Data storage device tracking log-likelihood ratio for a decoder based on past performance

1. A data storage device comprising:

a non-volatile memory (NVM); and

control circuitry operable to:

write first data to a first area of the NVM;

read a first estimated data sequence comprising a first plurality of bits from the first area of the NVM;

first decode the first estimated data sequence;

first update a log-likelihood ratio (LLR) based on the first decode;

write second data to a second area of the NVM;

read a second estimated data sequence comprising a second plurality of bits from the second area of the NVM;

second decode the second estimated data sequence in response to the first updated LLR, where each updated LLR corresponds to a target bit in a plurality of consecutive bits in the second plurality of bits; and

second update the LLR based on the second decode.

2. The data storage device as recited in claim 1 , wherein the control circuitry is further operable to second update the LLR based on a difference between the second estimated data sequence and the second decode.

3. The data storage device as recited in claim 1 , wherein the control circuitry is further operable to:

write a test pattern to a third area of the NVM;

read a third estimated data sequence from the third area of the NVM; and

initialize the LLR based on a difference between the test pattern and the third estimated data sequence.

4. The data storage device as recited in claim 1 , wherein the control circuitry is further operable to:

first decode the first estimated data sequence by correcting an error in the first estimated data sequence; and

first update the LLR based on the corrected error.

5. The data storage device as recited in claim 1 , wherein the consecutive bits comprises at least two consecutive bits.

6. The data storage device as recited in claim 1 , wherein the consecutive bits comprises at least three consecutive bits.

7. The data storage device as recited in claim 1 , wherein the control circuitry is further operable to:

track a plurality of LLRs each corresponding to an operating condition; and

first update the LLR that corresponds to the operating condition when first decoding the first estimated data sequence.

8. The data storage device as recited in claim 7 , wherein the operating condition comprises a retention time of data stored in the NVM.

9. The data storage device as recited in claim 8 , wherein the operating condition comprises an ambient temperature over the retention time.

10. The data storage device as recited in claim 7 , wherein the NVM comprises a non-volatile semiconductor memory and the operating condition comprises a number of program/erase cycles of the non-volatile semiconductor memory.

11. The data storage device as recited in claim 1 , wherein the NVM comprises a non-volatile semiconductor memory.

12. The data storage device as recited in claim 1 , wherein the NVM comprises a disk of a disk drive.

13. A method of operating a data storage device comprising a non-volatile memory (NVM), the method comprising:

writing first data to a first area of the NVM;

reading a first estimated data sequence comprising a first plurality of bits from the first area of the NVM;

first decoding the first estimated data sequence;

first updating a log-likelihood ratio (LLR) based on the first decode;

writing second data to a second area of the NVM;

reading a second estimated data sequence comprising a second plurality of bits from the second area of the NVM;

second decoding the second estimated data sequence in response to the first updated LLR, where each updated LLR corresponds to a target bit in a plurality of consecutive bits in the second plurality of bits; and

second updating the LLR based on the second decode.

14. The method as recited in claim 13 , further comprising second updating the LLR based on a difference between the second estimated data sequence and the second decode.

15. The method as recited in claim 13 , further comprising:

writing a test pattern to a third area of the NVM;

reading a third estimated data sequence from the third area of the NVM; and

initializing the LLR based on a difference between the test pattern and the third estimated data sequence.

16. The method as recited in claim 13 , further comprising:

first decoding the first estimated data sequence by correcting an error in the first estimated data sequence; and

first updating the LLR based on the corrected error.

17. The method as recited in claim 13 , wherein the consecutive bits comprises at least two consecutive bits.

18. The method as recited in claim 13 , wherein the consecutive bits comprises at least three consecutive bits.

19. The method as recited in claim 13 , further comprising:

tracking a plurality of LLRs each corresponding to an operating condition; and

first updating the LLR that corresponds to the operating condition when first decoding the first estimated data sequence.

20. The method as recited in claim 19 , wherein the operating condition comprises a retention time of data stored in the NVM.

21. The method as recited in claim 20 , wherein the operating condition comprises an ambient temperature over the retention time.

22. The method as recited in claim 19 , wherein the NVM comprises a non-volatile semiconductor memory and the operating condition comprises a number of program/erase cycles of the non-volatile semiconductor memory.

23. The method as recited in claim 13 , wherein the NVM comprises a non-volatile semiconductor memory.

24. The method as recited in claim 13 , wherein the NVM comprises a disk of a disk drive.