Back to tutorials
Beginner

PLC Programming Fundamentals – XIO Instruction

By
Vladimir Romanov
|
July 17, 2018
Table of Contents

Introduction

The XIO, also known as Examine If Open, instruction perform the function opposite to the XIC (Examine if Closed). It’s a fundamental instruction for working with Programmable Logic Controllers (PLCs). This instruction can be found on the left side of a ladder logic rung and will evaluate to true if the specified bit is set to a LOW state. If that’s the case, the instruction will allow the rest of the rung to execute.

Example & Usage of XIO

Here’s a real-world scenario of an XIO instruction:

  1. A Micrologix 1100 Allen Bradley PLC is used to control a process.
  2. A normally open push button (“System Stop”) is connected to Input 1 (I0/1 of the PLC).
  3. An operator presses the stop button.
  4. The XIO instruction is tied to I0/1.
  5. The XIO instruction evaluates to FALSE while the button is pressed.
  6. The XIO instruction evaluates to TRUE while the button is released.

Programming example in RSLogix 500:

XIO Examine if Open Instruction in RSLogix 500

Outcome:
The XIO will stop the process when the momentary push button is pressed by the operator.

Data Types Allowed for XIO

The XIO instruction will work with the following data types within the RSLogix 500 environment:

  • Boolean – The XIO may only evaluate TRUE/FALSE or 1/0 or HIGH/LOW.

Important Notes

  • Note 1 – The XIO instruction was initially used to evaluate the status of inputs landed on the PLC. However, it may be used on any boolean within the program. In other words, it can examine if any boolean within the program is energized. This makes the XIO instruction powerful and versatile.

Video Tutorial

Back to tutorials

Related Tutorials

Intermediate

HMI Software - Different Tools, Applications and Solutions to Meet Your Needs

HMI Software is commonly referred to as the development application that will be used to create the runtime application for an HMI terminal. It’s important to understand this distinction as we will be going over the HMI development environments used by PLC and HMI programmers to create the screens rather than the end-user applications you will see at the plant level.Numerous HMI programming software solutions are found on the market. Although they aim to achieve the same result, different packages have a distinct advantage over others in terms of price, reliability, ease-of-use and technical capability. It is therefore possible to find the right solution that will fit your specific application if you spend the time to research all options.

September 25, 2020
|
By
Vladimir Romanov
Intermediate

PLC Programming Example Project - Batching Tank Ladder Logic PLC and HMI Tutorial

Generally speaking, there are two types of processes in manufacturing: discrete and analog. A discrete process is a manufacturing methodology that will produce separate widgets. In other words, a production line may output one item, two items, three items, etc. An analog production process is where the plant will create a quantity of product that is quantifiable by weight. Examples include the production of beverages, sauces, raw ingredients, etc. Although it is possible to design a flow that will continuously output the product, such production is often managed in batches. It is important to note that although batches are considered to be analog or continuous flow, most of them end up being packaged for consumption which converts them into a discrete manufacturing process.

September 14, 2020
|
By
Vladimir Romanov
PLC Programming Career

PLC Programming Certification - Complete Guide

You may choose to pursue a traditional college degree, learn through online tutorials, or take a course that will issue a plc programming certification upon completion. However, what is the best option, and what are the best PLC programming certifications?

August 6, 2020
|
By
Vladimir Romanov