Dynamic magnetic information storage or retrieval – General processing of a digital signal – Data clocking
Reexamination Certificate
2000-12-27
2004-03-16
Sniezek, Andrew L. (Department: 2697)
Dynamic magnetic information storage or retrieval
General processing of a digital signal
Data clocking
C360S053000
Reexamination Certificate
active
06707626
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to disk memory devices, and more particularly, to an apparatus and method for detecting synchronous (SYNC) signals written on a disk memory device.
2. Description of the Related Art
Typically, a magnetic disk device is used to store and reproduce the data downloaded to a data processing device, such as a personal computer. In general, the data is recorded in every sector of each recording track contained on the magnetic disk medium of the magnetic disk device. Each sector includes a predetermined number of symbols. Typically in order to reproduce the data from the magnetic disk device, it is necessary to include a mechanism to accurately detect a head symbol provided in front of the recorded data. To achieve this objective, a SYNC signal pattern (hereinafter, referred to as a SYNC pattern) is typically written in front of a data area contained in each sector.
As illustrated in
FIG. 9
, a recording format for a data sector in the magnetic disk medium usually includes a preamble area
91
, a SYNC pattern area
92
, an actual data area
93
, an error detecting code (EDC) area
94
, and an error correcting code (ECC)
95
.
The EDC
94
decodes and synchronously converts the serial data into parallel data. The ECC
95
corrects errors that develop in the reproduced data. In order to reduce the probability of detecting errors in the data, the EDC decoding is performed after the ECC corrects the data.
The preamble area
91
performs a phase lock on the reproduced data. In order to reliably maintain the synchronization of the reproducing data, the SYNC pattern area
92
detects a head position contained in the data area
93
.
Thus, if the device begins to reproduce the data without correctly detecting the SYNC pattern, a timing error for reproducing the data may develop in several of the symbols. Such a shift of the reproducing time is referred to a flaming error. If such flaming errors occur in all of the sectors of the recording medium, such an occurrence is referred to as a burst error. When a burst error occurs, it may be impossible to correct an error detected in the data even if the ECC
95
coding is used on the reproduced data. In essence, it is extremely important to accurately detect the SYNC pattern since the SYNC pattern decides the performances of the magnetic disk device.
Generally, the SYNC pattern detection process is performed by comparing a predetermined reference SYNC pattern, which is recorded when the data is recorded onto the magnetic disk device, with a reproduced SYNC pattern generated when the data is reproduced from the magnetic disk device and by counting a number of symbols that match between the reference SYNC pattern and the reproduced SYNC pattern. Thus, when the number of matching symbols exceeds a predetermined number, then, the synchronization of the reproduced data is successful. Consequently, the device outputs a SYNC detected signal used to convert the serial data into the parallel data.
However, if the SYNC pattern area
92
in a recording sector contains a defect due to a flaw on the magnetic disk medium, it may be impossible to detect the SYNC pattern from the reproduced data. In an attempt to detect the SYNC pattern area
92
, conventional techniques divide the SYNC pattern into groups and perform a comparison between the reference SYNC pattern and a reproduced SYNC pattern in the divided groups. The reproduced SYNC pattern is divided into a plurality of groups so as to assign a symbol only once to each of the divided group. A SYNC detected signal is generated when a predetermined number of symbols in the divided groups matches the symbols in the reference SYNC pattern. Thus, the conventional method for detecting the SYNC pattern area
92
aims to detect a match between a predetermined number of symbols in each of the divided groups with a predetermined number of symbols in the reference SYNC pattern.
However, the conventional method contains a serious defect that will be explained with reference to FIG.
10
.
FIG. 10A
illustrates an example of dividing a SYNC pattern that includes six symbols (S
1
, S
2
, . . . , S
6
), into two groups as shown in FIG.
10
B. Thus, the six symbols of the SYNC pattern is divided into two groups so as to include three symbols in each groups, i.e., the group G
1
includes of the first half of the symbols (S
1
, S
2
, S
3
) and the group G
2
includes of the remaining second half of the symbols (S
4
, S
5
, S
6
). Similarly,
FIG. 10C
shows another example for dividing of the SYNC pattern according to the conventional method. In this case, the SYNC pattern is divided into three groups so as to include two symbols in each groups, i.e., the group G
1
includes two symbols (S
1
, S
2
), the group G
2
includes two symbols (S
3
, S
4
) and the group G
3
includes two symbols (S
5
, S
6
).
As illustrated in
FIG. 10B
, if, for example, two symbols (S
3
, S
4
) among the six symbols (S
1
, S
2
, . . . , S
6
) of the SYNC pattern contain a defect due to a flaw in the recording area, it may be impossible to detect the SYNC since both of the divided groups G
1
, G
2
include one of the defected symbols (S
3
, S
4
).
In comparison, in the case where the SYNC pattern division is divided into three groups G
1
, G
2
, G
3
, as shown in
FIG. 10C
, there are two groups G
1
and G
3
that do not include the defected two symbols S
3
, S
4
. Accordingly, by using either of the two groups G
1
or G
3
, the comparison procedure may be able to successfully match the symbols between the reference pattern and the divided group of either group G
1
or G
3
. Consequently, it may be possible to detect the SYNC signal.
However, since the example of
FIG. 10B
increases the number of the divided groups of the SYNC pattern in comparison to
FIG. 10A
, the number of symbols included in each of the divided groups naturally decreases. In
FIG. 10B
, each of the divided groups includes three symbols. However, in the case of
FIG. 10C
, each of the divided groups includes only two symbols. This creates another problem.
When the comparison between the reference SYNC pattern and the divided group is performed on such a small number of symbols as shown in
FIG. 10C
, the chances of detecting an error in the SYNC pattern increases. For example, as illustrated in
FIG. 9
, the detection of the SYNC pattern usually begins at the preamble pattern area
91
that is written in front of the SYNC pattern
92
. If the preamble pattern
91
receives some influences of noises, since the SYNC pattern has been divided into such a small number of symbols, this increases the probability that the preamble pattern
91
is read as a part of the SYNC pattern
92
during the comparison procedure, which causes a SYNC detection error to occur.
Thus, although it is possible to eliminate the defected symbols from a group by increasing the number of the divided groups of the SYNC pattern. Conversely, such a case also increases the probability of generating an error detection of the SYNC pattern due to the comparison of such a small number of symbols included in each of the divided groups.
Accordingly, the conventional apparatus and method for detecting the SYNC contains serious shortcomings even if the SYNC pattern is divided into a plurality of groups in order to compensate for a defect due to flaws in a disk medium.
SUMMARY OF THE INVENTION
Therefore, there is a need for a device and method to perform a reliable SYNC detection on a disk storage medium even when the storage medium contains a defective recording area.
An apparatus and method for detecting SYNC signals according to the invention solve the aforementioned problems and defects of a conventional apparatus and method. Namely, the object of the present invention is to provide a novel apparatus and method for reliably detecting SYNC signals even when the SYNC pattern area includes defects created by flaws contained in the recording medium.
In order to achieve the above-mentioned objectives, the invention provides an apparatus for detec
Colon Rocio
Kabushiki Kaisha Toshiba
Pillsbury & Winthrop LLP
Sniezek Andrew L.
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