JPH06208770A - Off-track canceling system for magnetic disc unit - Google Patents

Abstract

PURPOSE:To prevent read error by canceling previously measured and stored off-track of a magnetic head from a target track due to temperature difference automatically during seek operation. CONSTITUTION:A control circuit 8 controls a positioning circuit 5, a read/write circuit 7, and an off-track cancel circuit 10 based on temperature information received from a temperature monitor circuit 11 and an instruction received from a host unit 9. The circuit 10 measures off-track amount at each measuring point determined by dividing the circumference of two check cylinders, to which a cylinder to be positioned approaches, equally into (n) sections and then stores the measurement data in a memory. Based on the data thus measured, the circuit 10 delivers information for canceling the off-track to the circuit 5 which then seeks and positions a magnetic head 3 at a target cylinder thus correcting positional shift of the head 3. This constitution prevents read error due to positional shift of the head 3 caused by temperature difference and the like.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an off-track amount canceling method for a magnetic disk device, and more particularly between a magnetic head and a cylinder when the magnetic disk device is initialized and when a certain temperature difference occurs in the magnetic disk. The present invention relates to an off-track amount canceling method for a magnetic disk device that automatically cancels the off-track amount that occurs in one round of the magnetic disk.

[0002]

2. Description of the Related Art A magnetic disk device is used as a device in which a magnetic head reads / writes information from / to a magnetic disk rotating at high speed.

As shown in FIG. 8, this magnetic disk device includes a magnetic disk 1, a motor 4 for rotating the magnetic disk 1 at high speed, and a magnetic head 2 for exclusive use in positioning for positioning the magnetic disk 1 on a target cylinder. , A positioning control circuit 5 for performing positioning control, a plurality of magnetic heads 3 (represented by one in FIG. 8) for reading / writing data on the magnetic disk 1, and one magnetic head among the plurality of magnetic heads 3. Head selection circuit 6 for selecting a head
And a read / write circuit 7 for controlling data read / write, and a control circuit 8 for controlling the positioning control circuit 5 and the read / write circuit 7.

The plurality of magnetic heads 3 positioned on the target cylinder by the positioning-only head 2 may cause relative positional deviation with the target cylinder due to a temperature change or some cause, resulting in a data read failure. There is.

There is also a sector servo system in which the data surface is divided into sectors and a part of the data is used for positioning information to cancel the positional deviation between the magnetic head 3 and the target cylinder.

[0006]

Generally, there are a magnetic head dedicated to positioning and a plurality of data heads for reading and writing information as magnetic heads.

The data head is positioned on the target cylinder by a magnetic head dedicated to positioning, but as shown in the example of FIG. 6, the motor 4 is affected by temperature changes or some cause.
The upper head causes off-track on the inner circumference side, and the lower head causes off-track on the outer circumference side.

Further, due to the position shift of the positioner P, the inner cylinder and the outer cylinder also cause off-track, which may cause a reading failure.

However, the conventional magnetic disk device is
There is a fatal defect that it does not have the function of canceling such a positional deviation, it becomes a reading failure of information, and it cannot be read even if rereading.

There is also a sector servo system in which the data surface is divided into sectors and the positioning information is captured in part of the data for positioning, but the format of the data to be read and written is fixed length, and the model of the host device is restricted. Since the positioning information is written on the data surface, there is a drawback that the amount of data information is reduced accordingly.

The object of the present invention is to eliminate the above-mentioned drawbacks, to automatically calculate the off-track, and to cancel the off-track amount by the completion of the seek operation without compressing the information amount. It is to provide an off-track amount canceling method.

[0012]

According to the off-track amount canceling method of a magnetic disk drive of the present invention, at least two check cylinders for checking are provided for each head, and one round is divided at equal intervals for each check cylinder. A plurality of measurement points are provided to measure the off-track amount of the positional deviation between the target cylinder and the magnetic head in advance when the magnetic disk device is initialized and when a constant temperature difference occurs in the magnetic disk. When the seek operation is performed by access from the device, the offset amount canceling means is provided for automatically canceling the off-track amount when the seek operation is completed based on the off-track amount.

Further, in the off-track amount canceling method of the magnetic disk device of the present invention, a control circuit for performing various control operations under the control of the host device, and reading and writing of the magnetic head based on the instructions of the control circuit. Read / write circuit, a head selection circuit for selecting an arbitrary magnetic head from a plurality of magnetic heads, and measurement of the off-track amount or the off-track based on the output of the head selection circuit and the instruction of the control circuit. An off-track amount canceling circuit for calculating information for canceling the amount, a positioning control circuit for positioning a magnetic head on a target cylinder based on an output of the off-track amount canceling circuit and an instruction from the control circuit, and a magnetic disk A temperature monitoring circuit that detects a certain temperature difference between It has the configuration and the off-track canceling means.

