Maybe my imagination isn't strong enough, but I don't see how a processor could work without being reducible to a series of instructions. The lowest level of "code" you give it might be more "functional", but there's a direct mapping between that and a sequence of states the processor goes through to actually do anything.
In looking for such a thing, I've seen http://en.wikipedia.org/wiki/SECD_machine and http://en.wikipedia.org/wiki/Graph_reduction_machine, but I'm not sure either of these fit your description. Do you have experience with them or another machine you could share?