Research On Time Synchronization Technology Of Distributed System Based On AS6802

With the rapid development of society,whether it is a military control system or a civilian control system,various distributed systems have put forward higher and higher requirements for the real-time of the control information interaction between the various devices in the system.Among them,military control systems such as integrated avionics systems and ship control systems,as well as civil control systems such as industrial control and high-speed train control systems,require that the control information in the system can be completed in a very short time from generation to execution.Real-time execution is inseparable from the time synchronization between devices.Therefore,how to construct time synchronization in a distributed system has become a hot issue that needs to be solved.As a time synchronization standard that emerged after the NTP protocol and the 1588 protocol,the SAE AS6802 standard is a brand-new time synchronization method published in 2011.With the development of time-sensitive networks,the AS6802 protocol has attracted more and more attention.The sensitive business in the time-sensitive network has very similar characteristics with the key control information in the distributed system.If the distributed system is configured as a sensitive network and its key control information is configured as a sensitive business,the real-time of the key control information can be well guaranteed.Therefore,the AS6802 protocol,which is the basis of sensitive business transmission,has very important research significance.This article combines the research project in the laboratory,based on the FPGA hardware development platform to design and implement a set of time synchronization unit that meets the AS6802 standard.Firstly,it summarizes the relevant knowledge of AS6802 time synchronization technology,including the research background and research status.Secondly,introduce the basic concepts and synchronization mechanism of the AS6802 protocol,focusing on three functional models of CM,SM,and SC,three synchronization functions of message permanence function,and clique detection function,compression function,as well as three synchronization services of cold start service,restart service,and time Synchronization services.Then,according to the actual needs of the project,determine the plan design of the time synchronization unit,and clarify the detailed design of each module,especially the receiving and listening module,the compression calculation module,the cache management module,and the transparent transmission management module.Finally,a simulation environment is built to verify the functions of each module,and the overall function and performance are verified through hardware platform testing.The innovative work of this article mainly includes the following points.Firstly,analyze the synchronization principle in depth and summarize the SDL flow chart of the three functional models of the AS6802 time synchronization protocol after power-on,which includes the operation flow of all possible situations after the initial power-on of each functional model.Secondly,during the synchronization process,the sending time point and the receiving time point of the synchronization frame interaction are monitored,and the response time interval is added to the newly defined reserved field of the response synchronization frame,In this way,the dynamic measurement of the transparent clock value between the compressed host and the synchronization host is completed,and the high accuracy of the transparent clock value is ensured,thereby improving the synchronization accuracy of each device in the system.Thirdly,the design and realization of the transparent transmission function of the synchronization client solves the problem of large-scale integration of the system,and minimizes the transmission delay under the premise of ensuring that no synchronization frame is lost during the transmission process,thereby ensuring the bandwidth waste introduced by the system due to synchronization least.Finally,the three functional models designed and implemented can be configured in any type of equipment(switch or end system),and both the end system and the switch can be configured to implement a variety of different functional models.At the same time,it supports dynamic switching between various working modes,ensuring the flexibility of equipment working mode selection.