U.S. patent application number 09/838127 was filed with the patent office on 2002-02-21 for method and apparatus for recording and reproducing disk-type recording medium with dual head including reading head and writing head having offset cores.
Invention is credited to Hirose, Tsuneo, Kaneda, Yasunori, Katayama, Yukari, Kojima, Akira, Miyazawa, Shoichi, Ogawa, Hitoshi, Saiki, Eisaku, Takashi, Terumi, Tsuneta, Katsuhiro, Tsunoda, Motoyasu.
Application Number | 20020021517 09/838127 |
Document ID | / |
Family ID | 27280762 |
Filed Date | 2002-02-21 |
United States Patent
Application |
20020021517 |
Kind Code |
A1 |
Katayama, Yukari ; et
al. |
February 21, 2002 |
Method and apparatus for recording and reproducing disk-type
recording medium with dual head including reading head and writing
head having offset cores
Abstract
A magnetic disk recording and reproducing apparatus comprising a
unit for inserting an error correcting code related to control
information into said control information on data; a recording
control unit for recording in a plurality of sectors formed by
dividing the recording area of a magnetic disk, each sector having
an ID area for recording said control information and a data area,
provided adjacent to and behind said ID area, for recording said
data; and a error correcting unit for correcting said control
information of said ID area by said error correcting code before
data is read from said data area corresponding to said ID area or
data is recorded in said data area corresponding to said ID
area.
Inventors: |
Katayama, Yukari;
(Yokohama-shi, JP) ; Ogawa, Hitoshi;
(Yokohama-shi, JP) ; Tsunoda, Motoyasu;
(Fujisawa-shi, JP) ; Hirose, Tsuneo; (Odawara-shi,
JP) ; Kojima, Akira; (Odawara-shi, JP) ;
Saiki, Eisaku; (Yokohama-shi, JP) ; Kaneda,
Yasunori; (Yokohama-shi, JP) ; Tsuneta,
Katsuhiro; (Odawara-shi, JP) ; Miyazawa, Shoichi;
(Yokohama-shi, JP) ; Takashi, Terumi;
(Odawara-shi, JP) |
Correspondence
Address: |
ANTONELLI TERRY STOUT AND KRAUS
SUITE 1800
1300 NORTH SEVENTEENTH STREET
ARLINGTON
VA
22209
|
Family ID: |
27280762 |
Appl. No.: |
09/838127 |
Filed: |
April 20, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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09838127 |
Apr 20, 2001 |
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09641772 |
Aug 21, 2000 |
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6236528 |
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09641772 |
Aug 21, 2000 |
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08858460 |
May 19, 1997 |
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6108158 |
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08858460 |
May 19, 1997 |
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08128072 |
Sep 28, 1993 |
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5715105 |
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Current U.S.
Class: |
360/48 ; 360/53;
G9B/19.005; G9B/20.027; G9B/20.053; G9B/27.033; G9B/5.033 |
Current CPC
Class: |
G11B 2020/1265 20130101;
G11B 2220/2516 20130101; G11B 20/1217 20130101; G11B 2020/1297
20130101; G11B 27/3027 20130101; G11B 5/012 20130101; G11B 20/1833
20130101; G11B 2020/1222 20130101; G11B 5/09 20130101; G11B 5/4886
20130101; G11B 2220/20 20130101; G11B 19/04 20130101; G11B
2020/1267 20130101; G11B 2020/1232 20130101 |
Class at
Publication: |
360/48 ;
360/53 |
International
Class: |
G11B 005/09 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 28, 1992 |
JP |
04-257781 |
Feb 1, 1993 |
JP |
05-014781 |
May 20, 1993 |
JP |
05-118593 |
Claims
What is claimed is:
1. A method for recording on and reproducing from a magnetic disk,
the magnetic disk having a recording area divided into a plurality
of sectors, each of the sectors having an ID area for recording
control information relating to data and a data area for recording
the data, the data area corresponding to the ID area and being
provided adjacent to and behind the ID area in the same sector as
the ID area, the method comprising the steps of: recording the
control information in the ID area, the control information
including an error correcting code; correcting errors in the
control information in the ID area using the error correcting code
before reading the data from the data area corresponding to the ID
area and provided in the same sector as the ID area or before
recording data in the data area corresponding to the ID area and
provided in the same sector as the ID area; and reading the data
from the data area corresponding to the ID area and provided in the
same sector as the ID area or recording data in the data area
corresponding to the ID area and provided in the same sector as the
ID area immediately after the control information in the ID area is
read out.
2. A method for recording on and reproducing from a magnetic disk
according to claim 1, wherein in the error correction, an expected
value of the ID of a sector where information is to be read or
written, added with an expected value of the error correcting code
calculated from the expected value of the ID, is compared with a
value actually read from the magnetic disk, and if a discordant
quantity of data exceeds a correctable quantity of data, the ID and
the read value are regarded as discordant.
3. A method for recording on and reproducing from a magnetic disk
according to claim 1, wherein in the error correction, an expected
value of the ID of a sector where information is to be read or
written, added with an expected value of the error correcting code
calculated from the expected value of the ID, is compared with a
value actually read from the magnetic disk, and if a discordant
quantity of data does not exceed a correctable quantity of data,
the ID and the read value are regarded as accordant.
4. A method for recording on and reproducing from a magnetic disk
according to claim 1, wherein the error correcting code is an
instantly correctable code.
5. A method for recording on and reproducing from a magnetic disk
according to claim 4, wherein the error correcting code is a
Hamming code.
6. A method for recording on and reproducing from a magnetic disk
according to claim 4, wherein the error correcting code is a code
formed by being interleaved with an instantly correctable code.
7. A method for recording on and reproducing from a magnetic disk
according to claim 1, wherein the error correcting code has the
same value as in the ID area.
8. A method for recording on and reproducing from a magnetic disk
according to claim 1, wherein magnetic disk control is performed by
an LSI circuit.
9. A magnetic disk recording and reproducing apparatus comprising:
means for inserting an error correcting code relating to control
information in the control information, the control information
relating to data; recording control means for recording the control
information and the data in a recording area of a magnetic disk,
the recording area having a plurality of sectors, each of the
sectors having an ID area for recording the control information and
a data area for recording the data, the data area corresponding to
the ID area and being provided adjacent to and behind the ID area
in the same sector as the ID area; error correcting means for
correcting errors in the control information in the ID area using
the error correcting code before the data in the data area
corresponding to the ID area and provided in the same sector as the
ID area is read or recorded; and means for reading the data from
the data area corresponding to the ID area and provided in the same
sector as the ID area or recording data in the data area
corresponding to the ID area and provided in the same sector as the
ID area immediately after the control information in the ID area is
read out.
10. A magnetic disk recording and reproducing apparatus according
to claim 9, wherein the error correcting means includes means for
comparing an expected value of the ID of a sector where information
is to be read or written, added with an expected value of the error
correcting code calculated from the expected value the ID, with a
value actually read from the magnetic disk, and wherein if the
discordant quantity of data exceeds a correctable quantity of data,
the ID and the read value are regarded as discordant.
11. A magnetic disk recording and reproducing apparatus according
to claim 9, wherein the error correcting means includes means
comparing an expected value of the ID in a sector where information
is to be read or written, added with an expected value of the error
correcting code calculated from the expected value of the ID, with
a value actually read from the magnetic disk, and wherein if a
discordant quantity of data does not exceed a correctable quantity
of data, the ID and the read value are regarded as accordant.
12. A magnetic disk recording and reproducing apparatus according
to claim 9, wherein the error correcting code is an instantly
correctable code.
13. A magnetic disk recording and reproducing apparatus according
to claim 12, wherein the error correcting code is a Hamming
code.
14. A magnetic disk recording and reproducing apparatus according
to claim 12, wherein the error correcting code is formed by being
interleaved with an instantly correctable code.
15. A magnetic disk recording and reproducing apparatus according
to claim 9, wherein the error correcting code has the same value as
in the ID area.
16. A magnetic disk recording and reproducing apparatus according
to claim 9, wherein the respective means are formed on an LSI
circuit.
17. A method for recording on and reproducing from a magnetic disk,
the magnetic disk having a recording area divided into a plurality
of sectors, each of the sectors having an ID area for recording
control information relating to data and a data area for recording
the data, the data area corresponding to the ID area and being
provided adjacent to and behind the ID area in the same sector as
the ID area, the method comprising the steps of: recording the
control information in the ID area, the control information
including an error correcting code; and correcting errors in the
control information in the ID area using the error correcting code
before reading the data from the data area corresponding to the ID
area and provided in the same sector as the ID area or before
recording data in the data area corresponding to the ID area and
provided in the same sector as the ID area; wherein the error
correcting code is a code formed by being interleaved with a
Hamming code which is an instantly correctable code, the error
correcting code having the same value as in the ID area; and
wherein the step of correcting errors includes the steps of: adding
an expected value of an ID of a sector where information is to be
read or written to an expected value of the error correcting code
calculated from the expected value of the ID to obtain a sum value;
comparing the sum value with a value actually read from the
magnetic disk; determining, based on a result of the comparing
step, if a discordant quantity of data exceeds a correctable
quantity of data; regarding the ID and the read value as discordant
if it is determined in the determining step that a discordant
quantity of data exceeds a correctable quantity of data; and
regarding the ID and the read value as accordant if it is
determined in the determining step that a discordant quantity of
data does not exceed a correctable quantity of data.
18. A magnetic disk recording and reproducing apparatus comprising:
means for inserting an error correcting code relating to control
information in the control information, the control information
relating to data; recording control means for recording the control
information and the data in a recording area of a magnetic disk,
the recording area having a plurality of sectors, each of the
sectors having an ID area for recording the control information and
a data area for recording the data, the data area corresponding to
the ID area and being provided adjacent to and behind the ID area
in the same sector as the ID area; and error correcting means for
correcting errors in the control information in the ID area using
the error correcting code before the data in the data area
corresponding to the ID area and provided in the same sector as the
ID area is read or recorded; wherein the error correcting code is a
code formed by being interleaved with a Hamming code which is an
instantly correctable code, the error correcting code having the
same value as in the ID area; and wherein the error correcting
means includes: means for adding an expected value of an ID of a
sector where information is to be read or written to an expected
value of the error correcting code calculated from the expected
value of the ID to obtain a sum value; means for comparing the sum
value with a value actually read from the magnetic disk; means for
determining, based on an output of the comparing means, if a
discordant quantity of data exceeds a correctable quantity of data;
means for regarding the ID and the read value as discordant if the
determining means determines that a discordant quantity of data
exceeds a correctable quantity of data; and means for regarding the
ID and the read value as accordant if the determining means
determines that a discordant quantity of data does not exceed a
correctable quantity of data.
Description
BACKGROUND OF THE INVENTION
[0001] This invention relates to a method and an apparatus for
recording on and reproducing from a magnetic disk having its
recording area divided into a plurality of sectors, each sector
including an ID area and a data area, and more particularly to a
method for recording on or reproducing from a magnetic disk, which
method contributes to increasing the access speed.
[0002] This invention relates to a magnetic recording and
reproducing apparatus for recording on a magnetic disk having a
plurality of divided recording areas, each divided recording area
including an identification area and a data area, and more
particularly to a magnetic recording and reproducing apparatus, a
control circuit for the magnetic recording and reproducing
apparatus and a magnetic recording and reproducing method, which
are most suitable for magnetic recording and reproduction with a
dual head (hereafter referred to the dual head) combining a
reproducing head, such as an MR (magneto-resistive effect) head and
a recording head.
[0003] The bit error rate of data transferred from a magnetic disk
unit to a computer is generally desired to be 1.0E-14 or less.
However, it is virtually impossible to keep the bit error rate of
data read from the magnetic disk at a level of this order.
