JPH01285082A - Magnetic disk device - Google Patents

Abstract

PURPOSE:To improve the using efficiency of a system by sending offset data stored in a register corresponding to a selected data head to an offset seek circuit. CONSTITUTION:Offset registers 210-240 corresponding to data head 52-55 respectively are provided. Only one is selected out of the offset registers 210-240 by head select signals 41-44 which are the output signals of a head address decoder 40 and offset data 250 which are the output of the selected offset register are inputted to an offset seek circuit 30. Consequently, when another data head is selected, after that, the same data head is selected again and a reading operation is performed, the an offset seek can be executed without receiving an offset instruction from a host device. Thus, the operational efficiency in the system can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a magnetic disk device, and more particularly to a head positioning circuit system for a magnetic disk device.

[Conventional technology]

Conventionally, this type of magnetic disk device uses various methods to retry the read operation when a read error occurs during a normal read operation. For example, the relative positions of the servo surface and multiple data surfaces in the same cylinder are the same in the initial state R (at the time of shipment from the factory), but over a long period of time, mechanical parts may wear out and manufacturing variations may occur. As a result, the spindle shaft is tilted and a relative positional deviation (referred to as off-track) occurs between the servo head and the data head, so that data recorded on the target track may not be read out.

In such a case, an offset command is given from the host device, and the magnetic disk device moves the carriage a predetermined distance forward or backward from the physical track center position (referred to as an offset leak operation) to restart the read operation. Make a trial.

FIG. 2 is a block diagram of the offset control circuit section of the conventional magnetic disk device described above, in which offset data sent from a host device prior to an offset command is set by bus out signal 1 and set difference signal 2. It consists of a difference counter and an offset register 20 that is set by an offset start signal 3 and sends offset data to the offset leak circuit 30. For example, when a read error is detected, a read error is detected by retrying the normal read operation. If it is not possible to correct the offset, the host device sends an offset command each time, and the read operation is retried, and each time when reading becomes possible, the contents of the offset register 20 are reset by the offset reset signal 4. It had been reset.

[Problem to be solved by the invention]

The above-mentioned conventional magnetic disk drive is equipped with only one offset register, so when a different head is selected, the off-track amount is usually different, so the offset amount is also different, and each time a different head is selected, An offset command is required for HDA (Head Disk Assembly) that has already gone off-track.
For the trunk that has retried the read operation using the offset command in step y), the above-mentioned offset command will be used for each read operation, unless reformatting (rewriting the track including the home address for the full rotation) is performed afterwards. This has the major drawback of significantly reducing the efficiency of system usage.

[Means to solve the problem]

The magnetic disk device of the present invention holds a plurality of magnetic disks on one spindle shaft, uses a servo surface servo method for track positioning of the data head, and is capable of retrying a read operation by an offset command from a host device. In a magnetic disk device, offset data indicating the amount of offset, offset direction, etc. sent prior to an offset command from a host device is stored in a register corresponding to a selected data head each time an offset start command is issued, and It has an offset register that sends the offset data stored in the register corresponding to the selected data head to the offset leak circuit whenever one data head is selected.

〔Example〕

Next, the present invention will be explained with reference to the drawings.

FIG. 1 shows an embodiment of the invention. In FIG. 1, this embodiment shows a case where there are, for example, four data heads.
It has an offset control circuit for the positioning circuit. In this embodiment, instead of the offset register 2° of the conventional magnetic disk drive shown in FIG.
Offset registers 210 to 24, one each corresponding to 5.
0 is set. This offset register 210~
Only one of 240 is selected by the head select signals 41 to 44 which are output signals of the head address decoder 40. For example, when the fourth data head 55 is selected, only the fourth offset register 240 is selected, and the offset data 250 that is the output of the simultaneously selected offset register is transmitted to the offset leak circuit 30. is input.

Next, the operation of this embodiment will be explained. Assume that when the information written when no off-track occurred is read out at a later date, the spindle shaft 70 tilts, and as a result, off-track occurs.

At this time, the off-track amount increases as the distance from the rad 51 to the servo increases. (The data head 55 is larger than the data head 52.) For example, when reading recorded information by the fourth data head 55, an offset amount is set in the difference counter 10 from the host device, and an offset start signal 3 The offset operation is started.

At this time, the contents of the difference counter 10 are set in the fourth offset register 240, and the output of the offset data 250 is transmitted to the offset leak circuit 30.
The offset leak operation is performed, and the read operation is retried. If the read error is not corrected, a new correct offset amount is similarly set in the offset register, the process is repeated until the read error is corrected, and the final offset amount is stored in the offset register.

A similar operation occurs when retrying the read operation for other data heads, and the offset data stored in each offset register 210 to 240 is transmitted by the offset reset signal 4.
It will continue to be held until it is input.

〔Effect of the invention〕

As explained above, in the present invention, once a read error is successfully corrected by an offset operation, the offset amount required for each data head is stored and retained unless the contents of the offset register corresponding to each data head are rewritten. Therefore, after selecting another data head, when selecting the same data head again and performing a read operation, offset leak can be automatically executed without receiving an offset command from the host device, so the system This has the effect of increasing operational efficiency.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an offset control circuit of a positioning circuit of a magnetic disk device in an embodiment of the present invention;
FIG. 2 is a block diagram showing a conventional magnetic disk device. 10... Difference counter, 2o... Offset leak circuit, 30... Offset cell I/seek circuit,
50... Carriage, 51... Servo head, 52
~55...Data head, 60...Magnetic disk,
70... Spindle shaft, 210-240...
Offset register.

Claims (1)

[Claims] Multiple magnetic disks are held on one spindle shaft, and a servo surface servo method is used for track positioning of magnetic heads for writing and reading (hereinafter referred to as data heads), and read operations are performed by offset commands from the host device. In a magnetic disk device that is capable of retrying, the offset data indicating the offset amount, offset direction, etc. sent prior to an offset command from the host device is
It is stored in the register corresponding to the selected data head each time an offset start command is received from the host device, and whenever one data head is selected, it is stored in the register corresponding to the selected data head. What is claimed is: 1. A magnetic disk drive comprising: an offset register that sends offset data to an offset leak circuit.