Rockwell-automation 1771-N SERIES High Resolution Analog Module User M Bedienungsanleitung PDF herunterladen (Seite 33)

Chapter 3

Publication 1771ĆUM127B-EN-P - December 2002

Communicating With Your

Analog Module

In this chapter, we describe

• block transfer programming

• quick-startup sample programs for the PLC-3 and PLC-5

processors

• module scan time issues

Your module communicates with the processor through bidirectional

block transfers. This is the sequential operation of both read and

write block transfer instructions.

For the 1771-N series modules, block transfer writes (BTWs) can

perform two different functions.

If you want to: Description This type of BTW is called:

configure the module

This involves setting the bits which enable the

programmable features of the module, such as

scaling, alarming, real time sampling, etc.

the configuration BTW”

send data to the output channels

of those modules having outputs

This type of BTW is generally shorter in length

than the configuring BTW because it does not

configure the module each time it is initiated.

the output update BTW"

A configuration BTW is initiated when the analog module is first

powered up, and subsequently only when the programmer wants to

enable or disable features of the module.

An output update BTW is initiated when the programmer wants the

output channels on the module to change value. This shortened

version of the BTW allows faster response time from the output

channels.

The following example programs are minimum programs; all rungs

and conditioning must be included in your application program. You

can disable BTRs, or add interlocks to prevent writes if desired. Do

not eliminate any storage bits or interlocks included in the sample

programs. If interlocks are removed, the program may not work

properly.

Chapter Objectives

Block Transfer

Programming

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Rockwell-automation 1771-N SERIES High Resolution Analog Module User M Bedienungsanleitung Seite 33