Rockwell Automation Logix5000 Controllers Structured Text Programming Manual - Manual (Page 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