Easy To Use The Powerful Programming Languages - Siemens SIMATIC S7-1200 Manual

5.3

Easy to use the powerful programming languages

You have the option of choosing either the LAD (ladder logic) or FBD (Function Block
Diagram) programming language.
LAD is a graphical programming language. The representation is based on circuit
diagrams. To create the logic for complex operations, you can insert branches to create the
logic for parallel circuits. Parallel branches are opened downwards or are connected
directly to the power rail. You terminate the branches upwards. LAD also provides "box"
instructions for a variety of functions, such as math, timer, counter, and move.
Consider the following rules when creating a LAD network:
● Every LAD network must terminate with a coil or a box instruction. Do not terminate a
● You cannot create a branch that could result in a power flow in the reverse direction.
● You cannot create a branch that would cause a short circuit.
Mathematical functions and other complex functions can be represented directly in
conjunction with the logic boxes. To create the logic for complex operations, insert parallel
branches between the boxes.
Easy Book
Manual, 11/2009, A5E02486774-01
network with either a Compare instruction or an Edge-detection (Positive-edge or
Negative-edge) instruction.
Programming concepts made easy
5.3 Easy to use the powerful programming languages
Like LAD, FBD is also a graphical programming
language. The representation of the logic is
based on the graphical logic symbols used in
Boolean algebra.
The elements of a circuit
diagram (such as normally
closed contacts, normally
open contacts, and coils)
are linked to form networks.
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