Lenze PLC Designer PLC Designer (R3-1) - Manual (Page 751)

L-force | PLC Designer
General Editors
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DMS 4.1 EN 03/2011 TD29 749
13.13.8 Sequence of processing in SFC
In online mode the particular action types will be processed according a defined
sequence, see the table below.
First note the following use of terms:
• Active step: A step, whose step action is being executed, is called "active". In Online
mode active steps are filled with blue color.
• Initial step: In the first cycle after a SFC POU has been called, the initial step
automatically gets active and the associated step action is executed.
• IEC actions are executed at least twice: The first time when they have got active,
the second time - in the following cycle - when they have been deactivated.
• Alternative Branches: If the step preceding the horizontal start line of alternative
branches is active, then the first transition of each particular branch will be
evaluated from left to right. The first transition from the left whose transition
condition has value TRUE will be searched and the respective branch will be
executed, that is the subsequent step within this branch will get active.
• Parallel Branches: If the double-line at the beginning line of parallel branches is
active and the preceding transition condition has the value TRUE, then in all
parallel branches each the first step will get active. The branches now will be
processed parallel to one another. The step subsequent to the double-line at the
end of the branching will become active when all previous steps are active and the
transition condition after the double-line has the value TRUE.