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Learning RSLogix 5000 Programming
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Ladder logic was originally a written method for capturing the wiring of relay circuits also known as relay logic. The name ladder logic can be attributed to the diagrams resembling a ladder. Two vertical lines (often known as L1 and L2) represent the voltage of the circuit, and the horizontal lines and symbols represent the devices (buttons, motors, and breakers) connected to the circuit. Each horizontal line in the circuit is known as a rung. Once microprocessors enabled programmable logic in control systems, ladder logic evolved into a programming language rather than an engineering diagram. The following diagram is an example of a single relay logic rung:

Today, ladder logic is still the most popular industrial automation programming language.
Ladder logic is one the five IEC 61131-3 Compliant languages available in Logix. IEC 61131-3 defines a common set real-time automation programming language structure, which is shared across multiple vendor&apos...
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