Rockwell Automation Logix5000 Controllers Structured Text Programming Manual - Manual (Page 34)

34 Publication 1756-PM007D-EN-P - November 2012
Chapter 1 Program Structured Text
REPEAT…UNTIL Use the REPEAT…UNTIL loop to keep doing something until conditions
are true.
Operands:
Structured Text
Description: The syntax is:
Operand Type Format Enter
bool_
expression BOOL Tag
Expression
BOOL tag or expression that evaluates to
a BOOL value (BOOL expression)
REPEAT
<statement>;
UNTIL bool_expression
END_REPEAT;
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.
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;