Dynamic magnetic information storage or retrieval – General processing of a digital signal – Data in specific format
Reexamination Certificate
2002-08-13
2003-04-29
Faber, Alan T. (Department: 2651)
Dynamic magnetic information storage or retrieval
General processing of a digital signal
Data in specific format
C360S077120, C360S078140, C360S049000, C360S135000
Reexamination Certificate
active
06556365
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a servo format and a data format for a magnetic disk and a magnetic disk device having a wide tracking servo band and high head positioning performance.
FIG. 4
shows an example of constitution of a magnetic disk device (HDD)
100
. HDD
100
includes a head disk assembly (HDA)
200
including a magnetic disk
2
, a magnetic head
1
, a carriage
3
, a read/write integrated circuit (R/W IC)
4
attached onto carriage
3
, and a motor
5
and a package board (PCB)
300
including a read channel
31
, a hard disk controller chip (HDC)
32
, a servo control circuit (SC)
33
, a microprocessor (MP)
34
, a read-only memory (ROM)
36
, and a random access memory (RAM)
37
.
HDD
100
incorporated in a redundant arrays of independent disk (RAID) system or the like needs, in addition to a high-speed transfer rate and a large capacity, strength against external disturbance such as vibration for the following reasons. Many drives (HDDs) are disposed in a housing of the RAID system and operate at the same time and hence cause vibration stronger than that caused by operation of a single HDD. Therefore, to endure the environment, it is required to employ a positioning system which is strong again external disturbance of vibration.
FIG. 5
shows a layout of a servo area
27
and a data area
28
on magnetic disk
2
. The areas are subdivided into a plurality of data zones
29
in a direction from an inner circumference to an outer circumference, and each zone has a data transfer rate. In this situation, to dispose a positioning system which is strong against external disturbance primarily of vibration, it is necessary to decrease the servo sample period and to improve the servo control band. A wide tracking servo band is guaranteed by increasing the number of servo sectors per disk circumference as shown in
FIG. 12
, which will be described later.
FIG. 5
shows an example of construction in which the number of servo sectors is 32.
In a 3.5 inch HDD of 7200 rotations per minute (rpm) to 10000 rpm for the recent RAID system, the number of servo areas
27
can be increased and the servo sample period is reduced by minimizing the length of each servo area
27
per disk. In other words, this is because the physical length of the servo area can be reduced to about one half of the original length by changing the burst cycle frequency to a high value, i.e., from 20 MHz to 40 MHz as shown in
FIG. 12
, which will be described later.
This can be achieved primarily by a signal of a higher frequency (to be referred to as a servo frequency herebelow) for one bit of a servo signal (corresponding to one cycle of a signal in a position error signal (PES)). In the past several years, the servo frequency of the HDD for RAID has rapidly increased from about 10 MHz to a range from about 20 MHz to about 30 MHz, and the number of servo areas per circumference of a magnetic disk has increased from about 50/circumference to about 100/circumference. This has improved the servo band from about 400 Hz to about 800 Hz.
The total length of servo areas
27
in the circumferential direction little changes since the increase in the servo frequency is nearly of the same magnitude as that in the number of servo areas. Consequently, the ratio of allocation of data area
28
is kept unchanged. However, as shown in
FIG. 6
, as the number of servo areas increases, the chance in which a data sector is split (to be referred to as a split sector
25
) in data area
28
becomes greater. This increases additional areas (shade areas in
FIG. 6
) such as AGC (automatic gain control (AGC)/phase locked loop (PLL) acquisition area)
17
of the data sector, and hence the data formatting efficiency is reduced.
FIG. 6
shows in its upper section a reproduced waveform
6
of a servo sector of a full format (the servo sector in this case is a zone corresponding to each servo area
27
drawn with a bold line in the radial direction in FIG.
