ECC system for generating a CRC syndrome over randomized data in a computer storage device

• US 6,052,815 A
• Filed: 11/14/1997
• Issued: 04/18/2000
• Est. Priority Date: 11/14/1997
• Status: Expired due to Term

• Current Assignee: Cirrus Logic Incorporated
• Original Assignee: Cirrus Logic Incorporated
• Inventors: Zook, Christopher R.
• Primary Examiner(s): Moise, Emmanuel L.
• Assistant Examiner(s): ABRAHAM, ESAW T
• Application Number:
  US08/970,918
• Time in Patent Office: 886 Days
• Field of Search: 714/758, 714/787, 714/785, 714/781, 714/793
• US Class Current: 714/758
• CPC Class Codes: G11B 20/18 Error detection or correction; Testing , e.g. of drop-outs
• CPC Class Codes: G11B 20/1833 by adding special lists or symbols to the coded information G11B20/1806, G11B20/1866 take precedence
• CPC Class Codes: H03M 13/093 CRC update after modification of the information word
• CPC Class Codes: H03M 13/1515 Reed-Solomon codes
• CPC Class Codes: H03M 13/158 Finite field arithmetic processing
• CPC Class Codes: H03M 13/29 combining two or more codes or code structures, e.g. product codes, generalised product codes, concatenated codes, inner and outer codes
• CPC Class Codes: H03M 13/2909 Product codes

Abstract

An error correction processor is disclosed for correcting errors in randomized data read from a disk storage medium, where the randomized data comprises ECC redundancy symbols generated over the randomized data and check symbols generated over data before being randomized. The error correction processor comprises an ECC decoder for correcting errors in the randomized data using the ECC redundancy symbols; a syndrome generator, responsive to the randomized data, for generating a validation syndrome; a correction validator for comparing the validation syndrome to a predetermined value to verify the validity and completeness of the corrections to the randomized data; and a derandomizer for derandomizing the randomized data after the correction validator indicates that corrections to the randomized data are valid and complete.

Claims

1. An error correction processor for correcting errors in randomized data read from a disk storage medium, where the randomized data comprises ECC redundancy symbols generated over the randomized data and check symbols generated over data before being randomized, the error correction processor comprising:

(a) an ECC decoder for correcting errors in the randomized data using the ECC redundancy symbols;

(b) a syndrome generator, responsive to the randomized data, for generating a validation syndrome;

(c) a correction validator for comparing the validation syndrome to a predetermined value to verify the validity and completeness of the corrections to the randomized data; and

(d) a derandomizer for derandomizing the randomized data after the correction validator indicates that corrections to the randomized data are valid and complete.

2. The error correction processor as recited in claim 1, wherein:

(a) the randomized data comprises a first and second set of intersecting codewords; and

(b) the ECC decoder corrects errors in the randomized data by processing, in sequential passes, the first set codewords and the second set codewords.

3. The error correction processor as recited in claim 2, wherein:

(a) the syndrome generator generates a data validation syndrome during a first pass over the first set codewords;

(b) the syndrome generator generates an error validation syndrome using correction values generated by the ECC decoder for correcting the randomized data; and

(c) the syndrome generator combines the data validation syndrome with the error validation syndrome to generate a final validation syndrome compared to the predetermined value.

4. The error correction processor as recited in claim 2, wherein:

(a) the syndrome generator generates a partial validation syndrome concurrent with the ECC decoder processing the randomized data; and

(b) the syndrome generator comprises an offset controller for adjusting the partial validation syndrome according to a location of a particular randomized data symbol being processed by the ECC decoder.

5. The error correction processor as recited in claim 4, wherein when the ECC decoder generates a correction value for correcting a randomized data symbol:

(a) the offset controller adjusts the partial validation syndrome according to the location of the corrected data symbol; and

(b) the syndrome generator updates the partial validation syndrome using the correction value.

6. The error correction processor as recited in claim 4, wherein:

(a) the check symbols are generated according to a generator polynomial G(x) of a finite field; and

(b) the offset controller adjusts the partial validation syndrome by multiplying the partial validation syndrome by

space="preserve" listing-type="equation">X.sup.K mod G(x)

where K is an offset value and the mod operator performs modulo division.

7. The error correction processor as recited in claim 1, wherein:

(a) the check symbols are generated according to a generator polynomial of a finite field; and

(b) the predetermined value is based on the generator polynomial.

8. The error correction processor as recited in claim 1, wherein

(a) the derandomizer generates a random pattern according to a predetermined seed value;

and

(b) the random pattern is combined with the randomized data to derandomize the randomized data.

9. The error correction processor as recited in claim 8, wherein:

(a) the check symbols are generated according to a generator polynomial of a finite field; and

(b) the predetermined value is based on the generator polynomial and the random pattern.

