JP2665695B2 - 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 magnetic disk drive capable of canceling off-track over the entire circumference of a disk to prevent a magnetic head from being shifted from a specified position and causing a reading error.

[0002]

2. Description of the Related Art Conventionally, a magnetic disk device has been used as a device for reading and writing information from a magnetic disk in which a magnetic head rotates at a high speed. As shown in FIG. 7, the magnetic disk device includes a magnetic disk 1, a motor 4 for rotating the magnetic disk, a dedicated magnetic head 2 for positioning the magnetic disk at a target cylinder, and a positioning control circuit for controlling the positioning of the magnetic disk. 5 and a plurality of magnetic heads 3 for reading and writing data on the magnetic disk
A head selection circuit 6 for selecting one magnetic head from the magnetic heads; a read / write circuit 7 for controlling data read / write; and a positioning control circuit 5
And a control circuit 8 for controlling the read / write circuit 7.

As described above, the magnetic head includes a positioning dedicated head 2 and a plurality of data heads 3 for reading and writing information.
There is. As shown in FIG. 5, the data head is positioned at the target cylinder by the positioning head, but the shaft 12 of the motor is tilted due to a temperature change or some other cause, and the upper head causes off-track on the inner peripheral side, and the lower head Causes off-track on the outer peripheral side. In addition, since the inner cylinder and the outer cylinder also cause off-track due to the position shift of the positioner 11, when reading,
Reading may be poor. There is also a sector servo system in which the data surface is divided into sectors in order to avoid such off-track reading defects, and a part of the data surface is used as positioning information to cancel the positional deviation between the magnetic head 3 and the target cylinder.

[0004]

However, the above-mentioned conventional magnetic disk drive has no means for canceling such a positional shift, and has a drawback that information is read poorly and cannot be read even when rereading is performed. Was. Also,
There is also a sector servo system that divides the data surface into sectors and writes positioning information in a part of it to perform positioning.However, the format of the data to be read / written is fixed length, which limits the model of the host device. There is a disadvantage that the amount of data information is reduced because the positioning information is written.

[0005]

A magnetic disk drive according to the present invention includes a plurality of magnetic disks having a plurality of cylinders provided concentrically, and a plurality of magnetic disks corresponding to the plurality of magnetic disks on a one-to-one basis. A magnetic head, a control circuit for performing overall control, a read / write circuit for performing a read / write operation on the magnetic disk with the magnetic head under the control of the control circuit, and selecting an arbitrary head from the plurality of magnetic heads A head selection circuit, an off-track amount cancellation circuit for measuring an off-track amount and calculating off-track amount cancellation information from an output of the head selection circuit and control of the control circuit, and an off-track amount cancellation circuit. A positioning control circuit for moving the selected magnetic head to a target position by output and control from the control circuit. Path, the off-track amount canceling circuit includes an inner check cylinder and an outer check cylinder that sandwich the cylinder in which the magnetic head currently exists from among the plurality of concentrically provided cylinders. And calculating the off-track amount of the cylinder where the magnetic head is present from the off-track amount measured at a plurality of measurement points provided at equal intervals in one circumference of each check cylinder.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram of a magnetic disk drive according to an embodiment of the present invention, FIG. 2 is a block diagram of an off-track amount canceling circuit 1 as a main part of the embodiment, and FIG. 6 is an operation flowchart for measuring a track amount. FIG. 4 is a schematic diagram showing a relationship between a special check cylinder for measuring an off-track amount on a magnetic disk surface and a data zone for recording information, and FIG.
FIG. 3 is a schematic diagram showing an exemplary trajectory of a head in which an off-track amount of a target cylinder is canceled by two check cylinders.

The embodiment of FIG. 1 shows a magnetic head 3, a positioning control circuit 5, a head selection circuit 6, a read / write circuit 7, an off-track amount cancel circuit 1, a read / write circuit 7, and an off-track amount cancel. Circuit 1
And a control circuit 8 for controlling the positioning control circuit 5.

