@ musashi5150 - nice one, if you do all you'll see is static copper "effect" at the moment = lame
@ heavy - maybe I'm missing something obvious, and if so I apologise, but I don't see what difference that would make to the cycling - there doesn't seem to be any problem referencing custom register offsets from the base in a5 in the code running in the interrupt... Can you explain further to help me understand?