Ok,just because you taught me some Essex slang which ill definitively use in the future,ill give a hint on the speed trim.
The speed trim needs the N1 info,otherwise how can it work? remember it is about speed stability,(low thrust-high speed--->stab trim gives nose up and high thrust-low speed--->speed trim sends info to the the stab trim to give nose down trim)
The EEC has that info,it uses it to control your engine thrust and provide that info toyour speed trim.