-in your Special case (MaxNC controler board) the PIC is reading and handling the encorder, and only the PIC,
Mach3 knows nothing about this Encoder.
-in a good tuned stepper System it is normaly not necessary to use encoder's
-anyhow there there are stepper Motor drivers on the market witch can handle Encoders. then they are
closed Loop. Leadshine is only one example:
http://www.leadshine.com/ProductSubType.aspx?type=products&category=closed-loop-steppers&producttype=closed-loop-stepper-drives&subtype=general-closed-loop-stepper-drivesbut also here, only the stepper drives reads/handles the Encoder, not Mach3