1. Introduction In an automatic monitoring (Supervisory Control And Data Acquisition SCADA) system, the monitoring configuration software that is put into operation is the data acquisition and processing center, remote monitoring center and data forwarding center of the system. The monitoring configuration software in operation, together with various control and detection devices such as industrial control computers, PLCs, intelligent instruments and intelligent devices connected to the fieldbus, constitute a rapid response control center. Control schemes and algorithms are generally configured and executed on the equipment, or they can be configured on the industrial control computer and then downloaded to the equipment for execution, depending on the specific requirements of the equipment [1]. The position of the configuration software in the SCADA system is shown in Figure 1. After the monitoring configuration software is put into operation, the operator can complete the following tasks with its support: (1) View the real-time data and process screen of the production site, and browse the real-time historical trend screens; (2) Automatically print various real-time historical production reports; (3) Get various process alarms and system alarms in a timely manner; (4) When necessary, manually intervene in the production process and modify the production process parameters and status; (5) Connect with the computer of the management department to provide the management department with real-time production data. [align=center][img=467,353]http://www.e-works.net.cn/images/128352655907812500.JPG[/img] Figure 1 The position of the monitoring configuration software in the SCADA system[/align] As an open control network, the fieldbus can realize signal communication between field devices and between field devices and the control room[2]. Open communication is one of the foundations of information transmission and sharing. However, after field signals are transmitted to the monitoring computer, how to achieve information communication and transmission between various programs within the computer—that is, how to connect field signals with various application programs and make field information appear on various application platforms of the computer—still presents the issue of connection standards and specifications. In multi-user, multi-tasking computer systems, data exchange between programs is relatively convenient, and the operating system supports this operation. Since the advent of Windows and microcomputer versions of UNIX and LINUX operating systems, technologies, protocols, and standards for data exchange between programs have emerged, making data exchange between programs easier. In today's widely used industrial PC automation systems, enabling fieldbus control systems and human-machine interface software to effectively and fully utilize the rich and powerful software resources of PCs is a topic worthy of in-depth research. This article discusses some relevant technical issues in conjunction with engineering practice. 2. Basic Concepts of Dynamic Data Exchange Although the data exchange technology of industrial control configuration software has made great progress, in the current fieldbus control system configuration software, there are still some shortcomings in the specific application of DDE and OPC data exchange technologies—especially in how to further improve the real-time performance of data exchange between configuration software and other programs under the condition of microcomputer multitasking. These shortcomings are worth further discussion and research. Among them, Dynamic Data Exchange (DDE) technology has been practically applied in the integration of control networks. The reasons are: (1) This method has good real-time performance and can use standard Windows technology; (2) As a communication processor connecting the control network and the information network, it is relatively easy to implement in hardware. When the control network and the information network have a shared workstation or communication processor, the dynamic data exchange technology can be used to realize the dynamic exchange of real-time data in the control network and database data in the information network, thereby realizing the integration of the control network and the information network. DDE is a method of inter-process communication. In order to establish a session, DDE applications use three basic identifiers (or strings), namely a three-layer identification system, to distinguish other DDE applications. These are the application name, topic name, and item name. Each DDE session is uniquely defined by the application name and topic name. Before the DDE session is established, the client program and the server jointly decide the application name and topic name, while the client program fills in the three identifiers of the server. The application name is located at the top level of the hierarchy and is used to indicate the specific DDE server application name. The topic name defines the topic content of the server application session more deeply. The server application can support one or more topic names [2]. 