Next, the operation of this embodiment will be described. The control circuit 8 always monitors the access state from the host device 9 when the magnetic disk device is initialized, and instructs the off-track amount cancellation circuit 1 to measure the off-track amount when there is no access for a certain period of time. The control circuit 8
Causes the read / write circuit 7 to perform a read or write operation when a data read or write command is received from the host device 9. Further, the control circuit 8 sends a seek command to the positioning control circuit 5 and, at that time, also sends information on the currently accessed head and cylinder to the off-track amount cancel circuit 1. The off-track amount canceling circuit 1 measures the off-track amount according to a command from the control circuit 8, and sends an offset voltage to the positioning control circuit 5 as information for canceling the off-track amount based on the measured data during a seek operation. The positioning control circuit 5 positions the head to the target cylinder in accordance with a command from the control circuit 8. Further, the head misalignment is corrected based on the information of the off-track amount cancel circuit 1.

Next, the configuration and operation of the off-track amount cancel circuit will be described with reference to FIG. First, the configuration is memory 1A
, A CPU 1B, an amplitude measurement circuit 1C, and an offset control circuit 1D. This operation will be described separately in terms of (1) and (2).

(1) The CPU 1B measures the off-track amount from two cylinders, the inner check cylinder and the outer check cylinder, which are closest to the cylinder positioned by a command from the control circuit 8. In order to measure the off-track amount, the amplitude measuring circuit 1C and the offset control circuit 1
Send command to D. The inner and outer check cylinders are prepared for each head, and there are measurement points at which one circumference is divided into n, and data is written in advance to the measurement points in the disk device. This number of measurement points can be set arbitrarily. Amplitude measurement circuit 1C
Is a circuit for measuring the amplitude voltage at the measurement point. The memory 1A stores a program for the CPU 1B and various data such as an off-track amount. The offset control circuit 1D is a circuit for sending an offset amount to the positioning control circuit 5 in order to detect a position where the amplitude of the measurement point is maximum.

Next, the operation flow of the CPU 1B will be described with reference to the flowchart of FIG. First, the head is positioned on the inner check cylinder (step 21).
Next, a head is selected (step 22). The head is
Selected in order from youngest. Next, the position of a point obtained by dividing the circumference of the cylinder by n is measured (step 23).
In the measurement, the offset amount is output from the offset control circuit 1D to the positioning control circuit 5 in accordance with a command from the CPU 1B to move the head by a very small distance, and the offset amount when the output voltage of the head becomes maximum is obtained. The offset amount at that time is stored in the memory 1A as the off-track amount.
Here, the control range of the offset amount is from the positioning position to plus or minus 1/2 cylinder. The output voltage of the head is measured by the amplitude measuring circuit 1C.
Next, it is confirmed whether or not all the measurement points have been completed (step 24). If it has been completed, proceed to the next step. Points are incremented from the first point to the last point. Next, it is checked whether an interrupt has occurred from the control circuit 8 (step 25). If no interrupt has occurred, proceed to the next step. Next, it is confirmed whether the measurement has been performed for all the heads (Step 2).
6). Next, the head is positioned on the outer check cylinder (step 27). Step 28 to Step 32
Are the same as steps 22 to 26 of the inner check cylinder. If steps 25, 31
When the interrupt is confirmed from the control circuit 8, the measurement is immediately stopped, the current state is saved, and the processing is terminated (step 3).
3). Then, upon receiving a re-measurement command from the control circuit 8, the control circuit 8 restarts from the continuation by referring to the stored previous state.

(2) The CPU 1B cancels off-track according to a command from the control circuit 8, but first sends a target cylinder number to the CPU 1B when executing a seek operation.
The CPU 1B converts the off-track amount cancellation data of the target cylinder into the next off-track amount from the off-track amount stored in the memory 1A in advance based on the target cylinder number.
It is obtained from equation (1). Here, symbols e1 to e5 represent the following off-track amount and the number of cylinders.

