PLC Ladder Diagram Basics

What is a  PLC Ladder Diagram?

A Ladder diagram is a symbolic and schematic representation of both the process hardware and process control. It is  called a ‘Ladder’ because all the devices are connected across the supply lines making it look like a ladder.Each parallel connection is called a ‘Rung’, it can contain many inputs but only one output.

Logic Symbols:

A PLC can do Mathematical Instruction as well as Data handling Instructions also.

Math Instructions are:
a)   ADD: addition
b)  SUB: subtraction
c)   DIV: division
d)  DDV: double division
e)   CLR: clear
f)    SQR: square root

Data handling Instructions are:

a)   MOV: move
b)  MVM: masked move
c)   AND: AND gate Operation
d)  OR: OR gate Operation
e)   XOR: Exclusive OR gate Operation
f)    NOT: NOT gate Operation
g)  NEG: Negate

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