In this article we’ll look at converting SLC-500 programs to MicroLogix, including how to address two common errors.

Step 1) Start by opening RSLogix 500. In this example we open the SLC-500 sample program, IC500DMO.RSS:

NOTE: You can’t open and convert SLC-500 programs using RSLogix Micro

Step 2) Next, let’s take a look at the I/O Configuration of the sample program. It shows a 1746-IA4, IA8, and OA8:

Step 3) Before we make any changes, let’s save the existing SLC-500 program with a new name:

Step 4) Now we’ll open Controller Properties by double-clicking on it:

Step 5) In controller properties we’ll select a MicroLogix. In this case I choose a 1400:

Step 6) I’ll then click on OK on the confirmation screen:

Step 7) After the program is changed, you may see errors that need to be addressed. The two most common errors are “missing I/O” and “OSR” instructions:

Step 8) The reason for the missing I/O is that in the conversion all of the old SLC-500 I/O modules were removed:

Step 9) The easy way to resolve the missing I/O issue would be to add those I/O modules back in as we’ll do below. However, another solution would be to search and replace the old I/O addresses with the addresses of the embedded I/O:

Step 10) With the missing I/O replaced and the project verified again, we see all the the I/O error messages has been resolved. This leaves us with only “OSR” errors:

Step 11) The easiest way to resolve the OSR errors is to replace them with ONS instructions:

Step 12) To do so you can search and replace, or edit each line of code by double-clicking on the left side of the rung:

Step 13) Either way, the goal is to replace the OSR instructions with ONS instructions:

Step 14) Once done and re-verified, these errors will be eliminated from the error list:

If you’d like to watch a video of the above, check out Episode 24 of The Automation Minute Season 4 below:


If you have a comment or question you’d like to post, click on the “post a comment or question” link below.

And if you this article helpful and would like to support my work, you can pledge $1 a month at Automation.Locals.com and in return receive $3 in free downloads of my sample code, videos, and articles 😉

Until next time, Peace ✌️ 

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Shawn M Tierney
Technology Enthusiast & Content Creator

Eliminate commercials and gain access to my weekly full length hands-on, news, and Q&A sessions by becoming a member at The Automation Blog or on YouTube. You'll also find all of my affordable PLC, HMI, and SCADA courses at TheAutomationSchool.com.

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