JP2630003B2 - Magnetic storage device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a storage device such as a sector servo type magnetic disk device.

[Prior Art] A magnetic storage device that stores data by reversing the magnetization on a magnetic medium usually has a plurality of data tracks,
When recording and reproducing data, it is necessary to correctly position a magnetic head, which is an exchange, on a data track. As one of the positioning methods of the magnetic head, a sector servo method is known. Hereinafter, a magnetic disk device will be described as an example. In a magnetic disk drive, a plurality of data tracks exist concentrically, and a magnetic head is positioned at any of the tracks, and data is written or read.
In the sector servo method, various information (servo information) for positioning the magnetic head is written in a part of each.

As a conventional apparatus, for example, there is an apparatus described in JP-B-63-50761. FIG. 5 is a diagram showing a servo information array of the sector servo system, in which the recording surface of the magnetic disk (1) is divided into a plurality of sectors in a sector shape and the data area (2) and the servo area (3) are alternately arranged. I do. Note that (4) shows a data track. In FIG. 5, only one is shown for convenience, but a plurality of concentric data tracks are actually formed. An address code indicating the address of the data track is recorded in the servo area (3). FIG. 6 shows a configuration example of servo information in the servo area (3).

In the figure, PPA is the preamble, PAD is the address data, PP
OS is precise position data. SB1 to SB18 indicate servo bit cells. Information "1" or "0" is stored in each servo bit cell depending on the presence or absence of a magnetization reversal pair. Sixth
In the figure, the position of the magnetization reversal is indicated by an arrow. In the example of FIG. 6, the case where the magnetization reversal pair exists is indicated as “1”. The address data stored in the PAD unit is represented by a gray code. The advantages of using the Gray code are described in other documents, for example, Japanese Patent Publication No. 58-501644. That is, according to the Gray code, in adjacent tracks, the address data (or address code) is 1
Since only the bits are different, one of the address data is read even when the magnetic head is positioned over two tracks. FIG. 7 shows an example of the configuration of a servo area including address data based on a gray code. (4) shows each data track, (11) shows an erase gap portion where there is no magnetization reversal, (12) shows a preamble, (13) shows a sector mark, and (14) shows gray-coded address data. . Note that the example of FIG. 7 only shows an example as an information code, and does not show the correspondence with the magnetization reversal.

[Problems to be Solved by the Invention] Since the conventional magnetic storage device has the servo area as described above, if the address data is erroneously read, it may be recognized as a track at a position far apart from the actual position. is there. In Japanese Patent Publication No. 58-501644, the same gray code is repeatedly written three times as a countermeasure, but it requires a lot of space and is uneconomical. When the address data "1" and "0" correspond to the presence or absence of magnetization reversal,
With data in which "0" or "1" is continuous, there is a problem that magnetization reversal does not exist for a long time and is regarded as an erase gap.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and provides a magnetic storage device that can reproduce correct or close address information even if there is a 1-bit address error and that does not misidentify an erase gap. The purpose is to:

[Means for Solving the Problems] In the magnetic storage device according to the present invention, "1" and "0" of the address code in the sector servo information are made to correspond to the presence or absence of the magnetization reversal pair, and continuous "1" or "0". The information unit (address set) constituting the address code differs only by one bit between adjacent tracks, differs only by two bits between two adjacent tracks, and has three or more bits between three or more tracks. It shall be configured differently.

[Operation] The address code in the present invention is a sequence of "1".
Alternatively, since the number of “0” is limited, the length of the section where the magnetization reversal does not exist is limited to a value smaller than the length of the erase gap portion, so that this portion is not erroneously recognized.
In addition, by setting the address code for each track as described above, the address can be reproduced correctly or with an error of the first address even if one bit is read.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows an example of the configuration of the servo area (3), where (21) is a burst section, (11) is a gap section, and (22).
Is the synchronization unit, (13) is the identification unit, (14) is the address code,
(23) is a position detection unit. The position detection section (23) has written therein an information pattern that can detect a minute position change within the range of each track. Of the other servo information, except for the synchronization section (22), the case where the magnetization reversal pair exists in each servo beat portion is illustrated as “1”, and the case where it does not exist is illustrated as “0”. In the synchronizing unit (22), a special pattern is recorded so that magnetization reversal occurs not at each servo bit but at a boundary position of the servo bit so that the timing can be correctly detected. In the example shown in FIG. 1, there is a gap portion (11) having a length of 4 servo bits.

FIG. 2 shows the first half of the servo area (3) shown in FIG. 1 in detail. The boundaries between the servo bit portions are indicated by broken lines. The arrow indicates the portion of the magnetization reversal, and the direction is distinguished by the direction of the arrow. The servo bit portion indicating the address code (14) is called an address bit and is indicated by A1 to A10. Although FIG. 2 illustrates the case of 10 bits, the number of bits can be any number if necessary. P1 is a bit provided for separation from the subsequent position detection unit.

