Rockwell-automation 1771-DB BASIC MODULE Manual de usuario descargar pdf (Pagina 161)

100

101

Chapter

Statements

11 -9

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

program. This statement is similar to the DO-UNTIL rel expr (page

11 -8). All statements between the DO and the WHILE rel expr are

executed as long as the relational expression following the WHILE

statement is true. You can nest DO-WHILE statements.

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

control. The C-stack is 157 bytes long. DO-WHILE 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. An error

occurs and the module enters Command mode. For more information see

control stack, page 8 -1.

Syntax

DO-WHILE

rel expr

Example

Simple DO-WHILE Nested DO-WHILE

>10

10 A=0 : C=0

20 A = A + 1

20 DO

30 PRINT A

30 A=A+1

40 WHILE A < 2

40 DO

50 END

45 C=C+1

READY >

50 PRINT A,C,A*C

RUN

60 WHILE C<>3

70 C=0

80 WHILE A<4

90 END

READY

RUN

1 1 1

1 2 2

1 3 3

2 1 2

2 2 4

2 3 6

3 1 3

3 2 6

3 3 9

4 1 4

4 2 8

4 3 12

DO-WHILE

1 2 ... 156 157 158 159 160 161 162 163 164 165 166 ... 393 394

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