Therefore, normally, redundant bits for error check or error
correction are added to record data, and a magnetic disk controller
(hereafter referred to as the controller), provided between the
magnetic disk unit and the computer, is used to detect or correct
errors of data which is read by the controller so as to limit the
bit error rate of data from the controller to the computer to
1.0E-14 or less even when the tolerance limit for the bit error
rate of data from the magnetic disk unit is about 1.0E-9.
Incidentally, in view of the error correction capability of the
controller, it is possible to further tolerate the bit error rate
of data read by the controller. If more errors can be tolerated in
accordance with the difference between the current bit error rate
and the deteriorate bit error rate, for example from the current
1.0E-9 to 1.0E-6, in compliance with an increase in the so-called
window margin, the recording density, or the recording capacity of
the magnetic disk can be increased. However, as the bit error rate
is deteriorate, the greater number of times error bits are
corrected. If the correction process time for one error is long, a
large overhead for the error correction process causes the
performance of the apparatus to deteriorate. Heretofore, there has
been a problem that correcting errors takes time for the reason
described below, and after all, the bit error rate of data read
from the magnetic disk into the controller cannot be improved.
Specifically, the magnetic disk is normally divided into a
plurality of sectors for a more effective access. FIG. 2 shows a
recording format for each of the sectors 1, 2, . . . The sectors 1,
2, . . . are divided into the ID areas, ID0, ID1, ID2, . . . and
the data areas DATA0, DATA1, DATA2, . . . The data areas ID0, ID1,
ID2, . . . are each divided into information PROSYNC for phase
synchronization of a PLL (phase lock loop), AM indicating the
leading end of the ID area, C for a cylinder number of data, H for
a head number of data, S for a sector number of data, CRC
indicating whether or not an error has occurred, and ID PAD
indicating a border between the ID area and the data area.
Recording or reproduction of the record format on a data area of
the magnetic disk is executed after information of the ID area of
the same sector is verified. Error detection of the ID information
is performed by comparing an error check code generated by using
the ID information which has been read and an error check code CRC
recorded in advance. This error detection can be done at high
speed, but if an error is detected, data has to be read again (by
retry), for which a waiting time for one rotation of the disk is
required. In order to solve this problem, it has been proposed to
correct errors in the information of the ID area by adding an error
correcting code to the ID area as disclosed in JP-A-63-86160 (Prior
Art 1). However, the conventional method for error correction takes
time. Unless the error correction of the ID area is finished by the
time data is written in the data area specified by the ID, a disk
rotational delay occurs. To avoid this problem, there has been
proposed a method for placing the corresponding ID areas and data
areas in different sectors instead of placing in the same sectors
to thereby secure time for correcting errors, as shown in FIGS. 3A
to 3D.
[0004] In the past, magnetic heads, such as the inductive head or
the MIG (Metal In Gap) head capable of both reading and writing,
were used to read data from or write onto the magnetic disk
unit.
[0005] Recently, dual heads, containing a magnetic head for writing
(inductive, MIG, etc.) and a magnetic head for reading, are
mounted. In addition, an MR (Magneto-Resistive) head, which is not
dependent on the rotating speed of the disk and which is compatible
with small disks, has began to be used for the magnetic head for
reading.
[0006] The dual head as described has a problem that because it is
generally manufactured in a monolithic body including the writing
head and the reading head, a discordance occurs invariably between
the core centers of the two heads in the manufacturing process.
[0007] According to a technique revealed in JP-A-3-160675, in the
magnetic disk unit using a dual head, servo information is provided
separately for writing and reading in the areas on the magnetic
disk which are shifted with respect to each other by the amount
equal to the distance of a radial shift between with the reading
head and the writing head, and under this head configuration, data
can be written into the data area without moving the magnetic head.
(See FIG. 38.)
[0008] Though not disclosed in the above-mentioned patent
publication, the format pattern that the inventors presumed from
the description of the patent publication is shown in FIGS. 39A to
39C. Description will now be made of W.SPLICE. When writing data,
it is confirmed by reading information in the ID area whether or
not an object sector is accessed reading information of the ID area
and the magnetic head unit writes data in the next area. It is
necessary to gain time from this reading until the electronic
circuit for writing becomes ready for operation. The area provided
for gaining this time is W.SPLICE.
SUMMARY OF THE INVENTION
[0009] An object of the present invention is to provide a
high-speed error correction method wherein correction of an error
in the ID area can be finished by the time data is written in the
data area specified by the ID information provided physically in
the same sector, and the corresponding ID area and data area can be
placed in the same sector.
[0010] A second object of the present invention is to provide a
magnetic recording and reproducing apparatus which uses a dual head
and finishes error correction of the identification information by
the time of starting writing data into the data area corresponding
to the identification information placed in the same recording
area.
[0011] A third object of the present invention is to provide a
magnetic recording and reproducing apparatus which uses a dual
head, decodes coded data, such as maximum likelihood decoding, and
which is free from a decrease in formatting efficiency.
[0012] A fourth object of the present invention is to provide a
large-capacity small-size disk-type recording and reproducing
apparatus which uses a dual head.
[0013] A fifth object of the present invention is to provide a
disk-type recording and reproducing apparatus which uses a dual
head and which is capable of high-speed formatting.
[0014] The above-mentioned object of the present invention
(hereafter referred to as the first object) will be described.
[0015] The above-mentioned prior art has a problem that since the
corresponding ID area and data area are not set in the same sector
but are set in the physically different sectors, so that the
control operation of the controller is complicated and
malfunctioning is liable to occur.
[0016] In order to achieve the above-mentioned first object, a
first means is provided by which to finish error correction in the
ID area before data is read from or written into the data area
corresponding to the ID area. More specifically, there is provided
means whereby when an expected value of the ID of the sector where
information is to be read or written, added with an expected value
of an error correcting code calculated from the expected value of
the ID, is compared with a value actually read from the magnetic
disk, if the discordant quantity of data exceeds the correctable
quantity of data, the expected value of the ID and the read-out
value are regarded as discordant.
[0017] Further, to achieve the first object, a second means is
provided by which to finish the error correction of the ID area
before data is read from or written into the data area
corresponding to the ID area. To be more specific, when an expected
value of the ID in the sector where information is to be read or
written, added with an expected value of an error correcting code
calculated from the expected value of the ID is compared with a
value actually read from the magnetic disk, if the discordant
quantity of data does not exceed the correctable quantity of data,
the expected value of the ID and the read-out value are regarded as
accordant.
[0018] Further, to achieve the first object, there is provided a
third means by which to finish the error correction of the ID area
before data is read from or written into the data area
corresponding to the ID area. To be more specific, an error
correcting code in the ID area is formed by being interleaved with
a Hamming code, for example, which is instantly correctable and
relatively short and simple.
[0019] Further, to achieve the first object, as a fourth means, the
error correcting code in the ID area is arranged to have the same
value as in the ID area.
[0020] In the first means, when an expected value of the ID of the
sector where information is to be read or written, added with an
expected value of the error correcting code calculated from the
expected value of the ID, is compared with a value actually read
from the magnetic disk, if the discordant quantity of data exceeds
the correctable quantity t of data, the expected value of the ID
and the read-out value are regarded as discordant. According to the
coding theory, the t symbol error correcting code should have the
minimum Hamming distance of 2t+1 or more, and the distance from one
code to another should be 2t+1 symbols or more. Therefore, data
which, after corrected, can accord with a code including the
expected value of the ID and the expected value of the error
correcting code is never corrected erroneously to other data and
regarded as a discordant data. In addition, an accord/discord
decision can be made taking into account a result of correction
when the last data is read, and therefore, even if a data area
corresponding to an ID area is placed just behind the ID area, data
can be read from or written in the data area corresponding to the
ID area after the value in the ID area has been corrected by
ECC.
[0021] In the second means, when an expected value of the ID in a
sector where information is to be read or written, added with an
expected value of the error correcting code calculated from the
expected value of the ID is compared with a value actually read
from the magnetic disk, if the discordant quantity of data does not
exceed a correctable quantity of data, the value of the ID and the
read value are regarded as accordant. According to the coding
theory, the t symbol error correcting code should have the minimum
Hamming distance of 2t+1 or more, data which, after corrected, can
accord with a code including the expected value of the ID and the
expected value of the error correcting code is never corrected
erroneously to other data and regarded a discordant data. In
addition, an accord/discord decision can be made taking into
account a result of correction when the last data has been read,
and therefore, even if a data area corresponding to an ID area is
placed just behind the ID area, data can be read from or written in
the data area corresponding to the ID area after the value in the
ID area has been corrected by ECC.
[0022] In the third means, an error correcting code of the ID area
is formed by being interleaved with a Hamming code, for example,
which is instantly correctable. Since an accord/discord decision
can be made taking into account a result of correction when the
last data has been read, and therefore, even if a data area
corresponding to an ID area is placed just behind the ID area, data
can be read from or written in the data area corresponding to the
ID area after the value in the ID area has been corrected by
ECC.
[0023] In the fourth means, an arrangement is made so that the
error correcting code of the ID area has the same value as the
value of the ID area, and that when either one or both of the ID
agrees with the value read from the magnetic disk, a decision is
made that two compared values are regarded as accordant. Even if
either one ID cannot be read in a normal manner, an accord/discord
decision is made when the last data is read. Therefore, even if a
data area corresponding to the ID area is placed just behind the ID
area, data can be read from or written in the data area
corresponding to the ID area.
[0024] According to the present invention, even when a data area
corresponding to the ID area is placed just behind the ID area,
data can be read from or written in the data area corresponding to
the ID area by finishing an error correction of the ID area by ECC
without a rotational delay, so that even with a system of a high
bit error rate, a read/write operation can be conducted on the data
area without increasing the access time and furthermore, the
control operation by the controller does not become
complicated.
[0025] The second and third objects of the present invention will
be described. A technique which uses a dual head is disclosed in
Japanese Patent Application No. 3-254953, the contents of which
will be described with reference to FIG. 16.
[0026] FIG. 20 is a schematic diagram showing a track format. The
ID division 3002 in the Figure corresponds to the ID area mentioned
above. As shown in the Figure, an ID division 3002 includes two ID
divisions 3002-1 and 3002-2, in which the same contents are written
as in the conventional magnetic disk. The two ID divisions 3002-1
and 3002-2 are shifted with respect to each other by the amount of
shift (.delta.) between the recording head and the reproducing
head. At track No. N, by using a servo signal division set before
the ID division 3002 (at this time, the center line of the servo
signal division is supposed to coincide with the center line of the
recording head), the recording head 3005 is positioned to the
center line of writing (the data division), and under this
condition, the recording ID division 3002-2 is reproduced (read) by
the reproducing head 3004. At track No. N+1, by use of the servo
signal division, the center lines are set offset by .delta., with
the result that the reproducing head 3004 is positioned to the
center line of reading (the reproducing ID division and the data
division). In this case, the reproducing ID division 3002-1 is
reproduced and the data division 3003 is reproduced. In the manner
as described, by selectively using the two ID divisions 3002-1 and
3002-2, even if the positions of the heads are changed between the
recording and reproducing operations, the ID divisions can be
detected without any positional shift at all times.
[0027] As mentioned in the description of the prior art, it has
been proposed to add an error correcting code (ECC) also to the ID
area to correct errors in information in the ID area. However, in
the prior art, the corresponding ID area and data area are not
placed in the same sector but in physically different sectors,
which results in problems that the control operation of the
controller is complicated and malfunctioning is liable to
occur.
[0028] Also in the technique described in Japanese Patent
Application No. 3-254953, unless error correction of the recording
ID area is finished by the time data starts to be written into the
data area corresponding to the recording ID area, the recording
head passes the leading end of the writing area, so that it becomes
necessary to wait for the head to complete one rotation, thus
producing a rotational delay time. For this reason, a gap needs to
be provided just behind the recording ID area.
