Miprom 21 memory during power loss

I'm going to be removing all power from the final car on a 3 car mod. This is only for about 6-8 hours for sparky to do some work. Other than possibly going into fire service will I lose floor tables or have to re-initiate the drive? Is there even a battery backup on these systems? Thanks.

Should be fine. There is a battery backed Ram chip on the CPU. I’ve never lost a floor table from having power off that I can remember. When they go bad they’ll loose the floor table with the power on.

However, as a caveat to Dirts answer. If by chance you have an early analog Miprom, you can lose all the field programmable parameters, including the floor table, if you pull the main line without shutting down the CPU first. So to be safe dip the three switches's before flagging the dis-connect. This happens on analog units only.

I did not know that. You mean just the analog DC drive? This isn’t true of all the older model CPUs is it?

I have only had this happen on early analog units that were modded. They also had old-style dis-connect switches that were re-used. I think those old slow dis-connects had something to do with pulling out the programmable parameters. This would also happen after a power outage. Yes, they were DCV Analog Drive units.

Interesting

All parameters held. Thanks guys!

The older miproms with analog drives do not have a battery ram chip. They have a little 3volt nicad battery on top right corner of CPU. And if you got that setup, its at least 25yrs old. If you keep losing floor tables with power outages, buy a new battery and solder it in. The controller has no way of knowing how the power was shut off, with dips or disconnect. It makes no difference if you flip the dips if battery is bad. The newer 21s with digital drive stepped up the CPU to the ram chip setup