haj, let's just step back from all the details and think this thru for a minute.
You have this PLC to control your system. You also have this inverter which controls everything about the motor its connected to.
Surely, you will have to tell the motor to start and stop. And, surely, you will have to tell the motor to go fast or slow. Likely, you will have to tell the drive whether to run forward or backward.
That's three signals, two digital and one analog (speed). That should cover your most basic needs.
Now, there are dozens of other things that can be done but you need to think this thru first.
Remember, the drive can also send signals back to your system. For example, most drives have a relay output that will signal when the drive is faulted. Some have a relay that signals when it is running and when it isn't. Most have an analog signal (4-20ma usually) that can signal back how fast its running, how hard the motor is working, how hot the drive is, or many other things.
Again, what do you need to do on this job?