Research And Realization Of The MODBUS/TCP OPC DA Server

OLE for Process Control (OPC) was designed to bridge Windows based applications and process control hardware and software applications. OPC is a series of standards specifications. OPC servers use Microsoft's OLE technology (also known as the Component Object Model, or COM) to communicate with clients. Originally based on Microsoft's OLE COM (component object model) and DCOM (distributed component object model) technologies, the specification defined a standard set of objects, interfaces and methods.The advantage of The MODBUS/TCP is that devices from different manufacturers can communicate via a standardized protocol. MODBUS/TCP is a variant of the MODBUS family of simple, vendor-neutral communication protocols intended for supervision and control of automation equipment. Specifically, it covers the use of MODBUS messaging in an 'Intranet' or 'Internet' environment using the TCP/IP protocols. The most common use of the protocols at this time are for Ethernet attachment of PLC's, I/O modules, and 'gateways' to other simple field buses or I/O networks. Many leading drive manufacturers use MODBUS as their system bus. MODBUS bases its data model on a series of tables which have distinguishing characteristics. In the development of the communication software and the simulation software for MODBUS device, the socket communication and the MODBUS/TCP telegram set will be introduced especially in this paper.A simpler way to create OPC Servers is to use toolkits. Toolkits encapsulate the DCOM and OPC functionality. OPC Servers exchange information throught an API with a client application using the toolkits.Reusable software components made their entry in automation technology an repalaced monolithic, customized software applications, help the user heightening the efficiency when developing the OPC DA Server . Furthermore , the period of development is shortened, debugging and maintenance of the sytern gets very flexible with Reusable software components.The MODBUS/TCP OPC DA Server is an OPC compliant server that enables datainterchange between OPC clients and Modbus PLCs. The MODBUS/TCP OPC Server was developed on the basis of the OPC Server Development Kit of HUAFU and therefore supports all OPC interfaces in accordance with the Data Access Specification version 2.05a. It functions as a MODBUS/TCP Client according to the MODBUS/TCP Specificationg and supports conformance classes level 0 and level 1 .A diagnostic and monitoring component provides the user interface for diagnostic information and process data.Finally, the practical application of MODBUS/TCP OPC DA server in ControX2000 is introduced in this paper .