Research And Design Of A Real-time Communication Protocol Based On Ethernet

Recently,with the pervasive application of computer technology and internet technology,the Real-time system,now is already playing an important role in the areas such as industry,traffic,power,national defense science research and experiment.It has been nearly thirty years since the Ethernet came out.Now it is sparking with full of vigor becaue of continuous updated new technology.Especially,it is significantly noticed for its advantages as simple structure,cheap cost,extendable bandwidth,compatibility,stability,and reliability.Although the Medium Access Control that is unpredictable limits its application in the Real-time communication area,it is crucial to put Real-time and reliable communication between ethernet terminals into practice.This study has designed and set up a Real-time communication model under the above background,meanwhile,a new Real-time communication mode has been realized,so that,the mode fully support the Real-time communcation and thoroughly compatible with the communication protocol that already exists.In order to meet the need of Real-time demand,we should naturally combine the procedure of accessing and arbitrating which guarantees the Real-time of every nodes and the procedure of the transmitting and controlling which guarantees the Real-time of the whole network.So we can guarantee the communication protocol is Real-time.This study improves the Real-time of the network mainly from inverting the priority between the data that waiting to be sent in the sending queue.Analyzing the situation of the register of the net-adaptor during the packet sending period and the reading sequence of the buffer pages.We put forward a proposal that modifying the form of the data frame and the sending and receiving flow in order to make the Real-time data which is attached with a time stamp can reflect the time limitation information.So the transmission protocol would be able to process the data according to the stamp time and invert the priority of the corresponding pages of the received data.The procedure could permit the Real-time data sending prior to the Nonreal-time one in order to meet the Real-time needs.