Folks, apologies if I'm preaching to the choir here, but as I read the original question, it implied to me that the OP thought there was a digital signal going between the throttle quadrant and the FADEC. (I may be reading the question wrong - if so feel free to ignore the rest...)
I found this gem in the transport canada report into SR111:
"The FADEC receives inputs from the engine throttle resolvers located below the central pedestal on the throttle levers. There is a dual-throttle resolver per thrust lever. The dual resolver contains two resolvers in one package driven by a single, common shaft. One resolver provides
TRA input to Channel A and the second to Channel B. The FADEC provides electrical excitation for the resolvers."
Generally, there is a permanant magnet alternator on the accessory drive gearbox which powers the fadec once you get the HP spool speed about some fairly low value. So as long as the engine is lit and nothing has snapped the wires between the throttles and the engine, move the lever and the engine will get the signal that you want something to change.
Hope that helps a little