JPH02198075A - Magnetic disk device - Google Patents

Abstract

PURPOSE:To promote the application efficiency of a system by providing plural offset registers, storing each of them with its corresponding data head and outputting it to an offset seek circuit as occasion demands. CONSTITUTION:At least one spare track for diagnosing an off-track amt. is provided on a storage surface of a magnetic disk corresponding to the data heads 11-14 respectively. The spare track is divided into a prescribed number of records before delivery and each record is recorded with a test data in a position forcibly off-tracked before and behind a center position of a physical track. Now, a control signal 6A is outputted by a magnetic disk control circuit 6 to a read/write circuit 3, and also an address signal 6B is outputted to a head address decoder 2 to operate. Then, select signals H1-H4 are outputted by the decoder 2, and only one out of the offset registers 111-114 is selected to be stored by each corresponding head. Then, as occasion demands, this is outputted to the offset seek circuit 5. By this method, the application efficiency in the system can thus be promoted.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a magnetic disk device, and more particularly to a magnetic disk device that performs a data head positioning operation using a servo surface servo method.

[Conventional technology]

In conventional magnetic disk drives, when a read error occurs during a normal read operation, the read operation can be retried using various methods.
The relative positions of one servo surface and multiple data surfaces on the same cylinder are the same in the initial state (at the time of shipment from the factory), but after long-term operation, the magnetic disk The spindle shaft is tilted due to wear of the mechanical parts that make up the device, manufacturing variations, etc., resulting in relative positional deviation between the servo head and the data head (this is called off-track). For this reason, a situation occurs in which data recorded on a target track cannot be read out by normal read operations.

In such a case, the magnetic disk device is given an offset command from a host device (such as a magnetic disk control device) to move the carriage a predetermined distance from the physical center of the track forward or backward. (referred to as an offset seek operation), the read operation is retried.

FIG. 3 is a block diagram showing a positioning circuit section of an example of such a conventional magnetic disk device. The conventional example shown in FIG. 3 includes a difference counter 21 that sets offset data Ft sent out prior to an offset command from a host device using a bus out signal F2 and a set difference signal F3, and a difference counter 21 that sets offset data Ft that is sent out prior to an offset command from a host device. Offset seek circuit 30
offset data F! If a read error is detected and the read error cannot be corrected by retrying the normal read operation, the host device sends the offset each time. The instruction is issued to retry the read operation,
Offset reset signal F5 when reading becomes possible
A method is adopted in which the contents of the offset register 20 are reset by the following.

[Problem to be solved by the invention]

Normally, the off-track amount differs for each magnetic head, and therefore the offset amount required to retry the read operation also differs.
Since only one offset register 20 is provided, there is a complication that an offset command is required from the host device each time a different magnetic head is selected. In addition, a magnetic head magnetic disk assembly that has already gone off track (
HD A; Head Disk Assembly
), if the track requires a retry of the read operation using an offset command, the subsequent reformat (
Unless track-round rewriting (including the home address) is performed, the above-mentioned offset command must be used for every read operation, which has the major drawback of significantly reducing the operational efficiency of the system.

[Means to solve the problem]

The magnetic disk device of the present invention includes a head address decoder and a read/write circuit that selects and operates one data head among a plurality of data heads, and drives each of the data heads based on a servo surface servo method. The head movement control unit includes a head movement control unit, an offset seek circuit for positioning control that is attached to the head movement control unit, and a magnetic disk control circuit that controls operations of the head address decoder, the read/write circuit, and the head movement control unit. In the magnetic disk device, at least one spare track is provided on the storage surface of the magnetic disk corresponding to each of the plurality of data heads, and the spare track is divided into a predetermined number of records at the time of factory shipment. Test data is recorded on each record by forcibly off-tracking the physical track by a certain amount in the front and rear directions, including the center position of the physical track, and the data head is positioned on the spare track when the power is turned on and at fixed time intervals. perform an operation to read the test data, and generate offset data by diagnosing the off-track amount and off-track direction from the initial track center position from the record number of the spare track where no read error occurred. An off-track diagnostic circuit is provided, and offset data generated by the off-track diagnostic circuit is stored in an offset register provided for each corresponding data head, and if necessary, the offset data of the corresponding data head is stored in the offset register from the offset register. It is configured to output to a seek circuit.

〔Effect of the invention〕

Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing a positioning circuit according to an embodiment of the present invention.

The embodiment shown in FIG. 1 is a head address decoder 2 that selects and drives one of a plurality of data heads 11 to 14.
and read/write circuit 3 and data heads 11 to 14
The magnetic disk control circuit 6 controls the operation of these components.The magnetic disk control circuit 6 controls the operation of these components. control the
Specifically, the servo surface servo method performed by the head movement control section 4 involves writing servo track information dedicated to track positioning on the storage surface of one of a plurality of magnetic disks, and A system in which the servo track information is read by the servo head 42 and the track is positioned Equipped. As shown in Fig. 2, this track is divided into a predetermined number of records R1 to R9 when the magnetic disk device is shipped from the factory, and each record includes the center position C of the physical track, and the front and rear thereof. Test data was recorded in advance at positions where the vehicle was forced off-track by a certain distance.

