> The interrupt at $0038 isn't directly useful but the fact that the programmers > allowed for a jump to ram if certain conditions were met. This allows us to > take advantage of it. The NMI is not useful to us because (a) 66h is in the > mddle of the normal interrupt routine, and (b) nothing is wired to trigger it. Sure, but what's at $66? Are you saying that the calc doesn't use it?