Dynamic magnetic information storage or retrieval – General processing of a digital signal – Data clocking
Reexamination Certificate
2001-07-10
2003-12-09
Hudspeth, David (Department: 2651)
Dynamic magnetic information storage or retrieval
General processing of a digital signal
Data clocking
C360S053000
Reexamination Certificate
active
06661593
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of The Invention
The present invention generally relates to a servo information detection method and a disk apparatus using the same, and more particularly relates to a servo information detection method which detects servo information recorded at given intervals in a disk, as well as a disk apparatus using the servo information detection method.
2. Description of the Related Art
A description will be given of a magnetic disk drive with reference to
FIG. 1A
, FIG.
1
B and FIG.
2
.
As shown in FIG.
1
A and
FIG. 1B
, the magnetic disk drive
100
generally includes a disk enclosure (DE)
110
and a printed circuit board (PCB)
120
. The magnetic disk drive
100
is, for example, a hard disk drive (HDD).
In the disk enclosure
110
, a magnetic disk
111
, a spindle motor (SPM)
112
, an arm
114
, and a voice coil motor (VCM)
115
are provided. In a case of the hard disk drive (HDD), a plurality of magnetic disks are rotated by a spindle motor at the same time. However, in the following description, such magnetic disks are collectively referred to as the magnetic disk
111
, for the sake of convenience of description.
In the magnetic disk drive
100
, the printed circuit board
120
supplies a drive signal to the spindle motor
112
so that the spindle motor
112
is driven to rotate the magnetic disk
111
around the central axis of the spindle motor at a constant velocity in a rotation direction indicated by the arrow A in FIG.
1
B. The printed circuit board
120
supplies a drive signal to the voice coil motor
115
so that the voice coil motor
115
is driven to swing or rotate the arm
114
around the central axis of the voice coil motor in a rotation direction indicated by the arrow B in FIG.
1
B. The magnetic head
113
is attached to the leading edge of the arm
114
. By the swinging movement of the arm
114
in the direction B, the magnetic head
113
at the leading edge of the arm
114
is moved in a radial direction of the magnetic disk
111
.
As shown in
FIG. 2
, the disk enclosure (DE)
110
further includes a head controller (Head IC)
116
. During a read operation, the head
113
electromagnetically generates a readout signal from the disk
111
and supplies the readout signal to the head controller
116
. The head controller
116
amplifies the readout signal received from the head
113
. The amplified readout signal from the head controller
116
is supplied to the printed circuit board
120
. During a write operation, the head controller
116
amplifies a writing signal that is to be recorded in the disk
111
, and supplies the amplified writing signal to the magnetic head
113
.
As shown in
FIG. 2
, in the printed circuit board (PCB)
120
, a hard disk controller (HDC)
121
, a random access memory (RAM)
122
, a flash read-only memory (Flash ROM)
123
, a microprocessor unit (MPU)
124
, a read channel (RDC)
125
, a servo controller (SVC)
126
, and linear acceleration sensors
127
and
128
are provided.
As described above, the head
113
generates a readout signal from the disk
111
, and the readout signal from the head
113
is amplified by the head controller
116
. The amplified readout signal, output by the head controller
116
, is supplied to the hard disk controller (HDC)
121
through the read channel
125
in the printed circuit board (PCB)
120
. The amplified readout signal is subjected to a decoding process at the HDC
121
. The HDC
121
supplies the readout information, which is produced through the decoding process from the amplified readout signal, to an external host system
130
.
Further, writing information is supplied from the host system
130
to the HDC
121
. The writing information is subjected to an encoding process at the HDC
121
. The HDC
121
supplies the encoded signal, which is produced through the encoding process from the writing information, to the head controller
116
of the disk enclosure (DE)
110
via the read channel
125
. The encoded signal is amplified by the head controller
116
. The head controller
116
supplies the amplified signal to the head
113
, so that the writing information is electromagnetically recorded in the disk
111
by using the head
113
.
FIG.
3
A and
FIG. 3B
show a format of servo information of the magnetic disk
111
that is used by the magnetic disk drive.
As shown in
FIG. 3A
, a sequence of servo information blocks SB
0
, SB
1
, . . . , SBn is recorded at given intervals “t0” in the magnetic disk
111
. Normally, by using a servo track writer STW (not shown), the servo information blocks SB
0
, SB
1
, . . . , SBn are recorded, in advance, in the respective sectors of the magnetic disk
111
.
As shown in
FIG. 3B
, each of the servo information blocks SB
0
, SB
1
, . . . , SBn is comprised of servo sync mark SM, cylinder number CYL, and position information POS. Generally, when all of the servo sync marks SM are detected from the disk
111
, it is determined as detecting the sequence of servo information blocks SB
0
, SB
1
, . . . , SBn.
In a conventional disk apparatus, when the entire bit pattern of the servo sync marks SM, detected by the conventional disk apparatus from the magnetic disk
111
, matches with a given comparison bit pattern, the presence of the servo sync mark SM in the detection bit pattern is detected. However, if a medium defect with respect to at least one bit among the bit pattern of the servo sync marks exists in the disk, the match does not occur and the absence of the servo sync mark in the detection bit pattern is detected. In the latter case, the conventional disk apparatus generates indication of an error that indicates which sector of the disk is a defective sector including the defect. That is, the conventional disk apparatus cannot correctly detect the presence of the servo sync mark in the detection bit pattern if the detection bit pattern contains a bit affected by an insignificant defect on the disk.
SUMMARY OF THE INVENTION
An object of the present invention is to provide an improved servo information detection method that accurately and reliably detects the servo information in the disk without being influenced by an insignificant defect on the disk.
Another object of the present invention is to provide a disk apparatus using an improved servo information detection method that accurately and reliably detects the servo information in the disk without being influenced by an insignificant defect on the disk.
The above-mentioned objects of the present invention are achieved by a servo information detection method for detecting a servo sync mark of a disk, the method comprising the steps of: determining whether a pattern of detection bits, detected from a vicinity of the servo sync mark of the disk, matches with a given comparison bit pattern; and changing a pattern of tolerance bits based on a location of the disk where the servo sync mark is detected, so that the matching between the detection bit pattern and the comparison bit pattern is performed based on the changed tolerance bit pattern.
The above-mentioned objects of the present invention are achieved by a disk apparatus in which a servo sync mark of a disk is detected, the disk apparatus comprising: a determination unit which determines whether a pattern of detection bits, detected from the servo sync mark of the disk, matches with a given comparison bit pattern; and a control unit which changes a pattern of tolerance bits based on a location of the disk where the servo sync mark is detected, so that the determination unit is allowed to perform the matching between the detection bit pattern and the comparison bit pattern based on the changed tolerance bit pattern.
The servo information detection method and the disk apparatus of one preferred embodiment of the present invention are effective in accurately and reliably detecting the servo information in the disk without being influenced by an insignificant defect on the disk. Even if a medium defect of the size of 1 bit or more is included in the detection bit pattern, the presence of the servo syn
Ashikaga Hiroshi
Suzuki Nobuyuki
Davidson Dan I.
Fujitsu Limited
Greer Burns & Crain Ltd.
Hudspeth David
LandOfFree
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