Flash memory mass storage system

• US 5,933,368 A
• Filed: 04/27/1998
• Issued: 08/03/1999
• Est. Priority Date: 11/25/1996
• Status: Expired due to Term

• Current Assignee: Macronix International Co., Ltd.
• Original Assignee: Macronix International Co., Ltd.
• Inventors: Lee, Li-Jen, Lin, Chu-Hung, Lee, Ju-Xu, Lee, Tai-Yao, Ma, Chung-Wen, Hu, Ting-Chung
• Primary Examiner(s): Fears, Terrell W.
• Application Number:
  US09/067,449
• Time in Patent Office: 463 Days
• Field of Search: 365/185.33, 365/218
• US Class Current: 365/185.33
• 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
• CPC Class Codes: G06F 3/0616 in relation to life time, e.g. increasing Mean Time Between Failures [MTBF]
• CPC Class Codes: G06F 3/0656 Data buffering arrangements
• CPC Class Codes: G06F 3/0679 Non-volatile semiconductor memory device, e.g. flash memory, one time programmable memory [OTP]

Abstract

An architecture for a mass storage system using flash memory is described. This architecture involves organizing the flash memory into a plurality of blocks. These blocks are then divided into several categories. One of the categories is a working category used to store data organized in accordance with a pre-defined addressing scheme (such as the logical block address used in Microsoft'"'"'s operating system). The other category is a temporary buffer used to store data intended to be written to one of the working blocks. Another category contains blocks that need to be erased. When data is written into the mass storage system, a block in the second category is allocated from a block in the third category. The allocated block will then be changed to a block in the first category when writing to the allocated block is completed. The correspond block in the first category is placed into the third category. As a result, blocks can be recycled. Consequently, there is a constant supply of blocks in the second category. In another embodiment of the present invention, a new category is developed to handle random writing to the working blocks.

Claims

1. A method for using flash memory to implement a mass storage system, comprising:

dividing the flash memory into a plurality of blocks,

identifying a first set of blocks from the plurality of blocks, the first set of blocks being used to store data organized in accordance with a pre-defined addressing scheme;

identifying a second set of blocks from said plurality of blocks, the second set of blocks being used as a temporary buffer for storing data intended to be written to a block in the first set of blocks; and

updating data stored in a sector of a selected block in the first set of blocks by writing the updated data into a sector of a corresponding block in the second set of blocks and marking the sector of the corresponding block in the second set of blocks.

2. The method of claim 1, comprising:

determining sectors in a block in the second set of blocks which are not marked;

copying data from sectors in a block in the first set of blocks into the sectors in the block in the second set of blocks that are not marked; and

changing the identification of the block in the second set of blocks to a block in the first set of blocks.

3. The method of claim 1, comprising:

assigning a physical identification to each of the plurality of blocks;

assigning a logical address to each block in the set of blocks; and

mapping the physical identification to the logical address.

4. The method of claim 1, comprising:

determining which block in the second set of blocks corresponds to data in a sector to be read, determining if the sector in the determined block is marked;

obtaining the data from the determined block if the sector is marked, and obtaining the data from a block in the first set of blocks if the sector is not marked.

5. The method of claim 1, comprising:

identifying a third set of blocks that contain invalid data to be erased.

6. The method of claim 5, comprising:

changing blocks in the second set of blocks to blocks in the first set of blocks; and

changing blocks in the first set of blocks into blocks in the third set of blocks.

7. The method of claim 1,

wherein the marking a corresponding sector of the block in the second set, includes writing a parameter in a flash memory cell associated with the block.

8. A mass storage system, comprising:

a flash memory including a plurality of blocks;

logic to map a first set of blocks in the plurality of blocks for storing data organized in accordance with a pre-defined addressing scheme; and

logic to map a second set of blocks in the plurality of blocks for use as a buffer and to mark blocks in the second set of blocks that contain updated data by writing a parameter to flash memory associated with the blocks.

9. The system of claim 8, comprising:

a resource that determines which blocks in the second set of blocks were not marked, copies data from blocks in the first set of blocks into blocks in the second set of blocks that were not marked, and changes blocks in the second set of blocks into blocks in the first set of blocks.

10. The system of claim 8, comprising:

a resource that determines which block in the second set of blocks correspond to data to be read, and if the determined block is marked and obtains the data from the determined block, and obtains the data from a block in the first set of blocks if the determined block is not marked.

11. The system of claim 8, comprising:

logic to map a third set of blocks in the plurality of blocks, wherein the third set of blocks contains data to be erased.

12. The system of claim 11, comprising:

a resource that changes the mapping of blocks in the second set of blocks in the first set of blocks;

a resource that changes the mapping of blocks in the first set of blocks into blocks in the third set of blocks.

13. The system of claim 8, wherein:

a physical identification is assigned to blocks the plurality of blocks;

a local address is assigned to block in the plurality of blocks; and

the physical identification is mapped to the local address.