Rockwell Automation Publication 1756-RM003N-EN-P - October 2011 691
Structured Text Programming Appendix C
The following diagrams show how a WHILE...DO loop executes and how an
EXIT statement leaves the loop early.
Arithmetic Status Flags: Not affected
Fault Conditions:
Example 1:
While the bool_expression is true, the controller
executes only the statements within the WHILE…DO
loop.
To stop the loop before the conditions are true, use an EXIT
statement.
Statement 1
Statement 2
Statement 3
Statement 4
…
Exit ?
BOOL expression
True
False
Rest Of The Routine
Yes
No
Statement 1
Statement 2
Statement 3
Statement 4
…
BOOL expression
True
False
Rest Of The Routine
A major fault will occur if Fault type Fault code
The construct loops too long 6 1
If you want this Enter this structured text
The WHILE...DO loop evaluates its conditions first. If the conditions
are true, the controller then executes the statements within the loop.
This differs from the REPEAT...UNTIL loop because the
REPEAT...UNTIL loop executes the statements in the construct and
then determines if the conditions are true before executing the
statements again. 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 := 0;
While ((pos <= 100) & structarray[pos].value <> targetvalue)) do
pos := pos + 2;
String_tag.DATA[pos] := SINT_array[pos];
end_while;
To Next Page
Loading...
Need help?
General
