Each piece of GN&C; hardware is hard-wired to one of eight flight-critical multiplexers/demultiplexers, which are connected to each of the five GPCs by data buses. Each GPC is assigned to command on one or more data buses; assignments can be changed.

A sensor, controller or flight control effector cannot be assigned or rerouted to another MDM during flight, but the MDM it is wired to can be assigned to a different GPC. Each multiple unit of each type of GN&C; hardware is hard-wired to a different MDM. For example, there are four accelerometer assemblies on board the orbiter. AA 1 is wired to forward flight MDM 1 and is part of string 1, AA 2 is wired to FF MDM 2 on string 2, AA 3 is wired to FF MDM 3 on string 3, and AA 4 is wired to FF MDM 4 on string 4.