E1-the off-track amount of the inner check cylinder, e2-the off-track amount of the outer check cylinder,
e3-number of cylinders from the inner check cylinder to the target cylinder, e4-number of cylinders from the inner check cylinder to the outer cylinder, e5-off-track amount of the target cylinder, e5 = e1- {e3 (e1-e2) / e4}. (1) Here, the expression (1) is a calculation expression at one point. The obtained data is input to the offset control circuit 1D and stores data for the number of points in one round. The offset control circuit 1D outputs the stored data for the number of points in one round to the positioning control circuit 5 at any time in synchronization with the motor rotation speed. FIG. 6 shows an off-track amount e1 measured by the inner check cylinder and an off-track amount e2 measured by the outer check cylinder to calculate the off-track amount e5 of the target cylinder from equation (1) and cancel it. FIG. 9 illustrates an exemplary head trajectory e6 in which off-track does not occur.

[0015]

As described above, according to the present invention, the provision of the off-track amount canceling circuit enables the off-track to be canceled over one round of the disk. Therefore, there is an effect that data can be stably read without causing a catastrophic failure in which a magnetic head deviates from a specified position due to a temperature difference or some cause to cause a reading error.

[Brief description of the drawings]

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

FIG. 2 is a block diagram of an off-track cancel circuit as a main part of the embodiment.

FIG. 3 is an operation flowchart of a main part of the embodiment.

FIG. 4 is a schematic diagram of a magnetic disk surface according to the present embodiment.

FIG. 5 is a schematic diagram showing an example in which general off-track occurs.

FIG. 6 is a schematic diagram illustrating a trajectory of off-track cancellation according to the embodiment.

FIG. 7 is a block diagram of a conventional magnetic disk drive.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Off-track amount cancellation circuit 2 Positioning-dedicated head 3 Magnetic head 4 Motor 5 Positioning control circuit 6 Head selection circuit 7 Read / write circuit 8 -Control circuit 9 Host device 1A Memory 1B CPU 1C Amplitude measurement circuit 1D Offset control circuit

Claims (2)

(57) [Claims] 1. A plurality of magnetic disks having a plurality of cylinders provided concentrically, a plurality of magnetic heads corresponding to the plurality of magnetic disks on a one-to-one basis, and a control circuit for performing overall control. A read / write circuit for performing a read / write operation on the magnetic disk with the magnetic head under the control of the control circuit, a head selection circuit for selecting an arbitrary head from the plurality of magnetic heads, and an output of the head selection circuit An off-track amount canceling circuit for measuring the off-track amount and calculating the off-track amount canceling information from the control of the control circuit, and an output of the off-track amount canceling circuit and a target position by the control from the control circuit. A magnetic disk drive comprising a positioning control circuit for moving the selected magnetic head, The off-track amount canceling circuit selects an inner check cylinder and an outer check cylinder sandwiching the cylinder in which the magnetic head currently exists from among the plurality of concentrically provided cylinders, and selects the inner check cylinder and the outer circumference of each check cylinder. A magnetic disk drive which calculates an off-track amount of a cylinder in which a magnetic head currently exists, from an off-track amount measured at a plurality of measurement points provided at equal intervals. 2. A plurality of magnetic disks having a plurality of cylinders provided concentrically, a plurality of magnetic heads corresponding to the plurality of magnetic disks on a one-to-one basis, and a control circuit for performing overall control. A read / write circuit for performing a read / write operation on the magnetic disk with the magnetic head under the control of the control circuit, a head selection circuit for selecting an arbitrary head from the plurality of magnetic heads, and an output of the head selection circuit An off-track amount canceling circuit for measuring the off-track amount and calculating the off-track amount canceling information from the control of the control circuit, and an output of the off-track amount canceling circuit and a target position by the control from the control circuit. A magnetic disk drive comprising a positioning control circuit for moving the selected magnetic head, The amount of off-track was measured and stored in advance when performing initialization control of the magnetic disk device and when there was no access from an external host device, and was stored when performing a seek operation by access from the host device. A magnetic disk drive wherein an off-track amount at a target position is automatically calculated based on information, and the off-track amount is canceled when a seek operation is completed.