Method of Performing Wear Leveling with Variable Threshold

• US 20100100663A1
• Filed: 10/21/2008
• Published: 04/22/2010
• Est. Priority Date: 10/21/2008
• Status: Active Grant

• Current Assignee: YEESTOR Microelectronics Co., Ltd.
• Original Assignee: Skymedi Corporation
• Inventors: Ji, Yung-Li, Yen, Chih-Nan, Kao, Yu-Mao, Shone, Fuja
• Granted Patent: US 8,082,386 B2
• Time in Patent Office: Days
• US Class Current: 711/103
• CPC Class Codes: G06F 12/0246 in block erasable memory, e.g. flash memory
• CPC Class Codes: G06F 2212/7211 Wear leveling

Abstract

A wear leveling limit and/or an overall erase count threshold used for activating wear leveling in a non-volatile memory may be adjusted by determining a stage according to a highest erase count, and determining the wear leveling limit and/or the overall erase count threshold corresponding to the stage. Wear leveling may then be performed according to the wear leveling limit and/or the overall erase count threshold.

Claims

1. A method of performing wear leveling, the method comprising:

determining a stage according to a highest erase count;

determining a wear leveling limit corresponding to the stage; and

performing wear leveling according to the wear leveling limit.

2. The method of claim 1, wherein determining the stage according to the highest erase count comprises looking up the stage corresponding to the highest erase count in a table.

3. The method of claim 1, wherein determining the stage according to the highest erase count comprises calculating the stage from the highest erase count according to an algorithm.

4. The method of claim 3, wherein calculating the stage from the highest erase count according to the algorithm comprises calculating the stage according to a ratio of the highest erase count and a predetermined maximum erase count.

5. The method of claim 1, wherein determining the wear leveling limit corresponding to the stage comprises looking up the wear leveling limit corresponding to the stage in a table.

6. The method of claim 1, wherein determining the wear leveling limit corresponding to the stage comprises calculating the wear leveling limit from the stage according to an algorithm.

7. The method of claim 1, wherein determining the wear leveling limit from the stage comprises determining the wear leveling limit from a previous wear leveling limit.

8. The method of claim 7, wherein determining the wear leveling limit from the previous wear leveling limit comprises determining the wear leveling limit as a product of the previous wear leveling limit and a ratio.

9. The method of claim 1, wherein performing wear leveling according to the wear leveling limit comprises performing wear leveling when the highest erase count is greater than a lowest erase count by the wear leveling limit.

10. A method of performing wear leveling, the method comprising:

determining a stage according to a highest erase count;

determining an overall erase count threshold corresponding to the stage; and

performing wear leveling according to the overall erase count threshold.

11. The method of claim 10, wherein determining the stage according to the highest erase count comprises looking up the stage corresponding to the highest erase count in a table.

12. The method of claim 10, wherein determining the stage according to the highest erase count comprises calculating the stage from the highest erase count according to an algorithm.

13. The method of claim 12, wherein calculating the stage from the highest erase count according to the algorithm comprises calculating the stage according to a ratio of the highest erase count and a predetermined maximum erase count.

14. The method of claim 10, wherein determining the overall erase count threshold corresponding to the stage comprises looking up the overall erase count threshold corresponding to the stage in a table.

15. The method of claim 10, wherein determining the overall erase count threshold corresponding to the stage comprises calculating the overall erase count threshold from the stage according to an algorithm.

16. The method of claim 10, wherein determining the overall erase count threshold from the stage comprises determining the overall erase count threshold from a previous overall erase count threshold.

17. The method of claim 16, wherein determining the overall erase count threshold from the previous overall erase count threshold comprises determining the overall erase count threshold as a product of the previous overall erase count threshold and a ratio.

18. The method of claim 10, wherein performing wear leveling according to the overall erase count threshold comprises performing wear leveling when an overall erase count equals the overall erase count threshold.

19. The method of claim 10, wherein performing wear leveling according to the overall erase count threshold comprises performing wear leveling when an overall erase count exceeds the overall erase count threshold.