1. A system comprising: a controller unit; a controlled unit; and an interface unit; wherein the controller unit is coupled to the controlled unit through the interface unit; wherein the interface unit is operable to receive a first signal from the controller unit, a second signal corresponding to the first signal, from the controlled unit, and data originating from the controlled unit; wherein the interface unit includes a programmable delay element which is operable to receive a delay value; wherein the interface unit is further operable to generate an enable signal, and to conditionally propagate the second signal based on the enable signal; wherein the enable signal is generated from the first signal, using: the second signal; the programmable delay element; and the delay value; and wherein for a number of preferred delay values, said conditionally propagating the second signal results in a qualified second signal.