JPH04222973A - Magnetic disk device - Google Patents

Abstract

PURPOSE:To cancel an off-track over one round of a disk and to stably read out data by providing an off-track amt. canceling circuit. CONSTITUTION:An access state from a host device 9 is monitored by a control circuit 8, and when no access is made for a given period of time, a command is issued to the off-track amt. canceling circuit 1 to measure an off-track amt. A read and write circuit 7 is operated by the circuit 8 with a command of the host device 9. A seek command is sent by the circuit 8 to a positioning control circuit 5, and at that time, information about a presently accessing head and a cylinder is also sent to the off-track amt. canceling circuit 1. An off-track amt. is measured, and an offset voltage is sent as the information for canceling the off-track amt. based on a data measured at the time of a seek operation to the circuit 5 by the circuit 1 with such commands of the circuit 8. A target cylinder head is positioned and misalignment of the head is corrected by the circuit 5 in accordance with a command of the circuit 8.

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 that can cancel off-track over one rotation of the disk to prevent a magnetic head from shifting from a specified position and causing a read error.

0002

2. Description of the Related Art Conventionally, a magnetic disk drive has been used as a device for reading and writing information from a magnetic disk in which a magnetic head rotates at high speed. As shown in FIG. 7, this 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 in a target cylinder, and a positioning control circuit for controlling the positioning. 5, and a plurality of magnetic heads 3 for reading and writing data onto the magnetic disk.
, a head selection circuit 6 that selects one magnetic head from among the magnetic heads, a read/write circuit 7 that controls reading and writing of data, and a positioning control circuit 5.
and a control circuit 8 that controls the read/write circuit 7.

As mentioned above, the magnetic head includes a positioning 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 to the target cylinder by the positioning head, but due to temperature change or some other cause, the motor shaft 12 tilts, causing the upper head to off-track toward the inner circumference, and the lower head causes off-track on the outer circumferential side. Also, due to the positional deviation of the positioner 11, the inner circumferential cylinder and the outer circumferential cylinder each produce off-track, so when reading,
Reading may be poor. Furthermore, in order to avoid such off-track reading errors, there is also a sector servo method in which the data surface is divided into sectors and some of the sectors are used as positioning information to cancel the positional deviation between the magnetic head 3 and the target cylinder.

0004

[Problems to be Solved by the Invention] The above-mentioned conventional magnetic disk drive has the drawback that it does not have a means for canceling such positional deviation, resulting in a failure in reading information, and in that it cannot be read even if it is reread. Ta. Also,
There is also a sector servo method that divides the data surface into sectors and writes positioning information to some of them for positioning. There was a drawback that the amount of data was reduced because positioning information was written.

[0005]

[Means for Solving the Problems] A magnetic disk device of the present invention includes a magnetic disk having a check cylinder, a read/write circuit that performs read or write operations under the control of a control circuit that controls the entire magnetic disk device, and a plurality of a head selection circuit that selects an arbitrary head from among the magnetic heads; an off-track amount cancellation circuit that measures an off-track amount and calculates off-track amount cancellation information based on the output of the head selection circuit and control from the control circuit; A positioning control circuit is provided for positioning the magnetic head at a target position based on the output of the off-track amount canceling circuit and control from the control circuit.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be explained with reference to the 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 canceling circuit 1 which is the main part of this embodiment, and FIG. It is an operation flowchart when measuring track amount. FIG. 4 is a schematic diagram showing the relationship between a special check cylinder for measuring the off-track amount on the magnetic disk surface and a data zone for recording information. FIG. 3 is a schematic diagram showing an exemplary head trajectory in which the off-track amount of the cylinder has been canceled.

The embodiment shown in FIG. 1 includes 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. circuit 1
and a control circuit 8 that controls the positioning control circuit 5.

Next, the operation of this embodiment will be explained. The control circuit 8 always monitors the access state from the host device 9 when initializing the magnetic disk device, and instructs the off-track amount canceling circuit 1 to measure the off-track amount when there is no access for a certain period of time. Also, the control circuit 8
When receiving a data read or write command from the host device 9, it causes the read/write circuit 7 to perform a read or write operation. 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 cancellation 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 according to a command from the control circuit 8. In addition, head positional deviation is corrected using information from the off-track amount canceling circuit 1.

