Research & Development Of FF Data Link Layer Protocol Software

The t(?)ditional control system is not satisfied with the development of industrial scale now. And in the field of industrial automation, the analog transferring is now being replaced by digital communication with the development of the computer science, micro-electronic and communication technology. As the result fieldbus based control system has been brought forward. There are two main characters in Fieldbus: one is digital communication and intelligent process of field meters, and the other is that it's easy to intergreation. As the result, fieldbus becames the important technology in the field of industry control system.Data Link Layer (DLL) of FF H1 standard is the object in this paper, and this paper is based on the project of "FF H1 communication stack software research and development". The key technique of DLL, such as DLL initialization, data transmission and DL time synchronization, are mainly focused on. Some useful methods are brought forward to solve the problem of the development. There are six chapters in this paper. In chapter 1, some history of control system is described. In chapter 2, the system architecture of H1 protocol standard is introduced, and the modules of DLL are briefly described.The following three chapters are the mostly important contents in this paper. In chapter 3, the DLL initialization is analyzed. To solve the problem of address collision, the key method is given. In chapter 4, the process of data transmission is studied, and the reliability and timeliness of transmission are analyzed. In the beginning of chapter 5 the progress of DL time synchronization is studied. Then the key part of DL time named local counter (CNT) is designed. To improve the precision of synchronization, two kinds of CNT frequency adjustment is brought forward. And a kind of timer based on DL time, named Link Schedule timer (LS timer), is designed.In the last chapter this paper summarizes all the previous work and gives some advices for subsequent work. The protocol conformance test of communication stack software has been passed, that means the DLL works well.