Cyclone III Reset with unrelated HV pulses

We had a board quite some time ago, whose make up sounds similar, that suffered similar problems. For cost reasons we had our high tension circuitry on the same board as the FPGA - albeit a FLEX10K device. The device repeatedly lost it's configuration depending on the high tension input signal.

After much investigation we separated the circuitry over two boards, added more filtering and yet more protection and the problem went away.

The only explanation offered at the time was RF interference - something that never sat very well with me - but who was I to say 'absolutely not'. The only additional evidence to defend my stance was, no matter how close we placed the two boards in our new solution, we never saw the FPGA lose it's configuration.

Cheers,

Alex