Tiered error correction code (ECC) operations in memory

1. A method, comprising:

performing a first error code correction (ECC) operation on data read from a memory array;

performing a second ECC operation on the data in response to the first ECC operation failing;

performing a third ECC operation on the data in response to the second ECC operation failing; and

iteratively performing a fourth ECC operation on the data in response to the third ECC operation failing until a threshold number of bits is flipped.

2. The method of claim 1 , wherein performing the fourth ECC operation includes using an iterative product code decoder or an outer BCH decoder on codewords that have been changed in response to the codewords failing the third ECC operation.

3. The method of claim 1 , wherein performing the third ECC operation includes performing an operation using an inner code decode and an outer code decode.

4. The method of claim 1 , wherein performing the third ECC operation includes using codewords associated with an outer code along with a block-wise concatenated codeword associated with an inner code used in the second ECC operation.

5. The method of claim 1 , wherein performing the third ECC operation includes performing ECC operations on codewords that failed the second ECC operations and include changed bits from a bit flip candidate list selected based on a log likelihood ratio.

6. The method of claim 1 , wherein performing the second ECC operation includes generating a bit flip candidate list that includes bits at an intersection of a row codeword and a column codeword that failed the previous ECC operation based on a log likelihood ratio.

7. The method of claim 1 , further comprising performing additional ECC operations on codewords that failed previous ECC operations and include changed bits from the bit flip candidate list until one of the additional ECC operations is successful or until a threshold number of additional ECC operations are performed.

8. An apparatus, comprising:

a memory device;

a controller coupled to the memory device configured to:

perform a first error code correction (ECC) operation on data;

perform a second ECC operation using an inner code decode on the data in response to the first ECC operation failing; and

perform a third ECC operation using an inner code decode and an outer code decode, wherein the third ECC operation includes code words associated with the outer code along with block-wise concatenated codewords associated with the inner code.

9. The apparatus of claim 8 , further comprising the controller configured to perform one or more additional ECC operations in response to the third ECC operation failing.

10. The apparatus of claim 9 , wherein:

the additional ECC operations are soft decoding operations;

the controller is configured to;

perform the additional ECC operations on codewords that failed previous ECC operations; and

include changed bits from a bit flip candidate list selected based on a log likelihood ratio until one of the additional ECC operations is successful or until a threshold number of additional ECC operations are performed.

11. The apparatus of claim 9 , wherein the controller is configured to perform another of the previous first or second ECC operations on data in response to the third ECC operation failing.

12. The apparatus of claim 9 , wherein the controller is configured to perform a fourth ECC operation that includes generating a bit flip candidate list using log likelihood ratio masking, wherein the bit flip candidate list includes bits from intersections of component codewords that failed the first, the second, and the third ECC operations.

13. The apparatus of claim 9 , wherein the first ECC operation has a latency that is less than the second ECC operation and the third ECC operation and a fourth ECC operation has an error correction capability and a latency that is greater than the first, the second, and the third ECC operations.

14. The apparatus of claim 9 , wherein the controller is configured to perform the first ECC operation using hard data in a component code word to correct errors in the data.

15. A method, comprising:

performing a first error code correction (ECC) operation on data read from a memory array; and

performing a second ECC operation on the data in response to the first ECC operation failing and comprising creating a list of bit flip candidates responsive to an error occurring at one or more intersections of column codewords and row codewords.

16. The method of claim 15 , further comprising creating the list of bit flip candidates using bit flip candidates selected from bits at the one or more intersections of the row codewords and column codewords where an error remains.

17. The method of claim 15 , further comprising creating the list of bit flip candidates based on their respective log likelihood ratios.

18. The method of claim 15 , further comprising creating the list of bit flip candidates comprising all bits that are below a particular log likelihood ratio.

19. The method of claim 15 , further comprising:

flipping a particular number of bits from the bit flip candidate list; and

performing an additional ECC operation on the data with the flipped particular number of bits.

20. The method of claim 19 , further comprising

flipping a different particular number of bits from the bit flip candidate list responsive to the additional ECC operation being unsuccessful; and

performing another additional ECC operation on the data with the flipped different particular number of bits.