Delta-electronics Extension Digital I/O Module DOP-EXIO14RAE Instrukcja Użytkownika Pobierz pdf (Strona 92)

Appendix D Use of Application Instructions|DOP-EXIO Series

Revision March, 2008, Doc. Name: 2007PDD23000014 D-11

Mnemonic Operands Function

FOR

Start of a FOR-NEXT Loop

Bit Devices Word Devices

X Y M S K H KnX KnY KnM KnS T C D E F

          

y Note:

1. No contact to drive the instruction is required.

16-bit instruction (3 Steps)

FOR

Continuous

execution

- -

32-bit instruction

- - - -

y Flags: None

Operands:

: The number of repeated nested loops

Mnemonic Operands Function

None End of a FOR-NEXT Loop

Bit Devices Word Devices

X Y M S K H KnX KnY KnM KnS T C D E F

y Note:

1. No operand.

2. No contact to drive the instruction is required.

16-bit instruction (1 Step)

Continuous

execution

- -

32-bit instruction

- - - -

y Flags: None

Explanations:

1. FOR instruction indicates FOR ~ NEXT loops executing back and forth N times before escaping

for the next execution.

2. N = K1 ~ K32,767. N is regarded as K1 when N ≤ 1.

3. When FOR~NEXT loops are not executed, the user can use the CJ instruction to escape the

loops.

4. Error will occur when

a) NEXT instruction is before FOR instruction.

b) FOR instruction exists but NEXT instruction does not exist.

c) There is NEXT instruction after FEND or END instruction.

d) The number of instructions between FOR ~ NEXT differs.

5. FOR~NEXT loops can be nested for maximum five levels. Be careful that if there are too many

loops, the increased PLC scan time may cause timeout of watchdog timer and error. Users can

use WDT instruction to modify this problem.

Program Example 1:

After program A has been executed for 3 times, it will resume its execution after NEXT instruction.

Program B will be executed for 4 times whenever program A is executed once. Therefore, program B

will be executed 3 × 4 = 12 times in total.

1 2 ... 87 88 89 90 91 92 93 94 95 96 97 ... 156 157

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