Overview of Structured Text Programming 
 
648  Rockwell Automation Publication MOTION-RM002H-EN-P-February 2018 
 
Use IF_THEN to do something if or when specific conditions occur. 
Operands 
IF bool_expression THEN 
<statement>; 
Operand  Type  Format  Enter 
Bool_ 
expression 
BOOL  Tag expression  BOOL tag or expression that evaluates to a BOOL value 
(BOOL expression) 
Description 
The syntax is described in the table. 
 
To use ELSIF or ELSE, follow these guidelines. 
To select from several possible groups of statements, add one or more ELSIF 
statements. 
Each ELSIF represents an alternative path. 
Specify as many ELSIF paths as you need. 
The controller executes the first true IF or ELSIF and skips the rest of the ELSIFs 
and the ELSE.