[0014]

The present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention, FIG. 2 is a block diagram showing the configuration of the off-track amount cancel circuit 10 of FIG. 1, and FIG. 3 is a temperature monitoring circuit of FIG. 11 is a block diagram showing the configuration of FIG. 11, FIG. 4 is a flowchart showing the operation of measuring the off-track amount in FIG. 1, and FIG. 5 is a special cylinder for measuring the off-track amount of the magnetic disk surface and information is recorded. FIG. 7 is a diagram schematically showing a relationship with a data zone for the purpose of FIG. 7, and FIG. 7 is a diagram showing a locus of the magnetic head in which the off-track amount of the target cylinder is canceled by two check cylinders.

Referring to FIG. 1, 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 10, a read / write circuit 7 and an off-track. Quantity cancel circuit 1
0 and a control circuit 8 for controlling the positioning control circuit 5, and a temperature monitoring circuit 11 are provided, and FIG. 1 also shows a host device 9 together.

Next, the operation of this embodiment will be described.

The control circuit 8 constantly monitors the initialization of the magnetic disk device and the access state from the temperature monitoring circuit 11, and when there is an alarm from the temperature monitoring circuit 11, the off-track amount is measured off-track. The quantity cancel circuit 10 is instructed.

The control circuit 8 also causes the read / write circuit 7 to perform a read or write operation when it receives a data read or write command from the host device 9.

Further, the control circuit 8 sends a seek command to the positioning control circuit 5, and also sends information regarding the magnetic head and cylinder currently accessed to the off-track amount cancel circuit 10.

The off-track amount canceling circuit 10 measures the off-track amount according to an instruction from the control circuit 8,
During the seek operation, the offset voltage as information for canceling the off-track amount is sent to the positioning control circuit 5 based on the measured data.

The positioning control circuit 5 positions the head on the target cylinder according to an instruction from the control circuit 8. Also,
The positional deviation of the head is corrected by the information of the off-track amount cancel circuit 10.

Off-track amount cancel circuit 10 of FIG.
2, a memory 101, a CPU 102, an amplitude measuring circuit 103 and an offset control circuit 104 are provided.

Next, the off-track amount cancel circuit 10
The operation of will be described.

(1) The CPU 102 measures the off-track amount of the two check cylinders, the inner check cylinder closest to the cylinder positioned by the command from the control circuit 8 and the outer check cylinder.

Further, in order to measure the off-track amount,
A command is sent to the offset control circuit 104 of the amplitude measuring circuit 103.

The two check cylinders are prepared for each head and have n measurement points P1 to Pn that divide the circumference into n. Data is written in advance in the disk device for each measurement point. deep. The number of measurement points can be set arbitrarily.

The amplitude measuring circuit 103 measures the amplitude voltage at the measuring point.

The memory 101 stores a program of the CPU 102 and various data such as an off-track amount.

The offset control circuit 104 sends the amount of offset to the positioning control circuit 5 in order to detect the place where the amplitude of the measurement point is maximum.

Next, the operation sequence of the CPU 102 will be described.
This will be described with reference to the flowchart of FIG. 4 while referring to FIG. 1 and FIG.

The CPU 102 measures the off-track amount according to an instruction from the control circuit 8. First, the head is positioned in the inner circumference check cylinder (step 21).

Next, head selection (step 22) is performed. Heads are selected in order from the smallest number.

Next, the location of the point P1 obtained by dividing the circumference of the cylinder into n equal parts is measured (step 23). The measurement is CP
An offset amount is output from the offset control circuit 104 to the positioning control circuit 5 in response to a command from U102, the head is moved a minute 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 101 as an off-track amount. here,
The control range of the offset amount is ±
Up to 1/2 cylinder. The output voltage of the head is measured by the amplitude measuring circuit 103.

Next, it is confirmed whether all the measurement points have been completed (step 24). If it is finished, proceed to the next step. The measurement point is incremented from P1 to Pn.

Next, it is confirmed whether an interrupt has occurred from the control circuit 8 (step 25). If no interrupt has occurred, proceed to the next.

Next, it is confirmed whether or not the measurement has been performed on all the heads (step 26). The head is selected for increment.

Next, the head is positioned on the outer circumference check cylinder (step 27).

Since steps 28 to 32 are the same as steps 22 to 26, their explanations are omitted. If an interrupt from the control circuit 8 is confirmed in steps 25 and 31, the measurement is immediately stopped, the current state is saved (step 33), and the process is ended. Then, when the remeasurement command is received from the control circuit 8, the stored previous state is referred to and restarted from the continuation.

(2) The CPU 102 cancels off-track according to a command from the control circuit 8.

The control circuit 8 controls the CP during the seek operation.
Send the target cylinder number to U102.

The CPU 102 obtains the off-track amount cancel data of the target cylinder from the off-track amount previously stored in the memory 101 based on the sent out target cylinder number by the equation (1). e5 = e1-e3 (e1-e2) / e4 (1) Where, e1: off-track amount of inner check cylinder e2: off-track amount of outer check cylinder e3: number of cylinders from inner check cylinder to target cylinder e4: Number of cylinders from outer check cylinder to target cylinder e5: Off-track amount of target cylinder.

