Lenze DDS v2.0 - Manual (Page 18)

Introduction to IEC 61131-3 programming
Programming languages
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DDS-IEC61131 EN 2.0
5.4 Function Block Diagram (FBD)
(Function Block Diagram, FBD)
Function Block Diagram is a graphically oriented programming language.
It works with a list of networks. Each network has a structure which represents a logic or arithmetics,
a function block request, jump or a return instruction. Function block outputs are connected with
inputs of following function blocks. Jumps facilitate programming.
Based on defined function blocks, the Function Block Diagram enables the user to implement any
program sequence by means of connection elements. Furthermore, the schematic representation
of the data flow helps to understand program sequences.
As known from the 9300 Servo PLC and Drive PLC, many hardware components are offered with
the corresponding function blocks. That means that there are corresponding modules for both
levels, hardware and software.
Fig. 4 Example of a network in FBD
5.5 Ladder Diagram (LD)
(Ladder Diagram, LD)
Ladder Diagram is a graphically oriented programming language, similar to the principle of an
electric circuit.
On the one hand, Ladder Diagrams are used to build up logic circuits, on the other hand, they can
also be used to create networks (like in FBD). Thus, the Ladder Diagram is perfectly suitable to
control the request of organization units.
Ladder Diagrams consist of several networks.
A network is limited by vertical current leads on both ends. In between, there is a circuit diagram
consisting of contacts, coils and connection lines which transmit the status ” ON” and ” OFF” from
left to right (TRUE or FALSE):
Fig. 5 Example of a network in LD
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