Sequential function chart (SFC) is a graphical programming language used for Programmable logic controller. It is one of the five languages defined by IEC 61131-3 standard. The SFC standard is defined in IEC 848, Preparation of function charts for control systems , and was based on GRAFCET.

It fits well sequential programs which can be split into steps.

Main components of SFC are:

Screendump of a typical program.

Always starts in step 0 The blocks represent actions and the little crossing lines represent conditions eg. if the PLC was busy with step 13 and the leftmost condition is true then it goes back to the start (step 0). If the rightmost condition is true then jump back to step 11 and performs another cut. The programmer must make sure that conditons at the same level are exclusive as there must be only one active block at any moment. The action of the block is performed elsewhere in the program.. eg for as long as step 13 is active then activate the cutting valve.