GB2340290A

GB2340290A - A system and method for identifying track information on a hard disk drive

Info

Publication number: GB2340290A
Application number: GB9816978A
Authority: GB
Inventors: Me Van Le; E W William; Vien Nguyen
Original assignee: Samsung Electronics Co Ltd
Current assignee: Samsung Electronics Co Ltd
Priority date: 1998-08-04
Filing date: 1998-08-05
Publication date: 2000-02-16
Anticipated expiration: 2018-08-05
Also published as: CN1244705A; JP2000057716A; GB2340290B; DE19835882A1; DE19835882B4; GB9816978D0; CN1132177C

Description

1 2340290 PROVIDING POSITIONAL INFORMATION OF A DISK

BACKGROUND TO THE INVENTION

The present invention relates in general to disk storage systems and more particularly, to a method and apparatus for providing positional information on a disk in a hard drive assembly.

Disk drives are magnetic recording devices used for the storage of information. The information is typically recorded on concentric tracks on either surface of one or more magnetic recording disks. To facilitate the storage and retrieval of data in an orderly manner, disks are typically organised in blocks called sectors. These sectors are located on the disk by a set of unique specifiers called cylinder (or track), head (or side) and sector number. The disks are rotatably mounted to a spin motor and information is accessed by means of read/write heads that are mounted to actuator arms which are rotated by a voice coil motor. The voice coil motor is excited with a current to rotate the actuator and move the heads.

The movement of the actuator is controlled by a servo 25 system, utilising servo information recorded on one or more of the magnetic recording disks. By reading this servo information, the actual radial positions of the heads can be determined, and after comparison with the desired head radial positions, control signals can be sent to move the actuator accordingly. Servo information is typically stored on a disk in one of two ways. in the first, a dedicated servo system, a set of several tracks on the disk or the entire disk surface, is reserved 2 exclusively for storing information associated with the characteristic of the particular drive. Such information includes servo parameters and read/write channel parameters. A servo head reads this information to provide a continucs signal indicating the position of the servo head with respect to the servo disk. In the second type of servo system, the embedded servo system, sectors of servo information are interspersed with sectors of data on each disk surface. As a read head follows the data track around, it regularly reads a fresh sample of servo information from each servo sector with which to control its position.

Figure 1 illustrates a typical sector on a disk of a hard 00"C' 15 disk drive. As shown, a typical sector 10 has a preamble field 20 which includes automatic gain control (AGC) information and synchronisation information, a servo address mark 22 which signifies the beginning of a sector, an index field 24 which indicates the beginning of the first sector of the track, an identification field 26 which includes identification bits, a head identification field 28 for identification of head location, a gray code field 30 that identifies the particular cylinder (tracks) of the sector, a servo bit field 32 which includes a number of servo bits A, B, C, D and a data f ield 34 which contains the data. The servo bits A, 2, C and D are used to maintain the read/write head on the centerline CL of a corresponding track. The identification field 26 typically includes an index bit and 7 bits of angular position information; the head identification field 28 typically includes 3 bits of data

3 for identifying the head (or side) position of the disk pack and the gray code field 30 typically includes 13 bits of data for providing track identification. In conventional disk drives, absolute positional information is stored in graycode in the gray code field 30 of a particular sector 10. Due to power consumption, cost and throughput concerns, reduction of media space used in providing the servo information is highly desirable. However, most of the segments of the sector 10 are head and/or media dependent and reduction of these segments is difficult.

Accordingly, there is a need in the technology for a method and apparatus for providing servo information on a -7, 15 disk in a hard drive assembly while reducing the media space required for the provision of such information.

SUMMARY OF THE INVENTIO

Accordingly, the present invention provides a disk for a hard disk drive, comprising:

a disk having at least one side with a plurality of tracks, each of said tracks having a f irst burst in a first servo field and second burst in a second servo field, said first burst providing a first portion of track position information and said second burst providing a second portion of track position information, said first and second portions in combination providing a position of a corresponding track.

Preferably, said first burst and said second bursts are located on consecutive sectors of each track.

4 Each track may further comprise a third burst that provides a sector sequence number that identifies the sequence position of each of said consecutive sectors.

Each track may further comprise a third burst that provides a third portion of track position information, said first, second and third portions in combination providing a position of a corresponding track.

Preferably, said first, said second and said third bursts are located on consecutive sectors of each track.

Preferably, each track further comprises a fourth burst that provides a sector sequence number that identifies the sequence position of each of said consecutive sectors; said first, second and third portions and their corresponding sequence numbers in combination providing a position of a corresponding track.

