I have recently started using Allen-Bradley’s Micro820 PLC for simple machines that only have a couple dozen I/O and uncomplicated programming routines. On my very first system which used 5% of the user memory and very little ladder I would occasionally get fatal errors that I had to log on to clear. It was a fault code 0xF000 which is described as “The controller was reset due to a noisy environment or an internal hardware failure”. The odd thing was that this controller was set-up on my workbench with no possible interference in the area. The fault could be two days between occurrences. I replaced the controller, and the fault went away for good. That is until I sold three more units, now I am getting the same fault code on a different unit with no logical explanation. My only question is, is anyone else having “noisy environment” faults code 0xF000 with the Micro820 controller?