Rockwell Automation Publication 1756-RM003N-EN-P - October 2011 693
Structured Text Programming Appendix C
REPEAT…UNTIL
Use the REPEAT…UNTIL loop to keep doing something until conditions are
true.
Operands:
Structured Text
Description: The syntax is described in the table.
Operand Type Format Enter
bool_
expression
BOOL Tag
expression
BOOL tag or expression that evaluates to a
BOOL value (BOOL expression)
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.
REPEAT
<statement>;
UNTIL bool_expression
REPEAT
<statement>; statements to execute while bool_expression1
is false
Optional IF bool_expression2 THEN
EXIT; If there are conditions when you want to exit
the loop early, use other statements, such as an
IF...THEN construct, to condition an EXIT
statement.
END_IF;
UNTIL bool_expression1
END_REPEAT;
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