Click here to learn the biblical way to get to heaven! (The most important page on this site)

Disclaimer: This document is written in the hope that you can utilize for your own education to gain knowledge of PLC systems (should you decide to utilize this document). Although I believe the information in this document to be accurate, it is YOUR responsibility to verify this information before implementing it in any way, especially when damage to personnel or equipment could result. By continuing to read this document, you agree to hold no one who writes, modifies, or distributes this document liable in any way (even negligence). Due to the wide variety of plant applications, some of the examples in this document may be prohibited at your location, or could cause damage to equipment, or harm personnel.
[Visit my Church Website] -- [Return to Index Page] -- [View Training Courses] -- [Contact ATI for Training] *Copyright 2005
Author: Ricky Bryce (Montgomery County, IL)
VPS Hosting Referral Code MJDCDJYou can have your very own virtual server though VPSLink! Using REFERRAL code MJDCDJ you will receive a 10% discount on your new account, and I will get a service credit on my account. My personal preference is the Link 2 package running XEN for starting out (You can upgrade any time). You can choose from a variety of Linux distributions such as CENTOS, Fedora, Debian, and Ubuntu. This is a great package for learning Linux, and setting up your own web page, or email server.

Initiating a message instruction from the PLC to read a value from a ControlLogix processor.



In this example, the PLC-5 will initiate a message read instruction to read a value from the ControlLogix processor. There are several steps involved in this process:



A: The PLC initiates a message read instruction to read a value from what it believes to be another PLC-5 processor. The PLC-5 does not have the ability to directly read a controller tag in the ControlLogix processor.


B: The 1756-DHRIO module must be configured to map any messages received to slot 0 (for this example) because that is where the processor resides.


C: Since the ControlLogix processor does not support the PLC-5 data table structure, it must map all messages from a legacy PLC/SLC file number to an array in it's controller tag database.







  1. In the PLC-5, create a self-running timer.





  1. Create a Control file for the message instruction to operate. Do do this, Right click on the data file folder and create a new data file as shown.




  1. Next, Right click on the N7 Data file, and go to the file properties. We are going to expand the data table so we have a place for the message instruction to store data. Give yourself 10 elements. This should be plenty of space for future use in our classroom.




  1. Now, write the message instruction as shown. Then the Setup Screen will appear


  2. Next configure the message instruction similar to what is shown below:





  1. In the RSWho Screen, locate the 1756-DHRIO module. Right click on the module, and go to 'Module Configuration'. Be sure the processor is set to Slot 0.




  1. In the ControlLogix procesor, we must create an array that simulates the N7 integer file in a PLC5. Go to the Controller tag database, and add a tag as shown.






  1. .Next, this array must be mapped to file 7. When the ControlLogix receives a request for file 7, it will then know to go to MyInteger array to get the data. To set up this mapping, click Logic on the menubar in RSLogix 5000, then choose 'Map PLC/SLC Messages'. Set up the mapping as shown, then download your work and ensure the logic is working properly.