Dynamic magnetic information storage or retrieval – Automatic control of a recorder mechanism
Reexamination Certificate
1998-03-27
2001-02-13
Sniezek, Andrew L. (Department: 2753)
Dynamic magnetic information storage or retrieval
Automatic control of a recorder mechanism
C360S077080, C360S053000, C360S078040, C714S718000, C714S054000
Reexamination Certificate
active
06188533
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a data reading method, a recording medium used in the method and a storage apparatus (information recording and reproducing device) using the method. In particular, the present invention relates to a data reading method when tracking control is performed using servo information, a recording medium used in the method and a storage apparatus (information recording and reproducing device) using the method.
In a magnetic recording and reproducing device such as a hard disk device, reading of data written in a recording medium should be guaranteed. However, there is a possibility that data written in a recording medium is not properly read due to degradation of the characteristics of the recording medium, adhesion of dirt to the recording medium, damage on the recording medium due to an external shock, external electrical noises or the like.
Commonly, in order to prevent such a situation that written data cannot be properly read, redundant data called an error correction code is added to data. When data is read, error detection and error correction are performed. Thereby, normally, original data can be restored to a certain extent.
Recently, as a recording device has been miniaturized and the storage capacity thereof has been increased, the S/N ratio of a read signal has decreased. Therefore, a restoration function performing data correction using the error correction code has been necessarily enhanced.
For example, in a disk device in about 1985, an ECC (Error Checking Code) for correcting an 11-bit burst error was used; in a disk device in about 1990, an ECC for correcting a 20-bit burst error was used; and in a disk device in about 1995, an ECC for correcting a more-than-40-bit burst error was being used. However, as a side effect of the enhancement of the error correction ability, even information which should not be changed may be erroneously changed by the error correction function.
An object of the present invention is to provide a method for preventing such an erroneous restoration when data is read.
2. Description of the Related Art
FIG. 1
shows a block diagram of an example of a hard disk drive in the related art.
FIG. 2A
shows a plan view of the hard disk drive after partially removing a top plate thereof.
FIG. 2B
shows an elevational sectional view of the hard disk drive.
The hard disk drive
1
is connected to a host apparatus
21
, and stores, for example, a data processing result of the host apparatus
21
. The hard disk drive
1
includes hard disks
2
, a spindle motor
3
which rotates the hard disks
2
in the arrow A direction, magnetic heads
4
which perform information recording on the hard disks
2
and information reproduction from the hard disks
2
, an arm
5
which holds the magnetic heads
4
, and an actuator
7
which rotates the arm
5
in the arrow B directions about a rotation shaft
6
so as to move the magnetic heads
4
in radial directions of the hard disks
2
. (Actually, as shown in
FIG. 2B
, the hard disk drive
1
includes the plurality of hard disks
2
and the plurality of magnetic heads
4
. However, for the sake of simplification,
FIG. 1
shows only one hard disk
2
and one magnetic head
4
.) The hard disk drive
1
further includes a read/write control portion
8
which supplies recording signals to and receives reproduced signals from the magnetic heads
4
, a formatter control portion
9
which is connected with the read/write control portion
8
and formats the reproduced signals into reproduced data and formats recording data into the recording signals, a data buffer
10
which temporarily stores the recording data and reproduced data, a data buffer control portion
11
which controls storage of the recording data and reproduced data in the data buffer
10
, an I/F control portion
12
which acts as an interface between the host apparatus
21
and the hard disk drive
1
, and a servo control portion
13
which performs servo control of the spindle motor
3
and the actuator
7
. The hard disk drive
1
further includes an MPU (Micro Processing Unit)
14
, a ROM
15
and a RAM
16
which are used for controlling the total operation of the hard disk drive
1
Data to be recorded on and data reproduced from the hard disks
2
are transmitted from and received by the host apparatus
21
via the magnetic heads
4
, read/write control portion
8
, formatter control portion
9
, data buffer control portion
11
, data buffer
10
, and I/F control portion
12
.
On each of the hard disks
2
, a plurality of tracks are formed concentrically. Information is recorded on the tracks and recorded information is reproduced from the tracks. Each track is divided into a plurality of frames.
FIGS. 3A and 3B
show an example of the arrangement of the hard disk
2
of the hard disk drive
1
in the related art.
As shown in
FIG. 3A
, the plurality of tracks Tr
1
through Trn are formed on each hard disk
2
. Each track is divided into a plurality of frames S
1
through Sm.
The plurality of frames S
1
through Sm are formed as a result of dividing each hard disk
2
by every predetermined angle. As shown in
FIG. 3B
, each frame includes a servo information area SB and a data area D.
In each servo information area SB, servo information is recorded. The servo information is used for controlling the position of each magnetic head
4
so that each magnetic head
4
can scan a desired track.
FIG. 4
shows an example of the data arrangement of the servo information recorded on the hard disks
2
of the hard disk drive
1
in the related art.
As shown in
FIG. 4
, the servo information area SB includes an AGC (Automatic Gain Control) area
17
in which an AGC signal for automatically adjusting the amplification factor for the reproduced signal read through the magnetic head
4
is recorded. The servo information area SB further includes an SM (Servo Mark) area
18
in which a servo mark SM indicating the start of information is recorded and a cylinder area
19
in which a cylinder address for identifying the track is recorded. The servo information area SB further includes a position area
20
in which track tracking information is recorded, which information is patterns for detecting an amount of displacement of the magnetic head
4
with respect to the track.
In the AGC area
17
, an AGC signal, ‘1010 . . . 1010’ is recorded for 90 clock pulses. In the SM area
18
, the servo mark SM, ‘1000 . . . 00’ is recorded for 18 clock pulses.
In the cylinder area
19
, the cylinder address, ‘100X00X00 . . .’ (each ‘X’ is a value, ‘0’ or ‘1’, in accordance with the cylinder address) of a so-called Gray code, is recorded for 99 clock pulses. Further, in the position area
20
, the track tracking information, consisting of three patterns, each having a width approximately half the track width, is recorded for 240 clock pulses.
FIG. 5
shows an example of the data arrangement of the position area
20
of each track of the hard disks
2
of the hard disk drive
1
in the related art.
In the position area
20
, a pattern A is recorded on the arrow-C-direction side of the cylinder-area-side of the track Trx-
1
, for the width half the track width for 80 clock pulses. Then, a pattern B is recorded on the arrow-D-direction side of the track Trx-
1
, for the width half the track width for 80 clock pulses. Then, a pattern C is recorded so that the center of the pattern C is the same as the center of the track Trx-
1
, for the width half the track width for 80 clock pulses.
The track tracking information, the patterns A, B and C, shown in
FIG. 5
, is recorded at the corresponding positions of each track of the hard disks
2
.
In the hard disk drive
1
, the servo information is read through the magnetic heads
4
, and the servo control portion
13
controls the positions of the magnetic heads
4
so that the magnetic heads
4
scan desired tracks of the hard disks
2
.
FIG. 6
shows an example of the operation flowchart of the servo control portion
13
of the hard disk drive
1
in th
Fujitsu Ltd.
Greer Burns & Crain Ltd.
Sniezek Andrew L.
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