https://www.icas.org/icas_archive/IC...PAPERS/605.PDF Here's an interesting document that goes into this stuff, but at a super high level. I've taken the relevant part for this discussion, the simplified (hah!) diagrams of the C* and C*U laws. There's some extraneous stuff in there, but I added some explanations in green, as well as the arrows representing what happens as a result of the elevator position, feeding back toward the detectable parameters by sensors on the airplane, that actually forms it into a loop.
Notice the Boeing one is the same as the Airbus one, with the addition of (Vcas)ref (the trim airspeed set by the trim switch on the yoke), being compared to Vcas (the actual airspeed)... and then that feeds in to the rest to be subtracted against and the difference zeroed out. (Also note that "q" here means not dynamic pressure, but pitch rate.)
