Techniques For Identifying Servo Sectors In Storage Devices

• US 20080204926A1
• Filed: 02/22/2007
• Published: 08/28/2008
• Est. Priority Date: 02/22/2007
• Status: Active Grant

• Current Assignee: Western Digital Technologies Incorporated (Western Digital Corporation)
• Original Assignee: Hitachi Global Storage Technologies Netherlands BV (Western Digital Corporation)
• Inventors: Blaum, Mario, Yu, Mantle, Wilson, Bruce
• Granted Patent: US 7,869,152 B2
• Time in Patent Office: Days
• US Class Current: 360/77.05
• CPC Class Codes: G11B 20/1217 on discs
• CPC Class Codes: G11B 2020/1281 Servo information
• CPC Class Codes: G11B 2220/2516 Hard disks
• CPC Class Codes: G11B 5/59688 Servo signal format patterns or signal processing thereof, e.g. dual, tri, quad, burst signal patterns

Abstract

Techniques are provided for identifying the servo sectors in a track on a data storage device. A data storage device identifies the servo sectors in a track by reading distributed index bits from multiple servo sectors in a track. The data storage device analyzes only one index bit from each servo sector to identify the index of a track. In some embodiments, the index of a track can be identified after examining the index bits stored in a particular number of consecutive servo sectors, even in the presence of errors. The index bits in each track can have an error tolerance with a minimum Hamming distance greater than one. In other embodiments, a data storage device compares a sliding window of the index bits read from the servo sectors to all possible N-bit vectors that exist within a pattern of the index bits stored on a track.

Claims

1. A data storage device comprising:

a decoder that reads index bits from servo sectors on a data storage medium to identify an index of the servo sectors in a track, wherein only one of the index bits is stored in each servo sector, and

wherein a pattern of the index bits are stored in servo sectors in at least one track on the data storage medium, and the pattern of the index bits stored in the at least one track of the data storage medium has a fault tolerance defined by a minimum Hamming distance greater than one.

2. The data storage device defined in claim 1 wherein the data storage device is a hard disk drive that further comprises:

a disk comprising a plurality of concentric tracks containing the servo sectors;

a head configured to read data and servo information from the servo sectors on the disk;

an actuator connected to the head for positioning the head to different tracks and maintaining the head on the tracks; and

servo electronics coupled to the decoder for controlling the actuator in response to the servo information read by the head from the servo sectors.

3. The data storage device defined in claim 1 wherein the pattern of the index bits stored in the at least one track of the data storage medium has a fault tolerance defined by a minimum Hamming distance greater than two.

4. The data storage device defined in claim 1 wherein the pattern of the index bits stored in the at least one track of the data storage medium has a fault tolerance defined by a minimum Hamming distance greater than three.

5. The data storage device defined in claim 1 wherein the pattern of the index bits stored in the at least one track of the data storage medium has a fault tolerance defined by a minimum Hamming distance greater than four.

6. The data storage device defined in claim 1 wherein the data storage device compares an N-bit sliding window of the index bits read from the servo sectors to all possible N-bit vectors that exist within the pattern of the index bits stored in the at least one track.

7. The data storage device defined in claim 1 wherein the data storage device compares an N-bit sliding window of the index bits read from the servo sectors to a predefined set of N-bit vectors that exist within the pattern of the index bits stored in the at least one track, and the predefined set of N-bit vectors is less than all of the possible N-bit vectors within the pattern of the index bits stored in the at least one track.

8. A method for identifying an index of a track on a data storage device, the method comprising:

recording a pattern of index bits in servo sectors in tracks on a data storage medium, wherein only one index bit is stored in each servo sector; and

reading the index bits from the servo sectors to identify an index of the servo sectors in a track, wherein the pattern of index bits stored in at least one track has a fault tolerance defined by a minimum Hamming distance greater than one.

9. The method defined in claim 8 wherein the data storage device is a hard disk drive having a head, the data storage medium is a disk, and the method further comprises:

positioning the head to different tracks on the disk and maintaining the head on the tracks using an actuator; and

controlling the actuator using servo electronics in response to servo information read by the head from the servo sectors.

10. The method defined in claim 8 wherein the pattern of index bits stored in at least one track in the data storage medium has a fault tolerance defined by a minimum Hamming distance greater than two.

11. The method defined in claim 8 wherein the pattern of index bits stored in at least one track in the data storage medium has a fault tolerance defined by a minimum Hamming distance greater than three.

12. The method defined in claim 8 wherein the pattern of index bits stored in at least one track in the data storage medium has a fault tolerance defined by a minimum Hamming distance greater than four.

13. The method defined in claim 8 wherein reading the index bits from the servo sectors to identify the index of the servo sectors further comprises comparing an N-bit sliding window of the index bits read from the servo sectors to all possible N-bit vectors that exist within the pattern of index bits stored in a track.

14. The method defined in claim 8 wherein reading the index bits from the servo sectors to identify the index of the servo sectors further comprises comparing an N-bit sliding window of the index bits read from the servo sectors to a predefined set of N-bit vectors that exist within the pattern of index bits stored in a track, and the predefined set of N-bit vectors is less than all of the possible N-bit vectors within the pattern of index bits stored in the track.

15. A data storage device comprising:

a decoder that reads index bits from servo sectors on a data storage medium to identify an index of the servo sectors in a track,

wherein a pattern of the index bits is stored in servo sectors in a track of the data storage medium, only one of the index bits is stored in each servo sector, and

wherein the data storage device compares an N-bit sliding window of the index bits read from the servo sectors to all possible N-bit vectors that exist within the pattern of the index bits stored in the track.

16. The data storage device defined in claim 15 wherein the data storage device is a hard disk drive that further comprises:

a disk comprising a plurality of concentric tracks containing the servo sectors;

a head configured to read data and servo information from the servo sectors on the disk;

an actuator connected to the head for positioning the head to different tracks and maintaining the head on the tracks; and

servo electronics coupled to the decoder for controlling the actuator in response to the servo information read by the head from the servo sectors.

17. The data storage device defined in claim 15 wherein the pattern of the index bits stored in at least one track on the data storage medium has a fault tolerance defined by a minimum Hamming distance greater than one.

18. The data storage device defined in claim 15 wherein the pattern of the index bits stored in at least one track on the data storage medium has a fault tolerance defined by a minimum Hamming distance greater than two.

19. The data storage device defined in claim 15 wherein the pattern of the index bits stored in at least one track on the data storage medium has a fault tolerance defined by a minimum Hamming distance greater than three.

20. The data storage device defined in claim 15 wherein the pattern of the index bits stored in at least one track on the data storage medium has a fault tolerance defined by a minimum Hamming distance greater than four.