[0029] The foregoing process takes place after the signal read by
the head has been decoded to reproduce a digital value. With regard
to decoding, as shown in Nikkei Electronics 1991, 9, 30 pp. 77-106,
it has been proposed to combine an MR head, which is a read-only
head, and the maximum likelihood decoding (Viterbi decoding) in
order to improve reliability of data. However, a problem with this
technique is that the maximum likelihood decoding (Viterbi
decoding) requires a long decoding time, and therefore, the data
area cannot be placed just behind the ID area, with the result that
the formatting efficiency deteriorates.
[0030] The second and third objects of the present invention are to
solve the above-mentioned problems.
[0031] In order to achieve the second and third objects of the
present invention, there is provided a magnetic recording and
reproducing apparatus for magnetically recording and reproducing on
a magnetic disk with a dual head including separate recording and
reproducing heads, wherein the recording area on the magnetic disk
is divided into a plurality of recording areas, each divided
recording area including an identification area having recorded
therein information for identifying the divided recording area,
wherein the identification area is further divided into an
identification area for recording, used when recording, and an
identification area for reproduction, used when reproducing,
wherein there is provided read-out means for reading identification
information from the identification area for recording when
recording and reading identification information from the
identification area for reproduction when reproducing, and wherein
in the same divided recording area, an identification area for
reproduction is placed between an identification area for recording
and a data area.
[0032] Further, the identification area for reproduction has an
error correcting code, and the magnetic recording and reproducing
apparatus comprises identification information memory means for
storing identification information supplied from outside to specify
the data area where data is to be reproduced; data memory means for
processing on a first-in first-out basis reproduced data from a
magnetic disk; a data buffer for storing data output from the data
memory means; error correcting means for correcting errors in the
identification information for reproduction, read from the magnetic
disk, by the error correcting code, and outputting a "not
correctable" signal when error correction is impossible; and data
transfer control means for transferring data stored in the data
memory means to the data buffer when the error-corrected
identification information for reproduction, accords with the
identification information supplied from outside, and not
transferring data to the data buffer when the error-corrected
identification information for reproduction does not accords with
the identification information supplied from outside or when a "not
correctable" signal is received.
[0033] Further, the identification area for reproduction has an
error correcting code, and the magnetic recording and reproducing
apparatus comprises identification information memory means for
storing identification information supplied from outside to specify
the data area where data is to be reproduced; a data buffer for
storing reproduced data read from the magnetic disk; error
correcting means for correcting errors in the identification
information for reproduction, read from the magnetic disk, by the
error correcting code, and outputting a "not correctable" signal
when error correction is impossible; and data invalidating means
for invalidating the data transferred to the data buffer when the
error-corrected identification information for reproduction does
not accord with the identification information for reproduction
supplied from outside or when a "not correctable" signal is
received.
[0034] Further, decoding the identification information for
recording is conducted while the magnetic head passes the
identification area for reproduction and is finished before data is
to be written into the data area corresponding to the
identification area for recording.
[0035] Further, the identification information for reproduction and
data are recorded respectively in the identification area for
reproduction and the data area without having intervene between
those areas at least any one of a data area indicating a border
between the identification area for reproduction and the data area,
a gap area between the identification area for reproduction and the
data area, a synchronization pattern area, and an area indicating a
leading end of the data area.
[0036] Further, formatting means is provided by which when
formatting, identification information for recording is written
during the first rotation, then the written identification
information for recording is reproduced during the second rotation,
and if the information has been written correctly, during the same
rotation, identification information for reproduction is written
just behind the identification information for recording.
[0037] In the present invention, identification information for
recording is added with an error correcting code, the
identification area for recording is placed ahead of the
identification information area for reproduction, and after the
identification information for recording is read, while the
magnetic head passes the identification area for reproduction,
error detection and correction of the identification information
for recording are finished, and therefore, after errors of the
identification area for recording have been corrected, data can be
written in the data area corresponding to the recording
identification area. If error correction of the identification
information for recording has failed, or if the recording
identification information that has been read differs from what is
expected, writing data is terminated, so that data is prevented
from being written into a wrong sector.
[0038] After the identification information for reproduction has
been read, error detection and correction of the identification
information for reproduction is conducted, and data which has been
read during the error detection and correction of the
identification information for reproduction is stored in an FIFO
(first-in first-out) memory (the data memory means for processing
on a first-in first-out basis), and after the error correction is
finished, if the identification information is determined to be
information of the object sector, the data in the FIFO unit is
transferred to the data buffer for storing data to be sent to the
host computer, or if error correction is impossible or the
error-corrected identification information is determined not to be
information of the object sector, the data in the FIFO unit is
invalidated, so that the data area corresponding to the
above-mentioned identification area can be read, and wrong data is
not transferred to the host computer.
[0039] Further, after the identification information for
reproduction has been read, error detection and correction of the
identification information for reproduction is conducted, and data
which has been read during the error detection and correction of
the identification information for reproduction is sent to the data
buffer, when error correction is impossible or the error-corrected
identification information is determined not to be information of
the object sector, the data in the data buffer is invalidated, so
that the data area corresponding to the above-mentioned
identification area can be read, and wrong data is not transferred
to the host computer.
[0040] Further, in the present invention, since the identification
area for recording is placed ahead of the identification area for
reproduction, after the identification information for recording is
read, Viterbi decoding of the identification information for
recording can be executed and finished while the magnetic head
passes the identification area for reproduction, and it is not
necessary to provide an idle area to gain time for Viterbi coding
and correction between the identification area for recording and
the data area, with the result that the formatting efficiency is
improved.
[0041] Further, an identification area for reproduction and a data
area are successively placed behind one gap and a synchronization
pattern area, so that the gap, the synchronization pattern, etc.
which are provided conventionally, can be omitted, and the decrease
of the formatting efficiency attributable to the increase to the
two identification areas can be reduced.
[0042] Further, when formatting, identification information for
recording is written during the first rotation, the identification
information for recording is read during the next rotation, and
after the identification information is compared with its expected
value and if its adequacy is verified, identification information
for reproduction is written during the same rotation. For this
reason, in the same manner as in the conventional formatting
method, in the next rotation, only the identification information
for recording is checked, so that formatting can be completed with
a smaller number of movements (rotations) than the method in which
the identification information for reproduction is written during
the third rotation after the next.
[0043] According to an aspect of the present invention, in a
magnetic disk apparatus which uses a dual magnetic head and changes
the position the magnetic head for recording and reproducing
operations, and under a system of separately providing
identification information for recording and identification
information for reproduction, designed not to deteriorate the
accuracy of detecting an address division when positioning the
magnetic head for recording or reproduction, the identification
information for recording and the identification information for
reproduction are respectively added with an ECC code and an
identification area for recording is placed ahead of an
identification area for reproduction, and therefore, a little
leeway is provided for error correction between the recording
identification area and the data area, and when writing data, after
errors of the identification area for recording are corrected by
ECC, data can be written in the data area placed physically in the
same sector without deteriorating the formatting efficiency. It
ought to be noted that even in the case where an error correcting
code is not added, an effect is offered that the formatting
efficiency is high because no gap is required behind the recording
identification area.
[0044] According to another aspect of the present invention, while
errors of the identification area for reproduction are being
corrected by ECC, data is stored in the FIFO unit, and after the
correction by ECC is finished, and if the identification area for
reproduction accords with an object identification information,
data is transferred from the FIFO unit to the data buffer, and if
the identification information for reproduction does not accords
with the object identification information, the data in the FIFO
unit is invalidated, and therefore, when reading data, after errors
of the identification area for reproduction have been corrected by
ECC, since no area needs to be provided to gain time, data can be
read from the data area placed physically in the same sector
without reducing the formatting efficiency.
[0045] Further, according to yet another aspect of the present
invention, since the identification area for recording is placed
physically ahead of the identification area for reproduction, time
can be secured for the maximum likelihood decoding (e.g., Viterbi
decoding) and a digital signal process between the recording
identification area and the data area, when writing data, after the
maximum likelihood decoding of the identification area for
recording and the digital signal process are conducted, data can be
written in the data area placed in the same sector without reducing
the formatting efficiency.
[0046] According to a still further aspect of the present
invention, since the identification area for recording is placed
physically ahead of the identification area for reproduction, when
an identification area for reproduction is to be recorded during
formatting, before that, the identification area for recording is
read and the identification information for recording is compared
with an expected value and its adequacy is checked, and after this,
an identification information for reproduction can be recorded
during the same rotation, with the result that the formatting time
can be reduced and moreover, the reliability of the identification
areas can be enhanced.
[0047] The fourth and fifth objects of the present invention will
be described.
[0048] According to a technique revealed in JP-A-3-160675, there is
a problem in the down-sizing and capacity-increasing of the
magnetic disk unit. Because it was necessary to provide twice as
much servo information and ID information as in the case where a
single head is used both for reading and writing.
[0049] The presence of twice as much servo information requires to
used an expensive servo writer or formatting the magnetic disk
which has to be occupied for a long period of time. Because the
format process using such a servo writer continues for long time,
the production cost of the magnetic disk unit increases and it is
difficult to provide a less expensive disk unit, which has been a
problem.
[0050] The fourth and fifth objects of the present invention are to
solve this problem.
[0051] In order to achieve the above object, according to the
present invention, there is provided a disk type recording and
reproducing apparatus comprising a disk type recording medium, and
a dual head including a reading head for reading from the disk type
recording medium and a writing head for writing into the disk type
recording medium, wherein the disk type recording medium having a
plurality of recording tracks, each track having a plurality of
sectors, wherein each of the sectors has an data division and an ID
division provided ahead of a data division disposed in the
circumferential direction of the disk type recording medium,
wherein the ID division has recorded thereon identification
information of the sector, wherein the ID divisions are provided in
positions shifted with respect to each other in the radial
direction of the disk type recording medium by the amount of shift
between the core centers of the reading head and the writing head,
and wherein the data division has identification information of the
sector stored is placed in a position ahead of data to be recorded
and reproduced.
[0052] According to an embodiment of the disk type recording and
reproducing apparatus, by providing only a servo area for reading,
the memory area of the disk type recording and reproducing
apparatus can be utilized to store user data. In this case, to read
data, the dual head has only to be controlled such that the reading
head is positioned to the center of the track. To write data, it is
only necessary to realize control such that the reading and the
writing heads of the dual head offset-positioned by the amount of
shift between the two heads with the reading head positioned to the
center of the track. Meanwhile, if head positioning is done in the
range where the linearity of the position signal cannot be
maintained, the accuracy with which the magnetic head is positioned
to a target position deteriorates, and the track density cannot be
increased. So, considering the linearity of the position signal,
both the write ID area and the read ID area may be positioned
offset with respect to the position signal.
[0053] According to this embodiment, both ID areas for writing and
reading are provided, but, since ID information for reading is
recorded in the data area, in contrast to the case where the ID
division for reading is provided independently of the data area,
the SYNC area, etc. required to read the read ID division can be
removed, so that the storage space for user data is increased.
[0054] In this embodiment, the ID divisions need to be recorded on
the recording medium by being shifted with respect to each other
accurately by the amount of shift between the core centers of those
heads and under this condition, offset positioning of the heads is
performed. When writing servo data, if a laser length measuring
system is used to record the ID divisions, the ID divisions can be
recorded in accurate positions and the heads can be
offset-positioned in the accurate positions. Also in this case, if
the area for ID information and the data area are placed taking the
range of linearity of the position signal into consideration, the
track density can be increased, and the capacity of the disk type
recording and reproducing apparatus can be increased, so that and
it is possible to provide a large-capacity disk type recording and
reproducing apparatus.
[0055] Moreover, when writing servo data, data is recorded on the
medium by completing one track after another, but owing to a blur
in writing between the adjacent tracks, in case positioning the
reading head, there is a possibility that the track center deviates
a little from where it was when servo data was written. In
anticipation of such a case, if a pattern for measuring a shift
between the core centers is recorded on a specific track of the
medium and if this pattern is read with the reading head and the
writing head, the value of shift between the cores can be measured,
and by writing the ID division based on the value of shift, offset
positioning of the heads can be achieved.
