Rockwell Automation Logix5000 Controllers Structured Text Programming Manual - Manual (Page 28)

28 Publication 1756-PM007D-EN-P - November 2012
Chapter 1 Program Structured Text
FOR…DO Use the FOR…DO loop to do something a specific number of times before
doing anything else.
Operands:
Structured Text
Operand Type Format Description
count SINT
INT
DINT
Tag Tag to store count position as the
FOR…DO executes
initial_ value SINT
INT
DINT
Tag
Expression
Immediate
Must evaluate to a number
Specifies initial value for count
final_ value SINT
INT
DINT
Tag
Expression
Immediate
Specifies final value for count, which
determines when to exit the loop
increment SINT
INT
DINT
Tag
Expression
Immediate
(optional) Amount to increment count
each time through the loop
If you don’t specify an increment, the
count increments by 1.
FOR count:= initial_value TO final_value BY
increment DO
<statement>;
END_FOR;
IMPORTANT
Make sure that you do not iterate within the loop too many times in a single
scan.
• The controller does not execute any other statements in the routine until
it completes the loop.
• If the time that it takes to complete the loop is greater than the
watchdog timer for the task, a major fault occurs.
• Consider using a different construct, such as IF...THEN.