Circuit Diagram Conversion; Program Structure; Linear Programming - Siemens SIMATIC S5 Manual

Introduction to STEP 5
2.1.3

Circuit Diagram Conversion

If your automation task is in the form of a circuit diagram, you must convert it to STL, CSF, or LAD.
Example: Hard-wired control
A signal lamp is to light up when a normally open contact (S1) is activated and a
normally closed contact (S2) is not activated.
Programmable control
The signal lamp is connected to a PLC output (Q 2.0). The signal voltages of the two
contacts are connected to two PLC inputs (I 1.1 and I 1.2).
The PLC scans to see if the signal voltages are present (signal state "1" at the activated
normally open contact or nonactivated normally closed contact). Both signal states are
combined through logic AND. The result of the logic operation (RLO) is assigned to
output 2.0 (the lamp lights up).
Circuit Diagram
S1
A
S2
AN I 1.2
=
2.2

Program Structure

An S5-115F program can be one either linear or structured.
Sections 2.2.1 and 2.2.2 describe these program types.
2.2.1

Linear Programming

Programming individual operations in one section (block) is sufficient for handling simple auto-
mation jobs.
For the S5-115F, this is organization block 1 (OB 1) ( 2.3.1). The S5-115F scans this block cyclically
(i.e. after it scans the last statement, it goes back to the first statement and begins scanning again).
A linear program can have 8 Kbytes.
Please note the following:
• When OB 1 is called, five words are assigned to the block header.
• Normally, a statement takes up one word in the program memory. Two-word statements also
exist (e.g. with the operation "Load a constant"). Count these statements twice when calcu-
lating the program length.
• Like all blocks, OB 1 must be terminated by a Block End statement (BE).
2-4
STL
I 1.1
I 1.1
I 1.2
Q 2.0
CSF
I 1.1
&
Q 2.0
S5-115F Manual
LAD
I 1.2 Q 2.0
( )
EWA 4NEB 811 6149-02