Hybrid mapping implementation within a non-volatile memory system

• US 7,188,228 B1
• Filed: 10/01/2003
• Issued: 03/06/2007
• Est. Priority Date: 10/01/2003
• Status: Active Grant

• Current Assignee: SanDisk Technologies LLC (Western Digital Corporation)
• Original Assignee: SanDisk Corporation (Western Digital Corporation)
• Inventors: Qawami, Bahman, Sabet-Sharghi, Farshid, Chang, Robert C
• Primary Examiner(s): Bataille; Pierre
• Assistant Examiner(s): PATEL, HETUL B
• Application Number:
  US10/676,652
• Time in Patent Office: 1,252 Days
• Field of Search: 711/103, 711/171, 711202-209, 711/5, 707/205, 703/23, 365/51
• US Class Current: 711/202
• CPC Class Codes: G06F 12/0246 in block erasable memory, e.g. flash memory

Abstract

Methods and apparatus for allow different mapping implementations, including a many-to-one logical to physical block mapping, to be used within a memory system are disclosed. According to one aspect of the present invention, a method for mapping a plurality of logical blocks to a physical block includes identifying a first logical block meets at least one criterion. The method also includes identifying a second logical block which is substantially complementary to the first logical block, and providing contents associated with the first logical block and contents associated with the second logical block to the physical block.

Claims

1. A method for mapping a plurality of logical blocks to a physical block, each logical block including a plurality of logical pages arranged in groups, the plurality of logical blocks and the physical block being associated with a non-volatile memory system, the method comprising:

identifying a first logical block of the plurality of logical blocks that meets at least one criterion, the at least one criterion comprising contents of the first logical block being associated with a number of groups of logical pages fewer than a first limit;

identifying a second logical block of the plurality of logical blocks that is substantially complementary to the first logical block; and

providing contents associated with the identified first logical block and contents associated with the identified second logical block to the physical block.

2. The method of claim 1 wherein the at least one criterion further comprises a relatively low erase count.

3. The method of claim 1 wherein identifying the second logical block of the plurality of logical blocks that is substantially complementary to the first logical block includes determining that contents associated with the second logical block are associated with a number of groups of logical pages fewer than a second limit.

4. The method of claim 1 wherein identifying the second logical block of the plurality of logical blocks that is substantially complementary to the first logical block includes determining that a number of groups associated with the second logical block that have associated data and a number of groups associated with the first logical block that have associated data is less than or equal to a total number of groups of physical pages associated with the physical block.

5. The method of claim 1 wherein the first logical block is mapped to the physical block when it is identified, the method further including:

reclaiming a first block associated with the second logical block after providing the contents associated with the first logical block and the contents associated with the second logical block to the physical block.

6. The method of claim 1 further including:

reclaiming a first block associated with the first logical block after providing the contents associated with the first logical block and the contents associated with the second logical block to the physical block; and

reclaiming a second block associated with the second logical block after providing the contents associated with the first logical block and the contents associated with the second logical block to the physical block.

7. A non-volatile memory system comprising:

a non-volatile memory, the non-volatile memory having an associated physical block;

means for identifying a first logical block of a plurality of logical blocks that meets at least one criterion, each logical block including a plurality of logical pages arranged in groups, and the at least one criterion being met by the contents of the first logical block being associated with a number of groups of logical pages fewer than a first limit;

means for identifying a second logical block of the plurality of logical blocks that is substantially complementary to the first logical block; and

means for providing contents associated with the first logical block and contents associated with the second logical block to the physical block.

8. The non-volatile memory system of claim 7 wherein the means for identifying the first logical block of the plurality of logical blocks which meets the at least one criterion include at least one of means for determining if the physical block has a relatively low erase count and means for determining whether the contents of the first logical block are associated with a number of groups of logical pages fewer than the first limit.

9. The non-volatile memory system of claim 7 wherein the means for identifying the second logical block that is substantially complementary to the first logical block include means for determining whether the contents associated with the second logical block are associated with a number of groups of logical pages fewer than a second limit.

10. The non-volatile memory system of claim 7 wherein the means for identifying the second logical block that is substantially complementary to the first logical block include means for determining whether a number of groups of logical pages associated with the second logical block that have associated data and a number of groups of logical pages associated with the first logical block that have associated data is less than or equal to a total number of groups of physical pages associated with the physical block.

11. The non-volatile memory system of claim 7 wherein the non-volatile memory system is one of an embedded system, a Smart Media card, a Compact Flash card, a Secure Digital Card, and a MultiMedia card.

12. A memory system comprising:

a non-volatile memory, the non-volatile memory having an associated physical block;

code devices that identify a first logical block of a plurality of logical blocks that meets at least one criterion, each logical block including a plurality of logical pages arranged in groups, and the at least one criterion being met by the contents of the first logical block being associated with a number of groups of logical pages fewer than a first limit;

code devices that identify a second logical block of the plurality of logical blocks that is substantially complementary to the first logical block;

code devices that provide contents associated with the first logical block and contents associated with the second logical block to the physical block; and

a memory area that stores the code devices.

13. The memory system of claim 12 wherein the code devices that identify the first logical block of the plurality of logical blocks that meets the at least one criterion include at least one of code devices that determine if the physical block has a relatively low erase count and code devices that determine whether the contents of the first logical block are associated with a number of groups of logical pages fewer than the first limit.

14. The memory system of claim 12 wherein the code devices that identify the second logical block that is substantially complementary to the first logical block include code devices that determine whether the contents of the second logical block are associated with a number of groups of logical pages fewer than a second limit.

15. The memory system of claim 12 wherein the code devices that identify the second logical block that is substantially complementary to the first logical block include code devices that determine whether a number of groups of logical pages associated with the second logical block that have associated data and a number of groups of logical pages associated with the first logical block that have associated data is less than or equal to a total number of groups of physical pages associated with the physical block.

16. The memory system of claim 12 wherein the first logical block is mapped to the physical block when it is identified, and the memory system further includes:

code devices that reclaim a first block associated with the second logical block after the contents associated with the first logical block and the contents associated with the second logical block are provided to the physical block.

17. The memory system of claim 12 further including:

code devices that reclaim a first block associated with the first logical block after the contents associated with the first logical block and the contents associated with the second logical block are provided to the physical block; and

code devices that reclaim a second block associated with the second logical block after the contents associated with the first logical block and the contents associated with the second logical block are provided to the physical block.

18. The memory system of claim 12 wherein the non-volatile memory system is one of n embedded system, a Smart Media card, a Compact Flash card, a Secure Digital Card, and a MultiMedia card.