Can the clock speed be changed on the fly?
Internal programmable phase locked loops (PLL) for clock generation make the job of controlling power consumption much easier. These allow the processor to dynamically change the speed of operation based on instantaneous demand for computing power. What is the nominal supply current? Look at IDD, this seems obvious, so don’t forget. On a processor designed for low power systems this will often be given in the form of a graph of current vs. operating frequency. There may also be specifications for various sleep and low power modes. Is the sleep mode practical for your application? Read everything you can about the sleep and low-power modes supported by the processor. Some of the nasty surprises you don’t want to discover after you have committed to using a particular device include slow wake up times and power-down modes that turn off a function that is critical to your device waking up. (That low power mode won’t do much good if it turns off the on-chip UART and you have to wake up bas
