Programming Languages

Direct reference to physical memory location or I/O point.

Debug point where program execution pauses for inspection of variables and logic.

Extended graphical programming method for complex control strategies, similar to FBD with free positioning.

Non-executable text in program providing documentation and explanations for code.

Programming tool showing all locations where a variable or address is used in the program.

Reusable code block with inputs and single output, no internal memory between calls.

Reusable code with inputs, outputs, and persistent internal memory (instance data) between calls.

Graphical programming language using interconnected function blocks to represent control logic flow.

Variable accessible from any POU in the project, used for data sharing between programs.

GRAFCET (Graphe Fonctionnel de Commande, Étape/Transition) is the French national standard for sequential control specification, the direct predecessor to IEC 61131-3 Sequential Function Charts (SFC). Defines control flow as steps connected by transitions.

International standard defining five programming languages for PLCs, ensuring consistency across manufacturers.

Using pointer or index to dynamically access memory locations during runtime.

Specific occurrence of a function block with its own data memory, allowing multiple uses of same FB.

Low-level text-based language similar to assembly code, being phased out in favor of Structured Text.

A visual programming language for PLCs that resembles electrical relay logic diagrams, using symbols for contacts and coils to represent logic operations.

Collection of reusable functions and function blocks for common tasks.

Variable only accessible within its declaring POU, preventing unintended interactions.

Primary program file executed cyclically by PLC, typically calling other routines and function blocks.

Container for identifiers preventing naming conflicts in large programs.

Programming unit in Siemens PLCs equivalent to a rung, containing one logical operation.

Capability to modify PLC program while running, allowing changes without stopping production.

Self-contained code section that can be called multiple times.

Reusable code block in IEC 61131-3 including Programs, Function Blocks, and Functions.

A rung in ladder logic is one horizontal line of code containing contacts (input conditions) on the left and coils or functions (output actions) on the right, executed top-to-bottom each PLC scan. Named after the rungs of a ladder.

Graphical language for programming sequential control systems using steps, transitions, and parallel branches.

Programming pattern organizing code into discrete states with defined transitions, ideal for sequential control.

A high-level textual programming language for PLCs similar to Pascal, defined in IEC 61131-3, ideal for complex math, data manipulation, and algorithm implementation.

Reusable program segment called from main program or other subroutines to modularize code.

Using descriptive names instead of physical addresses for variables.

Manufacturer-provided function blocks for system-level operations.

Execution unit that calls POUs with specific priority and timing, managing program execution order.

Pass-by-reference parameter in IEC 61131-3, allowing direct modification of external variables.

Input parameter declaration in IEC 61131-3 POUs, read-only within the block.

Output parameter declaration in IEC 61131-3 POUs, writable within the block.