Each track may further comprise a third burst that provides a quadrant position of said disk.

Preferably, said disk has a second side with a second plurality of tracks, wherein each track on each side of said disk includes said first burst and said second burst.

Each track on each side of said disk may further comprise a third burst and a fourth burst, said third and fourth bursts providing a first portion and a second portion of disk side position information respectively, said first and second portions of disk side position information in combination providing a position of a side of the disk.

The present invention also provides a hard disk drive, 5 comprising:

housing; spin motor mounted to said housing; an actuator arm mounted to said spin motor; a disk attached to said spin motor, said disk having at least one side with a plurality of tracks, each of said tracks having a first burst in a first field and second burst in a second field, said first burst providing a first portion of track position information and said second burst providing a second portion of track position information, said first and second portions in combination providing a position of a corresponding track; and a read/write head mounted to said actuator arm for reading said at least one side of said disk. 20 The present invention also extends to a method of providing servo information on a disk in a hard disk drive, comprising the steps of: (a) providing a disk having at least one side with a plurality of tracks, each of said tracks having a first in a first servo field and a second burst in a second servo field, said first burst providing a first portion of track position information and said second burst providing a second portion of track position information; 30 (b) reading said first burst; (c) reading said second burst; and

6 (d) combining said first and said second portions to provide a position of a corresponding track.

BRIEF DESCRIPTION OF THE DRAWINGS 5 The present invention will now be described by way of example with reference to the accompanying drawings in which:

Figure 1 illustrates a typical data sector of a disk in a conventional disk drive assembly; Figure 2 is a top view of a hard disk drive assembly which utilises the apparatus and method of the present invention; Figure 3A illustrates exemplary sectors on heads HO H3 sides 1-4) of the disk pack 100 of Figure 2; 0 cc 15 Figure 3B illustrates an enlarged view of a typical c C- sector of on one side of the disk pack 100 of Figure 3A as provided in accordance with the present invention; Figure 4A illustrates a plurality of consecutive sectors on one side of the disk pack 100, in accordance with the present invention; Figure 4B illustrates four bits of head position information as provided by the SDAT fields of sectors 2 and 3 in Figure 4A respectively; and

Figure 4C illustrates the thirteen bits of track position information, of which bits 8-13 are provided by the SDAT fields of sectors 4-6 of Figure 4A and of which bits 0-7 are provided by the Graycode field from each sector of Figure 4A.

DETAILED DESCRIPTION OF THE INVENTION

The present invention is an apparatus and method for 7 referring to the drawings more particularly by reference numbers. Figure 2 illustrates a hard disk drive 50 which utilises the method of the present invention. The disk drive 50 includes a disk pack 100 with a plurality of disks 102 that are collectively rotated by a spin motor 104. The spin motor 104 is mounted to a base plate 106.

Also mounted to the base plate 106 is an actuator arm assembly 108. The actuator arm assembly 108 includes a number of read/write (R/W) heads 110a-d mounted to corresponding flexure arms 112. The flexure arms 112 are attached to an actuator arm 114 that can rotate about a bearing assembly 116. The assembly 108 also contains a voice coil motor 118 which moves the heads 110a-d collectively relative to the disks 102. There is typically a single head 110a, 110b, 110c or 110d for disk head side HO, H1, H2 or H3 (not shown), respectively, of the disk pack 100. The spin motor 104, voice coil motor 118 and the R/W heads 110a-d are coupled to a number of electronic circuits 120 typically include a read channel chip, a microprocessor-based controller and a random access memory (RAM) device.

As shown in Figure 3A, data is typically stored within sectors 1401 1402 and 1403 of radially concentric tracks located across any one of the disk heads HO-H3 of the disk pack 100. For discussion purposes, any one of the sectors 1401 1402 and 1403 will be referred to as sector 140. In one embodiment, as shown in Figure 3D, each sector 140 has a preamble field 150 which includes automatic gain control (AGC) information and synchronisation information, an address mark 152 which 8 signifies the beginning of the sector 140, an index field 154 which indicates the beginning of the f irst sector of the track, a servo sector sequence number (SSN) field 156 that identifies the sector sequence location number of sector 140 as identified among a plurality of consecutive sectors, a servo multiplex data (SDAT) field 158 that provides the higher order bit information related to positional information of the particular cylinder (track) of the sector 140, a gray code field 160 that provides the lower order bit information related to positional information of the particular cylinder (track) of the sector 140, a synchronisation field 162, a servo bit f ield 164 which includes a number of servo bits A, B, C, D and a data field 166 which contains the data. For present purposes, fields 150-164 will be referred to as the servo field while field 166 will be referred to as the data field. The electronic circuits 120 (see Figure 2) utilise the servo bits A, B, C and D to maintain the heads 110a-d can magnetise and sense the magnetic field of the disk heads HO-H3 so as to provide the information located on the above-described fields 150-166.

