Research Of Fieldbus Equipment Based On PROFINET Protocol

PROFINET is the latest field-bus protocol based on industrial Ethernet. It has very high real-time performance and its response time could reach to microsecond level. And it is generally accepted by the industrial control field and PROFINET protocol will be the communication standard of industry in the future.At present, the research of PROFINET is still at an initial stage. Especially in China, a few researchers take part in the study of protocol and most of them are engaged in the application fields. In contrast, the need for PROFINET is becoming increasingly urgent in the industrial control field.Initially, the history and research status of PROFINET technology are described in this paper. And then, the system model of PROFINET IO,the services and protocol provided by PROFINET are analyzed. As a next step, this paper mainly does the following things: Communication dispatch mechanism of PROFINET RT and IRT protocol are discussed here; Methods used for calculating the refresh time are proposed respectively; The real-time performance of the two IRT protocols are compared; And according to the analysis of real product, the problem of distributing bandwidths when the communication datas of RT, IRT, and NRT coexist is also researched. Finally, on the basis of application-specific PROFINET processor of ERTEC400 and protocol stack of PROFINET IO obtained from Siemens Company, and using the system model of PROFINET IO, an IO slave station experiment board was designed in the two aspects of hardware and software. The slave station communicated with Siemens PLC successfully and realized the data exchange of RT.The calculating method of refreshing time of RT and IRT and the way of distributing bandwidths proposed in this topic are helpful for correctly configuring devices in practical engineering application, rationally utilizing bandwidth resource, and effectively avoiding the appearance of the errors during data exchange. The successful design of IO slave station experimental board provides a good foundation for putting the product of IO slave station into market and the wide application of protocol stack of PROFINET IO.