SYSTEMS AND METHODS FOR RETRIEVING DATA

• US 20110239061A1
• Filed: 05/26/2011
• Published: 09/29/2011
• Est. Priority Date: 06/07/2007
• Status: Active Grant

• Current Assignee: Micron Technology, Inc.
• Original Assignee: Micron Technology, Inc.
• Inventors: Li, Tieniu
• Granted Patent: US 8,930,771 B2
• Time in Patent Office: Days
• US Class Current: 714/704
• CPC Class Codes: G06F 11/073 in a memory management context, e.g. virtual memory or cache management memory management G06F12/00; testing of static memory units G11C29/00
• CPC Class Codes: G06F 11/076 by exceeding a count or rate limit, e.g. word- or bit count limit
• CPC Class Codes: G06F 11/1068 in sector programmable memories, e.g. flash disk G06F11/1072 takes precedence
• CPC Class Codes: G06F 11/2017 where memory access, memory control or I/O control functionality is redundant redundant communication control functionality G06F11/2005; redundant storage control functionality G06F11/2089
• CPC Class Codes: G06F 2201/85 Active fault masking without idle spares active fault masking without idle spare hardware where processing functionality is redundant G06F11/2035
• CPC Class Codes: G11C 16/349 Arrangements for evaluating degradation, retention or wearout, e.g. by counting erase cycles

Abstract

Apparatus and methods, such as those that read data from non-volatile integrated circuit memory devices, such as NAND flash. For example, disclosed techniques can be embodied in a device driver of an operating system. Errors are tracked during read operations. If sufficient errors are observed during read operations, the block is then retired when it is requested to be erased or a page of the block is to be written. One embodiment is a technique to recover data from uncorrectable errors. For example, a read mode can be changed to a more reliable read mode to attempt to recover data. One embodiment further returns data from the memory device regardless of whether the data was correctable by decoding of error correction code data or not.

Claims

1. A method comprising:

updating a count at least partially in response to determining that an error was detected in a page of data read from a block of memory cells;

resetting the count upon power up of a device that includes the block of memory cells; and

indicating the block for retirement in response to the count reaching a threshold value.

2. The method of claim 1, wherein updating a count comprises incrementing the count.

3. The method of claim 1, further comprising retiring the block when it is to be erased.

4. The method of claim 1, further comprising retiring the block when a page of the block is to be written.

5. A method comprising:

maintaining at least a partial history of errors during read operations for a block of memory cells, wherein maintaining comprises using a counter to maintain the at least a partial history;

providing an indication of the reliability of the block responsive to the at least a partial history; and

resetting the counter upon power up of a device including the block of memory cells.

6. The method of claim 5, wherein providing an indication of the reliability of the block comprises indicating the block for retirement.

7. The method of claim 5, wherein providing an indication of the reliability of the block comprises indicating the block for retirement when the counter reaches a threshold.

8. The method of claim 7, further comprising retiring the block when it is to be erased.

9. The method of claim 7, further comprising retiring the block when a page of the block is to be written.

10. A method comprising:

if an error is detected for a page of data read from a block of memory cells, determining whether the error is correctable; and

if the error is not correctable, indicating that the block of memory cells should be retired.

11. The method of claim 10, further comprising:

if the error is correctable, determining an extent to which the error is corrected; and

if the extent is greater than a threshold, indicating that the block of memory cells should be retired.

12. The method of claim 11, further comprising, if the extent is not greater than the threshold, updating a history of errors encountered while reading pages of data from the block.

13. The method of claim 10, further comprising:

receiving a request for the page of data;

requesting the particular page of data from a device including the block of memory cells, wherein the device provides the page of data responsive thereto; and

determining whether an error was detected for the page of data.

14. The method of claim 13, wherein determining whether an error was detected for the page of data comprises decoding error correction code data to determine whether an error was detected.

15. A method comprising:

if an error is detected for a page of data read from a block of memory cells, determining whether the error is correctable;

if the error is correctable, determining an extent to which the error is corrected; and

if the extent is greater than a threshold, indicating that the block of memory cells should be retired.

16. The method of claim 15, further comprising, if the extent is not greater the threshold, updating a history of errors encountered while reading pages of data from the block.

17. The method of claim 15, wherein determining whether the error is correctable comprises decoding ECC data.

18. The method of claim 15, wherein determining whether the error is correctable comprises determining whether the error is correctable within the limitations of ECC.

19. The method of claim 15, wherein determining an extent to which the error is corrected comprises comparing uncorrected data with corrected data to obtain a number of errors.

20. The method of claim 15, wherein the threshold comprises a threshold value and indicating that the block of memory cells should be retired comprises setting a counter to the threshold value.

21. The method of claim 15, wherein indicating that the block of memory cells should be retired comprises indicating that the block of memory cells should be retired early.