Then, when the power is turned on and at regular intervals, each data head is positioned on this spare track for off-track amount diagnosis, and the above-mentioned pre-recorded test data for off-track amount diagnosis is read out. , is equipped with an off-track diagnostic circuit 10 for diagnosing the off-track amount and off-track direction from the initial track center position based on the record numbers (R1-R9) that did not cause a read error, and generating offset data. . A plurality of offset registers 11 store the offset data generated by the off-track diagnostic circuit 10 in this way and output it to the offset seek circuit 5.
1 to 114 are equipped.

The magnetic disk control circuit 6 outputs a read/write control signal 6A to the read/write circuit 3 and outputs a head address signal 6B to the head address decoder 2.
output to control these operations.

A plurality of offset registers 111 to 114 are provided, one each corresponding to each of the data heads 11 to 14. These offset registers 111-114
is selected by head select signals H1 to H4 which are output signals from head address decoder 2.
For example, when selecting the fourth data head 14, only the fourth offset register 114 is selected. At the same time, offset data F, which is the output from the selected offset registers 111 to 114,
is input to the offset seek circuit 5 as described above.

The off-track diagnostic circuit 10 receives the output signal Y from the read/write circuit 3. is input, and an off-track diagnosis control signal J is output to the magnetic disk control circuit 6, and an offset data input signal Fs is output to the offset registers 111-114. Offset registers 11 to 1 to which this offset data input signal Fs is input
4 uses an offset register set signal R1 and an offset register reset signal R, which are sent from the off-track diagnostic circuit 10 at the same time to
Set or reset every 14 seconds.

Head select signals H1 to H4 output from the above-mentioned head address decoder 2 to the read/write circuit 3 are separately sent to each of the offset registers 111 to 114, respectively. The head movement control section 4 includes a carriage 40 equipped with the data heads 11 to 14 described above, a motor 41 that drives the carriage 40, and a servo head 12 equipped on the carriage 40. The head movement control section 4 also includes a servo signal demodulation circuit 43 that demodulates a servo signal 42A sent from the servo head 42, and a servo signal demodulation circuit 43 that demodulates a servo signal 42A sent from the servo head 42.
and the output signal of the offset seek circuit 5 as a correction control signal 43A and an operation command signal, respectively, and a positioning drive circuit 44 that operates under the control of a device determination control signal S9 constituted by the magnetic disk control circuit 6. It is equipped with

Next, the offset data setting operation in the above embodiment will be explained.

The off-track diagnostic circuit 10 operates for a predetermined period of time when the power is turned on and at predetermined time intervals. First, in order to diagnose the off-track amount in advance, the data head is positioned with respect to a spare track using the off-track diagnosis control signal Jo. Next, a test data read operation is performed sequentially for all data. When the spare track is shipped from the factory, it is divided into predetermined records, and each record includes the physical track center position and records data that has been forcibly off-track by a certain amount in front and behind it. Only some of the records can be read normally. Therefore, by determining which record data could be read, the off-track amount at the time of diagnosis is determined, offset data Fs is generated, and this is set in the corresponding offset registers 111 to 114. to end the off-track diagnostic operation.

〔Effect of the invention〕

As explained above, the magnetic disk device of the present invention uses the test data for diagnosing the off-track amount, which is written in advance on the spare track, to diagnose the amount of off-track when the power is turned on and at regular intervals. By diagnosing the off-track amount for each data head and setting the offset data in the offset register provided corresponding to each data head, after the off-track diagnosis operation is completed, reading from the host device is possible. During operation,
Even if an HDA with off-track is used, an offset seek operation can be performed automatically when selecting a data head, so read errors due to off-track do not occur, thus improving system operational efficiency. It has the effect of increasing

2... Head address decoder, 3... Read/write circuit, 4... Head movement control section, 5.30... Offset seek circuit, 6... Magnetic disk control circuit,
DESCRIPTION OF SYMBOLS 10... Off track diagnostic circuit, 11-14... Data head, 20, 111-114... Offset register, 21... Difference counter, 43...
- Servo signal demodulation circuit, 44... positioning drive circuit.

Claims (1)

[Claims] a head address decoder and read/write circuit that selects and operates one data head among a plurality of data heads; a head movement control unit that drives each data head based on a servo surface servo method; A magnetic disk drive comprising: an offset seek circuit for positioning control provided in conjunction with a movement control section; and a magnetic disk control circuit that controls operations of the head address decoder, the read/write circuit, and the head movement control section. At least one spare track is provided on the storage surface of the magnetic disk corresponding to each of the data heads, and the spare track is divided into a predetermined number of records at the time of shipment from the factory, and each divided record is assigned a physical track center. Forcibly off-track by a certain amount in the front and back direction including the position and record test data.
When the power is turned on and at regular intervals, the data head is positioned on the spare track to read the test data, and the record number of the spare track where no reading error occurred is determined from the initial track center position. An off-track diagnostic circuit is provided that diagnoses the off-track amount and off-track direction to generate offset data, and the offset data generated by the off-track diagnostic circuit is stored in an offset register provided for each corresponding data head. 1. A magnetic disk device characterized in that the offset data of a corresponding data head is output from the offset register to the offset seek circuit in accordance with the offset register.