Book Image

Mastering PLC Programming

By : Mason White
Book Image

Mastering PLC Programming

By: Mason White

Overview of this book

Object-oriented programming (OOP) is a new feature of PLC programming that has taken the automation world by storm. This book provides you with the necessary skills to succeed in the modern automation programming environment. The book is designed in a way to take you through advanced topics such as OOP design, SOLID programming, the software development lifecycle (SDLC), library design, HMI development, general software engineering practices, and more. To hone your programming skills, each chapter has a simulated real-world project that’ll enable you to apply the skills you’ve learned. In all, this book not only covers complex PLC programming topics, but it also removes the financial barrier that comes with most books as all examples utilize free software. This means that to follow along, you DO NOT need to purchase any PLC hardware or software. By the end of this PLC book, you will have what it takes to create long-lasting codebases for any modern automation project.
Table of Contents (25 chapters)
1
Part 1 – An Introduction to Advanced PLC Programming
6
Part 2 – Modularity and Objects
10
Part 3 – Software Engineering for PLCs
14
Part 4 – HMIs and Alarms
19
Part 5 – Final Project and Thoughts

Getting to know enums

Similar to a struct, an enumeration is also a user-defined data type that is composed of comma-separated values. These values are predefined constants. Essentially, when a value in an enumeration is set, it cannot be changed. As such, enumerations are excellent tools for defining threshold limits, motor speeds, temperature values, and more. You declare an enumeration with the same wizard that we used to declare a struct, so be sure to view Figure 4.12.

For this example, create an enum name, motorSpeeds, using the same DUT wizard as before but by checking Enumeration as opposed to Structure, and leaving Textlistsupport unchecked. Once the code is generated, you can remove the enum_member attribute that is auto generated. Once that is done, modify the code to match the following:

{attribute 'qualified_only'}
{attribute 'strict'}
TYPE motorSpeeds :
(
     maxSpeed := 2000,
     minSpeed ...