Lenze DDS v2.0 - Manual (Page 16)

Introduction to IEC 61131-3 programming
Programming languages
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DDS-IEC61131 EN 2.0
5.3 Sequential Function Chart (SFC)
(Sequential Function Chart, SFC)
Sequential Function Chart is a graphically oriented language that enables the description of a time
sequence of different actions within a program.
An organization unit written in SFC consists of steps which are linked by means of directed
connections (transitions).
Fig. 3 Example of a network in SFC
The graphical representation of transitions and steps reminds of a flow chart, is easily readable and
perfectly suitable for programming higher level status sequences.
Steps
Steps consist of flags and one or several actions or Boolean variables.
•
The actions of steps are separated from the steps and can be used repeatedly in an
organization unit.
•
Qualifiers activate and deactivate actions and Boolean variables (sometimes with time delay).
•
Concurrences are possible because an action can still be active when the next step is already
being processed, e.g. the qualifier S (set).
Actions
Actions can contain instructions in IL or ST, networks in FBD or LD, or a sequential function (SFC).
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