Campbell-scientific CR9000X Measurement and Control System Instrukcja Użytkownika Pobierz pdf (Strona 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.

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.

Reply = Volt(1)

LOOP UNTIL Reply > 1 And Reply < 9

9-4

1 2 ... 329 330 331 332 333 334 335 336 337 338 339 ... 441 442

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