| PROFIBUS was developed in the world during mid-eighties in 20 century, it was a serial,digital,multipoint and intercommunication data bus which was installed between field device of industrial area and auto-control device of control centre.Because of its better real-time in communication, high transmitting rate, low cost, high redundancy flexibly topological structure, and applicability ,PROFIBUS has been widely used among all existing field bus standards in all kinds of industry control fields.PROFIBUS includes PROFIBUS-DP, PROFIBUS-PA and PROFIBUS-FMS.Besides, PROFIBUS-DP, which has been used in the control system of device-level and distributed I/O communication, was the market leader in field bus technology.PROFIBUS products on the market today is mainly Siemens, ABB and other foreign companies, PROFIBUS-DP interface product development relatively easy, there were some enterprises in China have developed PROFIBUS-DP interface products, but PROFIBUS-PA Bus product development is relatively difficult, PROFIBUS-PA bus interface products is imported from abroad, which is very expensive.The DP and PA has different agreements. The PROFIBUS-DP use RS-485 transmission technology: data coding is used NRZ, each eight-bit binary number of the 11 bits are transmitted in order, add the beginning bit, 8bits datas,the termination bit and the parity bit.And data transmating is from 9.6Kbps-12M bps.While PA use Manchester code,IEC61158-2 transmission technology,which is a bit synchronization protocol with data transmating 31.25Kbps. With a coupler to change, DP can easily be connected to the bus.The coupler on the market today is mainly Siemens, ABB and other foreign companies, which is very expensive, On domestic the coupler has not been empoldered.This paper is based on site-specific bus in the application and development of our current situation,in studying the basic theory of PROFIBUS field bus (mainly including basic features,system components,protocol strcture,data acess mechanisms for packet analysis,from the station and the communication principle, Carried out a detailed comparative study of PROFIBUS-DP and PROFIBUS-PA. This paper choose the intelligent protocol chip SPC3,SPC4,SIM1-2 and 51 microcontroller to develop product. The agreement SPC3,SPC4 as a bus controller chip is responsible for completing the data conversion and realize receiving and sending of data,unpacking the data from the bus came,sent to AT89S52,packing the data from AT89S52,transmitted to the bus.According to the design,the completion of the hardware from station and circuit design,the hardware circuit and lap of software programming from are analyzed and finally tested in the laboratory.The test result shows that we achieve a desired outcome.This means that the coupling device designed in this paper has good development prospects of industrial applications.Therefore, the subject of the study was filled in a timely manner with a great market potential in the areas of research, it has importance significance to automation and control technology progress, to reduce the gap between the domestic and the foreign technologies level, to improve our country Domestic rates in the field of automation.Finally, this article summarize the work of the investigate, and bring forward the further development of research directions and methods on the coupler. |
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