CASE

The CASE statement selects one of several statement groups based on the value of an integer expression.

IEC 61131-3	Section 3.3.2.3
Support	Supported

Syntax

CASE expression OF
    case_value { ',' case_value } ':' statement_list
    { case_value { ',' case_value } ':' statement_list }
[ ELSE
    statement_list ]
END_CASE ;

Each case_value is an integer literal or a subrange (low .. high). Multiple values can be listed separated by commas.

Description

The CASE statement evaluates the expression and compares it against each case value in order. When a match is found, the corresponding statement list executes and control passes to the statement after END_CASE. If no match is found and an ELSE clause is present, its statement list executes.

Unlike C-style switch statements, there is no fall-through between cases.

Example

Try it

Source

PROGRAM main
    VAR
        command : INT := 2;
        motor_on : BOOL;
        alarm : BOOL;
    END_VAR

    CASE command OF
        0:
            motor_on := FALSE;
            alarm := FALSE;
        1:
            motor_on := TRUE;
        2, 3:
            motor_on := TRUE;
            alarm := TRUE;
    ELSE
        alarm := TRUE;
    END_CASE;
END_PROGRAM

See Also

• IF — conditional branching