22. The method of claim 15, further comprising, if the extent is greater than a threshold, attempting to recover the page of data.

23. A method comprising:

if an error is detected for a page of data read from a block of memory cells, determining whether the error is correctable;

if the error is correctable, determining an extent to which the error is corrected; and

if the extent is not greater than a threshold, updating a history of errors encountered while reading pages of data from the block of memory cells.

24. The method of claim 23, wherein updating a history of errors encountered while reading pages of data from the block of memory cells comprises updating a counter.

25. The method of claim 24, wherein updating a counter comprises incrementing the counter.

26. The method of claim 25, wherein incrementing a counter comprises incrementing the counter by a first increment, and further comprising incrementing the counter by a second increment if the extent is greater than the threshold, wherein the second increment is equal to or larger than the first increment.

27. The method of claim 26, wherein the second increment is larger than the first increment, and further comprising incrementing the counter by a third increment if the error is not correctable, wherein second increment is smaller than third increment.

28. A device driver configured to configured to perform a method comprising:

maintaining at least a partial history of errors during read operations for a block of memory cells, wherein maintaining comprises using a counter to maintain the at least a partial history;

providing an indication of the reliability of the block responsive to the at least a partial history; and

resetting the counter upon power up of a device including the block of memory cells.

29. The device driver of claim 28, wherein the device driver is embodied in software.

30. The device driver of claim 28, wherein the device driver is embodied in hardware.

31. A device driver configured to configured to perform a method comprising:

if an error is detected for a page of data read from a block of memory cells, determining whether the error is correctable; and

if the error is not correctable, indicating that the block of memory cells should be retired.

32. A device driver configured to configured to perform a method comprising:

if an error is detected for a page of data read from a block of memory cells, determining whether the error is correctable;

if the error is correctable, determining an extent to which the error is corrected; and

if the extent is greater than a threshold, indicating that the block of memory cells should be retired.

33. A device driver configured to configured to perform a method comprising:

if an error is detected for a page of data read from a block of memory cells, determining whether the error is correctable;

if the error is correctable, determining an extent to which the error is corrected; and

if the extent is not greater than a threshold, updating a history of errors encountered while reading pages of data from the block of memory cells.

34. A method comprising:

retrieving an error history associated with a block of memory cells;

determining whether the block of memory cells is reliable responsive to the error history; and

if the block is determined to be reliable, instructing a device to perform a requested operation on the block of memory cells.

35. The method of claim 34, wherein the block of memory cells comprises a block of memory cells to be erased and the operation comprises erasing the block of memory cells.

36. The method of claim 34, wherein the block of memory cells comprises a block of memory cells to be written to and the operation comprises writing to a page of the block.

37. The method of claim 34, wherein the error history comprises a count.

38. The method of claim 34, further comprising, if the block is determined to be unreliable, refusing the requested operation.

39. The method of claim 38, wherein the block is deemed unreliable if a counter is at or above a threshold value.

40. The method of claim 34, wherein retrieving an error history associated with a block of memory cells comprises retrieving the error history associated with the block of memory cells responsive to receiving a request for the operation.

41. The method of claim 34, further comprising determining whether an error occurred during the requested operation within the device.

42. A device driver configured to configured to perform a method comprising:

retrieving an error history associated with a block of memory cells;

determining whether the block of memory cells is reliable responsive to the error history; and

if the block is determined to be reliable, instructing a device to perform a requested operation on the block of memory cells.

43. The device driver of claim 42, wherein the device driver is embodied in software.

44. The device driver of claim 42, wherein the device driver is embodied in hardware.

45. A method of recovering data, the method comprising:

changing a mode of a read of a page of data from a device;

requesting a read of the page of data from the device, wherein the device provides the page of data responsive thereto;

if the page of data provided by the device includes an error, determining whether the page of data provided by the device is correctable; and

if the page of data provided by the device is not correctable, changing the mode of the read to a different mode.

46. The method of claim 45, wherein changing a mode of a read of a page of data comprises changing the mode to a more reliable read mode.

47. The method of claim 45, wherein changing a mode of a read of a page of data comprises changing the mode from a direct memory access mode to a mode using a processor to control access.

48. The method of claim 45, wherein changing a mode of a read of a page of data comprises slowing down timing for the device.

49. The method of claim 45, further comprising, if the page of data provided by the device is not correctable, determining whether to provide the data with the error.

50. A device driver configured to configured to perform a method comprising:

changing a mode of a read of a page of data from a device;

requesting a read of the page of data from the device, wherein the device provides the page of data responsive thereto;

if the page of data provided by the device includes an error, determining whether the page of data provided by the device is correctable; and

if the page of data provided by the device is not correctable, changing the mode of the read to a different mode.

51. The device driver of claim 50, wherein the device driver is embodied in software.

52. The device driver of claim 50, wherein the device driver is embodied in hardware.