A method and accompanying circuitry for asynchronous data demodulation uses sorted pulsewidth measurement based on an asynchronous clock. Lock-on of the data stream by such a system is accomplished by measured pulsewidth, rather than inferred frequency. The method broadly comprises the steps of measuring a temporal aspect of the asynchronous clock, and locking onto the data stream in accordance with the measured periods. In the preferred embodiment, the temporal aspect is a ratio of measured periods. Conveniently, a ratio of 2:1 may be used.