Rockwell-automation Logix5000 Controllers Structured Text Programming Instrukcja Użytkownika Pobierz pdf (Strona 16)

16 Publication 1756-PM007D-EN-P - November 2012

Chapter 1 Program Structured Text

For example:

Use Relational Operators

Relational operators compare two values or strings to provide a true or false

result. The result of a relational operation is a BOOL value.

Use these relational operators.

Use this format Example

For this situation You’d write

value1 operator value2 If gain_4 and gain_4_adj are DINT tags and your

specification says: "Add 15 to gain_4 and store the

result in gain_4_adj."

gain_4_adj := gain_4+15;

operator value1 If alarm and high_alarm are DINT tags and your

specification says: “Negate high_alarm and store

the result in alarm.”

alarm:= -high_alarm;

function(numeric_expression) If overtravel and overtravel_POS are DINT tags and

your specification says: “Calculate the absolute

value of overtravel and store the result in

overtravel_POS.”

overtravel_POS :=

ABS(overtravel);

value1 operator (function((value2+value3)/2) If adjustment and position are DINT tags and

sensor1 and sensor2 are REAL tags and your

specification says: “Find the absolute value of the

average of sensor1 and sensor2, add the

adjustment, and store the result in position.”

position := adjustment +

ABS((sensor1 + sensor2)/2);

If the comparison is The result is

True 1

False 0

For this comparison: Use this operator: Optimal Data Type:

Equal = DINT, REAL, string

Less than < DINT, REAL, string

Less than or equal <= DINT, REAL, string

Greater than > DINT, REAL, string

Greater than or equal >= DINT, REAL, string

Not equal <> DINT, REAL, string

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Rockwell-automation Logix5000 Controllers Structured Text Programming Instrukcja Użytkownika Strona 16