beautypg.com

Considerations for add-on instructions, Instruction functionality, Encapsulation – Rockwell Automation Logix5000 Controllers Add-on Instructions Programming Manual User Manual

Page 22

background image

Chapter 1

Designing Add-On Instructions

The Instruction Help Preview shows how your instruction will appear in the

various languages, based on parameters defined as required or visible.

When deciding whether to develop an Add-On Instruction, consider the

following aspects.

Instruction functionality

Complex instructions tend to be highly application specific and not reusable, or

require extensive configuration support code. As with the built-in instructions,

Add-On Instructions need to do one thing, do it well, and support modular
coding. Consider how the instruction will be used and manage interface

complexity for the end user or application.

Add-On Instructions are best at providing a specific type of functionality or device

control.

Encapsulation

Add-On Instructions are designed to fully encapsulate the code and data

associated with the instruction. The logic inside an Add-On Instruction uses only

the parameters and local tags defined by the instruction definition. There is no

Considerations for Add-On

Instructions

22

Rockwell Automation Publication 1756-PM010F-EN-P - October 2014