Method for copying data in reprogrammable non-volatile memory

• US 20060156189A1
• Filed: 12/21/2004
• Published: 07/13/2006
• Est. Priority Date: 12/21/2004
• Status: Active Grant

• Current Assignee: SanDisk Technologies LLC (Western Digital Corporation)
• Original Assignee: Sandisk Technologies Incorporated (Western Digital Corporation)
• Inventors: Tomlin, Andrew
• Granted Patent: US 7,849,381 B2
• Time in Patent Office: Days
• US Class Current: 714/763
• CPC Class Codes: G06F 11/1068 in sector programmable memories, e.g. flash disk G06F11/1072 takes precedence
• CPC Class Codes: G06F 12/0246 in block erasable memory, e.g. flash memory
• CPC Class Codes: G06F 2212/7203 Temporary buffering, e.g. using volatile buffer or dedicated buffer blocks

Abstract

The present invention presents methods for improving data relocation operations. In one aspect, rather than check the quality of the data based on its associated error correction code (ECC) in every relocation operation, it is determined whether to check ECC based on predetermined selection criteria, and if ECC checking is not selected, causing the memory to perform an on-chip copy the data from a first location to a second location. If ECC checking is selected, the data is transferred to the controller and checked; when an error is found, a correction operation is performed and when no error is found, an on-chip copy is performed. The predetermined selection criteria may comprise a sampling mechanism, which may be random based or deterministic. In another aspect, data transfer flags are introduced to indicate data has been corrected and should be transferred back to the memory. A further aspect considers the header and user data separately if each has a distinct associated ECC.

Claims

1. In a memory system comprising a controller and a programmable non-volatile memory, a method for relocating data from a first location of the memory to a second location of the memory, the method comprising:

reading the data from the first location into a register on the memory;

determining in the controller whether to perform an error detection and correction operation on said data; and

in response to determining that an error detection and correction operation not be performed on said data, writing the data from the register to the second location.

7. The method of either of claims 1 or 2, wherein said determining whether to perform an error detection and correction operation is deterministic mechanism.

8. The method of either of claims 1 or 2, wherein said determining whether to perform an error detection and correction operation is randomly or pseudo-randomly based.

9. The method of either of claims 1 or 2, wherein said determining whether to perform an error detection and correction operation is based on a sampling mechanism.

10. The method of claim 9, wherein said sampling mechanism is based on overhead data associated with said data.

11. The method of claim 10, wherein said sampling mechanism comprises comparing a time stamp associated with the data to logical address information of the data.

2. In a memory system comprising a controller and a programmable non-volatile memory, a method for relocating data from a first location of the memory to a second location of the memory, the method comprising:

reading the data from the first location into a register on the memory;

determining in the controller whether to perform an error detection and correction operation on said data;

in response to determining that an error detection and correction operation be performed on said data, transferring a copy of said data to the controller while maintaining said data in the register; and

performing an error correction and detection operation on the data in the controller.

3. The method of claim 2, wherein said data includes an associated error correction code (ECC) and the error correction and detection operation comprises:

determining, based on said associated ECC, whether the data contains an error; and

in response to determining that said data contains an error, performing a correction operation on said data.

4. The method of claim 3, wherein if the error correction operation is successfully completed, the method further comprises:

transferring the corrected data from the controller to memory; and

writing the corrected data to the second location.

5. The method of claim 3, wherein if the error correction is not successfully completed the method further comprises:

setting an error flag associated with the data.

6. The method of claim 5, wherein the data comprises a header portion and a user data portion and said error flag is written into the header portion.

12. The method of claim 2, further comprising:

setting a flag value based on whether the data has been corrected as part of said performing an error detection and correction operation;

if the flag value is set to indicate that said data has been corrected, transferring the corrected data back to the register; and

subsequently writing the contents of register to the second memory location.

13. The method of claim 12, wherein the data has an associated error correction code (ECC) and said error detection and correction operation comprises:

determining based on said associated ECC whether the data contains an error; and

correcting the data using said associated ECC,

wherein said flag value is set in response to a successfully completing said correcting.

14. The method of claim 13, further comprising:

setting an error flag associated with the data in response to not successfully completing said correcting.

15. The method of claim 14, wherein the data comprises an overhead portion and a user data portion and said error flag is written into the overhead portion.

16. The method of claim 12, wherein the data comprises a user data portion and an overhead portion and wherein the user data has an associated error correction code (ECC) and the overhead portion has a distinct associated error correction code (ECC), wherein said transferring a copy the of the data and said performing an error detection and correction operation

transferring a copy the of the overhead portion of the data from the register to the controller while maintaining said data in the register;

and

performing in the controller an error detection and correction operation on the overhead portion of the data based on the associated overhead ECC and, in response to completing a successful correction operation on the overhead portion of the data, transferring the corrected overhead portion back to the register;

and, in response to a successful error detection and correction operation on the overhead portion of the data,

transferring a copy the of the user portion of the data from the register to the controller while maintaining said data in the register; and

performing in the controller an error detection and correction operation on the user portion of the data based on the associated user data ECC,

where said flag value is set based on whether the user data portion has been corrected.

17. In a memory system comprising a controller and a programmable non-volatile memory, a method for relocating data from a first location of the memory to a second location of the memory, wherein the data comprises a user data portion and an overhead portion and wherein the user data has an associated error correction code (ECC) and the overhead portion has a distinct associated error correction code (ECC), the method comprising:

reading the data from the first location into a register on the memory;

subsequently transferring a copy of the header portion of the data to the controller while maintaining said data in the register;

performing in the controller an error correction and detection operation on the overhead portion based on the associated overhead ECC;

if the error correction and detection operation on the overhead portion requires correcting the overhead portion, subsequently transferring the corrected overhead back to the register in response to successfully completing the error correction and detection operation on the overhead; and

subsequent to said performing an error correction and detection operation on the overhead portion, determining in the controller whether to perform an error detection and correction operation on the user data portion of the data.

