Ok, i'm pretty new to hardware and specifically, this is a hardware question.

I've got a 8051 controller that could be hooked up to one of two different power supplies or even both at the same time!

Both power sources are a nice regulated +5v. Is there a goodsafe way to handle the two "Vcc's" such that damage doesn't occur? I've spent like two days trying to picture some way to isolate both supplies or safely combine them if both are being used.

Thanks for any assistance!
Mike