Siemens SIMATIC S7-1200

Programming concepts
7.5 Programming language
S7-1200 Programmable controller
System Manual, V4.2, 09/2016, A5E02486680-AK
199
7.5
Programming language
STEP 7 provides the following standard programming languages for S7-1200:
● LAD (ladder logic) is a graphical programming language. The representation is based on
circuit diagrams (Page 199).
● FBD (Function Block Diagram) is a programming language that is based on the graphical
logic symbols used in Boolean algebra (Page 200).
● SCL (structured control language) is a text-based, high-level programming language
(Page 201).
When you create a code block, you select the programming language to be used by that
block.
Your user program can utilize code blocks created in any or all of the programming
languages.
7.5.1
Ladder logic (LAD)
The elements of a circuit diagram, such as normally closed and normally open contacts, and
coils are linked to form networks.
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 provides "box" instructions for a variety of functions, such as math, timer, counter, and
move.
STEP 7 does not limit the number of instructions (rows and columns) in a LAD network.
Note
Every LAD network must term
inate with a coil or a box instruction.