JPH0628793A - Offtrack correction system - Google Patents

Abstract

PURPOSE:To immediately execute a command from a host device even during the update of an offtrack correction quantity and to improve a processing efficiency regarding the offtrack correction system on a magnetic disk device. CONSTITUTION:A work area for at least one head is provided for storing an updated offtrack correction quantity at the time of a calibration. Also, a transfer controlling means 10A is provided for transferring all the offtrack correction quantities updated after the storing from the work area 14 to an offtrack correction table 13.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an off-track correction system in a magnetic disk device. In recent years, with the increase in capacity and speed of computer systems, there has been a demand for high-speed and large-capacity magnetic disk devices. For this reason, a magnetic disk device having a large number of disks and a high TPI is provided, but it is difficult to accurately position the track on the track only by the servo surface servo information due to tilting and whirling of the spindle, stacking deviation of the actuator, and the like. It has become to.

Therefore, it is necessary to have servo information on the data surface as well, and to perform off-track correction for each head using this data surface servo information.

[0003]

2. Description of the Related Art As a conventional off-track correction method,
For example: The data surface servo information is read by the data head from the magnetic disk having the servo surface on the outer periphery of the data surface, and the read data surface servo information is demodulated by the data surface servo demodulation circuit. And
After converting to digital signal by A / D converter,
The MPU calculates the off-track correction amount, and the off-track correction amount is stored for each head in the off-track correction table on the RAM.

The contents of the off-track correction table before execution of this calibration are shown in FIG. On the other hand, when performing calibration, seek to a cylinder with data surface servo information, read the data surface servo information, demodulate, and after A / D conversion, calculate a new offset correction amount with the MPU, and use this for the off-track correction table. To update the off-track correction amount.

That is, the off-track correction table is directly changed and updated when the calibration is executed.

[0006]

However, in such a conventional off-track correction method, when the updating work is interrupted, the off-track correction amount before the update is displayed on the off-track correction table. The remaining offset correction amounts are mixed. As shown in FIG. 7 (b),
In the head 0, the first three offset correction amounts are updated, but the rest are not updated and remain the old offset correction amount.

As described above, when the offset correction amount is discontinuous, when the instruction is executed after the off-track correction, as shown in FIG. The deviation D from the locus C becomes large, leading to read errors and write-off tracks. Therefore, when the update of the off-track correction amount is started, there is a problem that the command of the host device cannot be executed for at least one rotation until all the correction amounts for at least one head are updated.

The present invention has been made in view of the above-mentioned conventional problems, and it is possible to immediately execute a command from the host device even while updating the off-track correction amount, and improve the processing efficiency. It is intended to provide an offset correction method capable of

[0009]

FIG. 1 is a diagram for explaining the principle of the present invention. In FIG. 1, 13 is an off-track correction table for storing the off-track correction amount calculated based on the data surface servo information read by the data head 7, and 11
Is a servo head that reads servo surface servo information for performing off-track correction by adding the off-track correction amount,
14 is a work area for at least one head that stores the off-track correction amount updated at the time of calibration,
10A shows the off-track correction amount updated from the work area 14 after the storage of all the off-track correction table 13
It is a transfer control means for transferring to.

[0010]

In the present invention, the off-track correction amount at the time of executing calibration is calculated and stored in the work area,
After all the off-track correction amount for one head is obtained,
Transferred to the off-track correction table. Therefore, except when the correction amount is transferred from the work area to the off-track correction table, it is possible to prevent the old and new off-track correction amounts from being mixed in the off-track correction amounts of the same head. There is no problem because the time required to transfer the correction amount from the work area to the off-track correction table is sufficiently shorter than the seek time.

Even if the update of the off-track correction amount is stopped when a command is received from the host device during the calculation of the off-track correction amount, the off-track correction amount at the time of the previous calibration remains on the off-track correction table. Therefore, there is no discontinuity in the off-track correction amount, no read error or write-off track occurs, and the off-track correction amount can be used to execute the command based on this old off-track correction amount. In this case, calibration is executed again after the command is completed, and the off-track correction amount of the head that has not been updated is updated.

