An Introduction to the GRAPH Language in TIA Portal (Sequential Function Chart)

In industrial automation, the five IEC 61131-3 languages are pivotal tools for control system programming. Among these, Sequential Function Chart (SFC) language, often called GRAPH in the Siemens environment, plays a significant role. SFC provides a graphical representation of sequential control logic, breaking it down into Steps (actions) and Transitions (conditions). These visual elements offer a powerful way to design and implement sequential control logic for industrial automation tasks.

This is a companion discussion topic for the original entry at

So what happens with the Graph output “S_NO” (the active step number) when processing simultaneous active steps (with parallel branches)?