Overview of Structured Text Programming
Rockwell Automation Publication MOTION-RM002H-EN-P-February 2018 653
Leaves the step of an SFC if you configure the SFC for Automatic reset. (This
applies only if you embed the assignment in the action of the step or use the action
to call a structured text routine via a JSR instruction.)
Use the FOR_DO loop to do something a specific number of times before doing
anything else.
Operands
FOR count:= initial_value TO
final_value BY increment DO
<statement>;
END_FOR;
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.
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.
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