[0056] According to another embodiment, the apparatus is provided
with another head with a core width which covers the
circumferential widths of the writing head and the reading head,
for example. With this head, the ID area is recorded on the medium.
By this arrangement, recording the ID area on the medium or
rewriting the ID division in the alternate sector process, for
example, can be finished by a single operation, so that high-speed
processing becomes possible.
[0057] According to the present invention described above, it is
possible to provide a disk type recording and reproducing apparatus
of a large capacity and a small size. The present invention has
been described taking the magnetic disk unit for example, but the
present invention can be applied to disk type recording media in
general, including the optical disk.
BRIEF DESCRIPTION OF THE DRAWINGS
[0058] FIGS. 1A to 1D are configuration diagrams showing the format
of the magnetic disk according to a first embodiment of the present
invention;
[0059] FIGS. 2A to 2D are configuration diagrams showing the format
of a conventional magnetic disk;
[0060] FIGS. 3A to 3D are configuration diagrams showing the format
of another conventional magnetic disk;
[0061] FIG. 4 is a configuration diagram of a system according to
the first embodiment of the present invention;
[0062] FIG. 5 is a block diagram of the ECC block for ID according
to the first embodiment of the present invention;
[0063] FIGS. 6A to 6C are operation timing charts of the first
embodiment of the present invention;
[0064] FIG. 7 is other examples of format of the magnetic disk
according to the first embodiment of the present invention;
[0065] FIGS. 8A to 8D are configuration diagrams showing the format
of the magnetic disk according to a second embodiment of the
present invention;
[0066] FIG. 9 is a block diagram showing the ECC block for ID
according to the second embodiment of the present invention;
[0067] FIG. 10 is an operation timing chart of the second
embodiment of the present invention;
[0068] FIG. 11 is a detailed block diagram of the ECC correction
circuit according to the second embodiment of the present
invention;
[0069] FIGS. 12A to 12D are configuration diagrams showing the
format of the magnetic disk according to a third embodiment of the
present invention;
[0070] FIG. 13 is a block diagram showing the ECC block for ID
according to the third embodiment of the present invention;
[0071] FIG. 14 is an operation timing chart of the third embodiment
of the present invention;
[0072] FIG. 15 is an operation timing chart in a fourth embodiment
of the present invention;
[0073] FIG. 16 is an explanatory diagram showing a track format of
the magnetic disk unit of the prior art;
[0074] FIGS. 17A to 17C are explanatory diagrams showing the record
format of the magnetic disk according to the fourth embodiment of
the present invention;
[0075] FIG. 18 is a block diagram of the ECC circuit for
identification information and the drive control section according
to the fourth embodiment of the present invention;
[0076] FIG. 19 is a block diagram of a small-size disk for
realizing a fifth embodiment of the present invention;
[0077] FIG. 20 is an operation timing chart of the fifth embodiment
of the present invention;
[0078] FIG. 21 is a timing chart in a case where the maximum
likelihood decoding is conducted and identification information for
reproduction is written ahead of that for recording;
[0079] FIG. 22 is an operation timing chart in a sixth embodiment
of the present invention;
[0080] FIG. 23 is a block diagram of a small-size disk for
realizing the sixth embodiment of the present invention;
[0081] FIG. 24 is a format operation timing chart in a case where
identification information for reproduction is written ahead of
that for recording;
[0082] FIG. 25 is an operation timing chart in a seventh embodiment
of the present invention;
[0083] FIG. 26 is a block diagram of a small-size disk for
realizing an eighth embodiment of the present invention;
[0084] FIG. 27 is an explanatory diagram of head positions for
recording and reproduction in the prior art;
[0085] FIG. 28 is an explanatory diagram regarding how to obtain
the amount of shift of the heads with respect to each other;
[0086] FIG. 29 is an explanatory diagram showing a format pattern
in a ninth embodiment of the present invention;
[0087] FIGS. 30A to 30C are explanatory diagrams showing details of
a track format in the ninth embodiment of the present
invention;
[0088] FIG. 31 is a flowchart showing a first half of the
formatting procedure in the ninth embodiment of the present
invention;
[0089] FIG. 32 is a flowchart showing a second half of the
formatting procedure in the ninth embodiment of the present
invention;
[0090] FIG. 33 is an explanatory diagram showing a format pattern
in a tenth embodiment of the present invention;
[0091] FIGS. 34A to 34C are explanatory diagrams showing details of
the track format in the tenth embodiment of the present
invention;
[0092] FIG. 35 is an explanatory diagram showing the construction
of the magnetic head according to the tenth embodiment of the
present invention;
[0093] FIG. 36 is a diagram for explaining the relation between the
center of the servo signal and the center of the data area using a
two-phase servo as an example;
[0094] FIG. 37 is a block diagram showing the construction of the
magnetic disk unit;
[0095] FIG. 38 is an explanatory diagram showing the conventional
format pattern; and
[0096] FIGS. 39A to 39C are explanatory diagrams showing details of
the conventional track format.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0097] A first embodiment of the present invention will be
described with reference to FIGS. 1A to 1D, 4, 5, 6A to 6C, and
7.
[0098] FIGS. 1A to 1D are diagrams showing a record format of the
magnetic disk according to the first embodiment of the present
invention. FIG. 1A shows an index signal, one period of which
corresponds to one rotation of the disk. The pulse spacing of the
index signal corresponds to a track length, and the track length is
divided into a plurality of sectors. FIG. 1B shows sector pulses
which occur at every sector. FIG. 1C is a diagram showing a record
format, and FIG. 1D is an enlarged view of the record format in
each sector.
[0099] FIG. 4 is a diagram showing the configuration of a system
which realizes the first embodiment. Reference numeral 101 denotes
a hard disk controller (HDC) for controlling the format and
read/write operation of the hard disk, 102 denotes a CPU for
controlling a servo control circuit 107 and the HDC 101, 103
denotes a host interface for transferring data to the host
computer, 104 denotes a data buffer for temporarily storing data
received through the SCSI bus from the host computer or data
received from the drive, 109 denotes a hard disk, 108 denotes a
head for reading magnetic information on the hard disk and
converting it into electrical signal information, 106 denotes a
read/write control circuit for converting an analog signal read by
the head 108 and converting it into a digital signal, 105 denotes
an encoder/decoder for converting a digital signal such as a 1-7
code converted by the read/write circuit 106 into an NRZ signal or
an NRZ signal supplied from the HDC 101 into a code formed taking
the characteristics of the hard disk into consideration, such as a
1-7 code.
[0100] The HDC 101 comprises a host interface control section 110
for controlling the host interface, a drive control section 111 for
controlling the encoder/decoder 105 and controlling writing and
reading on the hard disk, an ECC control section 112 for
calculating an error correcting code to be added to data which is
written on the hard disk or performing an error detection
calculation on data read from the hard disk, and correcting an
error if there is in the data, a buffer control section 113 for
controlling the data buffer 104, and a CPU input/output control
section 114 for controlling transmission of information from CPU to
the host interface control section 110, the drive control section
111, the ECC control section 112 and the buffer control section
113. And, the ECC control section 112 includes an ECC block 115 for
data and an ECC block 116 for ID. Numeral 121 denotes a drive data
input line for inputting a signal read from the hard disk to the
drive control section in the form of an NRZ signal, 122 denotes a
drive data output line for outputting data to be written on the
hard disk in the form of an NRZ signal, 123 denotes a write gate
which becomes active when data is going to be written on the hard
disk, 124 denotes a read gate which becomes active when data is
going to be read from the hard disk, 120 denotes a data input line
for inputting data for ECC calculation to the ECC control section,
and also serves as a signal line for inputting data from the hard
disk or data sent through the SCSI bus from the host computer into
the ECC arithmetic section. Numeral 119 denotes an ECC output line
for transferring an ECC calculation result, which is to be written
on the disk in a write operation, to the drive control section, 118
denotes an accord signal indicating that the ECC correction result
of ID area accords with ID being searched, 117 denotes a discord
signal indicating that the ECC correction result of ID area does
not accord with ID being searched. Numeral 125 denotes a CPU
setting signal line by which the CPU sets an expected value of ID
or the like. FIG. 5 is a block diagram of the ECC block for ID.
Numeral 126 denotes an ID register for storing an ID number of a
sector set by the CPU setting signal line 125, where data is to be
read or written, and outputting the ID number on an ID signal 136,
and 128 denotes a CRC code generating circuit for generating a CRC
code to be added to the ID area from the ID signal 136 and
outputting the CRC code as a CRC signal 137. Numeral 127 denotes a
ECC signal generating circuit for generating an ECC code from the
ID signal 136 and the CRC signal 137 and outputting the ECC code to
an ECC signal 138. Numeral 130 denotes a selector for selecting one
of the ID signal 136, the CRC signal 137, and the ECC signal 138 to
output onto an ECC output line 119. Numeral 131 denotes a control
circuit for controlling output timing of the ID register 126 and
the selector 130. Numeral 132 denotes a comparator which compares
ID information read from the hard disk and input from the data
input line 120 with an expected value of ID information input from
the ECC output line 119, and if they accord with each other,
controls an increment signal to be "false" and if they do not
accord with each other, controls the increment signal to be "true".
Numeral 133 denotes a counter which counts up when the increment
signal 140 is "true" and outputs the count on a count signal 141,
134 denotes a comparator which compares the count signal 141 and a
correctable symbol number 135 and when the count signal 141 is
greater than the correctable symbol number 135 at the end of code
comparison, outputs a discord signal 117, and when the count signal
141 is smaller than the correctable symbol number 135, outputs an
accord signal 118.
[0101] The ECC block for ID operates as shown in FIGS. 6A to 6C.
When writing ID, as shown in FIG. 6A, the control circuit 131
controls the selector control signal 139 to be 1 so that the value
of the ID register set by the CPU is first output on the ECC output
line 119. In the cases shown in FIGS. 6A to 6C, "00000000" in
hexadecimal notation is output onto the ECC output line 119. At the
same time, the CRC code generating circuit 128 and the ECC code
generating circuit 127 respectively divide the supplied value of
the ID register by a generating polynomial GCRC (x) of the CRC code
and a generating polynomial GECC(x) of the ECC code and obtain the
remainder. On completion of outputting the value of the ID
register, the control circuit 131 controls the selector control
signal so as to be 2 so that the calculation result of the CRC code
is output to the ECC output line 119. In the cases of FIGS. 6A to
6C, since the remainder of the division of "00000000" by GCRC(x) is
"00", "00" is output onto the ECC output line 119. The ECC code
generating circuit 127 further divides the calculation result of
the CRC code by the generating polynomial GECC(x) and obtains the
remainder. When finishing outputting the calculation result of the
CRC code, the control circuit 131 controls the selector control
signal to be 3 so that the calculation result of the ECC code is
output onto the ECC output line 119. In the cases of FIGS. 6A to
6C, since the remainder of a division of "0000000000" by GECC(x) is
"0000", "0000" is output onto the ECC output line 119. The drive
control circuit 111 asserts the write gate 123 so that
"00000000000000" on the ECC output line 119 is output on the drive
data output line 122 and "00000000000000" is written on the hard
disk.
[0102] When ID is read and data is read or written on the hard
disk, operations take place as shown in FIGS. 6B and 6C.
