Flash memory mass storage system

• US 5,745,418 A
• Filed: 11/25/1996
• Issued: 04/28/1998
• Est. Priority Date: 11/25/1996
• Status: Expired due to Term

• Current Assignee: Macronix International Co., Ltd.
• Original Assignee: Macronix International Co., Ltd.
• Inventors: Lin, Chun-Hung, Lee, Li-Jen, Lee, Ju-Xu, Lee, Tai-Yao, Ma, Chung-Wen, Hu, Ting-Chung
• Primary Examiner(s): Fears, Terrell W.
• Application Number:
  US08/756,304
• Time in Patent Office: 519 Days
• Field of Search: 365/185.33, 365/189.01, 365/230.01
• 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 the steps of:

(a) dividing said flash memory into a plurality of blocks;

(b) forming a first type of blocks from said plurality of blocks, said first type of blocks being used to store data organized in accordance with a pre-defined addressing scheme;

(c) forming a second type of blocks from said plurality of blocks, said second type of blocks being used as a temporary buffer for storing data intended to be written to one of said first type of blocks;

(d) forming a third type of blocks that contain invalid data that will be erased; and

(e) changing at least one of said plurality of blocks from one of said first, said second and said third types of blocks to another type.

2. The method of claim 1 further comprising the step of

(a) assigning a physical identification to each of said plurality of blocks;

(b) assigning a logical address to each block in said first type of blocks; and

(c) mapping said physical identification to said logical address.

3. The method of claim 2 further comprising a step of updating data already stored in a selected one of said first type of blocks.

4. The method of claim 3 wherein said updating step comprising the steps of:

(a) identifying a block in said first type containing data that needs to be updated;

(b) allocating a block from said third type and changing said allocated block into a block of said second type; and

(c) writing said updated data into said allocated block.

5. The method of claim 4 further comprising the step of marking said identified block in said first type dirty after said updated data has been written into said allocated block.

6. The method of claim 4 wherein said updating step further comprising the steps of:

(a) changing said identifying block into said third type; and

(b) changing said allocated block into said first type.

7. The method of claim 6 wherein said identifying block has a pre-assigned logical address, said step of changing said allocated block changes said allocated block to a block having said pre-assigned logical address.

8. The method of claim 1 wherein said pre-defined addressing scheme is a sector-based addressing scheme.

9. The method of claim 8 wherein said pre-defined addressing scheme is logical block address.

10. A flash memory system comprising a plurality of blocks being divided into (i) a first type of blocks for storing data logically organized in a linear addressing scheme, (ii) a second type of blocks for temporarily storing data intended to be written to one of said first type of blocks, and (iii) a third type of blocks including blocks that should be erased, each of said plurality of blocks comprising a plurality of flash memory cells, said second type of blocks being changeable to said first type of blocks and said first type of blocks being changeable to said third type of blocks.

11. The system of claim 10 wherein each of said plurality of blocks is assigned a physical identification and said first type of blocks is used to implement a logical addressing scheme, said system further comprising a buffer for mapping said physical identification to said logical addressing scheme.

12. The system of claim 11 wherein said logical addressing scheme comprises a sector-based addressing scheme.

13. The system of claim 10 wherein each block comprises a region;

said region being used to store attribute information related to a block associated with said region.

14. The system of claim 10 wherein each block contains a plurality of sectors.