Memory controller, flash memory system, and method for recording data on flash memory

• US 20050162930A1
• Filed: 12/27/2004
• Published: 07/28/2005
• Est. Priority Date: 12/26/2003
• Status: Active Grant

• Current Assignee: TDK Corporation
• Original Assignee: TDK Corporation
• Inventors: Mukaida, Naoki
• Granted Patent: US 7,315,870 B2
• Time in Patent Office: Days
• US Class Current: 365/185.330
• CPC Class Codes: G06F 12/0246 in block erasable memory, e.g. flash memory
• CPC Class Codes: G06F 2212/7209 Validity control, e.g. using flags, time stamps or sequence numbers
• CPC Class Codes: G11C 16/10 Programming or data input circuits
• CPC Class Codes: G11C 29/76 using address translation or modifications
• CPC Class Codes: Y10S 707/99954 Version management

Abstract

There is disclosed a controller included in a flash memory system attachable to a memory interface of a host system. If a block in which new data is written and a block in which old data is written are present simultaneously, the controller determines in which block the newest data is written, based on version identifier stored in a redundant area f a flash memory. Specifically, the controller has an access control function for controlling access to the flash memory, an address managing function for managing correspondence between a logical block address supplied from the host system and a physical block address in the flash memory, a version identifier setting function for writing version identifier in the redundant area of the flash memory, and a version identifying function for identifying a block in which newest data corresponding to a same logical block address is written based on the version identifier.

Claims

1. A memory controller comprising:

an access unit which accesses a flash memory;

an address managing unit which manages correspondence between a logical block address in a host system and a physical block address in said flash memory;

a version identifier setting unit which writes version identifier in a redundant area of said flash memory; and

a version identifying unit which identifies a block in which newest data is written, from a plurality of blocks corresponding to a same logical block address, based on the version identifier.

2. The memory controller according to claim 1,

wherein the version identifier includes information representing a value which is increased or decreased each time data corresponding to the same logical block address is rewritten.

3. The memory controller according to claim 1,

wherein the version identifier includes information which is based on a physical block address of a block in which prior data corresponding to the same logical block address is stored.

4. A flash memory system comprising:

a flash memory;

an access control unit which controls access to said flash memory;

an address managing unit which manages correspondence between a logical block address in a host system and a physical block address in said flash memory;

a version identifier setting unit which writes version identifier in a redundant area of said flash memory; and

a version identifying unit which identifies a block in which newest data is written, from a plurality of blocks corresponding to a same logical block address, based on the version identifier.

5. The flash memory system according to claim 4,

wherein the version identifier includes information representing a value which is increased or decreased each time data corresponding to the same logical block address is rewritten.

6. The flash memory system according to claim 4,

wherein the version identifier includes information which is based on a physical block address of a block in which prior data corresponding to the same logical block address is stored.

7. A method for recording data on a flash memory comprising the steps of:

writing data in a data area of a flash memory;

setting version identifier in a redundant area of said flash memory; and

identifying a block in which newest data is written, from a plurality of blocks corresponding to a same logical block address, based on the version identifier.

8. The method according to claim 7,

wherein the version identifier is information representing a value which is increased or decreased each time data corresponding to the same logical block address is rewritten.

9. The method according to claim 7,

wherein the version identifier is information which is based on a physical block address of a block in which prior data corresponding to the same logical block address is stored.

10. A memory controller comprising:

a receiver which receives data to be written in a flash memory and a logical block address thereof from a host system;

a physical address designator which designates a physical block address of a block of the flash memory into which the data received by said receiver is to be written;

a version identifier manager which assigns version identifiers to the data, the version identifiers representing versions of data to which a same logical block address is assigned, for each of logical block addresses;

an access unit which writes data supplied from the host system to an empty block of the flash memory whose physical block address is designated by the physical address designator, and a corresponding logical block address and a corresponding version identifier assigned by the version identifier manager to a redundant area of the corresponding block, and

an effective block identifying unit which searches blocks storing a same logical block address, and in case of finding blocks storing a same logical block address, identifies an effective block which stores newest data, from the blocks storing the same logical block address, based on the version identifiers stored in the redundant areas of the blocks.

11. The memory controller according to claim 10, wherein the version identifier includes information representing a value which is increased or decreased each time data corresponding to the same logical block address is written into the flash memory.

12. The memory controller according to claim 10, wherein the version identifier includes information which is prepared based on a physical block address of a block in which prior data corresponding to the same logical block address is stored.

13. The memory controller according to claim 10, further comprising an address managing unit which stores data representing correspondence between the logical block address designated by the host system and the physical block address of said flash memory into which corresponding data is stored,

wherein said access unit accesses the flash memory based on the data representing the correspondence stored in the address managing unit;

and

said effective block identifying unit, when the memory controller is initialized, performing a process of reading the flash memory, preparing the data representing the correspondence, and storing the prepared data to the address managing unit, performs said searching and identifying, based on the version identifies, and prepares the data representing the correspondence.

14. A flash memory system comprising:

a flash memory; and

the memory controller according to claim 10.

15. A memory controller comprising:

access means for accessing a flash memory;

address managing means for managing correspondence between a logical block address in a host system and a physical block address in said flash memory;

version identifier setting means for writing version identifier in a redundant area of said flash memory; and

version identifying means for identifying a block in which newest data is written, from a plurality of blocks corresponding to a same logical block address, based on the version identifier.