Omron CX-PROGRAMMER 5.0-FUNCTION BLOCK OPERATION - Page 169

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Structured Text (ST Language) Specifications Appendix B
Usage
Use the REPEAT statement to repeat processing for as long as a condition is met after specified processing,
when the number of iterations is undetermined beforehand (depends on whether the condition is met). This
statement can be used to determine whether to repeat processing according to the results of specified pro-
cessing execution (post-test loop).
Description
The expression will execute the first time without a condition. Thereafter, the condition equation will be evalu-
ated. If the condition is false, the expression will be executed again. If the condition is true, processing will end
without executing the expression.
Precautions
• REPEAT must be used together with END_REPEAT.
• Even if the condition equation is true before the expression has been executed, the expression will be exe-
cuted.
• Statements that can be used in the expression are assignment statements, IF, CASE, FOR, WHILE, or
REPEAT.
• Multiple statements can be executed in the expression. Be sure to use a semicolon (;) delimiter between
multiple statements in an expression.
• The condition can also be specified as a boolean variable (BOOL data type) only rather than an equation.
Examples
Example 1: Numeric values from 1 through 10 are incremented and the total is substituted for the variable
TOTAL.
A:=1;
TOTAL:=0;
REPEAT
TOTAL:=TOTAL+A;
A:=A+1;
UNTIL A>10
END_REPEAT;
EXIT Statement
Summary
This statement is used within iteration statements (FOR, WHILE, REPEAT) only to force an iteration statement
to end. This statement can also be used within an IF statement to force an iteration statement to end when a
specified condition is met.
Reserved Words
EXIT
Statement Syntax (Example: Using within IF Statement)
FOR (WHILE, REPEAT) expression
...
IF <condition> THEN EXIT;
END_IF;
...
END_FOR (WHILE, REPEAT);
Usage
Use the EXIT statement to force iteration processing to end before the end condition is met.
Description (Example: Using within IF Statement)
When the condition equation is true, the iteration statement (FOR, WHILE, REPEAT) is forced to end, and any
statements after EXIT will not be executed.