Attention

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

Retention

Retention qualifiers control whether variables preserve their values across power cycles and program restarts.

IEC 61131-3

Section 2.4.3

Support

Not yet supported

Qualifiers

Qualifier

Description

RETAIN

Value is preserved across power cycles

NON_RETAIN

Value is reset to initial value on restart

CONSTANT

Value cannot be modified after initialization

Example

PROGRAM main
    VAR RETAIN
        run_hours : DINT := 0;
    END_VAR
    VAR CONSTANT
        MAX_TEMP : INT := 150;
    END_VAR
    VAR
        current_temp : INT;
    END_VAR

    run_hours := run_hours + 1;
END_PROGRAM

See Also