Rockwell-automation 1772-LV Mini-PLC - 2/15 Programmable Controller (S Manual de usuario descargar pdf (Pagina 59)

Advanced Instruction Set

Chapter 6

62

Figure 6.1

Scan

Sequence

10150-I

Output

Image

Table

Input

Terminals

Input

Image

Table

Output

Terminals

Copy output image table status

into output terminal circuits.

Copy input terminal status into

input image table

Program Statement

Execute each program rung in

sequence, writing into bits in the

data table, including the output

image table.

( )

I/O

Scan

Program

Scan

Next, the CPU scans the program. It does this statement by statement. Each

statement is scanned in this way:

- First, for each condition, the CPU checks, or “reads,” the image table to

see if the condition has been met.

- Second, if the set of conditions has been met, the CPU writes a one into

the bit location in the output image table corresponding to the output

terminal to be energized. On the other hand, if the set of conditions has

not been met, the CPU writes a zero into the bit location, indicating that

the output terminal should not be energized.

1 2 ... 54 55 56 57 58 59 60 61 62 63 64 ... 214 215

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Rockwell-automation 1772-LV Mini-PLC - 2/15 Programmable Controller (S Manual de usuario Pagina 59