Rockwell Automation Logix5000 Controllers Structured Text Programming Manual - Manual (Page 18)

18 Publication 1756-PM007D-EN-P - November 2012
Chapter 1 Program Structured Text
Use Logical Operators
Logical operators let you check if multiple conditions are true or false. The
result of a logical operation is a BOOL value:
Use these logical operators:
For example:
If the comparison is The result is
True 1
False 0
For Use this operator Data Type
Logical AND &, AND BOOL
Logical OR OR BOOL
Logical exclusive OR XOR BOOL
Logical complement NOT BOOL
Use this format Example
For this situation You’d write
BOOLtag If photoeye is a BOOL tag and your specification
says: “If photoeye_1 is on then…” IF photoeye THEN...
NOT BOOLtag If photoeye is a BOOL tag and your specification
says: “If photoeye is off then…” IF NOT photoeye THEN...
expression1 & expression2 If photoeye is a BOOL tag, temp is a DINT tag,
and your specification says: “If photoeye is on
and temp is less than 100
⋅
then…”.
IF photoeye & (temp<100) THEN...
expression1 OR expression2 If photoeye is a BOOL tag, temp is a DINT tag,
and your specification says: “If photoeye is on
or temp is less than 100
⋅
then…”.
IF photoeye OR (temp<100) THEN...
expression1 XOR expression2 If photoeye1 and photoeye2 are BOOL tags and
your specification says: “If:
•
photoeye1 is on while photoeye2 is off or
•
photoeye1 is off while photoeye2 is on
then…"
IF photoeye1 XOR photoeye2 THEN...
BOOLtag := expression1 & expression2 If photoeye1 and photoeye2 are BOOL tags,
open is a BOOL tag, and your specification says:
“If photoeye1 and photoeye2 are both on, set
open to true”. open := photoeye1 & photoeye2;