Flash Memory Card File System

Flash Memory Card is now wildly used in various handsets, it is used to record datas such as music,vedio and pictures.Flash Memory has its' own advantages.It has small unit area,simple structure ,easy to use, no supply voltage required and can be repeated read,write and erase quickly.Besides that , it has high security standard and reliability,so it can fit all kinds of environments. The Flash Filesystem(FFS) is the core to management of data.It links the upper OS(operation system), executes the instructions from the OS and manage the Flash storage device in the bottom layer.In summary ,it supply a bridge between the real time operating system and the Flash Memory .There are two storage structures: chain and virtual block, FAT under Windows platform and FTL under Log-system, as its typical respectively. But either of the two filesystem has its' own limitations on efficiency and generality.The Flash storage device structures and various kinds of Flash filesystem as well as their application charcter and key technology are thorough analysised in this paper.A data stucture based on FTL ,combined with the merits of the chain filesystem and virtual block ,is proposed in this paper.It can be used on both DOS and Windows platform,requirements on write ,read ,erase and other operations are all met.And,the storage mechanisms of FAT table and FRT table are also improved to better fit the Flash storage requirements.Besides that, the KimLee algorithm in the Flash storage management is thoroughly discussed so that the efficiency and life of the Flash Memory are both improved. The filesystem proposed in this paper is now applied in the mobile storage device standard advocated by the MII(Ministry Of Information Industry), and it successfully solved the contradiction between the efficiency and generality, all the applications specifications are fully met.