Mitsubishi Electric MELSEC Q Series Structured Programming Manual page 88

(4) IF ...ELSIF conditional syntax
(a) Format
(b) Description
(c) Example
(5) CASE conditional syntax
(a) Format
(b) Description
(c) Example
5.1 ST
5-6
5.1.3 Syntax in ST language
IF <Boolean expression 1> THEN
<Syntax 1 ...>;
ELSIF <Boolean expression 2> THEN
<Syntax 2 ...>;
ELSIF <Boolean expression 3> THEN
<Syntax 3 ...>;
END_IF;
Syntax 1 is executed when the value of Boolean expression (conditional expression) 1
is TRUE. Syntax 2 is executed when the value of Boolean expression 1 is FALSE and
the value of Boolean expression 2 is TRUE.
Syntax 3 is executed when the value of Boolean expression 1 and 2 are FALSE and the
value of Boolean expression 3 is TRUE.
CASE <Integer expression> OF
<Integer selection 1> : <Syntax 1 ...>;
<Integer selection 2> : <Syntax 2 ...>;
·
·
·
<Integer selection n> : <Syntax n ...>;
ELSE
<Syntax n+1 ...>;
END_CASE;
The result of the CASE conditional expression is returned as an integer value. The
CASE conditional syntax is used to execute a selection syntax by a single integer value
or an integer value as the result of a complicated expression.
When the syntax that has the integer selection value that matches with the value of
integer expression is executed, and if no integer selection value is matched with the
expression value, the syntax that follows the ELSE syntax is executed.