ABSTRACT
Safety automation had to be hard-wired and based on relay technology. This dichotomy, or gap, is quite natural due to the fact that safety relies on trusted technology, trust in experience, and experience accumulated over long time. It was merely a matter of time to introduce the necessary means for safety applications on PROFIBUS DP & PROFINET IO and to provide a similar flexibility and availability for powerful functional safety devices like remote I/O, laser scanners, light curtains, level switches, shutdown valves, drives and robots. This chapter discusses the mechanisms PROFIsafe employs for safely transporting the PROFIsafe protocol data units (PDUs). The PROFIsafe mechanisms are based on finite-state machines. Thus, it was possible via a validation tool for finite-state machines to mathematically prove that PROFIsafe is working correctly even in cases where more than two independent errors or failures may occur.
