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1592025400 – Vers. 1.0 - 56 -
8. PROGRAMMING LANGUAGES
8.1 ST language – General concepts
The environment of ST language is composed by:
• STATEMENT
:= assignment
( ) priority
IF, THEN, ELSE, ELSIF, END_IF; binary selection
CASE, OF, ELSE, END_CASE; selection
WHILE, REPEAT, END_WHILE, END_REPEAT; iterations
FOR, TO, BY, DO, END_FOR; indexed iterations
RETURN; program termination
EXIT; iteration statement termination
BOOLEAN OPERATOR (decreasing priority)
NOT boolean negation
AND boolean AND
OR boolean OR
XOR boolean exclusive OR
=, <>, >=, <=, <, > comparisons
+, -, *, / arithmetic operators
Beware of:
WHILE and REPEAT have to be used with special care.
arithmetic operator can be used for integer DINT or REAL.
• TIME
+ addition
- subtraction
Beware of subtraction: negative timer as result means nothing.
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