Communication components

In the VisiWin documentation, communication components are the device drivers that support the specific protocol of a PLC and exchange process values with the variable server of the visualisation.

The three decisive factors for finding the right communication components are

The PLC with which communication is to take place. The communication component must be adapted to the specific protocol.
The device used for communication. Some control units contain several interfaces or there are adapters that adapt the existing interfaces.
The availability of different communication components that match the PLC and the communication path.

So if there are various communication components to choose from, a decision has to be made.

Criteria for decision-making

The variable server supports two different categories of communication components:

VisiWin driver: VisiWin drivers are implemented on the basis of the .NET Framework and thus guarantee the greatest possible consistency in the various Windows operating systems. They include an optional browser-like mechanism for data transfer. The behaviour at runtime is specially optimised to eliminate synchronisation problems with OPC servers.
OPC server/OPC UA server: Universal, visualisation-independent interface specified by the OPC Foundation. OPC servers include the browser interface for data transfer, which can ideally be used to transfer configured process variable definitions directly from the PLC development environment to the project file. OPC servers include a network-compatible interface via DCOM, while OPC UA servers have their own protocol stack.

OPC servers are usually offered by the corresponding controller manufacturer, but third-party providers may also have alternative offerings. A wide range of controllers can be addressed via VisiWin drivers. The range of VisiWin drivers available is not limited to INOSOFT products. A driver toolkit is available that enables the implementation of customised protocols based on the C# programming language.

The categories listed above in the order in which they were created differ in terms of operating system, network capability and function. Below you will find the most important key data for decision-making in keywords.

Catalogue of questions for decision-making

Operating system: Under which operating system should the connection to the PLC be made?
Network capability: Is the connection located on the visualisation computer or another computer in the network?
Project planning support: Is the amount of data to be visualised extensive or does it change in the course of development? How easily can data changed by the PLC programmer be compared with the visualisation during the course of the project?
Visualisation independence: Do other applications have to exchange data directly with the communication component?
Data consistency: Are sequential communication sequences with timing to be implemented that exceed the usual requirements for consistency between display and PLC memory?
Optimisations: Does the volume of data to be transmitted put a strain on the communication interfaces, so that optimisation procedures have to be selected for the transmission?