Patent ID: 8680900

Claim:
An on-chip data processing apparatus configured to use an operating supply voltage selected from a range of supply voltages, said on-chip data processing apparatus comprising: voltage level detection circuitry configured to determine a level of said operating supply voltage within said range of supply voltages by comparison to a reference voltage and to generate a voltage level selection signal in dependence on a result of said comparison, wherein said voltage level detection circuitry comprises adaptive circuitry responsive to a variation in said reference voltage such that said determination of said level of said operating supply voltage is independent of said variation in said reference voltage; phase lock loop circuitry configured to generate a source clock signal from said operating supply voltage, said phase lock loop circuitry configured to receive said voltage level selection signal, to select a target frequency for said source clock signal in dependence on said voltage level selection signal, and to phase lock said source clock signal on said target frequency; and initialization circuitry configured to initialize said on-chip data processing apparatus for data processing in dependence on said level of said operating supply voltage with respect to said range of supply voltages after said phase lock loop circuitry has phase locked said source clock signal on said target frequency.