Patent ID: 8856558

Claim:
An electronic apparatus having stand-by mode, comprising: a first circuit having a plurality of first power supply modes, and comprising an interface and transferring data to an external device; a second circuit having a plurality of second power supply modes, and comprising a processor and a first register; and a third circuit, comprising a second register, wherein when the second circuit is powered on: the processor sets the first circuit with one of the first power supplying modes; the first register stores the one of the first power supplying modes; and the third circuit sets the second circuit with one of the second power supplying modes; and wherein when the second circuit is powered off: the processor sets the second register before the second circuit is powered off, such that the second register stores another of the first power supplying modes and another of the second power supply modes; and the third circuit sets the first circuit with the another of the first power supplying modes and sets the second circuit with the another of the second power supplying modes.