In one embodiment, positional information is provided by reading the SSN field 156, the SDAT field 158 and the graycode field 160 of six consecutive bursts of servo data. Table 1 illustrates an example of positional information that is provided in the SSN field 156, the SDAT field 158 and the graycode field 160, and the interrelationship between the fields. Together, ±he information located in the SSN field 156, the SDAT field 158 and the graycode field 160 provide a matrix of

9 positional information for identifying the quadrant, the head and track position of the disk pack 100.

As shown in Table 1, there are 72 servo sectors on a 5 exemplary head, head 4 (M) of the disk pack 100, each labelled from 0-71. The 72 servo sectors aredivided into groups each having six consecutive sectors. Each of the six consecutive sectors can be identified by an SSN of 0-7, since a minimum of 3 bits are required, as provided in the SSN field 156 of each sector 140 (see

Figure 3B). As discussed earlier, the (SDAT) field 158 provides the higher order bit information related to positional information of the particular cylinder (track) of the sector 140, while the gray code field 160 provides the lower order bit information related to positional information of the particular cylinder (track) ofthe sector 140.

In one embodiment, index information is provided in field

156o of section Oas 7 (binary 111). In one alternate embodiment, index information is provided in both sectors 0 and 1. In this case, the index information is provided in SSN f ield 156o as 7 (binary 111) and in SSN f ield 156o, as 6 (binary 110).

TABLE 1

Example of data in servo pattern at Cylinder 24CDH, Heads 4.

Binary CDH Graycode CDH Binary 24H Graycode 26H Servo SNN SDAT <1:0> OFFSET <7:0> COMMENTS Sector 0 7 1.1 CDH Index position, SSN = 7, SDAT = 00 for lst, Y4 rev 1 1 1,0 CDH SDAT = Hd <3:02> 2 2 O'l CDH SDAT = Hd <1:02> 3 3 1,0 CDH SDAT = Cyl <13:12> 4 4 O'l CDH SDAT = Cyl <11:10> 5 1,0 CDH SDAT = Cyl <9:8> 6 6 0,0 CDH SSN 0 so SDAT 0 7 1 1,0 CDH SDAT Hd <3:2> 8 2 O'l CDH SDAT Hd <1:0> 9 3 1,0 CDH SDAT Cyl <13:12> 4 O'l CDH SDAT Cyl <11:10> 11 5 1,0 CDH SDAT Cyl <9:8> 12 0 0,0 CDH 13 1 1,0 CDH ...........

18 0 O'l CDH SDAT 01 for 2nd /4 rev ...........

36 0 1,0 CDH SDAT = 10 for 3rd 1/4 rev ...........

54 0 1,1 CDH SDAT = 11 for 4th 1/4 rev ...........

68 2 O'l CDH 11 69 3 0,0 CDH 4 O'l CDH 71 5 O'l CDH In the present example, the combination of SSN = 0 and an SDAT number identifies the quadrant position on a disk in the disk pack 100. For example, the combination of SSN = 0 and SDAR = 00 identifies a particular position as the first quadrant of a disk, while the combination of SSN 0 and SDAT = 01 identifies a particular position as the second quadrant of the disk. Similarly, the combination of SSN = 0 and SDAT = 10 identifies a particular position as the third quadrant of the disk, while the combination of SSN = 0 and SDAT = 11 identifies a particular position as the fourth quadrant of the disk. However, where SSN = 7 and SDAT =00, it indicates that particular position is the first sector in the firs quadrant of the disk.

In addition, the combination of SSN = 1 or SSN 2 with an SDAT number identifies a particular position as the head (or side position) of the disk pack 100. With reference to Table 1, the combination of SSN = 1 and SDAT = 10 identifies a particular position as head 4 or H3 of the disk pack 100, while the combination of SSN = 1 and SDAT = 01 identifies a particular position as head 3 or H2 of the disk pack 100. Similarly, the combination of SSN = 2 and SDAT = 01 identifies a particular position as head 2 or H1 of the disk pack, while the combination of SSN = 2 and SDAT = 10 identifies a particular position as head 1 or HO of the disk pack 100.