5
). Full-format servo sector
6
includes an AGC/PLL acquisition area (AGC/PLL)
7
, a servo address mark area (AM)
8
, a servo sector address area (SSA)
9
-
1
, a track ID area (TID)
9
-
2
, and position error signal areas (PESA to PESD)
10
to
13
. This configuration includes PESA to PESD, for example, a signal of a fixed frequency is recorded at different positions in the tracking direction for A to D. Even two kinds thereof such as A and B can achieve the tracking control function.
These areas are arranged on magnetic disk
2
in its circumferential direction with an equal interval therebetween. The areas are discriminated from data to be demodulated according to a servo gate (SGATE)
14
. Data sectors
25
and
26
are formatted in areas other than servo area
27
. If the interval of SGATE
14
is sufficiently large, only a few data sectors are divided by a servo area at an intermediate point thereof as can be seen from a non-split sector
26
, and hence no problem occurs. However, when the interval of SGATE
14
becomes smaller, the number of split sectors
25
divided by a servo area at an intermediate point thereof increases.
Non-split sector
26
includes fields of time (ISG1/2)
16
and
22
necessary for the rise and fall time of a read/write circuit system or the like and for absorption of fluctuation in rotation of magnetic disk
2
, AGC
17
necessary to acquire AGC/PLL, SYNC
18
indicating a start point of data, encoded data (DATA), a cyclic check code (CRC)
23
, an error correction code (ECC)
24
, and PAD
21
necessary to determine data and to absorb a read delay of a read/write channel. However, since split sector
25
needs ISG1/2, AGC, SYNC, and PAD in duplication as indicated by shades, data area
28
is reduced.
One solution of this problem is to increase the servo frequency of servo area
27
. Namely, by minimizing the physical length of the servo area, data area
28
itself is further enlarged. This idea is implemented in a method which, as disclosed in U.S. Pat. No. 5,784,219 (as shown in FIG.
7
), employs a mixed configuration of servo sectors of full format
6
and short format
6
-
1
. Short-format servo sector
6
-
1
is disposed between full-format servo sectors
6
to remove from short-format sector
6
-
1
the AGC/PLL, AM, SSA, and TID fields of the full format, namely, only PES is used. Since full-format servo sector
6
and short-format sector
6
-
1
appear alternately, the difference in format can be discriminated. The prior art shown in
FIG. 7
as a configuration of the alternating arrangement of the full format and the short format of servo sectors. However, consideration has not been given at all to a relationship between this arrangement and the data split.
FIG. 10
shows a configuration example of servo sectors of the prior art. Full-format servo sector
6
of
FIG. 6
includes AGC/PLL, AM, SSA, TID, and PESA to PESD respectively having lengths of 40, 8, 8, 16, and 12×4 cycles, and hence the total length is 120 cycles as shown in FIG.
10
. Short-format servo sector
6
-
1
includes PESA to PESD each having a length of 16.5×4 cycles and the total length is 66 cycles. The PES length is elongated (from 12 cycles to 16.5 cycles) in consideration of fluctuation in the disk rotation and the like. The gain of AGC acquired in the preceding full format area is used for short format
6
-
1
. Since synchronization of PLL is not required to demodulate PES of short format
6
-
1
, AGC/PLL area
7
can be dispensed with.
By opening SGATE
14
-
1
for the short format using as a mark the AM position detected in the preceding full format area, SSA
9
-
1
and TID
9
-
2
can also be deleted for the short format
6
-
1
. In this operation, only full-format servo sector
6
is decoded in the seek operation of the head, and short-format servo sector
6
-
1
is demodulated only in the following operation (in a state in which the head position is held at a predetermined track position). All of four PES information items of PESA to PESD of short format
6
-
1
are not necessary, and it is assumed tha
Antonelli Terry Stout & Kraus LLP
Faber Alan T.
LandOfFree
Storage media having a wide servo band and high data format... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Storage media having a wide servo band and high data format..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Storage media having a wide servo band and high data format... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3041479