Campbell Scientific CR9000X Measurement and Control System - Manual (Page 334)

Section 9. Program Control Instructions
Syntax 2 Do
[statementblock]
[ Exit Do ]
[statementblock]
Loop [{ While or Until } condition]
Remarks
While or Until with corresponding condition, and Exit Do are not required. If
none of these are used, the Do .. Loop will continue indefinitely.
The Do...Loop statement has these parts:
Part Description
Do Must be the first statement in a Do...Loop control structure.
While Indicates that the loop is executed while condition is true.
Once the condition is false, the loop will be exited.
Until Indicates that the loop is executed while condition is false.
Once the condition is true, the loop will be exited.
condition Numeric expression that evaluates true (nonzero) or false (0
or Null).
statementblock Program lines between the Do and Loop statements that are
repeated while or until condition is true.
Exit Do Only used within a Do...Loop control structure to provide
an alternate way to exit a Do...Loop. Any number of Exit
Do statements may be placed anywhere in the Do...Loop.
Often used with the evaluation of some condition (for
example, If...Then), Exit Do transfers control to the
statement immediately following the Loop. When
Do...Loop statements are nested, control is transferred to the
Do...Loop that is one nested level above the loop in which
the Exit Do occurs.
Loop Ends of the Do...Loop structure.
Do...Loop Statement Example
The example creates an infinite Do...Loop that can be exited only if Volt(1)
is within a range.
Dim Reply
'Declare variable.
DO
Reply = Volt(1)
If Reply > 1 And Reply < 9 Then 'Check
range.
EXIT DO 'Exit Do Loop.
End If
LOOP
Alternatively, the same thing can be accomplished by incorporating the range
test in the Do...Loop as follows:
Dim Reply 'Declare variable.
DO
Reply = Volt(1)
LOOP UNTIL Reply > 1 And Reply < 9
9-4