PLCopen XML & IEC 61131-3 Industrial Automation (.xml, .st)

@modelscript/plcopen (languages/plcopen) provides compiler, Virtual PLC cyclic execution, sampled-data DAE lowering, and formal verification for IEC 61131-3 industrial control software and PLCopen XML interchange models.

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Supported Extensions & Standards

Extension	Standard / Format	Description
.xml, .plcopen	PLCopen XML v2.01 / v2.0	XML exchange format for IEC 61131-3 control programs, POUs, and configurations
.st	IEC 61131-3 Structured Text	Textual structured control language for PLCs and industrial controllers

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Key Capabilities

1. IEC 61131-3 Program Organization Units (POUs)

• Full support for standard control logic paradigms:
  • Structured Text (ST): Variable declarations, conditionals (IF-THEN-ELSE), case selection, loops (FOR, WHILE), and mathematical expressions.
  • Function Blocks (FB): State-retaining functional blocks including standard timers (TON, TOF, TP), counters (CTU, CTD, CTUD), and bistable multivibrators (SR, RS).
  • Functions (FUN): Pure stateless mathematical computations.

2. High-Speed Deterministic Virtual PLC Engine

• Features a cycle-accurate Virtual PLC execution runtime (VirtualPlc):
  • Sampled Scan Cycle: Deterministic three-phase execution: input latching $\to$ logic evaluation $\to$ output write.
  • Configurable Scan Period: Executes discrete scan rates (e.g., $1\text{ms}$, $10\text{ms}$, $50\text{ms}$) coupled with continuous physical models.

3. Direct Sampled-Data DAE Lowering

• Compiles discrete state variables, zero-order holds (ZOH), and timer registers into @modelscript/runtime's DAEBuilder arena.
• Enables closed-loop hardware-in-the-loop (HIL) simulation of PLC control algorithms coupled with continuous Modelica physics (e.g., thermal plants, robotic actuators, motor drives).

4. Polyglot Projections

• Modelica (plcopenToModelica): Lowers PLC function blocks into standard synchronous Modelica clocked state machines.
• SysML v2 (plcopenToSysML): Maps IEC 61131-3 control architectures to SysML v2 action def successions and state machines.

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Static Analysis & Safety Linter Rules

10 rules7 error3 warning Run with msx plcopen lint

Code	Rule	Severity	Message
M7701	unassigned-variable-read	error	Variable '<name>' is read before being assigned or initialized in POU '<pouName>'.
M7702	cyclic-task-overrun	warning	Computational complexity in task '<taskName>' (<stmtCount> statements) may exceed cycle time '<interval>'.
M7703	recursive-pou-call	error	Recursive invocation of POU '<calleeName>' detected in '<callerName>'. Recursion is prohibited in IEC 61131-3.
M7704	io-mapping-collision	error	Hardware I/O address collision at '<address>': multiple variables ('<var1>', '<var2>') assigned to same output.
M7705	type-mismatch-assignment	error	Type mismatch in assignment to '<varName>': expected '<expectedType>', got '<actualType>'.
M7706	timer-preset-negative	error	Timer preset time '<value>' for '<timerName>' cannot be negative.
M7707	unbounded-loop-detected	warning	Loop in POU '<pouName>' does not have a deterministic bounded termination condition.
M7708	unknown-pou-type	error	Unknown or unresolvable POU or function block type '<typeName>' instantiated in '<instanceName>'.
M7709	unreachable-code	warning	Unreachable code detected after '<stmtKind>' statement in POU '<pouName>'.
M7710	invalid-task-interval	error	Task '<taskName>' specifies invalid or non-positive periodic interval '<interval>'.

Generated from languages/plcopen/src/lints/rules.ts. All languages →

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CLI Usage

# Lint an IEC 61131-3 PLCopen XML project
msx plcopen lint AutomationController.xml

# Run 50 discrete scan cycles (dt = 10ms) through the Virtual PLC engine
msx plcopen run-scan AutomationController.xml --cycles 50 --dt 10

# Lower control logic to DAE arena for closed-loop physics co-simulation
msx plcopen to-dae AutomationController.xml --out=controller.dae.json

# Project into Modelica synchronous clocked state machine components
msx plcopen to-modelica AutomationController.xml -o ControllerBlocks.mo