Synchronized with a timing of reading ID data from the data input
line 120, the control circuit 131 controls the ECC code generating
circuit 127, the CRC code generating circuit 128 and the selector
circuit 130, and outputs an expected value of ID information to the
ECC output line 119. In the cases of FIGS. 6A to 6C,
"00000000000000" is output on the ECC output line 119. The
comparator 132 compares ID information read from the hard disk with
the expected value of ID information on the ECC output line 119,
and if those pieces of information discord with each other, the
counter 133 increments by one. In the case of FIG. 6B, since data
read from the hard disk is "0001000100000000" in hexadecimal
notation, supposing that one symbol is four bits, the count of the
counter is 2 at the end of comparison. If an ECC code which is of a
two-symbol-correctable type, in the case of FIG. 6B, because the
count 2 of the counter does not exceed the correctable symbol
number 2, the comparator 134 outputs an "accordance" signal 118 at
the end of comparison. By this signal, the drive control section
111 asserts the write gate or the read gate to enable data to be
read or written on the hard disk. By control arranged as described,
in this first embodiment, the ECC correction of the ID area can be
finished before access is made to the data area placed just behind
the ID area, and therefore, even if a data area corresponding to
the ID area is placed just behind the ID area, after ECC error
correction of the ID area has been finished, data can be read from
or written into the data area corresponding to the ID area without
any rotational delay. In the case of FIG. 6C, since the data read
from the hard disk is "00000000010B4800", supposing that one symbol
is four bits, the count of the counter at the end of comparison is
4. In the case of FIG. 6C, since up to two symbols can be
corrected, the comparator 134 outputs a discordance signal 117 at
the end of comparison. In response to this signal, the drive
control section 111 does not asserts the write gate or the read
gate, nor does it perform a read/write operation of data on the
hard disk. By such control, in the first embodiment, the ECC error
correction of the ID area is limited to the number of correctable
symbols, leaving no chances of malfunctioning. This embodiment is
possible even if any of the formats organized as shown in FIG. 7
are used. The contents of for the separation into ECC1 and ECC2 is
that ECC1 is the ECC code for the C, H and S records and ECC2 is
the ECC code for the F record. This embodiment is compatible with
any ID area formats.
[0103] A second embodiment of the present invention will be
described with reference to FIGS. 4, 8A to 8D, 9, 10 and 11.
[0104] FIGS. 8A to 8D are diagrams showing a recording format of
the magnetic disk according to the second embodiment of the present
invention. FIG. 8A shows an index signal, one period of which
corresponds to one rotation of the magnetic disk. The pulse spacing
of the index signal corresponds to a track length, and one track
length is divided into a plurality of sectors. FIG. 8B shows sector
pulses which occur at every sector. FIG. 8C shows a recording
format, and FIG. 8D shows an enlarged view of the recording format
of each sector.
[0105] FIG. 4 is a diagram showing the configuration of a system
which realizes the first embodiment, and FIG. 4 also serves as a
diagram showing the system configuration which realizes the second
embodiment.
[0106] FIG. 9 is a block diagram of the ECC block for ID. Numeral
201 denotes an ID register for storing an ID number of a sector set
by the earlier-mentioned CPU setting signal 125, where data is to
be read or written, and outputting the ID number on the ID signal
202, and 203 denotes an ECC correction circuit for ECC correction
on ID information read out through the data input line 120. When
the ID information is correctable, the ECC correction circuit
instantly corrects its error and outputs the error-corrected ID
information on an ID corrected signal 204, or if the ID information
is not correctable, the ECC correction circuit outputs an ECC-NG
signal 205 to the CPU. Numeral 206 denotes a comparator which
compares the ID signal 202 and the ID corrected signal 204, and if
those signals accord with each other and the ECC-NG signal 205 is
not "true", the comparator asserts the accord signal 118. FIG. 11
is a detailed block diagram of the ECC correction circuit 203.
Numeral 208 denotes a shift register, and data is shifted in the
order of
00.fwdarw.01.fwdarw.02.fwdarw.03.fwdarw.10.fwdarw.11.fwdarw.12.fwdarw.13.-
fwdarw.. . . FIG. 10 is the operation timing chart of the detailed
block diagram in FIG. 11, and shows a case where a burst error of
"000000111100 . . ." is superposed on a code of "0000000000000000 .
. .". In the elements "03, 13, 23, 33, 43, 53, 63, 73, 83, 93, A3,
B3" of the shift register 208, bits "000000010000" are stored at
the timing (a) in FIG. 10. At S0, S1, S2 and S4, the binary voltage
levels are 0,1,1,1, and as a result, at 2045 the signal is at an
inverted level of the level at 73. The points 2041, 2042, 2043,
2044, 2046, 2047 and 2048 have the binary digits at the elements
B3, A3, 93, 83, 63, 53, and 43. By the operation as described, the
ID corrected signal 204 has a code "0000000000000000 . . ." as the
result of correction and is output at timings (a), (b), (c), and
(d) in FIG. 10. By control implemented as described, in the second
embodiment, the ECC error correction of the ID area can be finished
before access is made to the data area placed just behind the ID
area. Therefore, even when the data area corresponding to the ID
area is placed just behind the ID area, after the ECC error
correction of the ID area has been finished, a read/write operation
on the data area corresponding to the ID area can be conducted
without any rotational delay.
[0107] Next, a third embodiment of the present invention will be
described with reference to FIGS. 4, 12A to 12D, 13, and 14.
[0108] FIGS. 12A to 12D are diagrams for showing the recording
format of the magnetic disk according to the third embodiment of
the present invention. FIG. 12A shows an index signal, one period
of which corresponds to one rotation of the disk. The spacing of
the index pulses corresponds to a track length, and one track
length is divided into a plurality of sectors. FIG. 12B shows the
sector pulses which occur at every sector. FIG. 12C is a diagram
showing the recording format, and an enlarged recording format is
shown in FIG. 12D.
[0109] FIG. 4 is a diagram showing the system configuration which
realizes the first embodiment of the present invention, but it also
serves as a diagram showing the system configuration which realizes
a third embodiment.
[0110] FIG. 13 is a block diagram of the ECC block 116 for ID.
Numeral 301 denotes an ID register for storing an ID number of a
sector set by the earlier-mentioned CPU setting signal 125, where
data is read or written, and outputting the ID number on an ID
signal 302, and 303 denotes a CRC checker which performs CRC check
on the ID information read through the data input line 120, and if
the result of CRC check is normal, controls the normalcy signal 305
to be "true", or if the result of CRC check shows an error,
controls the normalcy signal 305 to be "false". Numeral 304 denotes
a comparator which compares the ID number of the sector supplied by
the ID signal 302, where data is to be read or written and the ID
number read from hard disk and supplied through the data input line
120, and if they accord with each other, controls the ID accord
signal 304 to be "true" or if they discord with each other,
controls the ID accord signal to be "false". Numeral 307 denotes a
latch which is set when the ID accord signal 306 and the normalcy
signal 305 are both "true", and outputs an accord signal 118.
[0111] The operation of the third embodiment will be described with
reference to FIG. 14. Suppose that "00000000" is set by the CPU as
the ID number of the sector on which a read/write operation is
performed. The ID register 301 outputs "00000000" twice onto the ID
signal at the timing of input of ID information through the data
input line 120. Suppose that "0000000010" is read as the first ID
information as an error enters through the data input line 120.
Since the ID signal 302 and the ID number supplied by the data
input line accord with each other, the comparator 304 controls the
ID accord signal 306 to be "true". However, because the result of
CRC check shows an error, the normalcy signal 305 is not "true".
Suppose if "0000000000" is read as the second ID information,
because the ID signal 302 and the information on the data input
line 120 accord with each other, the comparator 304 controls the ID
accord signal 306 to be "true". In addition, since the result of
CRC check turns out to be normal, the normalcy signal 305 becomes
"true" and the latch 307 is set so that the accord signal 118 is
"true". By control arranged as described, in the third embodiment,
if one of two pieces of ID information in the ID area is read
correctly, data of the sector can be read correctly, thus making it
possible to improve the reliability of ID information. As an
accord/discord decision can be finished before access is made to
the data area placed just behind the ID area, even if a data area
corresponding to the ID area is placed just behind the ID area,
even when an error occurs in data in the ID area, data can be read
from or written in the data area corresponding to the ID area
without deterioration of access time to perform the read/write
operation. Note that though ID information is put twice in the ID
area, the ID information may be stored three or more times
repeatedly.
[0112] A fourth embodiment of the present invention will now be
described with reference to FIGS. 15, 4, 17A to 17C, and 18. FIGS.
17A to 17C are diagrams showing the recording format of the
magnetic disk according to the fourth embodiment of the present
invention. FIG. 17A shows sector pulses which occur at every
sector. FIG. 17B shows a recording format, and FIG. 17C is an
enlarged view of the recording format of the ID area of each
sector. FIG. 4 shows the first embodiment and also shows the
configuration of a system for realizing the fourth embodiment. This
embodiment shows a case where the present invention is applied to a
small-size disk serving as a magnetic recording and reproducing
unit.
[0113] This small-size disk comprises a hard disk controller 101
(referred to as HDC for short; functions as the control circuit and
reading means for the magnetic recording and reproducing unit) for
controlling the format, read and write operations on the hard disk,
CPU102 (data transfer control means, data invalidating means,
format means) for controlling the servo control circuit 107 and the
HDC101, a host interface 103 for transferring data to the host
computer, a data buffer 104 for temporarily storing data received
through the SCSI bus from the host computer or data received from
the drive controller, a disk 7 for storing data, a dual head 6
including a recording head for converting electrical signal
information into magnetic information on the disk 7 and a
reproducing head for reading magnetic information on the disk and
converting it into electrical signal information, a read/write
control circuit 106 for converting an analog signal read with the
dual head 6 into a digital signal or a digital signal to be written
on the disk into an analog signal, and an encoder/decoder for
converting a digital signal such as a 1-7 code converted by the
read/write control circuit 106 into an NRZ signal or converting an
NRZ signal supplied from the HDC101 into a code formed taking the
characteristics of the disk 7 into consideration, such as a 1-7
code.
[0114] The HDC 101 comprises a host interface control section 110
for controlling the host interface, a drive control section
(read-out directive outputting means) 3111 for controlling the
encoder/decoder 105 and controlling writing and reading on the disk
7, an ECC control section (error correcting means) 112 for
calculating an error correcting code to be added to data which is
written on the disk 7 or performing an error detection calculation
on data read from the disk 7, and correcting an error if there is
in the data, a buffer control section 113 for controlling the data
buffer 104, and a CPU input/output control section 114 for
controlling transmission of information from CPU to the host
interface control section 110, the drive control section 111, the
ECC control section 112 and the buffer control section 113. And,
the ECC control section 112 includes an ECC block 115 for data and
an ECC block 116 for ID.
[0115] Numeral 121 denotes a drive data input line for inputting in
the form of an NRZ signal a signal read from the hard disk to the
drive control section, 122 denotes a drive data output line for
outputting in the form of an NRZ signal data to be written on the
hard disk, 123 denotes a write gate which becomes active when data
is going to be written on the disk 7, 124 denotes a read gate which
becomes active when data is going to be read from the disk 7, and
120 denotes a data input line for inputting data for ECC
calculation to the ECC control section and also serves as a signal
line for inputting data from the disk 7 or data sent through the
SCSI bus from the host computer into the ECC arithmetic section.
Numeral 119 denotes an ECC output line for outputting the result of
ECC calculation, which is to be written on the disk in an write
operation, 118 denotes an accord signal indicating that the ECC
correction result of the ID area accords with the ID being
searched, 117 denotes a discord signal indicating that the ECC
correction result of the ID area does not accord with the ID being
searched. Numeral 125 denotes a CPU setting signal by which the CPU
sets an expected value of ID or the like. Numeral 126 denotes data
(ECC-NG signal 410, etc.) transferred between the ECC control
section 112 and the CPU input/output control section 114.
