ISPSoft User Manual 14.1 Knowing Sequential Function Charts 14.1.1 Structure of a Sequential Function Chart A sequential function chart is one of the five languages defined by IEC 61131-3 standard. It is a powerful graphical technique for describing the sequential behavior of a control program. A sequential function chart and its corresponding flowchart are shown below. The main components of a sequential function chart are steps with associated actions, transitions with associated logic conditions, and directed links between steps and transitions. 14-2