Non-volatile memory controller with error correction (ECC) tuning via error statistics collection

Patent metadata

Field	Value
Publication number	US-9407294-B2
Application number	US-201414325244-A
Country	US
Kind code	B2
Filing date	Jul 7, 2014
Priority date	Jul 7, 2014
Publication date	Aug 2, 2016
Grant date	Aug 2, 2016

Abstract

A non-volatile memory controller for a solid state drive includes a soft-decision LDPC decoder. The soft-decision LDPC decoder includes a probability generation module. A processor reads collected statistics collated from decoded frames and tunes the performance of the soft-decision LDPC decoder performance. Additional parameters may also be taken into account, such as the scramble seed and the type of non-volatile memory. An asymmetry in errors may also be detected and provided to a hard-decision LDPC decoder to adjust its performance.

First claim

What is claimed is:

1. A method of decoding non-volatile memory pages of a non-volatile memory, comprising:
collating error statistics in a decoded output of a soft-decision Low Density Parity Check (LDPC) decoder utilizing a probability to decode the non-volatile memory pages, the probability based on a set of soft-decision read values; and
updating, based on the error statistics, a probability lookup table (LUT) used to determine, from the set of soft-decision read values, the probability of a bit in the non-volatile memory page having a particular binary value.

2. The method of claim 1 , wherein the collating and updating is performed to adapt to aging related changes in multi-level cell threshold voltage distributions of the non-volatile memory.

3. The of claim 2 , wherein the collating and updating is performed periodically over a lifetime of the non-volatile memory.

4. The method of claim 1 , wherein the probability LUT is updated based on the collated error statistics and a set of parameters for the non-volatile memory pages being decoded that includes at least one of a type of page, a scramble seed type, and whether hard or soft information is read from the non-volatile memory.

5. The method of claim 1 , wherein the soft-decision LDPC decoder performs (2 N −1) (2 to the power N, minus 1) soft read decision reads, the results of which are encoded as N soft-decision read values R 0 , R 1 , . . . R N-1 , to determine a bit value and the probability LUT maps a composite read value R N-1 . . . R 1 R 0 to a probability value that the bit has a value of zero or one.

6. The method of claim 1 , wherein for each of the set of soft-decision read values, error statistics are collated on a number of times that a bit is correctly decoded to a binary zero and a number of times that a bit is correctly decoded to a binary one.

7. The method of claim 6 , wherein error statistics are collated for at least one frame that passes through the soft-decision LDPC decoder and are used to dynamically update the probability LUT for subsequent frames.

8. The method of claim 6 , further comprising determining asymmetry errors in the error statistics.

9. The method of claim 8 , further comprising providing asymmetry information to a hard-decision LDPC decoder to adjust a bit flipping voting decision in response to the determined asymmetry.

10. The method of claim 1 , wherein the non-volatile memory is a NAND flash memory.

11. The method of claim 1 , wherein the probability is provided by a probability generation module.

12. In a Low Density Parity Check (LDPC) decoder of a non-volatile memory controller, a method of decoding non-volatile memory pages of a non-volatile memory, comprising:
providing information to a soft-decision LDPC decoder to decode the non-volatile memory pages, the information relating a measured set of soft-decision read values to a probability that a bit value has a value of zero or one;
collating error statistics in the decoded output of the soft-decision LDPC decoder; and
updating based on the error statistics, the probability of the bit having a value of zero or one for the measured set of soft-decision read values.

13. The method of claim 12 further updating the probability based on the collated error statistics and a set of parameters for non-volatile memory pages being decoded that includes at least one of a type of memory page, a scramble seed type, and whether hard or soft information is read from the non-volatile memory.

14. The method of claim 13 , wherein the for each of the set of soft-decision read values, error statistics are collated on a number of times that a bit is correctly decoded to a binary zero and a number of times that a bit is correctly decoded to a binary one.

15. The method of claim 14 , wherein error statistics are collated for at least one frame that passes through the soft-decision LDPC decoder and the updates are used to dynamically tune a probability LUT for subsequent frames.

16. The method of claim 14 , further comprising determining asymmetry errors in the error statistics and providing asymmetry information to a hard-decision LDPC decoder to adjust a bit flipping voting decision in response to the determined asymmetry.

17. The method of claim 12 , wherein the information is provided by a probability generation module.

18. A solid state storage device, comprising:
a non-volatile memory controller to store data in a non-volatile memory via a plurality of channels, wherein the stored data is encoded using a low density parity check code;
a flash controller including a soft-decision Low Density Parity Check (LDPC) decoder to decode encoded data received from the non-volatile memory via respective channels of the plurality of channels; and
the non-volatile memory controller collating error statistics in a decoded output of the soft-decision LDPC decoder to adjust a relationship between a set of soft-decision read values to a probability, the probability used by the soft-decision LDPC decoder to decode the encoded data.

19. The solid state storage device of claim 18 , further comprising a hard-decision LDPC decoder wherein asymmetries in the monitored error statistics are used to adjust a bit flipping algorithm.

20. The solid state storage device of claim 18 , wherein the non-volatile memory controller includes a statistics collation module collating error statistics in the output of the soft-decision LDPC decoder.

21. The solid state storage device of claim 18 , wherein the probability is defined by a probability lookup table (LUT).

22. The solid state storage device of claim 21 , wherein probability LUT probabilities are determined based on a set of parameters for a non-volatile memory page and updates based on the statistics in the decoded output of the soft-decision LDPC decoder.

23. The solid state storage device of claim 22 , wherein the set of parameters comprises adjustable parameters for at least one of type of non-volatile memory page, scramble seed type, hard or soft information read from the non-volatile memory.

24. The solid state storage device of claim 22 , wherein the non-volatile memory is a NAND flash memory.

25. The solid state storage device of claim 18 , wherein the probability is provided by a probability generation module.

26. A method of decoding non-volatile memory pages of a non-volatile memory, comprising:
collating error statistics in a decoded output of a soft-decision Low Density Parity Check (LDPC) decoder utilizing a probability to decode the non-volatile memory pages, the probability relating a set of soft-decision read values to a particular value;
determining asymmetries in the collated error statistics of the soft-decision LDPC decoder; and
utilizing the determined asymmetries to adjust a bit flipping voting decision of a hard-decision LDPC decoder.

27. The method of claim 26 , wherein the probability is provided by a probability generation module.

28. A solid state storage device, comprising:
a non-volatile memory controller to store data in a non-volatile memory via a plurality of channels, wherein the stored data is encoded using a low density parity check code;
a flash controller including a soft-decision Low Density Parity Check (LDPC) decoder to decode encoded data received from the non-volatile memory via respective channels of the plurality of channels; and
the non-volatile me

Assignees

• Ocz Storage Solutions Inc
• Toshiba Kk

Inventors

• Hanham Paul Edward
• Symons David Malcolm
• Buxton Neil

Classifications

• H03M13/1102

  Codes on graphs and decoding on graphs, e.g. low-density parity check [LDPC] codes · CPC title

• G06F11/1012

  using codes or arrangements adapted for a specific type of error (G06F11/1048 takes precedence) · CPC title

• H03M13/458

  by updating bit probabilities or hard decisions in an iterative fashion for convergence to a final decoding result · CPC title

• H03M13/3715 Primary

  Adaptation to the number of estimated errors or to the channel state · CPC title

• G11C2029/0411

  Online error correction · CPC title