Research And Implementation Of The File System Based On NAND Flash

This paper focuses on designation and implementation of NAND Flash memory management software, which is more commonly called NAND Flash file system. This software packets a NAND Flash device, and provides a standard block device interface to the upper file system based on block devices.As one of the most advanced semiconductor non-volatile memory, NAND Flash shares common manufacturing technologies and erase/write specifics with EPROM. Compared with traditional memories based on blocks, NAND Flash's program operation must follow an erase operation to the target block; and every block's erase/program validity is not guaranteed if the erase/program time exceeds a certain limit. So there must be a middle layer between the NAND Flash device and the file system, to take the job of memory management and interface transformation, and that is NAND Flash file system.NAND Flash file system has to provide functions such as: Flash driver, logic memory blocks mapping and remapping, block recycling, wear-leveling, data recovery. This paper mainly analysis the requirements of these functions, and the algorithms to realize them; and then, a realization of these analysis and designation, based on a practical application environment, will be made and introduced; at last, this software realization will be tested and evaluated.This NAND Flash file system runs on the platform of VxWorks embedded operational system. It provides standard VxWorks block device interface to upper DOS file system; and contains inner modules to complete the NAND Flash memory block management and block recycling. As the test result shows, the NAND Flash File System software occupies no more than 15KB ROM memories after compressed, and consumes no more than 36KB dynamic memories in running. It supports writing speed up to 1MBps, and reading speed up to 2MBps, which fully satisfies the application requirements.