WinCC OA is a modularly built system. The required functionalities are handled by specificunits that were created for different tasks. In WinCC OA these units are called managers - the managers are own software processes.

Figure 1. A WinCC OA system is composed of function-specific units, managers

In the following, the most important managers of the figure above are briefly described. Thereby, it is merely a simple configuration and can be much more comprehensive in practice. In fact, there are a number of managers that are not dealt with in detail here.

Process interface

The process interface modules, which are called drivers(D) in WinCC OA, form the lowest level in a WinCC OA system. The drivers are special programs that handle the communication with the control and field level. Since there are numerous different communication forms with PLCs or remote control nodes, there are several differentdrivers available.

Therefore, the used PLC or the associated communication bus defines which WinCC OA driver should be used. To put it simply, the driver is a module that converts a certain protocol into the internal communication form of WinCC OA. The driver reads current states, measured values or counter values from the field and passes commands and set values to the subordinate controls (= the word "control" is used in this tutorial for all possible equipment of the basic automation (PLC, DDC, telecontrol system,...)

Process image, history

The central processing center in WinCC OA is called Event Manager (EV). This unit always keeps a current image of all process variables in the memory. Each other function unit (manager) that wants to access data, receives the data from the process image of the event manager and does not have to communicate directly with a control. A command from an operator station is only set as a value change in the process image of the Event manager at first. The forwarding to the appropriate target device (for example PLC) will be executed by the responsible manager automatically.

The Event manager is a kind of central data distributor, the communication center for WinCC OA. Furthermore, this manager also executes the alert handling and is able to execute different calculating functions stand-alone.

The data manager supports the Event manager. The Data manager is the link to a database. The Data manager handles the configuration data of an application that is saved in the database. Furthermore, the historical data - value changes and alerts are saved in a database. If you would like to query historic data later, the query is also executed by the Data manager and not the database itself.

The concept for archiving process data handles the saving and readout of information that occurs during process control or visualization. This involves values and messages that are generated by value changes. The process data is saved in Value Archives (VA). Each archive is managed by a separate archiving process. Each archive consists of a series of chronologically ordered archive files.

Processing, Control

In WinCC OA there are numerous possibilities to implement own algorithms and processing. The internal language control (CTRL) and the common programming interface API (Application Programming Interface) are the most important.

Control is a powerful scripting language. The code is processed interpretatively so compiling (= conversion process which interprets a source code into executable machine code for the processor) is required. The syntax corresponds to the ANSI-C (= "C"... international standardized and exquisitely widespread, higher-level programming language.) with some simplifying modifications. It is an advanced procedural high level language with multithreading (parallel processing of single programs, the processing control is executed by the system itself). The language provides a widespread function library for tasks of control and visualization technics. Control can be used asa stand-alone process(CONTROL manager) for animation anduser interface design(UI manager) or for standardized,data object based processing (Event manager).

The API (WinCC OA API) presents the most powerful form of function extensions. It is a C++ class library and allows the software developer to implement individual functions as an independent additional manager (prognosis system, simulation, planning tools, proprietary databases), ....

Present, handle

The User Interface Manager (UI) is the interface to the user. Thereby, there is the graphics editor (GEDI), a database editor (PARA) or the general user interface of the application (Module VISION). In the user interface, values are shown, commands are executed or alarms are tracked . Furthermore, trends or reports are normally part of the UI. In WinCC OA the user interaction is technically completely separated from the background processing. It is merely a view of the data of the current process image or the history.