Research And Implementation Of Flash Memory Device Management Technology In Embedded System

With the constantly growing requirements of applications, embedded system becomes more and more complicated. Flash memory is the most common nonvolatile memory used in embedded system, so the management and access technology of flash memory have great effects on performance and portability of the whole system. The management technology of flash memory device in embedded system is implemented through flash I/O software. At present, most flash management technologies are insufficient in portability and flexibility. So it is important for embedded system applications to develop a scheme of flash management, which is easy to be ported, has high efficiency and a unified access interface.Firstly, the paper studies the I/O software design ideas and principles of flash memory device in embedded system theoretically. Based on analysis of the principle of policy and mechanism separation which is widly used in operating system software design, the paper proposes a layered software architecture of flash memory device management technology, which divide the flash I/O software into hardware driver layer, raw device layer, and device layer. Also the paper compares the user space scheme with kernel space scheme of flash memory device I/O software. Secondly, the paper studies the I/O device management mechanism in embedded Linux, presents a flash management implementation scheme, which has high modularity, portability and flexibility. Then the paper analyzes the key technical problems in this scheme and presents the corresponding methods, such as blocked I/O, read and write request function design, and so on. Finally, the paper chooses embedded Linux based on a PowerPC860T board as the target system platform and implements the I/O software scheme of the flash memory device mentioned above on it.The portability of I/O software can be evaluated by proportion of device dependent and independent code size in the implemetation. So the paper is proved to have good portability because the proportion of device dependent code is 24.1%. Also the paper tests the typical performance of the scheme, as file operation cost and data throughput. The test results shows that the scheme above not only can provide the application program with a unified access interface which is easy to be used, but also have high modularity which make the scheme easy to be ported to other flash chips of different types.