Abstract: A method and apparatus to correct a periodic signal, such as a frequency reference, based upon another frequency reference. A lower accuracy frequency signal generator (104) provides an uncorrected frequency reference signal (122) to a frequency corrector (106). Frequency corrector (106) counts cycles of a frequency reference signal (124), as generated by a higher accuracy reference generator (102) for a time period derived from the uncorrected frequency signal. Based upon the cycles counted, pulses are added or removed from the uncorrected frequency signal (122) to produce a corrected frequency signal (126). A ratio of pulses to be removed from the uncorrected frequency signal (122) is determined from the number of cycles counted and a counter arrangement is provided to automatically remove the required ratio of pulses from the uncorrected frequency signal (122).

Abstract: Supply voltages within a data processing system may be controlled by a voltage control module which can provide digital signals to a power management unit to cause changes in supply voltages without software intervention. For example, in one embodiment, a voltage control signal and a standby signal may be provided to control the supply voltages output by a voltage regulator within the power management unit. In one embodiment having multiple processors, a voltage control signal and a standby signal corresponding to each processor may be provided to the power management unit which has a voltage regulator supplying an independently controlled supply voltage to each processor. Alternatively, a voltage regulator, a voltage control signal, and a standby signal may be shared by multiple processors, where the voltage control module may ensure that the supply voltage is changed only when the change is appropriate for all processors sharing the same voltage regulator.