ST instruction CASE

The CASE instruction is used to group multiple conditional instructions with the same conditional variable in a construct.

Syntax:

CASE <condition> OF
    <label-1> :
        <instruction-1>
    <label-2> :
        <instruction-2>
    <label-3, label-4, label-5> :
        <instruction-3>
    <label-6 .. label-10> :
        <instruction-4>
    ...
    <label-n> :
        <instruction-n>
    ELSE 
        <ELSE-instruction>}
END_CASE;

condition

Integer variable for the condition

Sample: nCondition

The value of the variables is compared with the labels declared in the construct.

Any number of labels, but at least two, can be used within a CASE instruction. Otherwise, the construct can be displayed more clearly with an IF-THEN-ELSE construct.

All labels must have different values.

label-n

Constant, literal or constant expression with the same data type as the condition

Functions as a label (jump target) within the CASE construct.

Sample: 1, 5, eState1, eState2

If this value is equal to condition, the following instructions are run through.

If this value is not equal to condition, the associated instruction is ignored and the system jumps to the next label.

<label-n >, < label-n1>

Comma-separated list with several labels that act as jump targets.

Sample: 1, 5

If one of the labels matches the condition condition, the following section is run through.

<label-n1>..<label-n2>

Area with lower and upper limit label

10..20

If condition assumes a value from the range from label-n1 to label-n2, the following section is run through.

ELSE

Optional, maximum once

Default jump target that is jumped to if all previous labels do not match the condition.

instruction-n

ELSE-instruction

Instruction or instruction section consisting of several instructions.

An instruction always ends with a ";".

Processing scheme of a CASE instruction:

If the <condition> variable has the value of <label-n>, the <instruction-n> is executed.
If the <condition> variable has none of the specified values, the <ELSE-instruction> is executed.
If you want to execute the same instruction for multiple values of the variable, you can write these values separated by commas.

Sample:

CASE nVar OF 
    1,5 : 
         bVar1 := TRUE; 
         bVar3 := FALSE; 
    2 : 
         bVar2 := FALSE; 
         bVar3 := TRUE; 
    10..20 :
         bVar1 := TRUE; 
         bVar3 := TRUE; 
    ELSE 
         bVar1 := NOT bVar1; 
         bVar2 := bVar1 OR bVar2; 
END_CASE;