JPH10255411A - Servo control method and magnetic disk drive - Google Patents

Abstract

(57) [Problem] To improve the yield of the HDA and relieve an unrecoverable error of a write fault during use by a user as a recoverable error in a retry operation. SOLUTION: Each servo information section on a medium is sequentially read, and it is determined whether or not there is an abnormality in the read servo information section, for example, an abnormality due to a medium defect in a burst section. If a write fault occurs while writing data, the AM section of the servo information section with the error is checked, the error occurrence location is confirmed and registered in the registration memory, the data is written again, and the write fault occurs again. When an error occurs, the location of the error is checked and compared with the contents of the registration memory, and if they match, the sampling process is not performed on the servo information portion at the location of the error.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a servo control method and a magnetic disk drive for making it possible to use a medium having a defect in a servo information portion, and to avoid writing failure due to an abnormal position signal.

[0002]

2. Description of the Related Art As a servo control system in a recent magnetic disk drive, an embedded servo system in which a servo information portion is embedded between data portions as shown in FIG. 1 is mainly used. The servo information section is written in hundreds of thousands of places on the entire disk surface and occupies an area of 3 to 4% of the entire surface. There are hundreds of media defects on the entire surface that affect servo information.
More than a dozen places may hit the servo information section.

FIG. 2 is an enlarged view of a servo information section. AM
(Address mark) section, Gray code section, and burst section. AM section is a section in which the gray code and reference timing for burst acquisition are recorded. The Gray code records physical position information on the disk. The burst is a portion used to generate a position signal indicating the amount of deviation from the on-track position (the amount of off-track). When a media defect hits each point, A
M error, gray code failure, and position signal abnormality due to burst abnormality occur, and cause a seek error.

An HDA (head disk assembly) on which servo information is written by a servo track writer (a facility for writing servo information on a disk) is subjected to a seek operation test by a servo information tester, and a seek error (AM). The availability is determined based on the occurrence of AM error due to abnormality, gray code failure due to gray code bit abnormality, and position signal output abnormality due to burst part abnormality. Conventionally, an HDA with a seek error
Had performed a disc replacement regeneration process as all defective. However, in the case of an AM mistake, a seek error occurs when a plurality of locations occur consecutively. However, in the case of only one location, there is a remedy that the servo information of the servo information section is not used and control is performed by referring to the immediately preceding servo information. Had been taken.

[0005]

Recently, MR (MAGNETO REISTIVE) heads have been used in magnetic disk devices, and the recording density has been rapidly increased and the track interval has been reduced. For this reason, even a minute defect that has not conventionally affected servo information has become a level that cannot be ignored in the occurrence of abnormal servo information. Therefore, the ratio of failure during the seek operation test and the product inspection test is high, and the yield of HDA is low. Also, M
R-head specific TA (THERMAL ASPERITY) and TA
Later defects also occur due to marks, film peeling, and the like.

If a defect occurs in the burst portion of the servo information, the position signal becomes abnormal and writing becomes impossible (hereinafter, write fault) due to a large amount of positional deviation. Depending on the degree of the defect, a reproducible write fault occurs.
Even a retry operation in which a write operation is repeated again cannot be remedied, resulting in an unrecoverable error. Further, if an unrecoverable error occurs during use by a user, the system will fail and the magnetic disk device will be replaced as an important failure of the magnetic disk device. SUMMARY OF THE INVENTION It is an object of the present invention to improve the yield of HDA and to relieve an unrecoverable error of a write fault during use by a user as a recoverable error in a retry operation.

[0007]

In order to achieve the above object, the present invention provides a servo control method in a magnetic disk drive for generating a position signal based on servo information written on a medium surface and performing positioning control. Each of the servo information sections on the medium is sequentially read, and it is determined whether or not the servo information of the read servo information section is abnormal. If it is determined that there is an abnormality, one of the servo information sections having the abnormality is determined. The section information is deleted.

A servo control method in a magnetic disk drive for generating a position signal based on servo information written on a medium surface and performing positioning control. When a write fault occurs during a data write operation,
The location of the error on the medium surface is checked, the location of the error is registered in the registration memory, data is written again, and when a write fault occurs again, the location of the error on the medium surface is checked. Compare the location of the error and the contents of the registration memory, and when the comparison result matches,
Sampling processing is not performed on the servo information portion at the location where the error has occurred.

Further, in a magnetic disk drive which generates a position signal based on servo information written on a medium surface and performs positioning control, there is an abnormality in servo information of each servo information portion on the medium which is sequentially read. Means for determining whether or not there is an error, and means for erasing a part of the information in the abnormal servo information section when it is determined that there is an error.

