Systems and methods of storing data

• US 8,874,994 B2
• Filed: 12/19/2011
• Issued: 10/28/2014
• Est. Priority Date: 07/22/2011
• Status: Active Grant

• Current Assignee: SanDisk Technologies LLC (Western Digital Corporation)
• Original Assignee: Sandisk Technologies Incorporated (Western Digital Corporation)
• Inventors: Sharon, Eran, Alrod, Idan, Litsyn, Simon
• Primary Examiner(s): Alphonse, Fritz
• Application Number:
  US13/329,757
• Publication Number:
  US 20130024746A1
• Time in Patent Office: 1,044 Days
• Field of Search: 714/766, 714/773, 714/794, 714/798, 714/796
• US Class Current: 714/766
• CPC Class Codes: G06F 11/1044 with specific ECC/EDC distribution
• CPC Class Codes: G06F 11/1068 in sector programmable memories, e.g. flash disk G06F11/1072 takes precedence
• CPC Class Codes: G06F 11/1072 in multilevel memories
• CPC Class Codes: G11C 11/5628 Programming or writing circuits; Data input circuits
• CPC Class Codes: G11C 11/5642 Sensing or reading circuits; Data output circuits
• CPC Class Codes: G11C 16/0483 comprising cells having several storage transistors connected in series
• CPC Class Codes: G11C 16/10 Programming or data input circuits
• CPC Class Codes: G11C 2211/5641 Multilevel memory having cells with different number of storage levels
• CPC Class Codes: G11C 29/78 using programmable devices
• CPC Class Codes: G11C 7/1006 Data managing, e.g. manipulating data before writing or reading out, data bus switches or control circuits therefor

Abstract

A method of storing data includes receiving data including a first group of bits and a second group of bits and initiating a shaping encoding operation on the second group of bits to generate a third group of bits. The third group of bits has more bits than the second group of bits. The shaping encoding operation is configured to produce a non-uniform probability distribution of bit values in the third group of bits. The first group of bits and first error correction coding (ECC) parity bits corresponding to the first group of bits are stored to a first logical page that is within a physical page of a MLC memory and the third group of bits and second ECC parity bits corresponding to the third group of bits are stored to a second logical page that is within the physical page of the MLC memory.

Claims

1. A method of writing data, the method comprising:

in a data storage device with a multi-level cell (MLC) memory, performing;

receiving data including a first group of bits and a second group of bits;

initiating a shaping encoding operation on the second group of bits to generate a third group of bits, wherein the third group of bits has more bits than the second group of bits, and wherein the shaping encoding operation is configured to produce a non-uniform probability distribution of bit values in the third group of bits;

storing the first group of bits and first error correction coding (ECC) parity bits corresponding to the first group of bits to a first logical page associated with a physical page of the MLC memory; and

storing the third group of bits and second ECC parity bits corresponding to the third group of bits to a second logical page associated with the physical page of the MLC memory.

2. The method of claim 1, wherein the first logical page is associated with a first error rate and the second logical page is associated with a second error rate that is less than the first error rate.

3. The method of claim 1, wherein the first ECC parity bits include more bits than the second ECC parity bits.

4. The method of claim 1, wherein the third group of bits includes the second group of bits and shaping parity bits, and wherein the first ECC parity bits includes a same number of bits as the second ECC parity bits plus the shaping parity bits.

5. The method of claim 1, wherein the first ECC parity bits enable correction of up to a first number of errors in the first logical page and the second ECC parity bits enable correction of up to a second number of errors in the second logical page, and wherein a first probability that a number of errors in the first logical page exceeds the first number substantially equals a second probability that a number of errors in the second logical page exceeds the second number.

6. The method of claim 1, wherein the shaping encoding operation increases a likelihood that individual cells of the physical page of the MLC memory would be programmed to intermediate states and decreases a likelihood that the individual cells of the physical page of the MLC memory would be programmed to a lowest state.

7. The method of claim 1, wherein the shaping encoding operation increases a likelihood that individual cells of physical page of the MLC memory would be programmed to intermediate states and decreases a likelihood that the individual cells of the physical page of the MLC memory would be programmed to a highest state.

