repeat_until

Use the repeat_until loop to continue performing an action until conditions are true.

Operands

REPEAT

<statement>;

Structured Text

Operand	Type	Format	Enter
bool_ expression	BOOL	Tag expression	BOOL tag or expression that evaluates to a BOOL value (BOOL expression)

IMPORTANT:

Do not iterate within the loop too many times in a single scan.

The controller does not execute other statements in the routine until it completes the loop.

A major fault occurs when completing the loop takes longer than the watchdog timer for the task.

Consider using a different construct, such as if_then.

Description

The syntax is:

The following diagrams show how a repeat_until loop executes and how an exit statement leaves the loop early.

While the bool_expression is false, the controller executes only the statements within the repeat_until loop.

To stop the loop before the conditions are false, use an exit statement.

Affects Math Status Flags

Fault Conditions

A major fault will occur if:	Fault type	Fault code
The construct loops too long	6	1

Example 1

If performing this:	Enter this structured text:
The repeat_until loop executes the statements in the construct and then determines if the conditions are true before executing the statements again. This differs from the while_do loop because the while_do the while_do loop evaluates its conditions first. If the conditions are true, the controller then executes the statements within the loop. The statements in a repeat_until loop are always executed at least once. The statements in a while_do loop might never be executed.	pos := -1;
	REPEAT
	pos := pos + 2;
	UNTIL ((pos = 101) OR (structarray[pos].value = targetvalue))
	end_repeat;

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