18. The method of claim 17, wherein said determining whether to perform an error detection and correction operation on the user data portion of the data comprises:

in response to determining that the overhead portion requires correcting, transferring a copy of said user data portion to the controller while maintaining said data in the register; and

performing an error correction and detection operation on the user data portion in the controller.

19. The method of claim 17, further comprising:

in response to determining that an error detection and correction operation not be performed on said user data portion, writing the data from the register to the second location.

20. The method of claim 17, further comprising:

in response to determining that an error detection and correction operation be performed on said user data portion, transferring a copy of said user data portion to the controller while maintaining said data in the register; and

performing an error correction and detection operation on the user data portion in the controller.

21. The method of either of claims 18 or 20, wherein the error correction and detection operation on the user data potion comprises:

determining, based on said associated user portion ECC, whether the user data portion contains an error; and

in response to determining that said user data portion contains an error, performing a correction operation on said data.

22. The method of claim 21, wherein if the error correction operation on the user data portion is successfully completed, the method further comprises:

transferring the corrected user data portion from the controller to memory; and

writing the corrected data to the second location.

23. The method of claim 21, wherein if the error correction of the user data portion is not successfully completed the method further comprises:

setting an error flag associated with the data.

24. The method of claim 23, wherein said error flag is written into the overhead portion.

25. The method of either of claims 19 or 20, wherein said determining whether to perform an error detection and correction operation on the user data portion is deterministic mechanism.

26. The method of either of claims 19 or 20, wherein said determining whether to perform an error detection and correction operation on the user data portion is random or pseudo-randomly based.

27. The method of either of claims 19 or 20, wherein said determining whether to perform an error detection and correction operation on the user data portion is based on a sampling mechanism.

28. The method of claim 27, wherein said sampling mechanism is based on the overhead data associated with said data.

29. The method of claim 28, wherein said sampling mechanism comprises comparing a time stamp associated with the data to logical address information of the data.

30. The method of claim 20, further comprising:

setting a flag value based on whether the data has been corrected as part of said performing an error detection and correction operation;

if the flag value is set to indicate that said data has been corrected, transferring the corrected data back to the register; and

subsequently writing the contents of register to the second memory location.

31. The method of claim 30, wherein the data has an associated error correction code (ECC) and said error detection and correction operation comprises:

determining based on said associated ECC whether the data contains an error; and

correcting the data using said associated ECC,

wherein said flag value is set in response to a successfully completing said correcting.

32. The method of claim 31, further comprising:

setting an error flag associated with the data in response to not successfully completing said correcting.

33. The method of claim 32, wherein the data comprises an overhead portion and a user data portion and said error flag is written into the overhead portion.

34. The method of claim 30, wherein the data comprises a user data portion and an overhead portion and wherein the user data has an associated error correction code (ECC) and the overhead portion has a distinct associated error correction code (ECC), wherein said transferring a copy the of the data and said performing an error detection and correction operation

transferring a copy the of the overhead portion of the data from the register to the controller while maintaining said data in the register;

and

performing in the controller an error detection and correction operation on the overhead portion of the data based on the associated overhead ECC and, in response to completing a successful correction operation on the overhead portion of the data, transferring the corrected overhead portion back to the register;

and, in response to a successful error detection and correction operation on the overhead portion of the data,

transferring a copy the of the user portion of the data from the register to the controller while maintaining said data in the register; and

performing in the controller an error detection and correction operation on the user portion of the data based on the associated user data ECC,

where said flag value is set based on whether the user data portion has been corrected.

35. A method for avoiding the transfer of data having an associated error correction code (ECC) from a first location of a reprogrammable non-volatile memory to a memory controller during a copy operation, comprising:

applying a sampling method to minimize degradation of the data being copied;

checking the ECC of the data at a predetermined frequency, wherein said frequency is sufficient to avoid significant degradation of the quality of the data.

36. The method of claim 35, wherein the predetermined selection criteria comprise a sampling mechanism.

37. The method of claim 36, wherein the sampling mechanism is random based.

38. The method of claim 36, wherein the sampling mechanism is deterministic.

39. The method of claim 36, wherein the sampling mechanism comprises:

comparing a plurality of bits associated with a the number of a logical sector in the reprogrammable non-volatile memory with a timestamp to produce a comparison result; and

selecting to check an ECC in accordance with the comparison result.

40. A method for copying data having an associated error correction code (ECC) from a first location to a second location of a reprogrammable non-volatile memory of a system that includes a memory controller, comprising:

reading the data from the first location into a cache on the memory;

determining whether to check the ECC based on predetermined selection criteria, and if ECC checking is not selected, causing the memory to copy the data from the cache to the second location; and

if ECC checking is selected, checking the ECC on the read data in the controller, including;

if an ECC error is found, correcting the ECC error on the read data in the controller and causing the controller to write the corrected data to the second location of the memory; and

if an ECC error is not found, causing the memory to copy the data from the cache to the second location.

41. The method of claim 40, wherein the predetermined selection criteria comprise a sampling mechanism.

42. The method of claim 41, wherein the sampling mechanism is random based.

43. The method of claim 41, wherein the sampling mechanism is deterministic.

44. The method of claim 41, wherein the sampling mechanism comprises:

comparing a plurality of bits associated with a the number of a logical sector in the reprogrammable non-volatile memory with a timestamp to produce a comparison result; and

selecting to check an ECC in accordance with the comparison result.