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TOPIC 4: PLC PROGRAMMING
4.1 Fundamental of PLC programming
4.1.1 Types of programming method
a) Ladder Diagram
b) Mnemonic Code
c) Sequential Function Chart
d) Function Block Diagram
e) Instruction List
Ladder Diagram
❖ Graphic programming language changed from relay control wiring circuit
diagram.
❖ The ladder diagram contains a contact track from left to right of thefigure
❖ The contact of this track is connected to the normally open - NO switching
element (normally closed - NC) through the current pathand loop of the
element.
❖ Consists of a vertical line on the left and right called the bus bar
Horizontal line to the right called the instruction lines.
❖ Along the lines of instructions there are logical combinations of conditions
that will determine when and how the instructions on the right will be
executed.
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