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

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

Next, the operation flow of the CPU 1B will be explained using the flowchart shown in FIG. First, the head is positioned on the inner check cylinder (step 21). Next, a head is selected (step 22). The head is
The numbers are chosen in order starting from the lowest number. Next, the locations of n points around the cylinder are measured (step 23). The measurement is performed by outputting an offset amount from the offset control circuit 1D to the positioning control circuit 5 in response to a command from the CPU 1B, moving the head a small distance, and determining the offset amount when the output voltage of the head becomes maximum. The offset amount at that time is stored in the memory 1A as an 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 an amplitude measuring circuit 1C. Next, check whether all measurement points have been completed (
Step 24). If finished, proceed to the next step. Points are incremented from the starting point to the final 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 measurements have been performed on all heads (step 26). Next, position the head to the outer check cylinder (
Step 27). From step 28 to step 32, step 22 to step 2 of the inner check cylinder
It is the same as up to 6. If an interrupt is confirmed from the control circuit 8 in steps 25 and 31, the measurement is immediately stopped, the current state is saved, and the process ends (step 33). When a re-measurement command is received from the control circuit 8, the stored previous state is referred to and restarted from where it left off.

(2) The CPU 1B cancels off-track according to a command from the control circuit 8. First, when executing a seek operation, the CPU 1B sends a target cylinder number. Based on this target cylinder number, the CPU 1B converts the off-track amount cancellation data of the target cylinder into the following (
1) Obtain from the formula. Here, the symbols e1 to e5 represent the following off-track amount and number of cylinders.

e1 - off-track amount of the inner check cylinder; e2 - 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, equation (1) is a calculation equation for one point. The obtained data is input to the offset control circuit 1D, and data corresponding to the number of points in one round is stored. The offset control circuit 1D synchronizes the stored data for the number of points in one round with the motor rotation speed and outputs it to the positioning control circuit 5 at any time. In FIG. 6, the off-track amount e5 of the target cylinder is calculated from equation (1) using the off-track amount e1 measured with the inner check cylinder and the off-track amount e2 measured with the outer check cylinder, and then canceled. This diagram shows an exemplary head trajectory e6 in which no off-track occurs.

[0015]

As described above, by providing the off-track amount cancel circuit, the present invention can cancel off-track over one revolution of the disk. Therefore, there is an effect that data can be read stably without causing fatal failures such as reading errors due to deviation of the magnetic head from the specified position due to temperature differences or some other cause.

[Brief explanation of the drawing]

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

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

FIG. 3 is an operational flowchart of main parts of this embodiment.

FIG. 4 is a schematic diagram of the magnetic disk surface of this embodiment.

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

FIG. 6 is a schematic diagram showing a trajectory in which off-track is canceled according to the present embodiment.

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

[Explanation 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 (3)

[Claims] 1. A magnetic disk having a check cylinder, a read/write circuit that performs read or write operations under the control of a control circuit that controls the entire magnetic disk device, and head selection that selects any head from a plurality of magnetic heads. an off-track amount cancel circuit that measures an off-track amount and calculates off-track amount cancellation information based on the output of the head selection circuit and control from the control circuit; the output of the off-track amount cancel circuit and the control circuit; A magnetic disk device comprising: a positioning control circuit that positions a magnetic head at a target position under control from the circuit. 2. As a means for measuring or canceling an off-track amount, which is a positional deviation of a magnetic head that reads or writes to a cylinder of the magnetic disk, each magnetic head has an inner check cylinder and an outer check cylinder. 2. A magnetic disk drive according to claim 1, wherein each cylinder has a plurality of measurement points spaced at equal intervals within one circumference. 3. The off-track amount is measured in advance when the magnetic disk device is initialized and when there is no access from an external host device, and when a seek operation is performed by access from the host device, this measurement is performed. The CPU in the off-track amount canceling circuit automatically calculates the off-track amount of the target position where the information is written based on the stored data, and cancels the off-track amount when the seek operation is completed. A magnetic disk device according to claim 1.