Disk unit and read/write control method

Details Disk unit and read/write control method Disk unit and read/write control method

1998-06-26

2001-01-23

Kim, W. Chris (Department: 2753)

Dynamic magnetic information storage or retrieval

General processing of a digital signal

Data clocking

Reexamination Certificate

active

06178057

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a disk drive which is used as an auxiliary storage device for an information processing system and a writing control method, and in particular, to the disk drive and a read/write control method which offers a simplification in the structure of the drive and high reliability.
2. Description of Related Art
Various techniques to improve a recording density are employed in hard disk drives which are used as auxiliary storage devices for information processing systems.
A known example of these techniques is a multi-zone bit recording technique disclosed in, for example, Japanese Patent Kokai Publication No. 147059/1995. In this technique, a recording surface of a magnetic disk is radially divided into several regions (zones Z
1
, Z
2
and Z
3
) as shown in
FIG. 2
, and the number of data sectors which are located between servo sectors is varied in accordance with the radial position of each zone so that the recording density in each zone, as viewed in the direction of track length of recording tracks, can be made uniform. In this multi-zone bit recording technique, a format is available in which no data sectors (D) are divided by the servo sectors (S) as shown in
FIG. 2
, and in addition, another format is also available in which some data sectors (D) are divided by the servo sectors (S) as shown in
FIG. 3
which is sometimes called a split data field design.
In the hard disk drive which employs the multi-zone bit recording technique, a writing position of each sector is determined using the length of time which has passed since the reading of an immediately preceding servo sector. Since the disk is accurately controlled to rotate at a given number of revolutions during reading/writing, the length of time mentioned above may be determined by providing an oscillator which generates a clock for position detection and counting an output from the oscillator. However, it may also be determined by counting data reading and writing clock (RDWTCLK). The position detection by counting the RDWTCLK offers a simplification in the structure of the drive.
As shown in FIG.
4
(
a
), each data sector is composed of a SYNC+DAM section at which a sync signal (SYNC), an identification information (DAM) for identifying each sector and other information are written, and a DATA+ECC section at which data (DATA) and an error correction code (ECC) are written. As shown in FIG.
4
(
b
), the information is written in each of the SYNC+DAM section and the DATA+ECC section using the RDWTCLK of the constant frequency.
When the RDWTCLK used in the DATA+ECC section is chosen to be of a higher frequency than that used in the SYNC+DAM section as shown in FIG.
5
(
a
) and FIG.
5
(
b
), the data recording density can be increased. Thus the RDWTCLK used in the DATA+ECC section has a different frequency from that of the RDWTCLK used in the SYNC+DAM section. When no reading/writing operation is performed on the recording track, the RDWTCLK of either frequency is generated. Normally, the SYNC+DAM section precedes in the reading/writing operation, and accordingly its associated RDWTCLK is generated.
In such an instance, if the reading/writing operation is started with a sector (as exemplified by XXX in
FIG. 2
) which immediately follows a servo sector, there would not be presented any substantial difficulty when the sector position is detected using the RDWTCLK associated with the SYNC+DAM section since any resulting positional difference will be minimal.
However, if the reading/writing operation is started with a servo sector (as exemplified by YYY in
FIG. 2
) which is located intermediately between the neighboring servo sectors, it will be seen that a read operation from a recording track is not performed until the magnetic head arrives at the intended sector by passing a sector or sectors which are interposed therebetween. Accordingly, the position of the intended sector must be detected using the RDWTCLK in the reading/writing operation of either the SYNC+DAM section or DATA+ECC section. Because the information is written in the SYNC+DAM section and the DATA+ECC section with mutually different clocks, it will be seen that there results in a significant difference in the detected position if only one clock is used in the detection.
To give an example, when it is desired to start the reading/writing operation of data from a sector
12
shown in FIG.
6
(
a
), because the reading of a sector
11
(DATA
2
) is not performed, the RDWTCLK used during the writing in the SYNC+DAM section will be used in detecting the position of the target sector
12
. If the position where the sector
12
begins is then determined using such the RDWTCLK and a count (such as the number of bytes in the DATA
2
) as usual, the detected position will go past beyond the leading portion of the sector
12
, as indicated in FIG.
6
(
b
).
For this reason, it is necessary to detect the beginning position of the target sector by either providing an oscillator which generates a position detecting clock and counting an output from the oscillator as mentioned above or providing oscillators which generates two different RDWTCLKs (RDWTCLK during the write operation in the SYNC+DAM section and RDWTCLK during the write operation in the DATA+ECC section) and counters which counts respective oscillator outputs and causing the HDC to suitably control the coefficient of the counters.
SUMMARY OF THE INVENTION
However, the provision of the oscillator, the counter and other components only for purpose of detecting the beginning position of the target sector results in increasing the drive cost unnecessarily, and adding to the complexity of the structure of the drive, and leaving much to be improved in respect of the reliability. Accordingly, it is an object of the present invention to contribute to reducing the cost and improving the reliability of the disk drive.
A disk drive according to the present invention has a disk-shaped record medium including a plurality of servo regions radially extending on a recording surface, data regions formed by dividing the recording surface by the servo regions, zones formed by dividing radially the data regions, and data sectors which number depends on a radial position on the recording surface and which includes a first region in which reading or writing is made on the basis of a clock (a first clock) of a first frequency and a second region in which reading or writing is made on the basis of a clock (a second clock) of a second frequency. The disk drive also has reference clock generator for generating a reference clock of the first frequency, at least when reading and writing are not made in the data sectors; target sector detector for counting the first clock from the reference clock generator to detect a position of the data sector (a target sector) for which reading or writing is commanded; compensator for compensating for a difference in the detected position of the target sector, said difference in the detected position being produced as a result of a difference in the frequency between the first clock and the second clock; and read/write controller for reading or writing data in the sector located at the position detected by the target sector detector.
Further, servo sectors are written in the servo regions; and the target sector detector may count the first clock to measure a length of time passed since the reading of the servo sector, thereby detecting the position of the target sector.
Furthermore, each of the data regions contains a predetermined number of data sectors, some of which are divided at an arbitrary position by the servo regions. The predetermined number is not limited to an integer. The disk drive may have a first non-volatile memory for storing information relating to positions where the data sectors are written, presence or absence of division of the each data sector and positions where the data sectors are divided, and the

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