FIG. 3 shows an address code in one embodiment of the present invention. In this example, an example is shown in which 32 track addresses are encoded by 10 bits. Therefore, the address following address 32 is repeated from address 1 again. In setting the address code, the following four conditions must be satisfied.

"0" does not continue for 4 bits.

The address codes of adjacent addresses differ only by one bit.

The address codes of two tracks separated by 2 bits are different.

The address codes of tracks that are three or more tracks apart differ by three bits or more.

Here, the condition is that the length of the gap is 4 servo bits, and if the length of the gap changes, it can be changed accordingly. Further, in this example, the case where the existence of the magnetization reversal pair is set to "1" is shown, so that the continuation of "0" is limited. Under this condition, since there is no DC erase portion equal to or larger than the gap portion, the gap portion is not erroneously detected except for the normal portion.

Next, the following conditions will be described with reference to FIG. FIG. 4 shows what address is determined when one bit of the address code of the address 1 is erroneously read somewhere. If the first bit (A1) is incorrect, the resulting code 1101010010 is a code that does not match any of the 32 codes shown in FIG. In this case, it is determined which code the read code is closest to.
Then, since both address 1 and address 31 have the same distance with a difference of 1 bit, address 32 between them is determined as the address code. Actually, since the address is at address 1, an error for one track is obtained, but control can be performed to such an extent that there is no problem in practical use. Next, consider the case where the second bit (A2) is incorrect. Also in this case, the address code 000010010 is the third
It does not exist in the 32 codes shown in the figure. In this case, the code at the address 1 is closest by a difference of 1 bit, and there is no other code having a difference of 1 bit.
Hereinafter, if A3, A4, A5, A6, and A9 are incorrect, it is similarly determined to be address 1. If the 7th bit (A7) and the 8th bit (A8) are incorrect, they match with the address codes of addresses 2 and 32, respectively, so judgment is made.
The difference from the actual address is one track, and can be controlled as described above. If the 10th bit (A10) is erroneous, it is the same case as the error of A1. Since the codes having one bit difference become addresses 1 and 3 this time, it is determined to be an intermediate address 2. This is also one track different from the actual value.

[Effects of the Invention] As described above, according to the present invention, even if one bit of an address code is erroneously read, the address can be corrected to a correct address or an adjacent address, and the DC erase existing in the address code part can be corrected. Since the part is shorter than the length of the gap part, there is no misidentification. Therefore, there is an effect that a highly reliable magnetic storage device can be obtained with a low probability of malfunction.

[Brief description of the drawings]

FIG. 1 is a diagram showing the configuration of a servo area according to one embodiment of the present invention, FIG. 2 is a detailed view of the first half of the servo area shown in FIG. 1, and FIG. 3 is an address code according to one embodiment of the present invention. FIG. 4, FIG. 4 is a diagram showing the situation of a one-bit error in the address code of FIG. 3, FIG. 5 is a diagram showing the arrangement of servo areas in the sector servo system, and FIG. 6 and FIG. It is a figure showing an example. (2) is a data area, (3) is a servo area, (4) is a data track, (11) is an erase gap, (12) is a preamble, (13) is an identification section, (14) is an address code, and (21). ) Indicates a burst section, (22) indicates a synchronization section, and (23) indicates a position detection section. In the drawings, the same reference numerals indicate the same or corresponding parts.

 ────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-2-27571 (JP, A) JP-A-2-137172 (JP, A) JP-A-2-137112 (JP, A) JP-A-3-137 130973 (JP, A)

Claims (1)

(57) [Claims] A magnetic storage device of a type in which data sectors for recording data on a magnetic recording medium and servo sectors for recording information for positioning a magnetic head are provided alternately.
The servo sector includes a burst portion in which a single-cycle magnetization reversal is recorded, a gap portion in which no magnetization reversal exists, a synchronization portion in which timing reference information is recorded, an index and sector identification, and guard band identification. And an address code indicating the address of the data track. Each of these parts is constituted by a combination of information units (servo bits) indicating 1-bit servo information. In each section except for the section, code information "1" or "0" is represented depending on whether or not a magnetization reversal pair exists in the servo bit, and the address code indicates the number of servo bits in which no continuous magnetization reversal pair exists in the gap. The number of servo bits is smaller than the number of servo bits in adjacent sections, and the adjacent track has only one bit different address code. Unlike 2-bit address code is click, magnetic storage apparatus characterized by being configured to different address code 3 bits or more is three or more apart tracks.