Non-Volatile Cells Having a Non-Power-of-Two Number of States

• US 20140281842A1
• Filed: 03/14/2013
• Published: 09/18/2014
• Est. Priority Date: 03/14/2013
• Status: Abandoned Application

• Current Assignee: SanDisk Technologies LLC (Western Digital Corporation)
• Original Assignee: Fusion-IO Incorporated (Western Digital Corporation)
• Inventors: Wood, Robert, Flynn, David, Fillingim, Jeremy, Losh, Warner
• Application Number:
  US13/831,047
• Publication Number:
  US 20140281842A1
• Time in Patent Office: Days
• US Class Current: 714/799
• CPC Class Codes: G06F 11/006 Identification G06F11/2289 takes precedence
• CPC Class Codes: G11C 11/5628 Programming or writing circuits; Data input circuits
• CPC Class Codes: G11C 16/10 Programming or data input circuits
• CPC Class Codes: G11C 16/349 Arrangements for evaluating degradation, retention or wearout, e.g. by counting erase cycles
• CPC Class Codes: G11C 2211/5641 Multilevel memory having cells with different number of storage levels
• CPC Class Codes: G11C 29/28 Dependent multiple arrays, e.g. multi-bit arrays
• CPC Class Codes: G11C 29/42 using error correcting codes [ECC] or parity check
• CPC Class Codes: G11C 29/52 Protection of memory contents; Detection of errors in memory contents

Abstract

An apparatus, system, and method are disclosed for accessing non-volatile cells. An interface module is configured to receive data for storage on a non-volatile memory medium. The non-volatile memory medium includes an array of cells, and each cell encodes a non-power-of-two number of states, or abodes per cell. A base conversion module is configured to convert the data from a binary representation to a representation in a non-binary base. The non-binary base uses a number of unique digits equal to the non-power-of-two number of abodes per cell. A write module is configured to store the converted data to the array of cells.

Claims

1. A method comprising:

receiving data for storage on a non-volatile recording medium, the non-volatile recording medium comprising an array of cells, each cell encoding a number of states per cell;

converting the data from a binary representation to a non-binary representation corresponding to the number of states per cell; and

storing the converted data to the array of cells.

2. The method of claim 1, wherein each cell of the array of cells encodes an ordered sequence of states, and storing the converted data to the array of cells comprises iteratively selecting cells that encode a data value other than a desired value from the converted data, and programming the selected cells to a next state in the ordered sequence of states, until the converted data is stored.

3. The method of claim 2, wherein selecting cells comprises marking bits associated with the selected cells in a write buffer for the array of cells.

4. The method of claim 2, wherein programming a cell to an intermediate state in the ordered sequence of states comprises changing a programming level for the cell to a program value other than a target program value for the intermediate state.

5. The method of claim 1, wherein storing the converted data to the array of cells comprises changing a programming level for at least one cell without verifying the change to the programming level.

6. The method of claim 1, wherein each cell of the array of cells encodes an ordered sequence of states, and storing the converted data to the array of cells comprises iteratively selecting cells for programming to a highest unprogrammed state in the ordered sequence of states, and programming the selected cells, until the converted data is stored.

7. The method of claim 1, further comprising:

reading the converted data from the array of cells;

translating the converted data to binary data; and

returning the binary data to one or more of a host device and a storage controller for the non-volatile recording medium.

8. The method of claim 7, wherein reading the converted data from the array of cells comprises setting a plurality of read thresholds for the array of cells and sensing cells that satisfy the read thresholds, until a state is determined for each cell in the array of cells.

9. The method of claim 8, wherein reading the converted data further comprises:

setting at least one additional read threshold in response to determining a state for each cell;

sensing cells that satisfy the at least one additional read threshold; and

detecting errors in the converted data using information derived from sensing cells that satisfy the at least one additional read threshold.

10. The method of claim 1, further comprising dynamically adjusting the number of states per cell over time.

11. The method of claim 10, wherein the number of states per cell is adjusted based on a health characteristic of the array of cells.

12. The method of claim 1, further comprising using an error correcting algorithm that operates on non-binary numbers to detect errors in the converted data.

