1. A method of operating an electronic system at a plurality of supply voltage levels without level shifting individual data signals, comprising: partitioning the system into a plurality of discrete voltage domains, the voltage domains interconnected by one or more data transfer buses; setting the supply voltage of a first voltage domain and second voltage domain equal or nearly equal for a first duration, during which the first and second voltage domains are connected in data transfer relationship via a bus; and setting the supply voltage of the first voltage domain to a different level than that of the second voltage domain for a second duration, during which the first and second voltage domains are electrically isolated from each other.