Magnetic disk having efficiently stored WRRO compensation value redundancy information and method for using the redundancy information
View Patent ↗The present invention may be embodied in a magnetic disk, of a disk drive, having eight-bit fields storing wedge repeatable runout (WRRO) compensation values and redundancy information. The WRRO compensation value of each field includes a six-bit binary value of which five bits represent a compensation magnitude and one bit represents a sign bit indicating a compensation direction. The redundancy information of each field has a first bit based on the sign bit.
1. A disk drive, comprising
a head magnetically coupled to a magnetic disk, wherein the magnetic disk comprises eight-bit fields storing wedge repeatable runout (WRRO) compensation values and redundancy information, the WRRO compensation value of each field including a six-bit binary value of which five bits represent a compensation magnitude and one bit represents a sign bit indicating a compensation direction, and the redundancy information of each field comprising a first bit based on the sign bit of the six-bit binary value of the same field; and
a servo control system to read the eight-bit fields from the magnetic disk and to compare the first bit to the sign bit to detect an error in the WRRO compensation value if the first bit is inconsistent with the one bit representing the sign bit.
2. A disk drive as defined in claim 1 , wherein the first bit of the redundancy information is a duplicate of the sign bit.
3. A disk drive as defined in claim 1 , wherein the first bit of the redundancy information is an inversion of the sign bit.
4. A disk drive as defined in claim 1 , wherein the one bit representing the sign bit and the first bit of the redundancy information are stored in the respective eight-bit field with a separation of at least two bits.
5. A disk drive as defined in claim 1 , wherein the redundancy information further comprises a second bit based on a most significant bit of the five bits representing the compensation magnitude.
6. A disk drive as defined in claim 5 , wherein the most significant bit and the second bit of the redundancy information are stored in the respective eight-bit field with a separation of at least two bits.
7. A disk drive as defined in claim 5 , wherein the first bit of the redundancy information is an inversion of the sign bit, and the second bit of the redundancy information is an inversion of the most significant bit.
8. A method for using redundancy information of wedge repeatable runout (WRRO) compensation values stored in eight-bit fields on a magnetic disk of a disk drive, the method comprising:
reading the WRRO compensation value and related redundancy information from an eight-bit field, the WRRO compensation value including a six-bit binary value of which five bits represent a compensation magnitude and one bit represents a sign bit indicating a compensation direction and the redundancy information of each field comprising a first bit based on the sign bit of the six-bit binary value of the same field;
comparing the first bit and the one bit representing the sign bit;
detecting an error in the WRRO compensation value if the first bit is inconsistent with the one bit representing the sign bit.
9. A method for using redundancy information as defined in claim 8 , wherein the one bit representing the sign bit and the first bit of the redundancy information are stored in the respective eight-bit field with a separation of at least two bits.
10. A method for using redundancy information as defined in claim 8 , wherein the redundancy information further comprises a second bit based on a most significant bit of the five bits representing the compensation magnitude.
11. A method for using redundancy information as defined in claim 10 , wherein the most significant bit and the second bit of the redundancy information are stored in the respective eight-bit field with a separation of at least two bits.
12. A method for using redundancy information as defined in claim 10 , wherein the first bit of the redundancy information is an inversion of the sign bit, and the second bit of the redundancy information is an inversion of the most significant bit.
13. A disk drive, comprising
a head magnetically coupled to a magnetic disk, wherein the magnetic disk comprises eight-bit fields storing wedge repeatable runout (WRRO) compensation values and redundancy information, the WRRO compensation value of each field comprising an six-bit binary value, and the redundancy information of each field comprising a first bit based on a most significant bit of the six-bit binary value of the six-bit binary value of the same field; and
a servo control system to read the eight-bit fields from the magnetic disk to compare the first bit and the most significant bit to detect an error in the WRRO compensation value if the first bit is inconsistent with the most significant bit.
14. A disk drive as defined in claim 13 , wherein the most significant bit and the first bit of the redundancy information are stored in the respective eight-bit field with a separation of at least two bits.
15. A disk drive as defined in claim 13 , wherein the redundancy information further comprises a second bit based on a second most significant bit of the six-bit binary value.
16. A disk drive as defined in claim 15 , wherein the second most significant bit and the second bit of the redundancy information are stored in the respective eight-bit field with a separation of at least two bits.
17. A disk drive as defined in claim 15 , wherein the first bit of the redundancy information is an inversion of the most significant bit, and the second bit of the redundancy information is an inversion of the second most significant bit.
18. A method for using redundancy information of wedge repeatable runout (WRRO) compensation values stored in eight-bit fields on a magnetic disk of a disk drive, the method comprising:
reading the WRRO compensation value and related redundancy information from a field, the WRRO compensation value including a six-bit binary value, and the redundancy information of each field comprising a first bit based on a most significant bit of the six-bit binary value of the same field;
comparing the first bit and the most significant bit; and
detecting an error in the WRRO compensation value if the first bit is inconsistent with the most significant bit.
19. A method for using redundancy information as defined in claim 18 , wherein the first bit of the redundancy information is a duplicate of the most significant bit.
20. A method for using redundancy information as defined in claim 18 , wherein the first bit of the redundancy information is an inversion of the most significant bit.
21. A method for using redundancy information as defined in claim 18 , wherein the most significant bit and the first bit of the redundancy information are stored in the respective eight-bit field with a separation of at least two bits.
22. A method for using redundancy information as defined in claim 18 , wherein the redundancy information further comprises a second bit based on a second most significant bit of the six-bit binary value.
23. A method for using redundancy information as defined in claim 22 , wherein the second most significant bit and the second bit of the redundancy information are stored in the respective eight-bit field with a separation of at least two bits.
24. A method for using redundancy information as defined in claim 22 , wherein the first bit of the redundancy information is an inversion of the most significant bit, and the second bit of the redundancy information is an inversion of the second most significant bit.
25. A method for using redundancy information of wedge repeatable runout (WRRO) compensation values stored on a magnetic disk of a disk drive, comprising:
reading a WRRO field on the magnetic disk, the WRRO field comprising a WRRO compensation value including a plurality of binary values and a WRRO compensation redundancy value comprising a first bit based on a portion of the WRRO compensation value of the same field;
comparing the portion of the WRRO compensation value and the first bit of the WRRO compensation redundancy value; and
detecting an error in the WRRO compensation value if the first bit is inconsistent with the portion of the WRRO compensation value.
26. The method as in claim 25 , wherein the first bit is based on the most significant bit of the WRRO compensation value.
27. The method as in claim 25 , wherein the first bit is based on a sign bit of the WRRO compensation value.
28. The method as in claim 27 , wherein the WRRO compensation redundancy value further comprises a second bit wherein the second bit is based on the most significant bit of the WRRO compensation value.