the S20-RS-UNI is part of the local bus of the S20-EC-BK, therefor you need the ESI of the bus coupler. Normally it's part of ctrlX IO Engineering. If you deleted, you can download the ESI from boschrexroth.com
Sorry i have seen that the project that i sent you was not the best.
Explains perfectly how to use the device 🙂