3. Dynamic parameter data exchange program design for process control For the convenience of discussion, an example is given below. According to the requirements of a certain production automation transformation project, it is necessary to design a configuration monitoring operation platform for the system. The configuration software IFIX2.2 and the Windows application software VB6.0 are used to develop and implement inter-process data exchange based on the DDE mechanism to meet the information exchange needs of the industrial control network SCADA industrial control computer. This enables various applications to exchange information through shared memory, realize the integration of the control network and the information network, and provide a reference for further development of data exchange between Windows programs [3]. The main integration technologies of the control network and the information network are shown in Figure 2. [align=center][img=455,201]http://www.e-works.net.cn/images/128352656163437500.JPG[/img] Figure 2 Main integration technologies of the control network and the information network[/align][align=left] 3.1 Network integration method of DDE information exchange The DDE technology of shared memory provides technical support for the integration of the control network and the information network, and has strong real-time performance. The engineering design uses an industrial control computer (IPC) as the communication processor. This IPC also serves as a workstation for both networks, bridging the control network and the information network, and acting as a bridge between the two networks. The communication processor (IPC) uses the DDE method to realize communication between stations on the two networks, which is the key to the entire integrated network. It can perform the following functions: (1) Collect real-time data information from each station on the control network and write it into the database of the information network so that information network users can browse and query it; (2) Send the control information of information network users to the designated workstations on the control network in a timely manner. The network integration method based on DDE information exchange of the communication processor is shown in Figure 3. [align=center][img=374,91]http://www.e-works.net.cn/images/128352656403906250.JPG[/img] Figure 3 Network Integration Method Based on Communication Processor DDE Information Exchange[/align][align=left] 3.2 DDE Implementation between iFix Configuration Software and VB The fieldbus control system uses iFix2.2 configuration software developed by Intellution as the SCADA monitoring and operation platform. iFix is ​​an industrial automation configuration software that uses a graphical user interface and provides monitoring and data acquisition functions. It provides a good monitoring environment for operators and developers, and can realize basic functions such as free configuration of objects and online configuration of dynamic attributes, field dynamic data acquisition, data processing, status monitoring, alarm, parameter setting, report generation, data storage, and interface, as well as network management functions. Versions on various operating systems share the same kernel, allowing iFix versions built on different operating systems to run in the same network structure. iFix includes a wealth of graphical tools, enabling users to quickly develop systems. It offers powerful features, including real-time process monitoring and supervisory control, alarms and alarm management, historical trends, statistical process control, user-based safety systems, convenient system expansion, and network functionality. VB6.0, a popular and powerful rapid development tool from Microsoft, effectively combines these two tools using DDE technology when developing SCADA systems, leveraging their respective advantages to achieve satisfactory results. The system is divided into a monitoring subsystem, a data acquisition subsystem, and a data exchange subsystem. The Taiwan-based IPC1 industrial PC is used as the SCADA monitoring hardware platform. The monitoring computer connects to the field monitoring instruments via remote I/O modules and data acquisition modules connected to the CC-Link bus—the acquisition subsystem. The acquisition subsystem is responsible for collecting data from various intelligent instruments in the field. The monitoring system connects to the acquisition subsystem via DDE, displaying various operating parameters in real time. The monitoring system issues control commands as needed, which are transmitted by the acquisition subsystem to the CC-Link master PLC connected to the CC-Link bus. The PLC is responsible for controlling various field devices. The data exchange subsystem exchanges data with the monitoring subsystem via DDE, transmitting real-time information from the site to the information network via the control network. The real-time data flow of the monitoring layer of a certain workshop is shown in Figure 4. [/align][align=center][img=418,354]http://www.e-works.net.cn/images/128352656831250000.JPG[/img] Figure 4 Data flow diagram of VB as server and iFix as client[/align] iFix software provides powerful DDE client and server support. DDE client support allows information from other applications to be passed to iFix software for database and screen; server support allows process information from iFix software to be passed to other applications for processing. (1) DDE client support iFix software DDE client support allows reading and writing DDE addresses. Using the DDE IO driver and block configured DDE address, data information from other applications, DDE drivers or another SCADA node can be inserted into the process database. The information in the database can be used in the following ways: transmitting data in the chain, alarming DDE data, and creating trend curves with DDE data. DDE client support allows the use of DDE directly in the iFix screen without using points in the database. That is, DDE can be directly applied to data links, dynamic characteristics (foreground color, boundary color, X and Y coordinates, horizontal or vertical fill, visibility, etc.) settings, XY