Supported ST syntax

Supported Structured Text syntax

logiccloud supports the following Structured Text (ST) syntax according to the IEC 61131-3 standard. The pages below document only the constructs that the logiccloud transpiler and runtime actually support.

A small program brings the main elements together — variables, a standard function block instance, a conditional and a standard-function call:

PROGRAM Blink
VAR
    pulse  : TON;          // standard on-delay timer
    output : BOOL;
END_VAR

pulse(IN := NOT pulse.Q, PT := T#500ms);
output := pulse.Q;
IF output THEN
    cycles := ADD(cycles, 1);   // standard function
END_IF
END_PROGRAM

Language basics

• Basic elements
  • Comments
  • Assignments
  • Expressions
• Operators and precedence
• Literals

Variables and types

• Variables
• Data types
• Derived types
• Type conversion
• Pragmas

Statements

• Command groups
  • Boolean operations
  • Arithmetic operations
  • Comparison operators
  • Conditional statements
    • IF / ELSE statement
    • IF / ELSIF statement
    • CASE statement
  • Loops and execution control
    • FOR loop
    • WHILE loop
    • REPEAT loop
    • EXIT statement
    • CONTINUE statement
    • RETURN statement

Program organization units (POUs)

• Programs
• Functions
• Function blocks
• Methods, classes and interfaces
• Namespaces

Standard library

• Standard functions
  • Math and arithmetic
  • Bit-string functions
  • Selection and comparison
  • String functions
  • Date and time
  • Array bounds and validation
  • Conversion and endianness
• Standard function blocks
  • Timers
  • Counters
  • Edge detection
  • Bistables