MULTILEVEL CELL NAND FLASH MEMORY STORAGE SYSTEM, AND CONTROLLER AND ACCESS METHOD THEREOF

• US 20100205352A1
• Filed: 03/27/2009
• Published: 08/12/2010
• Est. Priority Date: 02/10/2009
• Status: Active Grant

• Current Assignee: Emtops Electronics Corp. (Phison Electronics Corporation)
• Original Assignee: Phison Electronics Corporation
• Inventors: Tan, Kok-Yong, Yeh, Chih-Kang, Chu, Chien-Hua
• Granted Patent: US 8,225,067 B2
• Time in Patent Office: Days
• US Class Current: 711/103
• CPC Class Codes: G06F 12/0246 in block erasable memory, e.g. flash memory
• CPC Class Codes: G06F 2212/7202 Allocation control and policies
• CPC Class Codes: G11C 11/5628 Programming or writing circuits; Data input circuits
• CPC Class Codes: G11C 29/82 for EEPROMs

Abstract

A multi level cell (MLC) NAND flash memory storage system is provided. A controller of the MLC NAND flash memory storage system declares it a signal level cell (SLC) NAND flash memory chip to a host system connected thereto and provides a plurality of SLC logical blocks to the host system. When the controller receives a write command and a user data from the host system, the controller writes the user data into a page of a MLC physical block and records the page of the SLC logical block corresponding to the page of the MLC physical block. When the controller receives an erase command from the host system, the controller writes a predetermined data into the page of the MLC physical block mapped to the SLC logical block to be erased, wherein the predetermined data has the same pattern as a pattern of the erased page.

Claims

1. A multi level cell (MLC) NAND flash memory storage system, for simulating a single level cell (SLC) NAND flash memory chip, the MLC NAND flash memory storage system comprising:

a connector, for connecting a host system;

a MLC NAND flash memory chip, having a plurality of MLC physical blocks, wherein each of the MLC physical blocks has a plurality of pages; and

a flash memory controller, coupled to the MLC NAND flash memory chip and the connector, for providing a plurality of SLC logical blocks corresponding to the SLC NAND flash memory chip to the host system, wherein each of the MLC physical blocks is mapped to at least two of the SLC logical blocks.

2. The MLC NAND flash memory storage system according to claim 1, wherein when the flash memory controller receives a write command and first user data from the host system, the flash memory controller writes the first user data into the pages of the MLC physical blocks and records pages of the SLC logical blocks mapped to the pages of the MLC physical blocks for writing the first user data.

3. The MLC NAND flash memory storage system according to claim 1, wherein when the flash memory controller receives an erase command from the host system, the flash memory controller writes predetermined data into the pages of the MLC physical blocks to be erased, wherein the predetermined data has a pattern which is the same as a pattern of the erased pages.

4. The MLC NAND flash memory storage system according to claim 1, wherein when the flash memory controller receives an erase command from the host system, the flash memory controller marks the pages of the MLC physical blocks to be erased as invalid pages, and the flash memory controller erases the corresponding MLC physical block when all the pages in the corresponding MLC physical block have become the invalids pages.

5. The MLC NAND flash memory storage system according to claim 2, wherein the flash memory controller records the pages of the SLC logical blocks mapped to the pages of the MLC physical blocks for writing the first user data in a page index table.

6. The MLC NAND flash memory storage system according to claim 2, wherein the flash memory controller groups the MLC physical blocks into at least a storage area and a temporary area, and

wherein when the flash memory controller receives the write command and the first user data from the host system, the flash memory controller writes the first user data less than a page capacity into the temporary area.

7. The MLC NAND flash memory storage system according to claim 6, wherein when the flash memory controller determines that a data quantity of the first user data stored in the temporary area and a second user data to subsequently be written exceeds a page capacity or the pages of the SLC logical blocks mapped to the pages of the MLC physical blocks for writing the first user data and the second user data has been written by the host system for a predetermined number of times, the flash memory controller writes the first user data stored in the temporary area and the second user data together into the storage area in unit of pages.

8. The MLC NAND flash memory storage system according to claim 6, wherein when the flash memory controller receives the write command and the first user data from the host system, the flash memory controller writes the first user data and a part of first redundant data and second redundant data corresponding to the first user data into the storage area and writes the first user data and another part of the first redundant data and the second redundant data corresponding to the first user data into the temporary area, wherein the first redundant data is system data corresponding to the first user data, and the second redundant data is generated by the flash memory controller according to the first user data and the first redundant data.

9. The MLC NAND flash memory storage system according to claim 8, wherein the first redundant data and the second redundant data respectively comprise an error checking and correcting (ECC) code.

10. A flash memory controller, suitable for simulating a MLC NAND flash memory chip into a SLC NAND flash memory chip, wherein the MLC NAND flash memory chip has a plurality of MLC physical blocks and each of the MLC physical blocks has a plurality of pages, the flash memory controller comprising:

a microprocessor unit, coupled to a first flash memory interface and a second flash memory interface;

a SLC block simulation unit, coupled to the microprocessor unit, for providing a plurality of SLC logical blocks corresponding to the SLC NAND flash memory chip to a host system, wherein each of the MLC physical blocks is mapped to at least two of the SLC logical blocks;

a first flash memory interface unit, coupled to the microprocessor unit, for receiving a logical address and a command corresponding to the SLC logical blocks from the host system and providing the logical address and the command to the microprocessor unit; and

a second flash memory interface unit, coupled to the microprocessor unit, for electrically connecting the MLC NAND flash memory.

11. The flash memory controller according to claim 10, wherein when the microprocessor unit receives a write command and first user data from the host system, the SLC block simulation unit writes the first user data into the pages of the MLC physical blocks and records pages of the SLC logical blocks mapped to the pages of the MLC physical blocks for writing the first user data.

