Transition in SFC
Transitions are basic elements of SFC networks. A transition characterizes the condition when the controller passes from one step to another.
A transition is always associated with a transition condition. The transition condition must always be FALSE or TRUE. The transition condition may be a single Boolean variable, a Boolean constant or a coded transition written in the programming languages ST, LD or FBD that returns a Boolean result. Consequently 2 kinds of transitions can be used in SFC: coded transitions and direct connections.
Coded transitions are transitions with a code body as transition condition. Direct connections are transitions with variables with no own code body as transition condition. Transitions are represented graphically as a horizontal line.