12 Finally, the combination of SSN = 3, 4 or 5 and an SDAT number provides the higher order bit information related to positional information of the particular cylinder (track) of a disk in the disk pack 100. For example, the combination of SSN = 3 and SDAT = 10 or 01 provides the position information of bits 13 and 12, where the bit positions are identified from 0-13 (the 14th and 13th bits among 14 bits) of graycode information required to completely identify the cylinder or track on a disk.

Similarly, the combination of SSN = 4 and SDAT = 01 or 10 provides position information of bits 11 and 10 (the 12th and lith bits among 14 bits) of the graycode information required to completely identify the cylinder, while the combination of SSN = 5 and SDA = 10 or 01 provides positional information for hits 9 and 8 (the 10th and 9th bits among 14 bits) of graycode information required to completely identify the cylinder. The remaining 8 bits of graycode information is located in the graycode field located in each sector 140.

Figure 4A illustrates an example of how the present invention may be implemented utilizing six consecutive sectors on a typical track. The six sectors, SECTORS 0 5, each has an SSN field 156o - 1565, an SDAT field 158o - 1585 and a graycode field 160o - 1605. Each SSN field

1560o - 1565 provides 3 bits of information related to the sector sequence position of each sector SECTORS 0-5 among the 6 sectors, while each SDAT field 158o - 1585 provides 2 bits of information which provides any of the following information when used in combination with the SNN number: (1) identifies the quadrant position of a 13 disk in the disk pack 100: (2) identifies the head (or side) of the disk pack 100 or (3) provides 2 of six upper bits of information related to the track position information; and each graycode field 160o -1605 provides the 8 lower bits of information related to track position information.

As discussed earlier, the combination of SSN = 0 and an SDAT number identifies the quadrant position on a disk in the disk pack 100. In addition, the combination of SSN = 1 or SSN =2 with an SDAT number identifies a particular position as the head (or side position) of the disk pack 100. Finally, the combination of SSN = 3, 4 or 5 and an SDAT number provides the higher order bit information is related to positional information of the particular cylinder (track) of a disk in the disk pack 100.

Figure 4B illustrates the 4 bits of information that may be obtained from two of the six sectors, SECTORS 1 and 2, which together identifies head (or side) position of a disk pack 100. As shown, when the SSN field 1S6 preceding an SDAT field 158 indicates that the SSN is 1 (binary 001), the following SDAT field 158 will provide the upper 2 bits of head positional information. When the SSN field 156 preceding the SDAT field 158 indicates that the SSN is 2 (binary 1010), the following SDAT field

158 will provide the loser 2 bits of head positional information. After reading the SSN fields 1561 and 1562 of the sectors SECTORS 1 and 2, one will obtain the head position information of a particular location of the disk pack 100.

14 Figure 4C illustrates the 14 bits of information that may be obtained from three of six sectors, SECTORS 3 - 5, which together identifies the track (or cylinder) position of a disk pack 100. As shown, each graycode field 160o - 1605 provides the 8 lower bits of information related to track position information. When one of the R/W heads i0oa-d is reading from a track within a particular band of tracks, where there are 256 tracks in one band, the information from the 8 lower bits is sufficient to identify the position of the head.

However, when any of the R/W head 100a-d is moving from one band to another, additional information is required to identify its location. As shown, when the SSN f ield is 156 preceding an SDAT field 158 indicates that the SSN is

3 (binary 011), the following SDAT field will provide the two uppermost bits (bits 13 and 12) of the 14 bits of data required to provide track position. When the SSN field 158 indicates that the SSN is 4 (binary 100), the following SDAT field 158 will provide the following two uppermost bits (bits 11 and 10) of the 14 bits of data required to provide track information. Finally, when the SSN field 156 indicates that the SSN is 5 (binary 101), the following SDAT field 158 will provide the last of the

2S uppermost bits (bits 9 and 8) of the 14 bits of data required to provide track position. Thus, by scanning the SSN field 156, the SDAT field 158 and the graycode field 160 of at least 6 consecutive sectors as provided by the present invention, complete positional information of a particular location on the disk pack 100 may be obtained.

is Through the implementation of the technique of the present invention, servo information on a disk in a hard drive assembly may be provided while reducing the media space required for the provision of such information. As a result, more media space may be utilized for the storage of data.

16

Claims

1. A disk for a hard disk drive, comprising:

2. The disk as recited in claim 1, wherein said f irst burst and said second bursts are located on consecutive sectors of each track.

3. The disk as recited in claim 2, wherein each track further comprises a third burst that provides a sector sequence number that identifies the sequence position of each of said consecutive sectors.

