A digital baseband processor is provided which receives a system clock
generated by a system oscillator and generates a plurality of clock
signals from the system clock. The digital baseband processor includes a
digital signal processor for executing digital signal processor
instructions, a microcontroller for executing microcontroller
instructions, and other modules which may require one of the plurality of
clock signals for operation. The digital baseband processor also includes
a power management circuit which may power down the system oscillator
when modules such as the digital signal processor and microcontroller do
not require clock signals derived from the system oscillator. The power
management circuit may gate off clock signals to modules when those
modules do not require clock signals, without powering down the system
oscillator.