Patent ID: 7729205

Claim:
A computer-implemented method performed by one or more processors for determining a duration of a first period beginning from a startup time in a system including a first oscillator of an unknown frequency and a second oscillator of a known frequency, the method comprising performing the following by operation of one or more processors: generating a first count corresponding to a number of oscillations of the first oscillator during the first period; generating a second count corresponding to a number of oscillations of the first oscillator during a second period, the second period having a duration corresponding to a known number of oscillations of the second oscillator; converting the first count to an equivalent number of oscillations of the second oscillator during the first period; calculating the duration of the first period based on the converted number of oscillations of the second oscillator and the known frequency of the second oscillator; and calculating a system time since the startup time using the calculated duration of the first period.