[0116] The ID division provided on the magnetic disk will be
described with reference to FIG. 15. FIG. 15 is a schematic diagram
showing a track format. A track is divided into a plurality of
sectors (recording areas), and each sector has written therein an
ID (identification) area for recording 3011, an ID (identification)
area for reproduction 3012, and a data division (data area) 3013 of
a fixed length. Since the sector servo system is used, a servo
signal division, not shown, is written, too. Described in the
above-mentioned two ID areas are a synchronization pattern signal
(SYNC), an area showing a leading end of each area (AMI), a
cylinder number (C), a head number (H), a sector number (S), a flag
(F) showing whether or not the sector is defective, etc. The ID
areas have data already recorded before the magnetic disk is
shipped, and can be rewritten while in use.
[0117] The same contents are written in the recording ID area 3011
and the reproduction ID area 3012 as in the conventional magnetic
disk. The recording ID area 3011 and the reproduction ID area 3012
are located offset by the amount of positional shift (8) between
the recording head and the reproducing head. If, in a recording
operation, the reproducing head is positioned to the recording ID
area, the recording head 3005 can be positioned to the center
position of writing. In a reproduction operation, the reproducing
head 3004 is positioned to the reproduction ID area 3012. In the
manner as described, by selectively using the two ID areas between
the recording and reproducing operations, even if the positions of
the heads are changed between the recording and reproducing
operations, an ID division can always be detected without any
positional shift.
[0118] FIG. 18 is a block diagram of an ECC block 3116 for ID and a
drive control section 3111. Numeral 3401 denotes an ID register
(identification information memory means) for storing an ID number
of a register set by the above-mentioned CPU setting signal 3125,
where information is to be read or written, and outputting the ID
number on the ID signal 3402, 3403 denotes an ECC correction
circuit for performing ECC correction on ID information read
through the data input line 3120, and outputting a corrected ID
information on an ID corrected signal 3404 when error is
correctable or an ECC-NG signal 3410 to the CPU when the error is
not correctable. Numeral 3412 denotes a CRC checker which performs
CRC check on the ID corrected signal 3404, and if the result of CRC
check is OK, controls a CRC error signal 3413 to be "false" or if
the result of CRC check shows an error, controls the CRC error
signal 3413 to be "true". Numeral 3405 denotes a comparator which
compares the ID signal 3402 and the ID corrected signal 3404, and
if they accord with each other and the ECC-NG signal 3410 is
"false" and the CRC error signal 3413 is "false", asserts an accord
signal 3118, or if they discord with each other or the ECC-NG
signal 3410 is "true" or the CRC error signal 3413 is "true",
asserts a discord signal 3117. Numeral 3407 denotes an FIFO unit
for temporarily storing data read from the data area while ECC
decision/correction is in progress, 3408 denotes a gate for
performing control of whether or not to output data accumulated in
the FIFO unit to the data buffer according to the value of the
accord signal 3118. Numeral 3406 denotes a R/W register showing
whether data is being read or written, and if the R/W register 3406
shows "read", the read mode signal 3411 is "true". When the R/W
register 3406 shows "write", the read mode signal 3411 becomes
"false". Numeral 3129 denotes an ID read-in timing signal which is
asserted when ID is read in.
[0119] The operation of the fourth embodiment will be described
with reference to FIG. 15. Generally, when a burst error is
corrected by hardware, error correction requires about the same
time as time taken for reading data. Furthermore, when CRC check is
adopted, after errors are corrected, CRC check needs to be
conducted, so that an additional time of about the same length as
time for reading data is required.
[0120] Description will start with the operation in writing data.
In the fourth embodiment, a recording ID area is placed ahead of a
reproduction ID area, and therefore, when writing data, after ID
information is read in, while the dual head passes the reproduction
ID area, the error correction and CRC check of the recording ID
area can be finished. If, at the end of CRC check, the ID corrected
signal 3404 and the ID signal 3402 accord with each other and the
CRC error signal 3413 and the ECC-NG signal 3410 are both "false",
the comparator 3405 asserts an accord signal 3118. In a data write
operation, the read mode signal 3411 is set to be "false", so that
the write gate 3123 is asserted.
[0121] The operation in reading data will next be described. Also
when data is read, ID information is first read in, and then, the
ID information is subjected to error correction and CRC check. When
data is read, there is no time for error correction and CRC check
before the data area starts to be read by the head. Therefore, at
the start of the data area, the read gate 3124 is asserted
unconditionally, and data read in is accumulated in the FIFO unit
3407. After error correction is finished, if CRC check is OK, the
accord signal 3118 is asserted, the gate 3408 is put in the open
state to allow data to be transferred from the FIFO unit 3407
[0122] An example of the method for obtaining .delta. will be cited
in the following. For instance, the positional discrepancy between
the recording head and the reproducing head can be measured
directly by SEM (scanning electron microscope) or the like, but the
physical shape and the reproduced area do not necessarily agree
with each other. For this reason, it is desirable to obtain the
positional shift from reproduced output as shown in FIG. 28. In
FIG. 28, when the reproducing head (R) 3004 and the recording head
(W) 3005 are located with a certain positional shift, by changing
the head position (X) with respect to a recorded position (X=0) as
the datum, the recorded data is reproduced. By this operation, a
relation between reproduced output (V) and the head position (X) is
obtained. Output points A and B, which are a fixed value (.DELTA.V)
lower than the maximum output value, are obtained, and from
positions X.sub.A and X.sub.B, the value of positional shift
(.DELTA.X) is obtained as (X.sub.A+X.sub.B)/.sup.2. Or otherwise,
tangent lines (differential values of output) are drawn at points
X-.sub.A and X.sub.B, and from the point of intersection, the
positional shift (.DELTA.X) can be obtained (FIG. 28). The
above-mentioned methods can be used with a disk unit having the
heads mounted as described. Therefore, the positional shift between
the heads can be obtained automatically when servo information is
recorded, for example, which results in an improved
productivity.
[0123] A fifth embodiment of the present invention will be
described with reference to FIGS. 19, 20 and 21. FIG. 19 is a
diagram showing the configuration of a system for realizing the
fifth embodiment. This system configuration diagram is almost
identical with FIG. 4 showing the system construction of the first
embodiment, excepting that the ECC control section 3112 is related
only to ECC for the data division, and that the read/write control
circuit 3106 includes the digital filter 3126 and the Viterbi
decoder 3127.
[0124] Using FIG. 21, description will be made of problems
accompanying a case where the ID for reproduction is written ahead
of the ID for recording. As shown in FIG. 21, the use of a digital
signal process and Viterbi decoding improves the data reproduction
capability and reliability, but the process with a digital filter
and the Viterbi decoding process take time, so that a delay time is
required from when data is read in until the data is recognized by
the HDC. For a while after ID for recording is read until the HDC
recognizes that this ID information agrees with the ID of a sector
as the destination, the Data cannot be written on the disk 3007. As
a result, it is necessary to put an invalid area between the ID
area for recording and the data area as shown in FIG. 21, so that
the overall format efficiency falls.
[0125] Referring to FIG. 20, the second embodiment will be
described next. When data is written, after an ID for recording is
read before the head proceeds to the data area, there is an ID for
reproduction, and while the head is passing the ID for
reproduction, the ID for recording can be recognized, so that data
can be written in the data area without an invalid area being
required. When data is read, it takes time for the ID for
reproduction to be recognized, but likewise the digital filter
process on the data area and Viterbi decoding take time, so that no
problem arises when an ID area for reproduction and a data area are
arranged continuously. As illustrated, the delay by Viterbi
decoding and the digital signal process can be lessened by
arranging an ID for recording physically ahead of the ID for
reproduction.
[0126] A sixth embodiment of the present invention will be
described with reference to FIGS. 22 and 23. FIG. 23 is a diagram
showing the configuration of a system for realizing the sixth
embodiment. This system configuration diagram is almost identical
with FIG. 4 showing the system configuration of the fourth
embodiment, excepting that an ECC control section 3112 is only
related to ECC for the data division, and that an FIFO unit 3128
for storing data read from the drive is installed in the drive
control section.
[0127] The sixth embodiment will be described next with reference
to FIG. 22. The separate provision of ID for recording and ID for
reproduction so as to correspond to the construction of the dual
head 3006 gives rise to problems of an increased ID area and a
decreased formatting efficiency. In the sixth embodiment, when data
is written, the ID area for recording is read, and if the ID
information agrees with the ID of an object sector, ID for
reproduction and data are written successively. When data is read,
the ID area for reproduction and the data area are read
successively, and data is input into the FIFO 3128. If the ID
information is information to be written in the object sector, the
data stored in the FIFO 3128 is transferred to the data buffer
3104. If the ID information is not information to be written in the
object sector, the data stored in the FIFO 3128 is invalidated.
Since the ID for reproduction and data can be read with the same
reading head, by performing control as described, if the ID for
recording is placed physically ahead of the ID for reproduction,
the synchronization pattern area (DATA SYNC, DATA AMI) between the
ID area for reproduction and the data area can be omitted.
[0128] Then, a seventh embodiment of the present invention will be
described with reference to FIGS. 24 and 25. The seventh embodiment
concerns formatting. FIGS. 24 and 25 are schematic diagrams showing
the track format.
[0129] Referring to FIG. 24, description will be made of problems
with a case where the ID for reproduction is written. As shown in
FIG. 24, in formatting, in the first rotation, the center of the
recording head 3005 is positioned to the recording ID writing line
3014 and a recording ID division 2-2 is recorded. In the second
rotation, the center of the reproducing head 3004 is positioned to
the recording ID writing line 3014 and the recording ID 2-2 is
checked to read if it has been written correctly. In the third
rotation, with regard to the ID number written correctly, the
recording head 3005 is positioned to the reproduction ID writing
line 3015, and the reproduction ID and data are written. In the
final fourth rotation, the center of the reproducing head 3004 is
positioned to the reproduction ID writing line 3015 and the
reproduction ID and data are checked to read if they have been
written correctly. In the case where ID for reproduction is written
first as described above, a minimum time of four rotations and the
head positioning time is required to format one track. To know
whether the recording ID and the reproduction ID accord with each
other, there is no other way but to count the number of sectors
from the start of writing.
[0130] Next, a case where ID for recording is written first will be
described with reference to FIG. 25. As shown in FIG. 25, in
formatting, in the first rotation, the center of the recording head
3005 is positioned to the recording ID writing line 3014 and the
recording ID division 2-2 is recorded. In the second rotation, the
center of the reproducing head 3004 is positioned to the recording
ID writing line 3014, and the recording ID division 2-2 is checked
to read if it has been written correctly. In addition, at this
time, the recording head 3005 is positioned to the reproduction ID
writing line 3015, and the reproduction ID and data are written. In
the final third rotation, the reproducing head 3004 is positioned
to the reproduction ID writing line 3015, and the reproduction ID
and data are checked to read if they have been written correctly.
In the case where ID for recording is written first, formatting one
track can be done in a minimum time of three rotations and the head
positioning time. And, ID for reproduction can be written after the
ID for recording is read and confirmed, which results in an
improvement of reliability of ID.
[0131] An eighth embodiment of the present invention will be
described with reference to FIG. 26. FIG. 26 is a diagram showing
the configuration of a system for realizing the eighth embodiment.
This system configuration diagram is almost identical with FIG. 4
showing the system configuration of the fourth embodiment,
excepting that the buffer control section 3113 includes a pointer
3130 showing the address of a data buffer and a pointer start
position register 3132 for storing the start position of the
pointer of the sector. The operation in recording data is the same
as in the fourth embodiment. When data is reproduced, ECC
correction of the ID for reproduction is performed. If the data
area starts to be read by the head while ECC correction is in
progress, the moment data starts to be read data, the value "a" of
the pointer indicating an address of the data buffer is stored in
the pointer start position register 3132. Data read from the disk
3007 is sent through the drive control section 3111 and the buffer
control section 3113, and written from the address "a" of the data
buffer 3104. At the end of ECC correction of the ID for
reproduction, if the ECC correction is successful and the corrected
value of the ID for reproduction is the same as the expected value
of ID, the data to be read out continues to be read and transferred
to the data buffer. At the end of ECC correction of the ID for
reproduction, the ECC correction turns out a failure or if the
corrected value of the ID for reproduction does not accord with the
expected ID value, reading data is terminated and the transfer of
read-out data to the data buffer is terminated, too. Then, the
value "a" of the pointer start position register 3132 is loaded in
the pointer and a start of the next sector is waited. By the
arrangement described, data of the next sector is written again
from the address "a" of the data buffer. By control implemented as
described, in the eighth embodiment, even if a data area
corresponding to the ID area is placed just behind the ID area,
after the ECC correction of the ID area is finished, data can be
read or written in the data area corresponding to the ID area
without any rotational delay. Furthermore, wrong data is prevented
from being transferred to the host computer.
