How to clear a SLC-500 controller's memory and reset it to factory defaults.

In the SLC-500 family of controllers there are three different ways memory is backed up, and therefore three different ways to clear memory and reset the controller to factory defaults.

NOTE: Always upload and save any SLC-500 controller program you need prior to erasing the controller's memory.

Case 1) The SLC-5/03, 5/04, and 5/05

These three controllers have a built-in capacitor which is designed to keep the controller's memory powered for roughly thirty minutes.

This means if you simply disconnect the controller's battery, and wait over thirty minutes (actual time is based on a number of factors,) the memory on the controller will be erased.

That said, Rockwell also provides two connections on the controller board which you can short together for 60 seconds to drain the memory capacitor and clear the controller's memory.

These two connections are labeled as GND and VBB, and as shown below they're in slightly different positions depending on if you have a SLC-5/03, 5/04, or 5/05:

SLC-5/03 Memory Capacitor Connections

SLC-5/04 Memory Capacitor Connections

SLC-5/05 Memory Capacitor Connections

Case 2) The SLC-5/01 – 4K, and 5/02

Neither the SLC-5/01 4K model, nor the SLC-5/02, have a program backup capacitor.

This means that if you remove the controller's battery while these controllers are unpowered, the memory on the controllers will be erased.

Case 3) The SLC-5/01 – 1K, and Fixed Models

Both the SLC-5/01 1K model, and the Fixed SLC-500 series, have capacitor backed memory.

The capacitor was designed to keep these controller's memory powered for between 5 and 30 days (depending on ambient temperature.)

Rockwell also doesn't make connections available to drain these capacitors, so the only way to clear the memory on these units would be to leave them unpowered for the 5 to 30 days.

Conversely, if you can communicate to the controllers you may wish to just download a new blank program to them rather than wait for the capacitor to drain.

I hope today's article about how to reset SLC-500 controllers to factory defaults was helpful.

If you have any questions, comments, or suggestions, please feel free to post the by clicking on the “Click here to post a comment or question” link below.


Shawn Tierney
Automation Instructor and Blogger

Enjoy the benifits of membership! Insider news, rewards, & more:
If you enjoyed my article, you may like my courses at
Have a question on this topic? Click here to scroll down to the comment link
Have a news tip? Share it with us here

Shawn Tierney

Shawn began sharing automation news and know-how online in 1996 when he launched his first BBS. Then in 1999 he moved to the internet launching, which he later renamed In 2013 he moved his automation efforts to a new website,, which has since become the most popular independent industrial automation blog on the web.

Latest posts by Shawn Tierney (see all)

Click HERE to scroll down to view or leave comments

The Automation Blog's SLC-500 Library

Cables and Adapters
Connecting HMIs
Learning and Discussion:

Leave A Blog Reply Here

Please enter your blog comment!
Please enter your name here