Sequential Function Chart (SFC)

The SFC language is a state diagram. Graphical steps are used to represent stable states, and transitions describe the conditions and events that lead to a change of state. Using SFC highly simplifies the programming of sequential operations as it saves a lot of variables and tests just for maintaining the program context.

Important note

You must not use SFC as a decision diagram. Using a step as a point of decision and transitions as conditions in an algorithm should never appear in a SFC chart. Using SFC as a decision language leads to poor performance and complicate charts. ST must be preferred when programming a decision algorithm that has no sense in term of "program state".

Below are basic components of an SFC chart:

Steps and initial steps
Transitions and divergences
Parallel branches
Jump to a step
Actions within a step
Timeout on a step
Programming a transition condition

How SFC is executed

UDFBs programmed in SFC

The workbench fully supports SFC programming with several hierarchical levels of charts: i.e. a chart that controls another chart. Working with a hierarchy of SFC charts is an easy and powerful way for managing complex sequences and saves performances at run time. Refer to the following sections for further details:

Defining a hierarchy of SFC programs
How to control a SFC child