Please note that vCampus is not the right place to discuss Interface related questions. In the future please contact OSIsoft TechSupport with similar enquiries.
Because the answer to your question is of very general nature and may be of interest for other vCampus subscribers too, I will put it here:
Please consult the PI Interface for Modbus Ethernet PLC manual. As a registered user, please sign in to OSIsoft TechSupport page and move on to the OSIsoft interface search page (Products -> Interfaces -> Search all). Enter a search string e.g. "Modbus Ethernet" and press [Enter] on your keyboard. Select an Interface from the search results to move on to the details page for the selected interface. The details page offers additional information and links e.g. to Release notes and user manual of the current release.