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

Got a question or comment?

Related Tutorials

Beginner

Opto 22 groov RIO Getting Started

The groov RIO module from Opto 22 has been released only a few months ago. The groov RIO is a feature packed piece of hardware that is easy to install, configure and deploy for many different field applications. The module comes pre-loaded with an array of software tools used across the industry and is ready to hit the floor running out of the box. Furthermore, the module is equipped with user configurable input and output nodes that have the capability unlike anything else on the market.

August 2, 2020
|
By
Vladimir Romanov
Beginner

Micro800 PLC Programming Getting Started

The Micro800 Control Systems by Rockwell Automation provide a cost effective solution for small to medium automation systems. The controllers within this family are typically used on stand alone machines or small process applications. The family offers five distinct controller types that are further customizable through add-on modules: Micro810, Micro820, Micro830, Micro850 and Micro870.Micro800 Programmable Logic Controllers Getting StartedUnlike the other Rockwell Automation controllers, this line of PLCs is programmed through a dedicated software: Connected Components Workbench. From within this tool, the programmer can flash the firmware, load the program and monitor the state of the controller. Furthermore, Connected Components Workbench (CCW) is often used to program other non-PLC Rockwell Automation devices such as Variable Frequency Drives (VFDs) and certain Safety Relays.

July 26, 2020
|
By
Vladimir Romanov
Beginner

An Introduction to DeviceNet Industrial Networks

In this tutorial you will learn about the DeviceNet industrial network, go over a basic offline configuration, and explore some advanced features.

July 24, 2020
|
By
Jacques Venter