Sequential Function Charts (SFCs) are types of module algorithms that are useful for controlling time-event sequences, such as startup or shutdown of a process. SFCs are made up of steps and transitions. Steps contain a set of actions. A transition allows a sequence to proceed from one step to the next when the transition condition is true.
Each time the SFC scans, the system evaluates the active steps and transitions. When a transition evaluates as True, the step prior to the transition is made inactive and the step following the transition becomes active.
There are no predefined module templates for SFCs since process sequences are highly individual. In defining an SFC, you may find it helpful to first define the steps in the process, and then identify the conditions that must be met before proceeding from step to step.