8. The method of claim 1, wherein the MLC memory comprises a flash memory.

9. A method of reading data, the method comprising:

in a data storage device with a multi-level cell (MLC) memory, performing;

reading a group of storage elements to retrieve a first representation of a first group of bits and first ECC parity bits at a first logical page associated with a physical page of the MLC memory and to retrieve a second representation of a third group of bits and second ECC parity bits at a second logical page associated with the physical page of the MLC memory;

initiating a first ECC decode operation of the first representation to recover the first group of bits;

initiating a second ECC decode operation of the second representation to recover the third group of bits; and

initiating a shaping decoding operation on the third group of bits to generate a second group of bits, wherein the third group of bits has more bits than the second group of bits, and wherein the shaping decoding operation is configured to produce a uniform probability distribution of bit values in the second group of bits.

10. The method of claim 9, wherein the first ECC parity bits include more bits than the second ECC parity bits.

11. The method of claim 9, wherein the first ECC parity bits enable correction of up to a first number of errors in the first representation and the second ECC parity bits enable correction of up to a second number of errors in the second representation, and wherein a first probability that a number of errors in the first representation exceeds the first number substantially equals a second probability that a number of errors in the second representation exceeds the second number.

12. The method of claim 9, wherein the first logical page is associated with a first error rate and the second logical page is associated with a second error rate that is less than the first error rate.

13. The method of claim 9, wherein the MLC memory comprises a flash memory.

14. A data storage device comprising:

a multi-level cell (MLC) memory; and

a controller configured to;

receive data including a first group of bits and a second group of bits,

perform a shaping encoding operation on the second group of bits to generate a third group of bits, wherein a third group of bits has more bits than the second group of bits, and wherein the shaping encoding operation is configured to produce a non-uniform probability distribution of bit values in the third group of bits,

send the first group of bits and first error correction coding (ECC) parity bits corresponding to the first group of bits to the MLC memory to be stored at a first logical page associated with a physical page of the MLC memory, and

send the third group of bits and second ECC parity bits corresponding to the third group of bits to the MLC memory to be stored at a second logical page associated with the physical page of the MLC memory.

15. The data storage device of claim 14, wherein the first logical page is associated with a first error rate and the second logical page is associated with a second error rate that is less than the first error rate.

16. The data storage device of claim 14, wherein the first ECC parity bits include more bits than the second ECC parity bits.

17. The data storage device of claim 14, wherein the first ECC parity bits enable correction of up to a first number of errors in the first logical page and the second ECC parity bits enable correction of up to a second number of errors in the second logical page, and wherein a first probability that a number of errors in the first logical page exceeds the first number substantially equals a second probability that a number of errors in the second logical page exceeds the second number.

18. The data storage device of claim 14, wherein the shaping encoding operation increases a likelihood that individual cells of the physical page of the MLC memory would be programmed to intermediate states and decreases a likelihood that the individual cells of the physical page of the MLC memory would be programmed to a lowest state.

19. The data storage device of claim 14, wherein the shaping encoding operation increases a likelihood that individual cells of physical page of the MLC memory would be programmed to intermediate states and decreases a likelihood that the individual cells of the physical page of the MLC memory would be programmed to a highest state.

20. The data storage device of claim 14, wherein the MLC memory comprises a flash memory.

21. A data storage device comprising:

a multi-level cell (MLC) memory; and

a controller configured to;

retrieve a first representation of a first group of bits and first ECC parity bits from a first logical page associated with a physical page of the MLC memory,

retrieve a second representation of a third group of bits and second ECC parity bits from a second logical page associated with the physical page of the MLC memory,

initiate a first ECC decode operation of the first representation to recover the first group of bits,

initiate a second ECC decode operation of the second representation to recover the third group of bits, and

initiate a shaping decoding operation on the third group of bits to generate a second group of bits,

wherein the third group of bits has more bits than the second group of bits, and wherein the shaping decoding operation is configured to produce a uniform probability distribution of bit values in the second group of bits.

22. The data storage device of claim 21, wherein the first ECC parity bits include more bits than the second ECC parity bits.

23. The data storage device of claim 21, wherein the first ECC parity bits enable correction of up to a first number of errors in the first representation and the second ECC parity bits enable correction of up to a second number of errors in the second representation, the first number greater than the second number.

24. The data storage device of claim 23, wherein a first probability that a number of errors in the first representation exceeds the first number substantially equals a second probability that a number of errors in the second representation exceeds the second number.

25. The data storage device of claim 21, wherein the MLC memory comprises a flash memory.