Static information storage and retrieval – Floating gate – Particular biasing
Reexamination Certificate
2000-07-07
2001-07-03
Le, Vu A. (Department: 2824)
Static information storage and retrieval
Floating gate
Particular biasing
C365S185290, C711S006000
Reexamination Certificate
active
06256232
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to the field of flash memory and, more particularly, to a data access method capable of reducing the number of erasing to flash memory and a data patch and access device that utilizes the method.
2. Description of Related Art
Currently, the flash memory is in wide spread use to emulate a hard disk drive in embedded system application since flash memory can preserve the content thereof when the power is turned off. As shown in
FIG. 9
, the flash memory
911
and the hard disk emulator
912
constitute the emulation hard disk drive
91
. As such, the application system can perform read and write operations to the flash memory just like to a hard disk drive, such that the existing file system can work on it.
The use of the emulation hard disk drive emulated by flash memory is restricted by the characteristic of the flash memory. That is, although the flash memory can be read/written multiple times, it is required to erase the memory area before writing data thereto. The memory erase operation is processed by a physical segment. The number of erasing to a segment is limited (about 100000 time). Because such a limitation to the flash memory, the lifetime of the emulation hard disk drive is also limited.
To extend the lifetime of the emulation hard disk drive emulated by flash memory, the prior art is to reduce the number of erasing by improving the segment callback strategy. The callback strategy is focused on the time period and frequency of the data in use to avoid taking back the data segment that will be invalid soon. However, this approach neglects that the file system will produce many duplication data. Thus, the performance is poor and needs to be improved. Therefore, there is a need to have a novel design to access flash memory that can mitigate and/or obviate the aforementioned problems.
SUMMARY OF THE INVENTION
The object of the present invention is to provide a data access method capable of reducing the number of erasing to flash memory and a data patch and access device that utilizes the method, such that the lifetime of the flash memory is significantly increased.
With this object in view, the present invention resides in a method for reducing the number of erasing to flash memory. The method comprises: (a) a data write procedure for determining a difference between data to be written and existed data in the data block when writing data to a data block of the flash memory, and if the difference is less than a pre-determined value, writing the difference to a patch area instead of writing the data to the data block; and (b) a data read procedure for searching the difference recorded in the patch area when reading data from a data block of the flash memory, so as to patch the data.
REFERENCES:
patent: 5668976 (1997-09-01), Zook
patent: 6016530 (2000-01-01), Auclair et al.
Chang Li-Pin
Chen Hsiao-Hui
Cheng Huey
Lee Tzao-Lin
Institute for Information Industry
Le Vu A.
Lowe Hauptman & Gilman & Berner LLP
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