Lenze PLC Designer PLC Designer (R2-x) - Manual (Page 54)

L-force | PLC Designer
What is What in PLC Designer
52 DMS 3.2 EN 02/2011 TD29

4.2.2 Structured Text (ST)...
The Structured Text consists of a series of instructions which, as determined in high
level languages, ("IF..THEN..ELSE") or in loops (WHILE..DO) can be executed.
Example:
IF value < 7 THEN
WHILE value < 8 DO
value:=value+1;
END_WHILE;
END_IF;
Expressions
An expression is a construction which returns a value after its evaluation.
Expressions are composed of operators and operands. An operand can be a constant, a
variable, a function call, or another expression.
Valuation of expressions
The evaluation of expression takes place by means of processing the operators
according to certain binding rules. The operator with the strongest binding is
processed first, then the operator with the next strongest binding, etc., until all
operators have been processed.
Operators with equal binding strength are processed from left to right.