In a magnetic disk drive for generating a position signal based on servo information written on a medium surface and performing positioning control, when a write fault occurs during a data write operation, an error on the medium surface may occur. Confirmation means for confirming the location, means for registering the error occurrence location confirmed by the confirmation means in a registration memory, and instructing data writing again, and when a write fault occurs again in data writing again. Comparing means for comparing the error occurrence location on the medium surface confirmed by the confirmation means with the contents of the registration memory; and when the comparison result by the comparison means matches, the error occurrence location is compared with the servo information portion. A means for stopping the sampling process is provided.

[0011]

FIG. 3 shows the configuration of an embodiment of a magnetic disk drive to which the present invention is applied. The magnetic disk drive includes a plurality of disks on which servo information and data are written, a spindle motor mounted with the disks and rotating, a plurality of heads for recording / reproducing information, a R / W IC, and a circular head. Carriage to move on board, VCM
(Voice coil motor), an HDA (head disk assembly), a spindle motor driver 1, and V
A CM driver 2, an R / W channel 3, a drive control circuit 7 including an R / W control circuit 4, a servo control circuit 5, a servo microcomputer 6, and a SCSI control circuit 8 for controlling commands from a host controller are mounted. It is composed of a PCB (package board). As shown in FIG. 1, servo information is recorded on the entire disk surface of the HDA by a servo track writer in advance. The servo information is reproduced by the head, and as a read output signal R
After being amplified by the / W IC, it is input to the R / W channel 3. The servo information shaped by R / W channel 3 is
It is input to the servo control circuit 7. Position information (AM part, gray code) is detected by a servo data detector 9 in the servo control circuit 7 and output to the servo microcomputer 6, and positional deviation information is detected by a peak hold circuit 10 and A / D converted. Output to the servo microcomputer 6. The servo microcomputer 6 controls the VCM driver 2 based on the positional information and the positional deviation information, and performs a servo seek operation and a following control. Further, a write fault determination during a write operation is performed based on a position signal based on the positional deviation information.

A description will now be given of "AM crush relief" which is an embodiment of the present invention for improving the yield of HDA. AM crush relief is performed during the HDA manufacturing stage. A
The M busting remedy utilizes the fact that in the remedy of the prior art, when an AM error occurs, the servo information of the servo information section is not used and control is performed with reference to the servo information of the immediately preceding servo information section. In other words, the AM crush repair means crushing, that is, erasing, the AM portion of the servo information portion in which a defect has occurred, thereby causing an AM mistake. The AM crushing is performed when the servo microcomputer 6 determines that there is an abnormality in the servo information section read by the servo microcomputer 6 based on the position information (AM section, gray code) and the position shift information input from the servo control circuit 5. Generates an erase signal, outputs the erase signal to the R / W control circuit 4, and under the control of the R / W control circuit 4, is performed by crushing the AM section of the servo information section in which the abnormality has occurred. .

FIG. 4 shows a conceptual diagram of the AM crushing process.
It counts up from the time of occurrence of the servo sector pulse created based on the servo information in the normal servo information section, and
When the timing of the AM section of the servo sector to be crushed is reached, an erase signal is output from the servo microcomputer 6 to the R / W control circuit section 4. Based on the erase signal, the R / W control circuit unit 4 stops the data and performs a write operation to erase the AM unit.

FIG. 5 shows an example of the servo information section subjected to the AM crush processing. This example shows a case where there is a medium defect in the burst section of the servo information section.
Since the M part is erased and the AM part cannot be detected,
The position information by the gray code and the position shift information by the burst signal of the present servo information section cannot be acquired, and the information of the servo information section immediately before normal is used.

The defect servo information portion to be subjected to AM crushing is determined by the error content of the test result at the manufacturing stage, and is executed by manual intervention. Further, it is possible to automatically perform the determination during the test by setting the condition for determining the defective sector in the program of the servo microcomputer.

Next, an embodiment of "servo information unnecessary remedy" for relieving an unrecoverable error of a write fault during use by a user will be described below. The above-mentioned “AM crush relief” is applicable at the manufacturing stage, but is not a process that can be executed during user use after shipment. Even after shipment, late defects and T.V. A causes servo information failure.

FIG. 6 shows an abnormal position signal due to a defect in the burst portion. The level of the position signal changes for each servo information section. In the case of FIG. 6, the servo information is defective at one location, but the position signal is abnormal at several locations due to the transient response. During a write operation due to a position signal abnormality, the off-track write inhibition threshold is exceeded and a write fault occurs. No matter how many times the write operation is repeated in this state (usually a retry operation is performed for an error in a magnetic disk device), a write fault occurs. Will be. The "servo information unnecessary remedy" means that when a write fault occurs during a data write operation, the location of the error occurrence is checked and stored, and when a write fault occurs again during the retry operation, the error occurs at this time. Check the location and determine if a servo information failure has occurred at the same location as the memorized error location, and if a servo information failure has occurred at the same location, In this case, the sampling process is stopped and the defective servo information is ignored, thereby preventing the occurrence of the position signal abnormality and terminating the writing operation normally.

