. 5. The magnetic disk drive according to claim 1, wherein the positioning control circuit sends an off-track error to the microcomputer. 6. The error processing means according to claim 1, wherein at least one address before an address adjacent to an address of a track adjacent to the track on which the off-track error is detected and an address adjacent to the address of the track on which the off-track error is detected is written. 2. The magnetic disk drive according to claim 1, wherein the data is read and the read data is rewritten. 7. The error processing means includes means for calculating, from an address of a track in which an off-track error has been detected, an address adjacent to an address of a track in which an off-track error has been detected in an adjacent track in the off-track direction. 7. The magnetic disk drive according to claim 1, wherein: 8. The microcomputer according to claim 1, wherein the microcomputer calculates, from an address of the track on which the off-track error is detected, an address adjacent to the address of the track on which the off-track error of the adjacent track in the off-track direction is detected. The magnetic disk drive according to claim 1, 6 or 7, wherein 9. The magnetic disk drive according to claim 1, wherein the error processing means reads data of an adjacent track in an off-track direction and rewrites the read data. 10. The magnetic disk drive according to claim 1, wherein said error processing means offset-reads data of an adjacent track in an off-track direction. 11. The magnetic disk drive according to claim 1, wherein said error processing means offset-reads data of an adjacent track in an off-track direction under microcomputer control.