
B-2
Ladder Logic (LAD) for S7-300 and S7-400
C79000-G7076-C504-02
B.1 Overview
Each ladder logic instruction described in this manual triggers a specific
operation. When you combine these instructions into a program, you can
accomplish a wide variety of automation tasks. This chapter provides the
following examples of practical applications of the ladder logic instructions:
S Controlling a conveyor belt using bit logic instructions
S Detecting direction of movement on a conveyor belt using bit logic
instructions
S Generating a clock pulse using timer instructions
S Keeping track of storage space using counter and comparison instructions
S Solving a problem using integer math instructions
S Setting the length of time for heating an oven
The examples in this chapter use the following instructions:
S Add Integer (ADD_I)
S Assign a Value (MOVE)
S Compare Integer (CMP_I>=)
S Compare Integer (CMP_I<=)
S Divide Integer (DIV_I)
S Down Counter Coil ––( CD )
S Extended Pulse Timer Coil ––( SE )––
S Jump-If-Not ––( JMPN )––
S Multiply Integer (MUL_I)
S Normally Closed Contact ––| / |––
S Normally Open Contact ––| |––
S Output Coil ––( )
S Positive RLO Edge Detection ––( P )––
S Reset Coil ––( R )
S Return ––( RET )
S Set Coil ––( S )
S Up Counter Coil ––( CU )
S (Word) And Word (WAND_W)
S (Word) Or Word (WOR_W)
Practical
Applications
Instructions Used
Programming Examples
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