12. The flash memory controller according to claim 10, wherein when the microprocessor unit receives an erase command from the host system, the SLC block simulation unit writes predetermined data into the pages of the MLC physical blocks to be erased, wherein the predetermined data has a pattern which is the same as a pattern of the erased pages.

13. The flash memory controller according to claim 10, wherein when the microprocessor unit receives an erase command from the host system, the SLC block simulation unit marks the pages of the MLC physical blocks to be erased as invalid pages, and the SLC block simulation unit erases the corresponding MLC physical block when all the pages in the corresponding MLC physical block have become the invalids pages.

14. The flash memory controller according to claim 11, wherein the SLC block simulation unit records the pages of the SLC logical blocks mapped to the pages of the MLC physical blocks for writing the first user data in a page index table.

15. The flash memory controller according to claim 11, wherein the SLC block simulation unit groups the MLC physical blocks into at least a storage area and a temporary area, and

wherein when the microprocessor unit receives the write command and the first user data from the host system, the SLC block simulation unit writes the first user data less than a page capacity into the temporary area.

16. The flash memory controller according to claim 15, wherein when the SLC block simulation unit determines that a data quantity of the first user data stored in the temporary area and a second user data to subsequently be written exceeds a page capacity or the pages of the SLC logical blocks mapped to the pages of the MLC physical blocks for writing the first user data and the second user data has been written by the host system for a determined number of times, the SLC block simulation unit writes the first user data stored in the temporary area and the second user data together into the storage area in unit of pages.

17. The flash memory controller according to claim 15, wherein when the microprocessor unit receives the write command and the first user data from the host system, the SLC block simulation unit writes the first user data and a part of first redundant data and second redundant data corresponding to the first user data into the storage area and writes the first user data and another part of the first redundant data and the second redundant data corresponding to the first user data into the temporary area, wherein the first redundant data is system data corresponding to the first user data, and the second redundant data is generated by the flash memory controller according to the first user data and the first redundant data.

18. The flash memory controller according to claim 17, wherein the first redundant data and the second redundant data respectively comprise an ECC code.

19. The flash memory controller according to claim 17, wherein when the microprocessor unit receives the write command and the first user data from the host system, the SLC block simulation unit writes the first redundant data corresponding to the first user data into the temporary area.

20. The flash memory controller according to claim 14, wherein the SLC block simulation unit groups the MLC physical blocks into at least a system area, and

wherein the SLC block simulation unit stores the page index table in the system area.

21. The flash memory controller according to claim 10, wherein the first flash memory interface unit and the second flash memory interface unit both support a flash memory interface signal.

22. The flash memory controller according to claim 14, wherein the flash memory interface signal comprises a chip enable signal /CE, a command latch signal /CLE, an address latch signal /ALE, a data read control signal /RE, a data write control signal /WE, a write protection signal /WP, a chip state signal R/B, and a plurality of data input/output signals IO.

23. An access method, for simulating a MLC NAND flash memory chip into a SLC NAND flash memory chip, the access method comprising:

providing the MLC NAND flash memory chip, wherein the MLC NAND flash memory chip has a plurality of MLC physical blocks and each of the MLC physical blocks has a plurality of pages;

disposing a plurality of SLC logical blocks;

recording a mapping relationship between the MLC physical blocks and the SLC logical blocks, wherein each of the MLC physical blocks is mapped to at least two of the SLC logical blocks; and

writing data into the MLC physical blocks and reading the data from the MLC physical blocks according to the mapping relationship.

24. The access method according to claim 23, further comprising:

when a write command and first user data are received, writing the first user data into pages of the MLC physical blocks and recording pages of the SLC logical blocks mapped to the pages of the MLC physical blocks for writing the first user data.

25. The access method according to claim 23, further comprising:

when an erase command is received, writing predetermined data into the pages of the MLC physical blocks to be erased, wherein the predetermined data has a pattern which is the same as a pattern of the erased the pages.

26. The access method according to claim 23, further comprising:

when an erase command is received, marking the pages of the MLC physical blocks to be erased as invalid pages, and erasing the corresponding MLC physical block when all the pages in the corresponding MLC physical block have become the invalids pages.

27. The access method according to claim 23, further comprising:

recording the pages of the SLC logical blocks mapped to the pages of the MLC physical blocks for writing the first user data into a page index table.

28. The access method according to claim 23, further comprising:

grouping the MLC physical blocks into at least a storage area and temporary area; and

when the write command and the first user data are received, writing the first user data less than a page capacity into the temporary area.

29. The access method according to claim 28, further comprising:

when it is determined that a data quantity of the first user data stored in the temporary area and a second user data to subsequently be written exceeds a page capacity or the pages of the SLC logical blocks mapped to the pages of the MLC physical blocks for writing the first user data and the second user data has been written by the host system for a predetermined number of times, writing the first user data stored in the temporary area and the second user data together into the storage area in unit of pages.

30. The access method according to claim 28, further comprising:

when the write command and the first user data are received, writing the first user data and a part of first redundant data and second redundant data corresponding to the first user data into the storage area, and writing the first user data and another part of the first redundant data and the second redundant data corresponding to the first user data into the temporary area, wherein the first redundant data is system data corresponding to the first user data, and the second redundant data is generated according to the first user data and the first redundant data.

31. The access method according to claim 30, further comprising:

when the write command and the first user data are received, writing the first redundant data corresponding to the first user data into the temporary area.

32. The access method according to claim 27, further comprising:

grouping the MLC physical blocks into at least a system area; and

storing the page index table in the system area.