A portable electronic device operable in an active mode or an inactive mode comprises a first device operating system (109) for performing device operating functions during the active mode but not the inactive mode and a second device operating system (121) for performing device operating functions during both the active mode and the inactive mode. The first device operating system (109) includes a CPU (111) integrated on a first integrated circuit with a first timing circuit (148) for providing a first timing signal. The second device operating system (121) includes a second timing circuit (134) for generating a second timing signal during at least the inactive mode and being integrated on a second integrated circuit, and a power control circuit (128) coupled to receive the second timing signal for generating a first control signal for deactivating the first device operating system (109) for the inactive mode and for generating a second control signal for activating the first device operating system (109) for the active mode.