01
PLC Architecture
- Central processing unit executes control logic.
- Digital and analog inputs acquire process information.
- Digital and analog outputs command actuators.
- Communication modules exchange data with other devices.
- Engineering software provides configuration, programming, diagnostics, and monitoring.
02
PLC Scan Cycle
A traditional PLC repeatedly reads inputs, executes the control program, updates outputs, and performs communication and diagnostic work according to its runtime architecture.
inputs → program execution → outputs → repeat
03
PLC Programming Languages
IEC 61131-3:2025 specifies a unified suite of programmable-controller languages including Structured Text, Ladder Diagram, Function Block Diagram, and Sequential Function Chart.
- Ladder Diagram represents logic graphically in a form familiar to electrical-control engineers.
- Structured Text provides a textual programming model.
- Function Block Diagram represents reusable functional relationships graphically.
- Sequential Function Chart structures sequential behavior and state transitions.