Rockwell-automation 1771-DB BASIC MODULE Manual de usuario descargar pdf (Pagina 160)

100

101

Chapter

Statements

11 -8

Use the DO-UNTIL statement to set up loop control within a module

program. All statements between the DO and the UNTIL rel expr are

executed until the relational expression following the UNTIL statement is

true. You can nest DO-UNTIL loops.

The control stack (C-stack) stores all information associated with loop

control. The C-stack is 157 bytes long. DO-UNTIL loops use 3 bytes of

the C-stack.

Do not improperly exit this loop or a C-stack error occurs. See CLEARS

(page 11 -3).

Important: Excessive nesting exceeds the limits of the C-stack, generating

an error, and causing the module to enter Command mode.

For more information see control stack, page 8 -1.

Syntax

DO-UNTIL

rel expr

Example

Simple DO-UNTIL Nested DO-UNTIL

REM EXAMPLE PROGRAM

1 REM EXAMPLE PROGRAM

10 A=0

10 DO

20 DO

20 A=A+1

30 A=A+1

30 DO

40 PRINT A

40 C=C+1

50 UNTIL A=4

50 PRINT A,C,A*C

60 PRINT “DONE”

60 UNTIL C=3

70 END

70 C=0

RUN

80 UNTIL A=3

90 END

RUN

1 1 1

1 2 2

DONE

1 3 3

>READY

2 1 2

2 2 4

2 3 6

3 1 3

3 2 6

3 3 9

>READY

DO-UNTIL

1 2 ... 155 156 157 158 159 160 161 162 163 164 165 ... 393 394

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