Therefore, when an instruction comes from the host device, it is possible to shorten the time until the instruction is executed. As a result, the processing efficiency can be improved.

[0013]

Embodiments of the present invention will be described below with reference to the drawings. 2 to 6 are views showing an embodiment of the present invention.
In FIG. 2, reference numeral 1 denotes a magnetic disk which is a magnetic recording medium. The magnetic disk 1 is mounted concentrically on a spindle shaft 2 and is rotated by a spindle motor 3 together with the spindle shaft 2. The spindle shaft 2 is provided on a substrate (not shown).

Of these magnetic disks 1, a servo surface 5 on which servo surface servo information is recorded is formed on one surface of the central magnetic disk 1A. Other magnetic disk 1
As shown in FIG. 3, a data surface 5 on which data information is recorded is formed on both sides thereof, and further, a servo surface (servo track) 6 on which data surface servo information is recorded is formed on the outer periphery of the data surface 5. Are formed.

A data head 7 is mounted on a VCM carriage (not shown) via a head arm (not shown). The data head 7 is position-controlled by the VCM carriage to write data information on the data surface 5 of the magnetic disk 1, and , Data information is read from the data surface 5, and data surface servo information is read from the servo surface 6.

Reference numeral 8 is a data surface servo demodulation circuit, and the data surface servo information demodulation circuit 8 demodulates the data surface servo information read by the data head 7. The demodulated data surface servo information is converted into a digital signal by the A / D converter 9 and then output to the MPU 10. MPU1
0 calculates the off-track correction amount based on the input data surface servo information. That is, each member such as the substrate, the spindle shaft 2, and the head arm that constitutes the magnetic head device is formed of several types of members having different thermal expansion coefficients, and the substrate is distorted due to a change in ambient temperature. A position shift may occur between the head 7 and the servo head 11, and the MPU 10 calculates an off-track correction amount for correcting this position shift.

Reference numeral 12 denotes a RAM. An off-track correction table 13 is provided in the RAM 12, and the off-track correction table 13 stores the off-track correction amount calculated by the MPU 10 for each head. Reference numeral 14 denotes a work area provided on the RAM 12, and the work area 14 has a capacity for storing an off-track correction amount for at least one head. The updated off-track correction amount calculated by the MPU 10 is stored in the work area 14 for each calculation,
When one head is completely stored, it is transferred to the off-track correction table 12. The MPU 10 has a function as a transfer control unit 10A that transfers the updated off-track correction amount to the off-track correction table 12.

The time required to transfer the off-track correction amount from the work area 14 to the offset correction table 12 is sufficiently shorter than the seek time. Reference numeral 15 is an AG for inputting servo surface servo information from the servo head 11.
The AGC amplifier 15 is a C amplifier and outputs the servo surface servo information with a constant amplitude. A position signal demodulation circuit 16 receives an output signal from the AGC amplifier 15. The position signal demodulation circuit 16 demodulates the servo surface servo information adjusted to have a constant amplitude and outputs the position information to the position error detection circuit 17 Output to.

In the position error detection circuit 17, the off-track correction amount from the off-track correction table 12 is D.
The position error detection circuit 17 adds the off-track correction amount to the position information and outputs it to the power amplifier 19, and the power amplifier 19 outputs the position error detection circuit. 17
Drive control of the VCM carriage based on the output of In this way, off-track correction is performed.

Next, the operation will be described. The off-track correction table 13 and the work area 14 before execution of the calibration are shown in FIG. The off-track correction table 13 stores the old off-track correction amount (0) for each head, and the content of the work area 14 is indefinite (X).

