Storage device wear leveling

• US 7,689,762 B2
• Filed: 05/03/2007
• Issued: 03/30/2010
• Est. Priority Date: 05/03/2007
• Status: Active Grant

• Current Assignee: Atmel Corporation (Microchip Technology Incorporated)
• Original Assignee: Atmel Corporation (Microchip Technology Incorporated)
• Inventors: Hobson, Russell
• Primary Examiner(s): Chace; Christian P
• Assistant Examiner(s): Chen; Sam
• Application Number:
  US11/743,974
• Publication Number:
  US 20080276035A1
• Time in Patent Office: 1,062 Days
• Field of Search: 711/165, 711/103, 711/159, 365/239
• US Class Current: 711/103
• CPC Class Codes: G11C 16/349 Arrangements for evaluating degradation, retention or wearout, e.g. by counting erase cycles

Abstract

A reference memory location can be designated in a memory device. A memory location can be designated in response to storing data in the memory device. If the identified memory location is associated with the reference memory location then an allocated memory location can be designated relative to the reference memory location, and the allocated memory location can be leveled.

Claims

1. A method, comprising:

designating a reference memory location at a first physical memory address in a memory device;

designating a target memory location at a second physical memory address in the memory device, the target memory location being designated for storing data in the memory device;

in response to data being stored to the target memory location, incrementing the second physical memory address for the target memory location;

determining that the second physical memory address for the target memory location has been incremented to the first physical memory address for the reference memory location; and

in response to determining that the second physical memory address for the target memory location has been incremented to the first physical memory address for the reference memory location;

incrementing the first physical memory address for the reference memory location when the first physical memory address is not mapped to a logical address; and

leveling the reference memory location referenced by the first physical memory address when the first memory location is mapped to a logical address.

2. The method of claim 1, wherein leveling the first physical memory address for the reference memory location comprises:

identifying a first unallocated memory location having a nearest incremental physical memory address relative to the first physical memory address for the reference memory location;

allocating the first unallocated memory location to store data stored in the reference memory location; and

deallocating the reference memory location.

3. The method of claim 2, further comprising designating the reference memory location at a first allocated physical memory address relative to a physical memory address for the deallocated reference memory location.

4. The method of claim 1, wherein determining that the second physical memory address for the target memory location has been incremented to the first physical memory address for the reference memory location comprises determining that the second physical address for the target memory location is equal to the first physical memory address for the reference memory location.

5. The method of claim 1, wherein the memory device comprises a flash memory device.

6. The method of claim 3, wherein designating the reference memory location at the first allocated physical memory address relative to the physical memory address for the deallocated reference memory location comprises designating the reference memory location at a next sequential allocated physical memory address relative to the physical memory address of the deallocated reference memory location.

7. The method of claim 3, wherein designating the reference memory location at a first allocated physical memory address relative to the deallocated reference memory location comprises designating the reference memory location at a next sequential unallocated physical memory location relative to the physical memory address of the deallocated reference memory location.

8. The method of claim 2, further comprising associating memory locations with corresponding memory allocation flags, each allocation flag indicative of whether the memory location corresponding to allocation flag is mapped to a logical address.

9. The method of claim 8, wherein incrementing the first physical memory address for the reference memory location when the first memory address is not mapped to a logical address comprises incrementing the first physical memory address for the reference memory location to a physical memory address for a memory location having a memory allocation flag indicating that the memory location is mapped to a logical address.

10. The method of claim 1, wherein incrementing the first physical memory address for the reference memory location comprises incrementing a leveling pointer that references the first physical memory address for the reference memory location.

11. The method of claim 10, wherein leveling the reference memory location comprises:

leveling the reference memory location and each allocated memory location having a physical address included in a range of physical memory addresses between the physical memory address referenced by the leveling pointer and a free-leveling-pointer referencing a physical address of a last consecutive allocated memory location relative to the reference memory location.

12. A method, comprising:

identifying, by a data processing device, a contiguous block of allocated memory locations to level based on a target memory location matching a reference memory location and the reference memory location being mapped to a logical address, the block of allocated memory locations including the reference memory location and at least one contiguous allocated memory location adjacent to the reference memory location;

allocating, by the data processing device, data stored in the identified contiguous block of allocated memory locations to unallocated memory locations;

deallocating, by the data processing device, the contiguous block of allocated memory locations; and

redesignating, by the data processing device, the reference memory location at a highest physical memory address to which the data stored in the contiguous block of allocated memory locations is allocated.

13. A method, comprising:

determining, by a data processing device, that a free block pointer is incremented to a memory location being referenced by a leveling pointer, the free block pointer being a pointer for referencing a memory location that is eligible to receive data, the leveling pointer referencing a reference memory location;

identifying, by the data processing device, a first allocated memory location having a nearest incremental physical memory address relative to a physical memory address for the reference memory location;

identifying, by the data processing device, an unallocated memory location having an incremental physical memory address relative to the physical memory address that references the first allocated memory location;

storing data stored in the first allocated memory location at the unallocated memory location;

deallocating, by the data processing device, the first allocated memory location;

identifying, by the data processing device, a second memory location having a physical memory address that is within a specified range of the deallocated memory location; and

designating, by the data processing device, the identified second memory location as the reference memory location.

14. The method of claim 13, wherein identifying a memory location having a physical memory address that is within a specified range of the deallocated memory location comprises identifying an unallocated memory location having the physical memory address of the deallocated memory location.

15. The method of claim 13, wherein identifying a memory location having a physical memory address that is within a specified range of the deallocated memory location comprises identifying an allocated memory location having a physical memory address that is within a specified range of the deallocated memory location.

16. A memory device, comprising:

a memory array comprising memory cells defining memory blocks; and

a memory control circuit configured to;

define a leveling locator and a free block locator;

reference respective memory blocks indicated by the leveling locator and free block locator;

determine that the free block locator has been incremented to a memory block referenced by the leveling locator; and

in response to determining that the free block locator has been incremented to a memory block referenced by the leveling locator,

level a utilized memory block having a physical memory address that is within a threshold range of a physical memory address of a memory block referenced by the leveling locator.

17. The memory device of claim 16, wherein the memory control circuit is configured to:

define a free leveling locator respective to the utilized memory block; and

allocate the memory block referenced by the free leveling locator to store data stored in the utilized memory block; and

deallocate the memory block referenced by the utilized memory block.

18. The memory device of claim 17, wherein the memory control circuit is configured to:

redefine the leveling locator to reference a memory block within a specified physical address range of the deallocated memory block.

19. The memory device of claim 16, wherein each memory cell has a corresponding memory allocation flag.

20. The memory device of claim 16, wherein the memory device comprises a flash memory.

21. The memory device of claim 16, wherein the memory array and the memory control circuit are on a same substrate.

22. A system, comprising:

means for determining that a free block pointer is incremented to a memory location being referenced by a leveling pointer, the free block pointer being a pointer for referencing a memory location that is eligible to receive data, the leveling pointer referencing a reference memory location;

means for identifying a first allocated memory location at a nearest incremental physical memory address relative to the reference memory location;

means for identifying an unallocated memory location at a nearest incremental physical memory address relative to a first allocated memory location;

means for allocating the unallocated memory location to store data stored in the first allocated memory location;

means for deallocating the first allocated memory location; and

means for identifying a second memory location having a physical memory address that is within a specified range of the deallocated memory location; and

means for designating the second identified memory location as the reference memory location.