Expression (1) is a calculation expression for one point. The obtained data is the offset control circuit 104
It is input to and stores the data of the number of points of one round.

The offset control circuit 104 outputs the stored data corresponding to the number of points for one round to the positioning control circuit 5 at any time in synchronization with the motor rotation speed.

FIG. 7 shows the off-track amount e1 measured by the inner circumference check cylinder (check cylinder C1) and the off-track quantity e2 measured by the outer circumference check cylinder (check cylinder C2) from the equation (1). By calculating the off-track amount e5 and canceling it, the track e of the head causing the off-track e
This shows that the off-track amount of the target cylinder indicated by 0 is suppressed and an exemplary head locus e6 in which no off-track occurs is obtained.

Next, referring to the temperature monitoring circuit shown in FIG. 3, the temperature sensor 1101, the comparator 1102, the D / A
A converter 1103, an A / D converter 1104,
It is composed of a CPU 1105.

The CPU 1105 starts monitoring the temperature according to an instruction from the control circuit 8, and the A / D converter 1104
D / A converter 1 so that the output of
Give information to 103.

The output of the D / A converter 1103 is compared with the output of the temperature sensor 1101 by the comparator 1102. The output of the comparator 1102 is the A / D converter 110.
4 is input. The output of the A / D converter 1104 is
It is input to the CPU 1105.

The CPU 1105 uses the A / D converter 11
The above contents are repeated until the output of 04 is canceled, and the D / A converter 1103 when it is canceled
The value of is the reference data value. Also, the CPU 1105
The output from the / D converter 1104 is monitored, and when the difference between the output and the reference data value exceeds a predetermined value, C
The PU 1105 externally generates an alarm for a fixed time. At that time, the difference value is added to the reference data value, the value at that time is newly set as the reference data value, and the above-described operation is repeated.

The CPU 1105 also confirms that the reference data value is within a predetermined standard range and also functions to prevent the overflow of the circuit. Comparator 1
The output of 102 is set to a value such that circuit overflow does not occur.

[0051]

As described above, according to the present invention, the amount of off-track generated between each magnetic head is measured when the magnetic disk device is initialized and when a constant temperature difference occurs in the magnetic disk. When the seek operation is performed by the access from the host device, the off-track amount of the target cylinder is calculated based on the information stored in the memory, and the off-track amount is sequentially sent to the positioning circuit. This has the effect of canceling over the entire circumference of the disk and allowing stable reading without causing a fatal obstacle such as a read error in which the magnetic head deviates from the specified position due to a temperature difference or some reason.

[Brief description of drawings]

FIG. 1 is a block diagram of a magnetic disk device according to an embodiment of the present invention.

FIG. 2 is a block diagram of an off-track amount cancel circuit 10 of FIG.

3 is a block diagram of a temperature monitoring circuit 11 of FIG.

FIG. 4 is a flowchart showing an off-track amount measuring operation in the embodiment of FIG.

FIG. 5 is a diagram schematically showing the relationship between a special cylinder for measuring the amount of off-track on the magnetic disk surface and a data zone for recording information.

FIG. 6 is a diagram schematically showing an example in which an off-track is generated in the magnetic head based on the position shift of the positioner and the inclination of the motor shaft.

FIG. 7 is a diagram showing a locus of a magnetic head in which an off-track amount of a target cylinder is canceled by two check cylinders.

FIG. 8 is a block diagram of a conventional magnetic disk device.

[Explanation of symbols]

 1 magnetic disk 2 magnetic head for positioning 3 magnetic head 4 motor 5 positioning control circuit 6 head selection circuit 7 read / write circuit 8 control circuit 9 host device 10 off-track amount cancel circuit 11 temperature monitoring circuit

Claims (2)

[Claims] 1. At least two check cylinders for checking are provided for each head, and a plurality of measurement points are provided for each check cylinder at equal intervals to initialize a magnetic disk device and a magnetic disk device. When a certain temperature difference occurs in the cylinder, the off-track amount of the displacement between the target cylinder and the magnetic head is measured in advance, and the seek operation is performed based on the off-track amount when the seek operation is performed by the access from the host device. An off-track amount canceling method for a magnetic disk drive, comprising offset amount canceling means for automatically canceling the off-track amount when the operation is completed. 2. A control circuit for performing various control operations under the control of a host device, a read / write circuit for reading and writing the magnetic head based on an instruction from the control circuit, and a plurality of magnetic heads. A head selection circuit for selecting an arbitrary magnetic head, and an off-track amount cancellation for measuring the off-track amount or calculating information for canceling the off-track amount based on an output of the head selection circuit and an instruction from the control circuit. Circuit, a positioning control circuit for positioning the magnetic head on the target cylinder based on the output of the off-track amount canceling circuit and an instruction from the control circuit, and a constant temperature difference in the magnetic disk is detected and notified to the control circuit. And a temperature monitoring circuit for controlling the off-track canceling means. The off-track amount canceling method of the magnetic disk drive according to the item 1.