Programmable Logic Controller (PLC)

Programmable Logic Controller (PLC) is the logical capability of running deterministic, real-time control logic on an industrial-grade controller that drives sensors, actuators, motors, and HMIs on a manufacturing line. PLCs are the workhorse of factory automation — programmed in the IEC 61131-3 languages (ladder, function block, structured text) and networked via OPC UA, Profinet, EtherNet/IP, or Modbus.

What it covers

• Real-time scan loop — read inputs, execute logic, write outputs at deterministic cycle.
• IEC 61131-3 languages — ladder logic, function block diagram, structured text, sequential function chart.
• Field networks — Profinet, EtherNet/IP, Modbus TCP, Profibus, and OPC UA.
• HMI / SCADA integration for operator interaction and supervisory control.
• Functional safety variants conforming to IEC 61508 / IEC 62061 (safety PLCs).

Relationships (see sidebar)

• Supports Manufacturing Execution and CAM / Manufacturing Planning.
• Dependency of Industrial Connectivity (PLC tags are the canonical OT data source) and Virtual Commissioning (where simulated PLCs validate logic before plant deployment).
• Standardized by IEC 61131 and complemented by ISO 9001 quality requirements on plant-floor controls.