An integrated processor includes a microprocessor core and a bus interface unit. The integrated processor receives a reference clock signal and an external clock signal. The frequency of the reference clock signal is compared to the frequency of the external clock signal. Based upon this comparison, the appropriate frequency for the internal clock signal that controls the bus interface unit is determined. A clock generation circuit, such as a phase-locked loop, generates the appropriate frequency for the internal clock signal based upon the comparison of the reference clock signal and external clock signal.