The IEC 61131-3 ST IF statement executes a list of statements depending on a condition. The IF statement has this syntax:
IF condition THEN Statement; .. Statement; [ ELSEIF condition THEN Statement; .. Statement; ] [ ELSE Statement; .. Statement; ] END_IF;
Where:
The condition associated with the first IF clause is evaluated, and if the result is true, the statements immediately following the condition are executed. If the result of the condition is false, conditions associated with ELSEIF clauses are tried until one is found to be true. If the conditions are false, the statements in any ELSE clause are executed.
The ELSEIF and ELSE clauses are optional.
IF Level <= 2.0 THEN State := "Normal"; ELSEIF Level <= 3.5 THEN State := "High"; ELSE State := "Overflow"; END_IF
IEC 61131-3 Second Edition: Table 56.4.
IEC 61131-3 Third Edition: Table 72.4.
For other Structured Text (ST) statement types.
To learn about expressions that can be used as condition values.
For the meaning of terms used in Fernhill SCADA.