Attention

IronPLC supports IEC 61131-3 Structured Text excluding I/O mapping.

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

Statements

Statement	Description
Assignment	Assign a value to a variable
Bit Access	Access a single bit of an integer or bit-string variable
IF	Conditional branching
CASE	Multi-way selection by integer value
FOR	Counted loop
WHILE	Pre-tested loop
REPEAT	Post-tested loop
EXIT	Break from innermost loop
RETURN	Early exit from POU

Operators

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

Function Calls

Topic	Description
Function Call	Calling functions and function block instances

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