Abstract: Methods for activating operations of a communication device coupled to an external communication bus include detecting a communication event on the external communication bus at a wake up circuit while a host controller coupled to the external communication bus is in an inactive state. An interrupt signal is provided to a processor of the communication device that is operating using a first clock signal running at a first clock rate from a first clock responsive to detection of the communication event by the wake up circuit. A clock enable signal is provided from the processor of the communication device, responsive to the interrupt signal, to a second clock in an inactive state. The second clock is coupled to a second circuit of the communication device separate from the processor of the communications device. Active state operations of the second clock are initiated to generate a second clock signal at a second clock rate greater than the first clock rate responsive to the clock enable signal.

Abstract: A method and apparatus for initializing a radio transmission apparatus comprising a voltage control oscillator, a phase lock loop, and a power amplifier is disclosed so as to avoid generating unwanted interference in neighboring radio channels. First, the voltage control oscillator is enabled and the phase locked loop is switched from a narrow band mode to a wide bandwidth mode to give faster settling time and reduced overshoot. The power amplifier is then smoothly ramped up to a final power level. Finally, the phase locked loop is switched from the wide bandwidth mode to the narrow bandwidth mode after the power amplifier has substantially reached the final power level.