Attention

IronPLC can only run very simple programs. The steps described are accurate but many language features are not yet supported.

Structured Text

Structured Text (ST) is a high-level textual programming language defined by IEC 61131-3. It resembles Pascal and provides statements for assignment, selection, iteration, and function invocation.

IEC 61131-3	Section 3.3
Support	Partial

Statements

Statement	Description	Status
Assignment	Assign a value to a variable	Supported
IF	Conditional branching	Supported
CASE	Multi-way selection by integer value	Supported
FOR	Counted loop	Supported
WHILE	Pre-tested loop	Supported
REPEAT	Post-tested loop	Supported
EXIT	Break from innermost loop	Supported
RETURN	Early exit from POU	Supported

Operators

Category	Description	Status
Arithmetic Operators	Addition, subtraction, multiplication, division, modulo, power	Supported
Comparison Operators	Equality, inequality, less than, greater than	Supported
Logical Operators	AND, OR, XOR, NOT	Supported

Function Calls

Topic	Description	Status
Function Call	Calling functions and function block instances	Partial

Operator Precedence

Operators are listed from highest to lowest precedence.

Rank	Operator	Description
1	( )	Parenthesized expression
2	Function calls	Function and function block invocation
3	-, NOT	Negation, boolean complement
4	**	Exponentiation
5	*, /, MOD	Multiply, divide, modulo
6	+, -	Add, subtract
7	<, >, <=, >=	Comparison
8	=, <>	Equality, inequality
9	AND, &	Boolean AND
10	XOR	Boolean exclusive OR
11	OR	Boolean OR