[0132] Yet another embodiment of the disk type recording and
reproducing apparatus according to the present invention will be
described taking its application to a magnetic disk unit as an
example.
[0133] This embodiment relates to a magnetic disk unit which is
provided with a dual head and which positions the magnetic head by
the data surface servo system.
[0134] A ninth embodiment of the present invention will be
described.
[0135] FIG. 29 shows a format pattern of the magnetic disk type
recording medium according to this embodiment.
[0136] In FIG. 29, numeral 5101 denotes the magnetic head viewed
from a direction perpendicular to the disk surface. This magnetic
head is a dual head including a writing head 5102 and a reading
head 5103. As mentioned earlier, the use of a dual head is
accompanied by a problem of shift between the core centers of the
writing head 5102 and the reading head 5103. The reason is that
currently the following accuracy of the head permissible in reading
and writing data with the magnetic head is 0.5 .mu.mpp, but the
shift of the core centers that occurs in the manufacturing process
is as large as about 2 .mu.m.
[0137] As shown in FIG. 29, the format pattern in this embodiment
is formed by a servo area 5105 for servo control over the data
surface and a data area 5106. The data area includes an ID division
5107 and a data division 5108. The ID division 5107 is located in a
position shifted with respect to the servo area 5105 and the data
division 5108 by the amount of shift between the core centers of
the writing head 5102 and the reading head 5103.
[0138] In this case, only one servo area 5105 for servo control of
the data surface is provided for common use in writing and reading.
The center line of the servo area 5105 coincides with the center
line of the data area 5108. In a reading operation, the heads can
be positioned in the same as in the conventional manner, that is,
by reading the servo information in the servo area 5105 and the ID
information in the ID area 5109 of the data division with the
reading head 5103. In formatting, the amount of shift between the
core centers of the writing head 5102 and the reading head 5103 is
first obtained. When writing, the signal strength, as the target of
positioning, of the position signal of the servo area 5105 to be
read with the reading head 5103 is set so that the reading head
5103 is positioned offset by the offset amount X between the core
centers, and as a result, the reading head 5103 is positioned to
coincide with the center of the write ID 5107 and the writing head
is positioned to coincide with the center of the data division
5108. The positioning as described above is referred to as offset
positioning. By offset positioning, when writing data, the reading
head 5103 reads the write ID division 5107 and the writing head
5102 can write data correctly in the data division 5108.
[0139] In this embodiment, only the ID division for writing is
provided in advance, and ID for reading is added as ID information
5109 at the lead of the data division. By so doing, in contrast to
a case where ID information for reading is provided in the ID
division, information such as SYNC, AM, PAD, W.SPLICE other than
fundamental information such as a sector address can be
obviated.
[0140] Therefore, unlike with the conventional magnetic disk unit
using a dual head, the capacity for storing user data can be
increased in the whole disk unit.
[0141] FIGS. 30A to 30C show details of the format pattern.
[0142] Those portions shown in FIGS. 30A to 30C are the same as
those portions shown in FIGS. 39A to 39C using the same names.
[0143] As shown in FIGS. 30A to 30C, in this embodiment, ID
information for reading is included in the data area. Therefore,
though the number of bytes of the write ID area to represent the
same contents of ID information amounts to 31 bytes because the
write ID area has to include additional information, such as GAP,
etc. required for existence of this write ID area. In contrast, the
memory capacity for ID information for reading has only to be no
more than seven bytes, which is one-fourth of the capacity for ID
information for writing. Accordingly, in a magnetic disk unit
adopting a dual head, if this format is used, the sector capacity
is 642 bytes.
[0144] On the other hand, if both write and read ID areas are
provided in the conventional disk unit, the sector memory capacity
amounts to about 666 bytes. This means that according to this
embodiment, a sector with a smaller capacity, specifically 24 bytes
(about 4%) smaller than the capacity of the conventional sector can
store the same amount of user data as in the conventional
sector.
[0145] As described above, by using the format shown in FIG. 29, a
large-capacity magnetic disk unit compatible with the dual head can
be realized.
[0146] In the format shown in FIGS. 30A to 30C, only one piece of
HEADER information each is provided for writing and reading,
respectively. However, because today the recording medium is
acquiring a progressively higher density and the bit error rate is
deteriorating, in order to avoid the ID unreadability at sector
addresses resulting from bit errors, HEADER information may be
recorded more than once successively both for read ID and write
ID.
[0147] Also, in the ECC area in the data area, ECC data, including
ID information for reading and user data, may be stored. Or
otherwise, the ID information for reading and data may be added
respectively with special-purpose ECC data. By this arrangement,
the reliability of ID information is improved, so that the
verification step of the ID information, which has conventionally
been performed each time ID information is written, may be omitted
in the case of ID information for reading. Furthermore, the
reliability of the write ID area may be enhanced by adding ECC data
to CRC data in the write ID area.
[0148] The format used with the magnetic disk unit in the ninth
embodiment has been described. Description will now be made of a
format process to realize this format.
[0149] The format process is a series of steps, such as assigning
addresses to the sectors on the recording medium, verification to
check if recorded data can be read correctly from the medium to
detect defects of the medium, and the alternate sector process and
the alternate track process, which prevent sectors or tracks having
defective portions from place of used to store user data.
[0150] The format process is performed as described in the
following.
[0151] FIGS. 31 and 32 show the procedures of the format
process.
[0152] When data is written in the servo area by a servo writer
prior to the format process, the amount of shift between the core
centers is recorded on an ROM or the magnetic disk recording medium
in the magnetic disk unit. The amount of shift of the core centers
is measured as follows. Specifically, the position of the writing
head is measured accurately by a laser-applied length measuring
system (a laser length measuring system) and data is recorded on a
track on the medium. Then, the magnetic head is moved to a position
where the output of a read signal of data with the reading head is
maximum. The amount of travel of the magnetic head is the amount of
shift between the two cores, and this amount is recorded on the ROM
or the recording medium. Or otherwise, servo information is
recorded on the medium with the writing head, the servo information
recorded on the medium is read with the reading head, and from a
measured shift between the expected value of output of servo
information and the output value of the actual servo signal, a
shift between the centers of the writing and the reading heads is
obtained, and this shift information has only to be recorded on the
magnetic disk recording medium or the ROM.
[0153] In executing an actual format process, the recorded shift
between the core centers of the dual head is input to the
controller (chiefly the CPU) in the magnetic disk unit (Step 5301).
Or, instead of previously recording the shift between the core
centers of the dual head, a pattern for measuring a shift between
the core centers of the dual head is recorded on a specific track
on the medium, and each time a power is supplied to the disk unit
or at fixed periods, the magnetic head is moved to this track to
measure a shift between the core centers, and it stored RAM etc.
into controller and in a format process, the measured shift is
input into the controller in the magnetic disk unit.
[0154] In order to start formatting, the cylinder number is set to
0 (5302) and the head number to 0 (5303). The writing head is
positioned to record ID for writing at the object cylinder and head
(5304). This can be done by positioning the reading head to the
center of the servo area.
[0155] The write ID areas at the object cylinder and head are
recorded for one round of a track on the medium (5305).
[0156] Next, the head number is incremented by one (5306). If at
this time the magnetic head number is not larger than the number of
heads provided in the disk unit, the write ID areas are recorded
continuously at the same cylinder on the medium (5307). If the head
number is larger, the cylinder number is incremented by one (5308).
If the cylinder number is not larger than the number of cylinders
provided, the write ID areas are recorded on the tracks of this
cylinder (5309). If the cylinder number is larger than the number
of cylinders provided, this means that the write ID areas have been
recorded on all disk surfaces.
[0157] Then, the read ID information is recorded on the medium. In
this writing operation, by taking the amount of shift between the
core centers into consideration, the reading and the writing heads
are positioned offset with respect to each other in such a way that
the center of the writing head is positioned to the center of the
track. Like the write ID areas, the data areas including ID
information for reading are recorded (5310 to 5319).
[0158] Then, to detect defects on the medium, the verification
process is performed.
[0159] However, while the data areas are being recorded on the
medium, the reading head passes right above the write ID areas
previously recorded on all disk surfaces, and if the write ID areas
are read and verified when they are passed, the formatting time can
be reduced (5313 to 5315).
[0160] When any problem is detected in the write ID areas by this
verification, if there remains an alternate sector, an alternate
process is executed, and if there is no alternate sector remaining,
an alternate track process is executed (5315).
[0161] If no problem is found in the write ID areas, the magnetic
head number is incremented by one (5316). If at this time the
magnetic head number is not larger than the number of heads
provided, the data area including ID information for reading is
recorded continuously on the medium (5317). If the magnetic head
number is larger, the cylinder number is incremented by one (5318).
In this case, too, if the cylinder number is not larger than the
number of cylinders provided, the data areas including ID
information for reading are recorded on the tracks of this next
cylinder (5319). If the cylinder number is larger than the number
of cylinders provided, this means that the data areas including ID
information have been recorded on all disk surfaces.
[0162] Finally, as in the verification of the write ID areas, the
data areas including ID information for reading, recorded on all
disk surfaces, are verified (5320 to 5329).
[0163] The format as shown in FIG. 29 has thus been realized.
[0164] The ID divisions may be recorded at the same time when the
servo divisions are recorded. By so doing, the ID divisions can be
recorded more accurately.
[0165] By the format process according to this ninth embodiment,
while the write ID areas are checked, the data areas including ID
information for reading can be recorded on the medium, with a
result that a high-speed format process can be realized.
[0166] A tenth embodiment of the present invention will be
described.
[0167] FIG. 33 is a diagram showing the format pattern in the tenth
embodiment. Those parts which are the same as those in the format
pattern in the ninth embodiment in FIG. 29 are designated by the
same reference numerals.
[0168] The format pattern in the tenth embodiment realizes a
reduction of time for writing the ID divisions and time of
rewriting in the alternate sector process because of common use of
a write ID division and a read ID division.
[0169] As has been described, in the magnetic disk unit using the
dual head, the reason why separate ID divisions for writing and
reading are required is because of the shift which occurs between
the center cores of the two heads. However, since ID for writing
and ID for reading are composed of the same items of information,
basically it is enough to provide one sector with one ID.
[0170] In the tenth embodiment, in the case where the core width of
the writing head is denoted by M, the core width of the reading
head by N, and the amount of shift between the two heads by X, a
head 5501 for writing ID, which has a core width of a length of
about L, is prepared in addition to the writing head and the
reading head. The L is defined by equation 1.
((M+N)/2)+X.ident.L Eq. 1
[0171] where N is the width of the reading head, M is the width of
the writing head, and X is the shift between the core centers of
the reading head and the writing head. The ID writing head 5501, if
manufactured in the manufacturing process of thin film heads, can
achieve a balance with the reading head, so that the output of the
read signal hardly attenuates. By writing an ID division with this
ID writing head 5501, an ID division corresponding to the wide core
width can be realized. Since this core width L can be obtained from
the above equation, even in offset servo control by which the
writing head is positioned to the center of a track to enable data
to be written in the data division, or even when the reading head
is positioned to the center of a track, it never occurs that the
reading head 5103 extends beyond the writing width (in the radial
direction) of the ID division, so that one ID division is enough
for each sector.
