WinCC OA is a modularly
built system. The required functionalities are handled
by specific units
that were created for different tasks. In WinCC OA
these units are called managers
- the managers are own software processes.
Figure: 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 different
drivers 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 alarm
handling and is able to execute different calculating
functions stand-alone.
The data manager (DB)
supports the Event manager. It's
the link to the database. It handles the configuration
data of an application that is saved in this kind of database
and moreover, there is a historical
recording of value changes
and alarms. If a user
would like to query historic data later, the query will also be
executed by the Data manager and
not the database itself.
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 multithreadinguser
interface design (UI manager)
or for standardized,
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. |