Research On Access Mechanism And Predictability Of Embedded Real-Time Database

The problem of data access in real-time database of embedded system is the hot issue in embedded field. In the scene of industrial control, the embedded system for interaction is the tache connecting monitored equipment, person in scene, PC and remote database. The data from different source have characteristics themselves. For all data have same access mechanism and ignore their characteristics in traditional real-time database, the thought has been proposed that data classified by characteristics and different types use different index structure. Which index structure is adopted to furthest solve the contradiction between data capacity and index time is the key of the problem. According to in-depth analysis the difference of data update and query in different source, a method that classified the data by source has been proposed. Because the data which belong to static data field have the characteristic of big quantity and more select operations, a T-tree index structure is proposed to reduce space and save time. Because the data which belong to dynamic data field have the characteristics that operations of inserting and deleting are frequent, a structure which combines linear list and link list is proposed to reduce time complexity. Then the influence of data's period of validity for selecting operation and the time and space capability of classified data index structure has been analyzed. For slow speed in historical data selection, the tactics of prefetching historical data into RAM which similar with the thought of cache between CPU and RAM is proposed. And then the strategy of buffer data permuting based on value function is proposed. The influence of buffer prefetching to the cost of system is analyzed.In this paper, an embedded touch screen human-machine interface (HMI) is designed using S3C2410 chip based on ARM. This equipment can be used to control multi-models PLC and data collection part. Through the test of real-time data selecting operation and historical data trend chart, the results are well agreement with the theoretical analysis, and the methodological validity is verified. This paper dwells on the design of embedded system based on S3C2410X and Windows CE. A method of character extraction and data rebuilding is described to solve the problem of data transfering between PC and embedded equipment. The detail that application in PC transplants to embedded system is summarized. It also has some instructive value for practical projects.