Lenze PLC Designer PLC Designer (R2-x) Manuale Utente Scaricare il pdf (Pagina 54)

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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.

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Lenze PLC Designer PLC Designer (R2-x) Manuale Utente Pagina 54

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