FLASH MEMORY DEVICE WITH WEAR-LEVELING MECHANISM AND CONTROLLING METHOD THEREOF

• US 20100115186A1
• Filed: 03/03/2009
• Published: 05/06/2010
• Est. Priority Date: 10/31/2008
• Status: Active Grant

• Current Assignee: ADATA Technology Co., Ltd.
• Original Assignee: ADATA Technology Co., Ltd.
• Inventors: Chen, Ming-Dar, Huang, Chien-Ting, Chang, Li-Pin
• Granted Patent: US 8,103,821 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 2212/7211 Wear leveling

Abstract

A flash memory device with a wear-levelining mechanism includes at least one flash memory, a hot list, a bitmap, a source pointer, and a controller. The controller obtains a physical memory block with high erase count through the hot list, an erase count of the physical memory block, and an overall average erase count of the flash memory device. The controller further finds out a physical memory block which stores static data through managing the bitmap and the source pointer. The controller moves the static data to the physical memory block with high erase count, and releases the physical memory block which stores the static data to avoid the physical memory block with high erase count being worn down increasingly more seriously.

Claims

1. A flash memory device with a wear-leveling mechanism, comprising:

at least one flash memory, including a memory unit, and the memory unit including a plurality of physical memory blocks;

a hot list, for recording a plurality of recently written logical addresses;

a bitmap, including a plurality of bits, each indicating an erase status of the corresponding physical memory block;

a source pointer, for sequentially pointing at not-yet-erased physical memory blocks in the bitmap; and

a controller, for obtaining at least one physical memory block with high erase count according to the hot list and an erase count of the physical memory block, duplicating the data in physical memory block pointed to by the source pointer into the physical memory block with high erase count, and erasing the physical memory block pointed to by the source pointer.

2. The flash memory device with a wear-leveling mechanism as in claim 1, wherein the hot list, the bitmap and the source pointer are stored in a storage unit.

3. The flash memory device with a wear-leveling mechanism as in claim 2, wherein the storage unit further comprises:

a logical-to-physical address translation table, provided for the controller to map a logical block address and a physical block address; and

a log block table, collocated with the logical-to-physical address translation table, for recording a link relation of a block and a sub-block of the physical memory block.

4. The flash memory device with a wear-leveling mechanism as in claim 3, wherein the storage unit is embedded into the controller or connected to the controller externally.

5. The flash memory device with a wear-leveling mechanism as in claim 3, wherein the controller stores the accumulated erase count of each physical memory block and an overall average erase count, and confirms whether or not the physical memory block is a physical memory block with high erase count according to the erase count of the physical memory block and the overall average erase count.

6. The flash memory device with a wear-leveling mechanism as in claim 5, wherein the physical memory block is confirmed as a physical memory block with high erase count, if the controller determines that the erase count of any of the physical memory blocks is greater than a predetermined value of the overall average erase count.

7. The flash memory device with a wear-leveling mechanism as in claim 3, wherein the source pointer points at the bitmap sequentially and cyclically, and after the source pointer passes through an erased physical memory block marked in the bitmap, the bitmap sets the erased physical memory block as a not-yet-erased physical memory block.

8. The flash memory device with a wear-leveling mechanism as in claim 3, wherein the controller further comprises:

a system interface, coupled to an application system, and serving as a transmission interface for transmitting an instruction and data between the application system and the flash memory device;

a memory interface, coupled to the flash memory;

a data buffer, coupled between the system interface and the memory interface, for buffering a data transmitted between the application system and the flash memory; and

a microprocessor, coupled to the system interface, the memory interface and the storage unit, for executing an instruction issued by the application system to the flash memory device, and executing a wear leveling operation according to the hot list and the source pointer.

9. A controlling method of a flash memory device with a wear-leveling mechanism as in claim 1, comprising the steps of:

moving valid data in at least one desired recycle physical memory block into an erased physical memory block and storing the valid data into the erased physical memory block;

updating the source pointer, if the logical block address of the desired recycle physical memory block is on the hot list, and the erase count of the desired recycle physical memory block exceeds a predetermined erase count; and

moving data in the physical memory block pointed to by the source pointer to the desired recycle physical memory block, and storing the data into the desired recycle physical memory block.

10. The controlling method of a flash memory device as in claim 9, wherein after the flash memory device is started, the controlling method further comprises:

loading the hot list, the bitmap, the source pointer, a logical-to-physical address translation table and a log block table.

11. The controlling method of a flash memory device as in claim 9, wherein the predetermined erase count is the sum of an average erase count of the physical memory blocks and a predetermined value, and the predetermined erase count is used for confirming that the desired recycle physical memory block is a physical memory block with high erase count.

12. The controlling method of a flash memory device as in claim 9, further comprising the steps of:

erasing a physical memory block pointed to by the source pointer;

updating the erase count of the erased physical memory block and the average erase count of the physical memory blocks; and

updating an erase status in the bitmap.

13. The controlling method of a flash memory device as in claim 9, further comprising the steps of:

erasing the desired recycle physical memory block;

updating the erase count of the desired recycle physical memory block and the average erase count of the physical memory blocks; and

updating an erase status in the bitmap.

14. The controlling method of a flash memory device as in claim 9, wherein if the source pointer is updated, the source pointer will point at the bitmap sequentially and cyclically, and after the source pointer passes through an erased physical memory block marked in the bitmap, the bitmap sets the erased physical memory block as a not-yet-erased physical memory block.