Error correction methods and apparatuses using first and second decoders
Apparatuses and methods for error correcting data are provided. A first error correction code (ECC) decoder is configured to decode a first codeword to provide a first result and to decode a second codeword to provide a second result. The decoder is configured to run up to a particular number of iterations to provide each of the results. A second ECC decoder is configured to decode a third codeword to provide decoded data, wherein the third codeword includes the first result and the second result. An evaluation module is configured to initiate a recovery scheme responsive to the decoded data including an error.
1. A method for error correcting data, the method comprising:
reading a first codeword from memory, wherein the first codeword comprises first user data and error correction code (ECC) bits of a first type;
reading a second codeword from the memory, wherein the second codeword comprises second user data and ECC bits of the first type;
decoding the first codeword using a first decoder associated with a first ECC decoding procedure to provide a first result without inputting soft data to the first decoder, wherein the first decoder runs up to a particular number of iterations to provide the first result, and wherein the first decoder is capable of decoding using soft data;
decoding the second codeword using the first decoder associated with the first ECC decoding procedure to provide a second result without inputting soft data to the first decoder, wherein the first decoder runs up to the particular number of iterations to provide the second result;
grouping together the first result and the second result to form a third codeword before decoding the third codeword, wherein the third codeword is an outer codeword that comprises the first user data, the second user data, and ECC bits of a second type protecting the combined first and second codewords;
decoding the outer codeword using a second decoder associated with a second ECC decoding procedure to provide decoded data, wherein the second ECC decoding procedure is different from the first ECC decoding procedure; and
performing a recovery scheme only if the decoded outer codeword includes an error, wherein performing the recovery scheme includes:
reading, from the memory, soft data corresponding to the first and second codewords; and
providing the soft data to the first decoder in association with re-decoding the first and second codewords with the first decoder such that soft data is provided to the first decoder only if the decoded outer codeword includes an error.
2. The method of claim 1 , wherein the memory comprises flash memory.
3. The method of claim 1 , wherein decoding the outer codeword using the second decoder associated with the second ECC decoding procedure comprises decoding the outer codeword using the second decoder associated with a Bose-Chaudhuri-Hocquenghem (BCH) code decoding procedure.
4. The method of claim 1 , wherein performing the recovery scheme comprises:
providing third and fourth results from re-decoding the first and second codewords, respectively; and
decoding a fourth codeword using the second decoder to provide re-decoded data, wherein the fourth codeword comprises the third and fourth results.
5. The method of claim 1 , wherein reading the first and second codewords comprises receiving the first and second codewords at a controller over an interface coupled between the controller and the memory.
6. The method of claim 1 , wherein decoding the first and second codewords using the first decoder associated with the first ECC decoding procedure comprises decoding the first and second codewords using the first decoder associated with a low density parity check (LDPC) code decoding procedure.
7. The method of claim 1 , wherein reading the first and second codewords comprises:
sensing the first codeword from a first plurality of memory cells of the memory; and
sensing the second codeword from a second plurality of memory cells of the memory.
8. The method of claim 1 , wherein the particular number of iterations is one.
9. The method of claim 1 , wherein the third codeword further comprises a plurality of checksum bits.
10. An apparatus comprising:
a first decoder associated with a first error correction code (ECC) decoding procedure configured to:
decode a first codeword to provide a first result, wherein the first codeword comprises first user data and error correction code (ECC) bits of a first type, and wherein the first decoder is capable of decoding using soft data;
decode a second codeword to provide a second result, wherein the second codeword comprises second user data and ECC bits of the first type;
run up to a particular number of iterations to provide each of the results; and
group together the first result and the second result to form a third codeword before the third codeword is decoded, wherein the third codeword is an outer codeword that comprises the first user data, the second user data, and ECC bits of a second type protecting the combined first and second codewords,
a second decoder associated with a second ECC decoding procedure configured to decode the outer codeword to provide decoded data, wherein the second ECC decoding procedure is different from the first ECC decoding procedure; and
an evaluation module configured to:
initiate a recovery scheme only responsive to the decoded outer codeword including an error;
read, from memory, soft data corresponding to the first and second codewords; and
provide the soft data to the first decoder in association with re-decoding the first and second codewords such that soft data is provided to the first decoder only if the decoded outer codeword includes an error.
11. The apparatus of claim 10 , wherein the apparatus comprises a controller.
12. The apparatus of claim 10 , wherein the apparatus comprises a memory device; and
wherein the memory device includes a controller comprising the first decoder, the second decoder, and the evaluation module.
13. The apparatus of claim 10 , wherein the evaluation module is a component of the second decoder.
14. The apparatus of claim 10 , wherein the second ECC decoding procedure comprises a Bose-Chaudhuri-Hocquenghem (BCH) code decoding procedure.
15. The apparatus of claim 14 , wherein the BCH code decoding procedure has a correction capability in a range between 20 and 160.
16. The apparatus of claim 10 , wherein the first ECC decoding procedure comprises a low density parity check (LDPC) code decoding procedure.
17. The apparatus of claim 10 , wherein the particular number of iterations is one.
18. The apparatus of claim 10 , wherein the second decoder is a component of the evaluation module.
19. The apparatus of claim 10 , wherein the number of ECC bits of the first type is greater than the number of ECC bits of the second type.
20. The apparatus of claim 19 , wherein the number of ECC bits of the first type is about four times greater than the number of ECC bits of the second type.
21. The apparatus of claim 20 , wherein the number of ECC bits of the first and second types in the third codeword comprises about 10% of a number of bits in a page of memory.
22. The apparatus of claim 10 , wherein the outer codeword comprises a Bose-Chaudhuri-Hocquenghem (BCH) codeword; and
wherein the first and second codewords comprise low density parity check (LDPC) codewords.
23. The apparatus of claim 10 ,
wherein the memory is coupled to a controller comprising the first decoder, the second decoder and the evaluation module; and
wherein the controller is configured to read the first and second codewords from the memory while operating in a hard data only mode.
24. The apparatus of claim 23 , wherein the evaluation module being configured to initiate a recovery scheme comprises the evaluation module being configured to switch an operating mode of the controller from the hard data only mode to a soft data mode.
25. The apparatus of claim 24 , wherein while operating in the soft data mode, the controller is configured to:
provide third and fourth results from re-decoding the first and second codewords, respectively; and
decode a fourth codeword using the second decoder to provide re-decoded data, wherein the fourth codeword comprises the third and fourth results.
26. The apparatus of claim 23 , wherein the memory comprises a memory device.
27. The apparatus of claim 26 , wherein the memory device comprises a NAND flash memory device.
28. The apparatus of claim 27 , wherein the NAND flash memory device is coupled to the controller through an ONFI interface.