FIG. 8 shows a detailed sequence of the servo information unnecessary repair processing. When the data write operation starts (801), it is determined that a write fault has occurred in the data write operation (802). If no write fault has occurred, the process ends normally. If there is, a retry mode is entered and the retry mode is set ( 803), the number of retries N is set to 0 (804). The upper limit of the number of retries is set to M in advance. Next, the value of the registration memory (memory for setting the error sector in which the servo information section is abnormal) is reset (805). Next, the number of retries N is checked (806), and if it is determined that the number of retries N is equal to or greater than the set number M, the retry mode is reset (807) and reported as abnormal termination (unrecoverable error). . When it is determined that the number of retries N has not reached the set number of times M, a data write operation is performed again (808), and 1 is added to the number of retries N (809). Then, the occurrence of a write fault is determined (8
10) If it is determined that a write fault has not occurred, a retry mode is set (811), and a normal termination (recoverable error) is reported. If it is determined that a write fault has occurred, an error occurrence location is confirmed (812). It is determined whether or not the confirmed error occurrence location and the value set in the registration memory are the same (813). If it is determined that they are not the same, the error occurrence location is set in the registration memory (813). 81
4) Retry. That is, the process returns to the step of checking the number of retries N (806). If it is determined that the error location is the same as the value in the registration memory, servo information unnecessary processing (815) for stopping sampling of the servo information at the error location is performed, and then a retry is performed.

FIG. 7 shows a position signal when a servo information unnecessary process is performed on the servo information portion where the abnormal position signal shown in FIG. 6 has been generated. Since the sampling of the defective servo information section is stopped, the position signal abnormality at the defective servo information section does not occur, and no subsequent transient response occurs. Therefore, the rewrite operation is successfully completed and reported as a recoverable error.

[0020]

According to the present invention, a medium defect occurring in the servo information section can be tolerated, and the yield of HDA can be improved. Further, an unrecoverable error caused by a medium defect and a TA of the MR head can be remedied as a recoverable error.

[Brief description of the drawings]

FIG. 1 is a diagram showing servo information written on a disk in an embedded servo system.

FIG. 2 is an enlarged view of a servo information section.

FIG. 3 is a block diagram illustrating a configuration of a magnetic disk drive.

FIG. 4 is a conceptual diagram of an AM crushing process.

FIG. 5 is an enlarged view of a servo information section after AM crush processing.

FIG. 6 is a diagram showing an example of an abnormal position signal waveform due to a defect in a burst section.

FIG. 7 is a diagram showing an example of a position signal waveform after performing servo information unnecessary relief processing;

FIG. 8 is a diagram showing a detailed sequence of a servo information unnecessary relief process.

[Description of Signs] 1 Spindle motor driver 2 VCM driver 3 R / W channel 4 R / W control circuit 5 Servo control circuit 6 Servo microcomputer 7 Drive control circuit 8 SCSI control circuit 9 Servo data detector 10 Peak hold circuit

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI G11B 19/04 501 G11B 19/04 501D 21/10 21/10 W (72) Inventor Katsuhiro Tsuneda 2880 Kozu, Kozu, Odawara-shi, Kanagawa Stock Within Hitachi Storage Systems Division

Claims (4)

[Claims] 1. A servo control method in a magnetic disk drive for generating a position signal based on servo information written on a medium surface and performing positioning control, wherein each servo information portion on a medium is sequentially read out. A servo control method comprising: determining whether there is an abnormality in the read servo information of the servo information section; and, when it is determined that there is an abnormality, erasing a part of the information of the abnormal servo information section. . 2. A servo control method in a magnetic disk drive for performing position control by generating a position signal based on servo information written on a medium surface, wherein a write fault occurs during a data write operation. The error location on the medium surface is checked, the error location is registered in the registration memory, data is written again, and when a write fault occurs again, the error location on the medium surface is checked. A servo control method comprising: comparing the error occurrence location with the contents of the registration memory; and, when the comparison result matches, does not perform the sampling process on the servo information portion of the error occurrence location. 3. In a magnetic disk drive for generating a position signal based on servo information written on a medium surface and performing positioning control, there is an abnormality in servo information of each servo information portion on the medium which is sequentially read. A magnetic disk drive comprising: means for determining whether or not there is an abnormality; and means for erasing a part of information of the abnormal servo information section when it is determined that there is an abnormality. 4. A magnetic disk drive for generating a position signal based on servo information written on a medium surface and performing positioning control when an error on the medium surface occurs when a write fault occurs during a data write operation. Confirmation means for confirming the location, means for registering the error occurrence location confirmed by the confirmation means in the registration memory, and instructing rewriting of data, and when a write fault occurs again in rewriting of data. Comparing means for comparing the error occurrence location on the medium surface confirmed by the confirmation means with the contents of the registration memory; and when the comparison results by the comparison means match, the error occurrence location is compared with the servo information portion. A magnetic disk drive comprising means for stopping a sampling process.