13. An apparatus comprising:

an interface module configured to receive data for storage on a non-volatile memory medium, the non-volatile memory medium comprising an array of cells, each cell encoding a number of abodes per cell with a non-binary alignment;

a base conversion module configured to convert the data from a binary representation to a representation in a non-binary base, the non-binary base using a number of unique digits equal to the non-binary aligned number of abodes per cell; and

a write module configured to store the converted data to the array of cells.

14. The apparatus of claim 13, wherein each cell of the array of cells encodes an ordered sequence of abodes, and the write module is configured to store the converted data to the array of cells by iteratively selecting cells that encode a data value other than a desired value from the converted data, and programming the selected cells to a next abode in the ordered sequence of abodes, until the converted data is stored.

15. The apparatus of claim 13, wherein each cell of the array of cells encodes an ordered sequence of abodes, and the write module is configured to store the converted data to the array of cells by iteratively selecting cells for programming to a highest unprogrammed abode in the ordered sequence of abodes, and programming the selected cells, until the converted data is stored.

16. The apparatus of claim 13, wherein the base conversion module is further configured to separate a binary stream for the data into a plurality of binary numbers and to convert each binary number to the non-binary base, each binary number comprising a number of bits less than or equal to a word unit size for the array of cells.

17. The apparatus of claim 13, further comprising:

a read module configured to read the converted data from the array of cells;

a translate module configured to translate the converted data to binary data; and

a return module configured to return the binary data to one or more of a host device and a storage controller for the non-volatile memory medium.

18. The apparatus of claim 13, further comprising an abode adjust module configured to dynamically adjust the number of abodes per cell over time based on a health characteristic of the array of cells.

19. The apparatus of claim 13, further comprising an error module configured to use an error correcting algorithm that operates on non-binary numbers to detect errors in the converted data.

20. An apparatus comprising:

means for receiving data for storage on a non-volatile storage medium, the non-volatile storage medium comprising an array of cells, each cell encoding a non-power-of-two number of encoding states per cell;

means for converting the data from a binary representation to a representation in a non-binary base, the non-binary base using a number of unique digits equal to the number of encoding states per cell for storage by the non-volatile storage medium; and

means for dynamically adjusting the number of states per cell over time.

21. The apparatus of claim 20, further comprising:

means for storing the converted data to the array of cells;

means for reading the converted data from the array of cells;

means for translating the converted data to binary data; and

means for returning the binary data to one or more of a host device and a storage controller for the non-volatile storage medium.

22. A system comprising:

a non-volatile recording device comprising a non-volatile recording medium, the non-volatile recording medium comprising an array of cells, each cell encoding a non-power-of-two number of states per cell, the non-volatile recording device in communication with a host device over a communications bus; and

a write pipeline comprising,

an interface module configured to receive data for storage on the non-volatile recording medium;

a base conversion module configured to convert the data from a binary representation to a representation in a non-base-two base, the non-base-two base using a number of unique digits equal to the non-power-of-two number of states per cell; and

a write module configured to store the converted data to the array of cells.

23. The system of claim 22, further comprising a read pipeline, the read pipeline comprising:

a read module configured to read the converted data from the array of cells;

a translate module configured to translate the converted data to binary data; and

a return module configured to return the binary data to one or more of a host device and a storage controller for the non-volatile recording medium.

24. A computer program product comprising a computer readable storage medium storing computer usable program code executable to perform operations, the operations comprising:

reading non-binary data from a non-volatile memory medium, the non-volatile memory medium comprising an array of cells, each cell encoding a number of abodes per cell other than a power of two, the non-binary data encoded in a non-binary base, the non-binary base using a number of unique digits equal to the number of abodes per cell;

translating the non-binary data to binary data; and

returning the binary data to one or more of a host device and a storage controller for the non-volatile memory medium.

25. The computer program product of claim 24, wherein reading the non-binary data from the non-volatile memory medium comprises:

setting a plurality of read thresholds for the array of cells;

sensing cells that satisfy the read thresholds, until an abode is determined for each cell in the array of cells;

setting at least one additional read threshold in response to determining am abode for each cell;

sensing cells that satisfy the at least one additional read threshold; and

detecting errors in the non-binary data using information derived from sensing cells that satisfy the at least one additional read threshold.