Lenze PLC Designer PLC Designer (R3-1) - Manual (Page 681)

L-force | PLC Designer
General Editors

DMS 4.1 EN 03/2011 TD29 679
13.8.1 Languages
Function Block Diagram - FBD
The Function Block Diagram is a graphically oriented programming language. It works
with a list of networks whereby each network contains a graphical structure of boxes
and connection lines which represents either a logical or arithmetic expression, the call
of a function block, a jump, or a return instruction.
The FBD/LD/IL Editor is provided by the 'Network List Editor'-plug-in.
Abb. 368 Example of some Function Block Diagram networks
Ladder Diagram - LD
The Ladder Diagram is a graphics oriented programming language which approaches
the structure of an electric circuit.
On the one hand, the Ladder Diagram is suitable for constructing logical switches, on
the other hand one can also create networks as in FBD. Therefore the LD is very useful
for controlling the call of other POUs.
The Ladder Diagram consists of a series of networks, each being limited by vertical
current lines (power rail) on the left and on the right. A network contains a circuit
diagram made up of contacts, coils, optionally additional POUs (boxes) and connecting
lines. On the left side there is a series of contacts passing from left to right the
condition "ON" or "OFF" which corresponds to the Boolean values TRUE and FALSE. To
each contact a Boolean variable is assigned. If this variable is TRUE, the condition will
be passed from left to right along the connecting line. Otherwise value OFF will be
passed ON. Thus the coil(s), which is/are placed in the right part of the network,
receive(s) an ON or OFF value coming from left and correspondingly copy TRUE or
FALSE to an assigned boolean variable.