plots, bar charts, and command languages. The address syntax of iFix as a client DDE is =ApplicationTopicItem. For example, the IO address of field device point DO1 is =VBServerForm1Text1, where VBServer is the name of the application developed in VB, Form1 is the topic name, and Text1 is the project name. (2) DDE server support iFix software as a server allows its real-time or historical data to be transmitted to other DDE client applications. To use the iFix DDE server function, you need to start the DDE server program first, i.e., DMDDE.exe under the iFix software installation directory iFix32. The DDE addressing syntax provided by iFix as a server is shown in Table 1. [align=center]Table 1 DDE Programming Syntax[img=328,118]http://www.e-works.net.cn/images/128352657083437500.jpg[/img][/align] 3.3 VB's DDE Link Properties As a very popular rapid development tool in the Windows environment, VB, like the Windows operating system, comes from Microsoft and naturally supports DDE technology under Windows. VB can be used to easily and quickly develop DDE client or server applications. (1) VB's DDE Properties, DDE Events, and DDE Methods There are 5 types of objects in VB that support DDE: Form, MDI Form, Label, TextBox, and PictureBox. Among them, Form and MDI Form can act as DDE servers, i.e., data providers, while Label, TextBox, and PictureBox can act as DDE servers, i.e., data receivers. VB provides two DDE properties and four DDE events for the sending object to support DDE, and four DDE properties, four DDE events, and four DDE methods for the receiving object (see Table 2). [align=center]Table 2 Properties, Events, and Methods of the Receiving Object[img=325,118]http://www.e-works.net.cn/images/128352657606250000.jpg[/img][/align] (2) Developing DDE Client-Server Applications with VB In developing DDE client-server applications with VB, establishing a DDE link depends entirely on the DDE property settings of the objects. The different settings of DDE properties when VB acts as a DDE client and a DDE server are shown in Table 3. [align=center]Table 3 DDE Attribute Settings for VB as DDE Customer Service[img=330,227]http://www.e-works.net.cn/images/128352657790312500.jpg[/img][/align] (3) Dynamic Data Exchange Process The DDE Manager, as the server, collects data from the PLC's memory through the driver, exchanges data with the configuration, and then writes it back to the PLC's memory area through the driver. A schematic diagram of this process is shown in Figure 5. [align=center][img=466,94]http://www.e-works.net.cn/images/128352658023593750.JPG[/img] Figure 5 Actual Process of Dynamic Data Exchange[/align][align=left] (4) Establishment Process of Dynamic Data Exchange The establishment of a DDE project mainly includes the description of PLC details, network settings, and selection of data points, among which the main focus is on the configuration of equipment and the setting of points. Next, establish and edit the points to be monitored, including defining the names of the monitoring points, the type of PLC, the location of the monitoring points in the PLC memory, and the data type. Input and output words can be defined according to the number of input/output units on the PLC rack, and manual/automatic control flags can also be defined. 3.4 Actual Link between VB as DDE Server and iFix as DDE Client: Some parameters need to be transmitted from the remote field to iFix via the VBServer application developed in VB for display or trend chart generation. Examples include the measured temperature of the paint drying room, the inlet pressure of pure water, the pressure of the circulating water filter, the measured concentration of pigment, the speed of the electrophoresis circulating pump and the measured temperature of the glue furnace, the inlet and outlet pressures of the primary exhaust system booster, and the steam temperature of the air preheater. In VBServer, the collected real-time data is assigned to TextBoxes, and the project name of the DDE address of each point in iFix is ​​set to the corresponding TextBox. For example, the measured temperature of the paint drying room is named AI_Oven_Tem in iFix, and its DDE address is VBServerformMaintxtOvenTem (where VBServer is the application name, formMain is the form name as the theme, and txtOvenTem is the text box name as the project). In this case, iFix is ​​the client, and the VB application is the server. 3.5 The actual link between VB as a DDE client and the DDE server iFix. In general, the flow of field detection signals and motion parameters is from iFix to the VB-developed application VBSrvApp or other Windows applications. Then, the Windows application or VBSrvApp sends commands to remote field devices such as smart meters or PLCs via iFix, such as the set temperature of the paint drying room and glue oven, the set pressure of the pure water inlet, and the set concentration of pigment. In VBServer, the LinkItem property of the corresponding TextBox of each setting parameter is set to the corresponding iFix point, and then the content transmitted from the iFix point to the corresponding TextBox is sent to the remote field device. At this point, the VB application is the VBServer client, and iFix is ​​the server. 4. Conclusion Configuration software plays a crucial role in industrial DCADA systems, and its communication with third-party software is key to the system's success. The issues discussed in this article summarize the application of dynamic data exchange technology in the transformation of an automated production line. The production line is currently operating well, demonstrating the feasibility and effectiveness of this design.