Rockwell-automation 1747-PTxx Getting Started Guide for HHT Manual de usuario descargar pdf (Pagina 23)

Chapter 2

Control Basics

2–6

As we mentioned earlier, the program files you create contain the program

used for your controlling application. The programs are written in a

programming language called Ladder Logic. This name is derived from its

ladder–like appearance.

A ladder logic program consists of a number of rungs, on which you place

instructions. Instructions each have a data address associated with them and

based on the status of these instructions the rung is solved.

The figure below shows a simple 1–rung ladder program. The rung includes

two input instructions and an output instruction. Note, in the example below

each instruction has a name (Examine if Closed), a mnemonic (XIC), and an

address (I:1/0).

A simple rung, using bit instructions.

XIC

( )

O:3.0

] [

I:1.0

]/[

I:1.0

XIO OTE

Input Instructions Output Instruction

XIC = Examine if Closed

XIO = Examine if Open

Address I:1/0

Address I:1/1

Address O:3/0

OTE = Output Energize

True/False Status

The data file bits that these instructions are addressed to will be either a logic

0 (OFF) or a logic 1 (ON). This determines whether the instruction is

regarded as “true” or “false”:

The status of the instruction is

If the data file

bit is

XIC

Examine if Closed

] [

XIO

Examine if Open

]/[

OTE

Output Energize

( )

Logic 0 False True False

Logic 1 True False True

Ladder Logic Concepts

1 2 ... 18 19 20 21 22 23 24 25 26 27 28 ... 76 77

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