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S5-115U Manual
7
Introduction to STEP 5
This chapter explains how to program the S5-115U. It describes how to write a program, how the
program is structured, the types of blocks the program uses, and the number representation of
the STEP 5 programming language.
7.1
Writing a Program
A control program specifies a series of operations that tell the programmable controller (PLC)
how it has to control a system. You must write the program in a very special language and
according to specific rules so that the PLC can "understand" it. The standard programming
language that has been developed for the SIMATIC S5 family is called STEP 5.
7.1.1
Methods of Representation
The following methods of representation are possible with the STEP 5 programming language:
•
Statement List (STL)
STL represents the program as a sequence of operation mnemonics. A statement has the
following format:
002:
A I 0.1
Relative address of the statement in a particular block
The operation instructs the PLC what to do with the operand. The parameter indicates the
operand address.
•
Control System Flowchart (CSF)
CSF represents logic operations with symbols.
•
Ladder Diagram (LAD)
LAD represents control functions with circuit diagram symbols.
•
GRAPH 5
GRAPH 5 is a graphic representation of the structure of sequence controls.
The last three methods of representation indicated are only possible with CRT-based pro-
grammers (e.g. PG 635, PG 750).
EWA 4NEB 811 6130-02b
Introduction to STEP 5
Operation
Operand
Parameter
Operand ID
7-1
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