Granted Patent B1

US 9,025,269 · App. 14/152,129 · Granted May 5, 2015

Abstract

Claims (37)

1. A disk drive comprising:

a disk comprising a plurality of servo tracks defined by full sectors and intervening short servo sectors, where each full servo sector comprises a preamble, a sync mark, and servo bursts, and each short servo sector comprises a reference pattern and servo bursts;

a head; and

control circuitry configured to:

generate a first phase error based on the sync mark in a first full servo sector;

adjust a disk locked clock in response to the first phase error;

generate a second phase error based on the reference pattern in a first short servo sector; and

process the second phase error to determine whether the disk locked clock slipped a cycle before the head reaching the first short servo sector.

2. The disk drive as recited in claim 1 , wherein the control circuitry is further configured to adjust the second phase error to generate an adjusted phase error.

3. The disk drive as recited in claim 2 , wherein the control circuitry is further configured to synchronize the disk locked clock in response to the adjusted phase error.

4. The disk drive as recited in claim 2 , wherein the control circuitry is further configured to abort a write operation in response to the adjusted phase error.

5. The disk drive as recited in claim 2 , wherein the control circuitry is further configured to:

generate an estimated phase error corresponding to the second phase error; and

compare the estimated phase error to the adjusted phase error.

6. The disk drive as recited in claim 5 , wherein the control circuitry is further configured to adjust the disk locked clock in response to the adjusted phase error when the comparison is less than a threshold.

7. The disk drive as recited in claim 5 , wherein the control circuitry is further configured to abort a write operation when the comparison is less than a threshold.

8. The disk drive as recited in claim 1 , wherein the control circuitry is further configured to process the second phase error by comparing the second phase error to a threshold.

9. The disk drive as recited in claim 1 , wherein the control circuitry is further configured to:

adjust the second phase error by adding 360 degrees to the second phase error when the second phase error is negative; and

adjust the second phase error by subtracting 360 degrees from the second phase error when the second phase error is positive.

10. A method of operating a disk drive comprising a head and a disk comprising a plurality of servo tracks defined by full sectors and intervening short servo sectors, where each full servo sector comprises a preamble, a sync mark, and servo bursts, and each short servo sector comprises a reference pattern and servo bursts, the method comprising:

generating a first phase error based on the sync mark in a first full servo sector;

adjusting a disk locked clock in response to the first phase error;

generating a second phase error based on the reference pattern in a first short servo sector; and

processing the second phase error to determine whether the disk locked clock slipped a cycle before the head reaching the first short servo sector.

11. The method as recited in claim 10 , further comprising adjusting the second phase error to generate an adjusted phase error.

12. The method as recited in claim 11 , further comprising synchronizing the disk locked clock in response to the adjusted phase error.

13. The method as recited in claim 11 , further comprising aborting a write operation in response to the adjusted phase error.

14. The method as recited in claim 11 , further comprising:

generating an estimated phase error corresponding to the second phase error; and

comparing the estimated phase error to the adjusted phase error.

15. The method as recited in claim 14 , further comprising adjusting the disk locked clock in response to the adjusted phase error when the comparison is less than a threshold.

16. The method as recited in claim 14 , further comprising aborting a write operation when the comparison is less than a threshold.

17. The method as recited in claim 10 , further comprising processing the second phase error by comparing the second phase error to a threshold.

18. The method as recited in claim 10 , further comprising:

adjusting the second phase error by adding 360 degrees to the second phase error when the second phase error is negative; and

adjusting the second phase error by subtracting 360 degrees from the second phase error when the second phase error is positive.

Assignments (7)