X/Y nozzle offset calibration and printing

Are the x/y nozzle offsets a firmware function? Does the gcode expect separate axes for the two nozzles? I ask because I’m trying to set up a profile in Simplify3D 5.0 and want to be able to use the Artisan’s built-in calibration. Simplify3D does have the capability to treat each nozzle independently w.r.t. origin, e.g. the same x,y coordinates work for both nozzles to print in the same place on the bed.