Control logix Processor Losing Program


Thread Starter

Vijay Bharadva

I am using 1756-L61 processor in one of our machine. It is loosing the program on its own. I checked the battery healthiness and found Ok. What should be the possible reason to happen this ? Is there any suggestion to prevent this ?

If anybody knows please email me on vijay.bhardava [at]

David Ferguson

There is a known issue with I think "Admul" (spelling) chip processors. Go to knowledgebase and search for your issue, there was a recal. It also appears that if anything in the rack has that chip, could cause this.

Not sure if this is your issue or not.......

Dave Ferguson
Is the processor faulting? If so, can you go online with the processor? Or as soon as you try to go online does it only allow you to download??

If you expect other people to take the time to write a response, maybe you can take a few minutes of your precious time, to provide a detailed description.

AB has had similar issue with the L55 series. A buffer over flow would cause a "fatal fault" and drop the program. This was caused by a hardware malfunction. If I remember correctly the OK light would flash red when it encountered a fatal fault.
I agree; the first thing to rule out is the 2007 "Atmel 64" issue, in which a bad batch of backplane bridge chips caused a large number of unrecoverable processor faults.

You need to fully read and understand two Rockwell Automation technical documents from the RA Knowledgebase: Answer ID # 40149 and Answer ID # 41204

It's certainly possible for something else to be causing this, like high voltage transients or electrostatic discharge, but you should get the obvious possibilities out of the way first.

bob peterson

Your best bet is to get in touch with Rockwell tech support, or search the knowledge base there. They will be able to help you if it is osme kind of known problem. if not a known problem, they can help you run down what it is.
I am having similar problems with our AB Make PLC5/40 (Ethernet) Processor Modules. Exactly similar phenomenon. But this happens almost once a year (I would put it as very rare). I have contacted Rockwell Automation and their suggestion is to upgrade the processor EPROMs. It is more like a flash program upgrade. In some cases (depends on the family of processors) you can do it by getting the right version (latest) of the software and use the Flash utility to upgrade the EEPROMs and in others you need to procure EPROM chips form AB/Rockwell and install them on the processor board. Upgrades are not for free. Does this solve the problem? I am not too sure about it and neither AB/Rockwell !!!
I have had this problem before. Flash upgrading the firmware in the CPU did resolve the problem. You can find instructions on how to do this on Rockwell's website.