4. The disk as recited in claim 1, wherein each track further comprises a third burst that provides a third portion of track position information, said first, second and third portions in combination providing a position of a corresponding track.

5. The disk as recited in claim 4, wherein said first, said second and said third bursts are located on consecutive sectors of each track.

17

6. The disk as recited in claim 5, wherein each track further comprises a fourth burst that provides a sector sequence number that identifies the sequence position of each of said consecutive sectors; said first, second and third portions and their corresponding sequence numbers in combination providing a position of a corresponding track.

7. The disk as recited in claim 1, wherein each track further comprises a third burst that provides a quadrant position of said disk.

8. The disk as recited in claim 1, wherein said disk has a second side with a second plurality of tracks, wherein each track on each side of said disk includes said first burst and said second burst.

9. The disk as recited in claim 2, wherein each track on each side of said disk further comprises a third burst and a fourth burst, said third and fourth bursts providing a first portion and a second portion of disk side position information respectively, said first and second portions of disk side position information in combination providing a position of a side of the disk.

10. A hard disk drive, comprising: a housing; a spin motor mounted to said housing; 30 an actuator arm mounted to said spin motor; a disk attached to said spin motor, said disk having 18 at least one side with a plurality of tracks, each of said tracks having a f irst burst in a f irst f ield and second burst in a second field, said first burst providing a first portion of track position information and said second burst providing a second portion of track position information, said first and second portions in combination providing a position of a corresponding track; and a read/write head mounted to said actuator arm for 10 reading said at least one side of said disk.

11. The hard disk drive as recited in claim 1, wherein said first burst and said second bursts are located on consecutive sectors of each track.

12. The hard disk drive as recited in claim 11, wherein each track further comprises a third burst that provides a sector sequence number that identifies the sequence position of each of said consecutive sectors.

13. The hard disk drive as recited in claim 10, wherein each track further comprises a third burst that provides a third portion of track position information, said first, second and third portions in combination providing 25 a position of a corresponding track.

14. The hard disk drive as recited in claim 13, wherein said first, said second and said third bursts are located on consecutive sectors of each track.

15. The hard disk drive as recited in claim 14, where--n 19 each track further comprises a fourth burst that provides a sector sequence number that identifies the sequence position of each of said consecutive sectors; said f irst second and third portions and their corresponding sequence numbers in combination providing a position of a corresponding track.

16. The hard disk drive as recited in claim 10, wherein said disk further comprises a second side with a second plurality of tracks, wherein each track on each side of said disk includes said first burst and said burst, each track on each side of said disk further including a third burst and a fourth burst, said third and fourth bursts providing a first portion and a second portion of disk is side position information respectively, said first and second portions of disk side position information in combination providing a position of a side of the disk; and wherein said hard disk drive further comprises a 20 second read/write head mounted to said actuator arm for reading said second side of said disk.

17. A method of providing servo information on a disk in a hard disk drive, comprising the steps of:

(a) providing a disk having at least one side with a plurality of tracks, each of said tracks having a first in a f irst servo field and a second burst in a second servo field, said first burst providing a first portion of track position information and said second burst providing a second portion of track position information; (b) reading said first burst; (c) reading said second burst; and (d) combining said first and said second portions to provide a position of a corresponding track.

18. The method as recited in claim 17, wherein step (a) further comprises the step of:

providing a third burst that provides a sector sequence number that identifies the sequence position of each of said consecutive sectors; and further comprising the step of (e) combining said first and second portions and their corresponding sequence numbers to provide a position of a corresponding track.

19. The method as recited in claim 17, wherein step (a) further comprises the step of providing a third burst that provides a quadrant position of said disk.

20. The method as recited in claim 17, wherein in step (a), said disk has a second side with a second plurality of tracks, wherein each track on each side of said disk includes said first burst and said second burst; and wherein each track on each side of said disk further comprises a third burst and a fourth burst, said third and fourth bursts providing a first portion and a second portion of disk side position information respectively; wherein said method further comprises the steps of: (e) reading said first and second portions of disk side position information; and 30 (f) combining said first and second portions to provide a position of a side of the disk.

21 21. A disk for a hard disk drive, substantially as described herein with reference to FIGs. 2 et seq. of the accompanying drawings.

22. A hard disk drive substantially as described herein with reference to FIGs. 2 et seq. of the accompanying drawings.

23. A method of providing servo information on a disk in a hard disk drive, the method being substantially as described herein with reference to FIGs. 2 et seq. of the accompanying drawings.