S800 I/O is a comprehensive, distributed and modular process I/O system that communicates with parent controllers and PLCs over industry-standard field buses. The CI840 Fieldbus Communication Interface (FCI) module is a configurable communication interface that performs operations such as signal processing, gathering of various supervision information, OSP handling, Hot Configuration In Run, HART pass-through and configuration of I/O modules. CI840 is designed for redundant applications. The FCI connects to the controller by way of the PROFIBUS-DPV1 fieldbus. Module termination units to use, TU846 with redundant I/O and TU847 with non-redundant I/O.