PROFIBUS, standardized to EN 50170 and IEC 61158, provides communication between programmable controllers and ET 200 distributed I/O stations, HMI devices and numerous other field devices. Over the fieldbus start-up, testing and diagnosis of the complete automation is also possible.

PROFIBUS is open for field devices from any manufacturer. Siemens supports the connection of additional field devices to PROFIBUS with the open marketing of ASICs and interfaces as well as with technical support for the manufacturers for components for PROFIBUS.

The integrated fiber-optic interfaces of the ET 200 distributed I/O stations and the S7-400 support easy configuration of fiber-optic bus lines especially in environments charged with electromagnetic interference.