At the time of executing the calibration, the data surface servo information is read from the servo surface 6 of the magnetic disk 1 by the data head 7, demodulated by the data surface servo demodulation circuit 8 and converted into a digital signal by the A / D converter 9, An off-track correction amount to be updated is calculated based on the data surface servo information input by the MPU 10. The calculated off-track correction amount is sequentially stored in the work area 14. In this case, the offset correction amount may be calculated on the work area 14.

After all the off-track correction amounts for one head are obtained and stored in the work area 14, the updated off-track correction amount is transferred to the off-track correction table 13. FIG. 4B shows a state in which the new off-track correction amount (N) of the work area 14 is transferred to the off-track correction table 13.

Therefore, except when the off-track correction amount is transferred from the work area 14 to the off-track correction table 13, the old and new off-track correction amounts are mixed in the off-track correction amount of the same head. Can be prevented. Since the time required to transfer the off-track correction amount from the work area 14 to the off-track correction table 13 is sufficiently shorter than the seek time, the problem that old and new off-track correction amounts are mixed does not occur.

Even if the off-track update is stopped when an instruction is received from the host device during the calculation of the off-track correction amount,
As shown in FIG. 5, the work area 14 contains both new and old off-track correction amounts (N) and (0), but on the off-track correction table 13, the old off-track correction amount (0 ) Remains, it is possible to perform the off-track correction based on the old off-track correction amount (0) and execute the command.

In this case, as shown in FIG. 6, the center B of the data track and the locus C of the data head 7 do not match, but since there is no discontinuity in the offset correction amount, the center B of the data track and the data head 7 are not. Deviation E from the trajectory C
Is a constant amount, and overshoot A does not occur as in the conventional case, so that a read error or a write-off track is not caused.

Therefore, it is sufficient to perform the calibration again after the command from the higher-level device is completed, and update the off-track correction amount of the head that has not been updated yet. When an instruction is received from the host device, the instruction can be immediately executed even during the calibration, and the time until the instruction is executed can be shortened. As a result, the processing efficiency can be improved.

Although the position error detecting circuit 17 is composed of hardware, the position error may be detected by firmware. Although the RAM 12 is externally attached to the MPU 10, the internal RAM of the MPU 10 may be used. In this case, the off-track correction amount can be calculated on the work area 14.

[0028]

As described above, according to the present invention, even when the off-track correction amount is updated, the previous off-track correction amount can be used without waiting for the end of the update, and it is possible to directly use the higher-level device. The command can be executed, and the processing efficiency can be improved.

[Brief description of drawings]

FIG. 1 is an explanatory view of the principle of the present invention.

FIG. 2 is a diagram showing an embodiment of the present invention.

FIG. 3 is a diagram showing a magnetic disk.

FIG. 4 is a diagram showing an off-track correction table and a work area.

FIG. 5 is a diagram showing an off-track correction table and a work area when updating is interrupted.

FIG. 6 is a diagram showing the center of a data track and the locus of a data head.

FIG. 7 is a diagram showing a conventional off-track correction table.

FIG. 8 is a diagram showing a deviation of a center of a data track and a locus of a data head.

[Explanation of symbols]

 1, 1A: magnetic disk 2: spindle axis 3: spindle motor 4: servo surface 5: data surface 6: servo surface (servo track) 7: data head 8: data surface servo demodulation circuit 9: A / D converter 10: MPU 10A: Transfer control means 11: Servo head 12: RAM 13: Off-track correction table 14: Work area 15: AGC amplifier 16: Position signal demodulation circuit 17: Position error detection circuit 18: D / A converter 19: Power amplifier

Claims (1)

[Claims] 1. A servo surface read by a servo head (11) having an off-track correction table (13) for storing an off-track correction amount calculated based on data surface servo information read by a data head (7). In a magnetic disk device for performing off-track correction by adding the off-track correction amount to servo information, a work area for at least one head for storing the off-track correction amount updated at the time of calibration (14)
And a transfer control means (10A) for transferring the off-track correction amount updated after all storage from the work area (14) to the off-track correction table (13).
Is provided to perform off-track correction.