Study Of The Profibus-dp Slave System Based On Pc Epp Port And Its Implementation

The fieldbus technology is a band new technology, with the development of various technologies such as digital communication, computer, automatic control, network, intelligent instrument and modular compositive etc. The fieldbus technology is a full scattered, full digital, intelligent, bidirectional, interconnected, multivariable, multiconductor, serial communication technology, which used between the field instruments and the controllers.The fieldbus control system (FCS) which is based on the fieldbus technology, has become the development trend in the automatic control area.In the factory automation field, Profibus-DP bus technology, which widely used in data communication among the factory workshop monitoring stations and controlling device layers, is the main-stream technology standard in the current system of the fieldbus technology. Nowdays, in the real engineering applications in domestic, sets of devices are mainly inported from abroad, because of lacking of independent research achievements and devices on Profibus-DP, which caused the over-reliance on the products and technologies of the foreign companies. The imported-products are greatly incese the enginerring cost.In order to reduce the cost of the application of DP fieldbus technology, this paper proposes a technical solution of DP slave which based on PC platform, using DP bus protocol chip SPC3. This solution directly uses the enhanced parallel port (EPP) of the industrial PC and DP protocol chip SPC3, hardware cost is less and software platform is powerful (Windows environment and Visual Studio development tool). This solution can integrate the measurement and control system, which based on the existed industrial PC and detection module with RS-485 bus, into the DP fieldbus master system.Independent work during the research in this paper includes:(1) Discussed the technical features of the fieldbus technology, and put forward the goal and the research significance of research, combining the development status in domestic and abroad, and the application prospect in our country.(2) Researched the Profibus-DP fieldbus basic theory, mainly including Profibus-DP fieldbus control system composition, protocol structure, data communication principle and communication model, etc.(3) Studied the internal structure and the data read/write logic mechanism of the protocol chip SPC3, and proposed the hardware and software design scheme and realization method basing on the researches.(4) Provided the Schematic diagram of interface circuit between DP protocol chip SPC3 and industrial PC enhanced parallel port (EPP), basing on the analysis of internal register write/read logic of the SPC3 chip and the working mechanism of the EPP interface.(5) Provided the C language hardware-layer functional codes, which implementing read/write the internal RAM of the SPC3 chip though the enhanced parallel port (EPP).(6) Gave out relevant C language functions, which are used to config and read/write SPC3 chip, such as initialization function, interrupt source query function, data upload and download function, etc.