Techniques for detecting and correcting errors using multiple interleave erasure pointers

• US 20050229069A1
• Filed: 04/02/2004
• Published: 10/13/2005
• Est. Priority Date: 04/02/2004
• Status: Active Grant

• Current Assignee: Clemson University, Hitachi Global Storage Technologies Incorporated (Western Digital Corporation), Hitachi Global Storage Technologies Netherlands BV (Western Digital Corporation)
• Original Assignee: Hitachi Global Storage Technologies Netherlands BV (Western Digital Corporation)
• Inventors: Hassner, Martin, Srivastava, Vipul
• Granted Patent: US 7,231,578 B2
• Time in Patent Office: Days
• US Class Current: 714/746
• CPC Class Codes: G11B 20/18 Error detection or correction; Testing , e.g. of drop-outs
• CPC Class Codes: G11B 2020/1843 using a cyclic redundancy check [CRC]
• CPC Class Codes: H04L 1/0045 Arrangements at the receiver end
• CPC Class Codes: H04L 1/0057 Block codes H04L1/0061, H04L1/0064 take precedence
• CPC Class Codes: H04L 1/0064 Concatenated codes
• CPC Class Codes: H04L 1/0071 Use of interleaving interleaving per se H03M13/27

Abstract

Techniques for detecting and correcting burst errors in data bytes formed in a two-level block code structure. A second level decoder uses block level check bytes to detect columns in a two-level block code structure that contain error bytes. The second level decoder generates erasure pointers that identify columns in the two-level block structure effected by burst errors. A first level decoder then uses codeword check bytes to correct all of the bytes in the columns identified by the erasure pointers. The first level decoder is freed to use all of the codeword check bytes only for error byte value calculations. The first level decoder does not need to use any of the codeword check bytes for error location calculations, because the erasure pointers generated by the second level decoder provide all of the necessary error locations. This techniques doubles the error correction capability of the first level decoder.

Claims

1. A disk drive controller that corrects multiple burst errors in data bytes, the disk drive controller comprising:

a first level decoder; and

a second level decoder-that uses block level check bytes to detect columns in a two-level block structure of data bytes containing burst errors,

wherein the second level decoder generates erasure pointers that identify the columns in the two-level block structure containing the burst errors,

the first level decoder uses codeword check bytes in the two-level block structure to correct all of the data bytes in the columns identified by the erasure pointers, and

the first level decoder does not use any of the codeword check bytes for error location calculations.

2. The disk drive controller according to claim 1 wherein the first level decoder is configured to detect and correct random errors in the two-level block structure of data bytes using the codeword check bytes.

3. The disk drive controller according to claim 2 wherein the second level decoder uses the block level check bytes to correct random errors in a codeword if the first level decoder does not correct all of the random errors, and

the second level decoder only generates the erasure pointers if the first level and the second level decoders do not correct all of the random errors.

4. The disk drive controller according to claim 1 wherein the disk drive controller de-interleaves the two level block structure of data bytes to separate out the data bytes, the block level check bytes, and the codeword check bytes.

5. The disk drive controller according to claim 1 wherein the disk drive controller generates syndromes that are used for error correction for the data bytes in the two-level block structure.

6. The disk drive controller according to claim 1 wherein two-level block structure of data bytes is applied to an inverse of an integrating matrix V⁻

1 to redistribute the data bytes, the codeword check bytes, and the block level check bytes.

7. The disk drive controller according to claim 1 wherein the first and the second level decoders are Reed-Solomon decoders.

8. The disk drive controller according to claim 1 wherein the disk drive controller includes an ECC read processor and an ECC write processor.

9. A disk drive system that corrects multiple burst errors in data bytes, the disk drive system:

a disk assembly comprising a disk and a head stack assembly that includes a spindle motor; and

a disk drive controller chipset that includes first level and second level decoders,

wherein the second level decoder uses block level check bytes to detect columns in a two-level block structure of data bytes that contains burst errors,

the second level decoder generates erasure pointers that identify the columns in the two-level block structure containing the burst errors, and

the first level decoder uses codeword check bytes in the two-level block structure to correct all of the data bytes in the columns identified by the erasure pointers.

10. The disk drive system according to claim 9 wherein the first level decoder does not use any of the codeword check bytes for error location calculations, and the first level decoder uses all of the codeword check bytes used for error value calculations.

11. The disk drive system according to claim 10 wherein the first level decoder is configured to detect and correct random errors occurring in the data bytes using the codeword check bytes before the second level decoder is used to detect the burst errors.

12. The disk drive system according to claim 11 wherein the second level decoder uses the block level check bytes to correct random errors in a codeword if the first level decoder does not correct all of the random errors.

13. The disk drive system according to claim 9 wherein the disk drive controller chipset de-interleaves the two level block structure of data bytes to separate out the data bytes, the block level check bytes, and the codeword check bytes.

14. The disk drive system according to claim 9 wherein the disk drive controller chipset generates syndromes for codewords in the two-level block structure.

15. The disk drive system according to claim 9 wherein the disk drive controller chipset includes an ECC read processor and an ECC write processor.

16. The disk drive system according to claim 9 wherein the first and the second level decoders are Rood-Solomon decoders.

17. The disk drive system according to claim 9 wherein two-level block structure of data bytes is applied to an inverse of an integrating matrix V⁻

1 to redistribute the data bytes, the codeword check bytes, and the block level check bytes.