[0172] However, since the ID writing width in the radial direction
is wide, if the ID areas are located in the same positions in the
circumferential direction, the spaces between the tracks depends on
the radial recording width of the ID division. So, by shifting the
ID divisions in such a way that they have mutually overlapping
portions, the track pitch is shortened, by which better use can be
made of the recording medium.
[0173] As has been described, according to the tenth embodiment, ID
division writing can be finished by a single writing operation for
each sector, and the track pitch is not expanded so that the
recording medium can be used to advantage.
[0174] FIGS. 34A to 34C show details of the format presented in
FIG. 33.
[0175] As illustrated, in the tenth embodiment, in addition to the
ID area of a given sector itself, because the ID writing head has a
large core width, this given sector needs to have a portion of it
used as one end portion of the ID area of the adjacent track. As a
result, the sector capacity of a sector is 666 bytes. However,
unlike with a magnetic disk unit with a conventional type dual head
which requires two servo areas, one for writing and the other for
reading, in this embodiment it is only necessary to provide a
sector with a single servo area, so that the required number of
bytes is only 58B. This means that in comparison to the
conventional sector capacity of 725 bytes, in this embodiment, the
user area that can be used to store the user's information is
greater as much as 8%.
[0176] This formatting procedure is almost the same as in the
above-mentioned ninth embodiment (FIGS. 31 and 32). When writing
servo data, the amount of shift Y between the writing and the
reading heads 5103 is obtained and stored in advance. In the
flowchart in FIG. 31, when writing the write ID areas on the
medium, according to the servo information read with the reading
head 5103, the ID writing head with a wide core width is positioned
to the object track while keeping the offset amount of Y with
respect to the reading head 5103. In the manner as described, ID
information can be recorded in desired positions of the medium.
When writing data areas, the data areas may be recorded on the
medium by skipping over spaces for the ID areas of the adjacent
tracks. Needless to say, the data areas in this embodiment do not
include ID information for reading.
[0177] FIG. 35 shows the construction of the dual head according to
the tenth embodiment of the present invention.
[0178] The magnetic head 5101 has cores formed on a slider 5701 by
the thin film process. The magnetic head 5101 includes a data
writing head 5703, a data reading head, and an ID writing head
5501.
[0179] As for the types of heads, the data writing head 5703 and
the ID writing head 5501 are the inductive heads, while the data
reading head is an MR head utilizing an MR element 5706 having the
magneto-resistive effect. As described above, the tenth embodiment
requires three cores and the three cores can be manufactured easily
by the thin film process. For example, there has been a type of
head, which has inductive heads fabricated at the left and right
portions of the slider, and one of the inductive heads which has
better characteristics is selected and used.
[0180] If the core width of the ID writing head is denoted by L,
the core width of the data reading head by N, and the shift of the
cores of the data write/read head by X, by designing the magnetic
head so that L satisfies the equation 1, the ID area can be read at
the same rotational angle of the medium when reading and writing
data. By the arrangement described, a magnetic head capable of
recording the format pattern shown in FIG. 33 can be realized.
[0181] Accordingly, in the ninth and the tenth embodiments, in
reading, the reading head is positioned to the center of the track,
and in writing, the reading head is positioned to the offset
position, so that the servo information for reading and writing is
used by the reading and the writing heads by taking turns.
[0182] As shown in FIG. 36, in the case of a 2-phase position
signal used hitherto, to extract signal portions having linearity,
the position signal needs to be switched over from one track to
another. When the position signal is switched over, theoretically,
the position signal strength ought to continue accurately, but it
does not owing to switch-over timing or for other reasons,
resulting in discontinuity of signal strength at switch-over
points.
[0183] Therefore, if the position signal at points of such
discontinuity is used for offset positioning, the magnetic head
vibrates or cannot be positioned properly. Meanwhile, the range in
which the linearity of the position signal can be maintained is for
about .+-.1/4 track from the center of the position signal (in the
case of a 2-phase servo signal, the range depends on the travel of
the head in the radial direction of the servo signal when servo
information is written). In order that the position signal for
offset positioning may always stay away from the switch-over
points, the servo areas are located by being offset from the data
divisions, and not only in writing but also reading, the magnetic
head may be positioned with respect to the write ID division or the
read ID division (including the data division) by offset
positioning.
[0184] In FIG. 36, the hatched regions indicate the portions of the
position signal which lack linearity. The symbol a indicate the
change-over points of the position signal.
[0185] Description will then be made of the construction and the
operation of the magnetic disk unit which positions the magnetic
head according to the various formats described when the ninth and
tenth embodiments were explained.
[0186] FIG. 37 shows the construction of such a magnetic disk
unit.
[0187] As illustrated, the magnetic disk unit includes a mechanical
section 6001 and an electronic circuit section 6002.
[0188] The mechanical section 6001 includes a magnetic disk 6003
for recording data, a magnetic head 5101 for writing and reading
data to and from the magnetic disk 6003, a spindle motor 6005 for
rotating the magnetic disk, a guide arm 6006 supporting the
magnetic head 5101, a VCM (Voice Coil Motor) 6007 for moving the
magnetic head 5101, a case 6008 containing the above-mentioned
component parts, and a board 6009 having mounted thereon an
electronic circuit for controlling the component parts.
[0189] On the other hand, the electronic circuit section 6002
includes a read/write functional section 6010 for writing data on
the magnetic disk and reading data from the magnetic disk, a
mechanism control section 6011 for control of positioning the
magnetic head to position the magnetic head to a target track on
the magnetic head 5101 and for control of the number of revolutions
of the magnetic disk 6003, and a data control section 6012 to
transmit data between the read/write functional section 6010 and an
external system.
[0190] The read/write function section 6010 includes an R/W
amplifier 6013 for recording and reproducing data to and from the
magnetic disk 6003, a waveform shaping circuit 6014 for shaping the
waveform of the signal read from the magnetic head, a data
separator 6015 for extracting basic clock pulses from a read
signal, the waveform of which is shaped by the waveform shaping
circuit 6014, and a discriminator circuit 6016 for converting a
signal read from the magnetic disk into an NRZ code by using the
read signal which has been waveform-shaped by the waveform shaping
circuit 6014 and by also using the basic clock signal, and
converting an NRZ signal sent from the data control section 6012
into a code suitable for recording on the magnetic disk.
[0191] The mechanism control section 6011 includes a position
signal generating circuit 6017 for generating position information
from the positioning signal read with the magnetic head, a head
positioning controller 6018 for performing a magnetic head
positioning process from the generated position information, a
motor driver 6019 for sending an output result obtained by the
magnetic head positioning process to VCM 6007, a spindle motor
control/driver 6020 for controlling the number of spindle motor
revolutions, and a write clock signal generating circuit 6021 for
sending a write clock signal to the read/write function section
6010 according to output of the position signal generating
circuit.
[0192] The data control section 6012 includes an SCSI controller
6022 for transferring data to and from an external system according
to an SCSI (Small Computer System Interface) protocol, an HDC (Hard
Disk Controller) 6023 for converting parallel data received from an
external system into data (normally, serial data) suitable for
recording and reproduction on the magnetic disk, a buffer RAM 6024
for eliminating a difference between an external system-HDC 6023
data transfer speed and an HDC 6023-magnetic disk 6003 data
transfer speed, a CPU 6025 for control of the whole magnetic disk
unit, and a RAM 6026 as the working area of the CPU.
[0193] The magnetic head 5101 is a dual head having a reading head
5103 and a writing head 5102 provided separately.
[0194] As described above, in this embodiment, in reading and
writing data, the reading head 5103 and the writing head 5102 are
positioned to the center of the track (data division), and this
positioning of the heads is controlled by the mechanism control
section 6011.
[0195] The above-mentioned positioning operation will be described
in the following.
[0196] From an external system (host computer), a command is sent
to the magnetic disk unit according to the SCSI protocol. This
command is sent through the SCSI controller 6022 and the HDC 6023
to the CPU 6025. The CPU 6025 interprets the received command, and
decides if a request from the external system is to read data or
write data, and according to the result of decision, issues an
instruction to the section concerned. The CPU 6025, in compliance
with the result of interpretation of the command, issues an
instruction that the magnetic head should be positioned to an
object track.
[0197] The RAM 6026 stores in advance a correction value which
indicates the amount of shift from the track center, by which
amount of shift the magnetic head is to be offset when the magnetic
head is positioned for reading or writing. When the format pattern
shown in FIG. 29 or 33 is used, the correction value is zero in
reading, and the correction value is the amount of shift between
the core centers of the reading head and the writing head. As has
been described, not only in writing but also in reading, when the
magnetic head is positioned with respect to the write ID division
or the read ID division (including the data division) by offset
positioning, the correction value is not zero either in reading or
writing.
[0198] The CPU 6025 issues an instruction to the mechanism control
section 6011 to position the magnetic head to an object track, and
depending on whether the operation is to write or read, reads a
correction value from RAM 6026 and supplies it to the mechanism
control section 6011.
[0199] The head positioning controller 6018 of the mechanism
control section 6011, by using position information generated by
the position signal generating circuit 6017 and the specified
object track and a correction value, obtains the amount of travel
for positioning the magnetic head as discussed in the description
of the first and second embodiments, and sends the result to the
motor driver 6019. By those steps, offset positioning can be
achieved. Therefore, the dual head can be positioned accurately
both in writing and reading.
[0200] As mentioned earlier, as the correction value stored in the
RAM 6026, the amount of shift measured in the format process by
using a laser length measuring system may be stored on the magnetic
disk or in the ROM under supervision of the CPU, and read into the
RAM 6026 when turning on the power supply. Or, when the power is
supplied to the magnetic disk unit, the amount shift between the
writing head and the reading head may be measured and stored in
memory. If the amount of shift varies by the thermal expansion
resulting from the operation of the magnetic disk, the amount of
shift may be updated at specified time intervals.
[0201] In the preferred embodiments described above, since ID
information for reading is written in the data division, unlike in
the case where ID for reading is provided independently of the data
division, those areas which are required for reading, such as the
SYNC, AM, PAD, W.SPLICE areas can be obviated, resulting in an
expansion of the user data area. In terms of capacity, an ID
division has a capacity about 1.2 times as large as before, and
therefore can contain the ID divisions for writing and reading so
as to be compatible with the dual head, and as a result, the memory
capacity can be utilized to advantage to store user data.
[0202] Further, due to the provision of the head for writing ID
with a core width that can cover the amount of shift of the cores
of the dual head, the ID writing operation can be finished by a
single operation. This ID area shows the address of an object
sector and also serves as a place for storing a code to indicate if
the sector is defective. Therefore, even when an alternate sector
process or the like occurs and it becomes necessary to update the
ID information, it is only necessary to update the ID information
once. This operation can be finished in the same process time as in
the conventional updating of the ID area. As a result, a disk unit
with a dual head, which is capable of high-speed updating of ID
information, can be realized.
[0203] Further, by measuring the amount of shift between the core
centers of the writing and the reading heads when writing servo
data and writing the ID divisions by using a laser length measuring
system, ID divisions can be recorded on the medium with high
accuracy.
[0204] Considering the discontinuity at the coupling points of the
position signal, the write ID division and the read ID division
(including the data division) are recorded by being respectively
offset from the track center, so that accurate offset positioning
can be realized.
[0205] In order to realize the various formats explained in the
description of the embodiments, the format process function may be
built in the HDC (Hard Disk Controller) for the data process.
[0206] The embodiments of the disk type recording and reproducing
apparatus according to the present invention have been described by
taking applications to the magnetic disk unit for example, but the
present invention can be applied similarly to the floppy disk drive
unit and the other types of disk type recording medium, such as the
optical disk.
[0207] In the specification of the patent application for the
present invention, the objects of the present invention have been
referred to as the first to fifth objects, but this is only for
convenience of description, and this numerical order does not
represent the order of importance, for example.
* * * * *