10. The error correction processor as recited in claim 1, wherein the check symbols are generated according to a cyclic redundancy code (CRC).

11. A method of correcting errors in randomized data read from a disk storage medium, where the randomized data comprises ECC redundancy symbols generated over the randomized data and check symbols generated over data before being randomized, comprising the steps of:

(a) correcting errors in the randomized data using the ECC redundancy symbols;

(b) generating a validation syndrome in response to the randomized data;

(c) comparing the validation syndrome to a predetermined value to verify the validity and completeness of the corrections to the randomized data; and

(d) derandomizing the randomized data after the correction validator indicates that corrections to the randomized data are valid and complete.

12. The method of correcting errors as recited in claim 11, wherein:

(a) the randomized data comprises a first and second set of intersecting codewords; and

(b) the step of correcting corrects errors in the randomized data by processing, in sequential passes, the first set codewords and the second set codewords.

13. The method of correcting errors as recited in claim 12, wherein the step of generating the validation syndrome comprises the steps of:

(a) generating a data validation syndrome during a first pass over the first set codewords;

(b) generating an error validation syndrome using correction values for correcting the randomized data; and

(c) combining the data validation syndrome with the error validation syndrome to generate a final validation syndrome compared to the predetermined value.

14. The method of correcting errors as recited in claim 12, wherein the step of generating the validation syndrome comprises the steps of:

(a) generating a partial validation syndrome concurrent with processing the randomized data to generate ECC error syndromes; and

(b) adjusting the partial validation syndrome according to a location of a particular randomized data symbol being processed to generate the ECC error syndromes.

15. The method of correcting errors as recited in claim 14, wherein the step of generating the validation syndrome further comprises the steps of:

(a) adjusting the partial validation syndrome according to the location of a corrected data symbol; and

(b) updating the partial validation syndrome with a correction value used to correct the data symbol.

16. The method of correcting errors as recited in claim 14, wherein:

(a) the check symbols are generated according to a generator polynomial G(x) of a finite field; and

(b) the step of adjusting the partial validation syndrome comprises the step of multiplying the partial validation syndrome by

space="preserve" listing-type="equation">X.sup.K mod G(x)

where K is an offset value and the mod operator performs modulo division.

17. The method of correcting errors as recited in claim 11, wherein:

(a) the check symbols are generated according to a generator polynomial of a finite field; and

(b) the predetermined value is based on the generator polynomial.

18. The method of correcting errors as recited in claim 11, wherein

(a) the derandomizer generates a random pattern according to a predetermined seed value;

and

(b) the random pattern is combined with the randomized data to derandomize the randomized data.

19. The method of correcting errors as recited in claim 18, wherein:

(a) the check symbols are generated according to a generator polynomial of a finite field; and

(b) the predetermined value is based on the generator polynomial and the random pattern.

20. The method of correcting errors as recited in claim 11, wherein the check symbols are generated according to a cyclic redundancy code (CRC).

21. An error correction processor for correcting errors in data read from a disk storage medium, the data comprising ECC redundancy symbols and check symbols, the error correction processor comprising:

(a) an ECC decoder for correcting errors in the data using the ECC redundancy symbols;

(b) a syndrome generator, responsive to the data, for generating a validation syndrome;

(c) a correction validator for comparing the validation syndrome to a predetermined value to verify the validity and completeness of the corrections to the data; and

(d) a derandomizer for derandomizing the data after the correction validator indicates that corrections to the randomized data are valid and complete.

22. An error correction processor for correcting errors in randomized data read from a disk storage medium, where the randomized data comprises ECC redundancy symbols generated over the randomized data and check symbols generated over data before being randomized, the error correction processor comprising:

(a) a data buffer for storing the randomized data read from the disk;

(b) an ECC decoder connected to receive the randomized data from the data buffer, for generating ECC error syndromes and correction values for correcting errors in the randomized data;

(c) a syndrome generator connected to receive the randomized data from the data buffer concurrent with the ECC decoder receiving the randomized data from the data buffer, the syndrome generator for generating a validation syndrome;

(d) a correction validator for comparing the validation syndrome to a predetermined value to verify the validity and completeness of the corrections to the randomized data; and

(e) a derandomizer connected to receive the randomized data from the data buffer, for derandomizing the randomized data after the correction validator indicates that corrections to the randomized data are valid and complete.

23. The error correction processor as recited in claim 22, wherein the validation syndrome is generated according to a cyclic redundancy code (CRC).

24. The error correction processor as recited in claim 22, wherein the syndrome generator updates the validation syndrome using a correction value generated by the ECC decoder when a randomized data symbol is corrected.