Is not very common, but sometimes is needed to communicate our PLC´s directly to PC.
The typical applications use to be testing machines, who needs accurate response time, or complex machines who use the PLC to easy control over simple parts of the machine.
And some times (why not) because our PLC’s are cheaper than a digital/analog I/O PCI Cards!
Because of that we create some libraries and examples in the most updated PC programming software to help you on this.
Feel free to download and use them for your applications.