Jan,
PLC communication is a standard use-case for LabVIEW applications. There are several options to do this.
Here you can find a whitepaper that explains all options in detail.
For your application OPC might be a good option you can use the DataSocket API to talk to an OPC server. For very fast communication a direct communication via Profibus is recommended. E. g.
Comsoft provides an easy to use LabVIEW driver for their Profibus boards (DF Profi II).
If you plan to build a high channel count application and OPC you may want to consider
LabVIEW DSC as an option as it has a much better perfromance than DataSocket and it provides a lot of valuable features as historical datalogging, alarm & event monitoring and logging, user managment and a lot of more features that are useful in industrial applications.
I hope this helps,
Jochen Klier
National Instruments Germany
