Patent ID: 7348857

Claim:
An integrated circuit comprising: a first counter; a second counter; a variable oscillator that has an oscillation time period that varies within an expected range with variations in one or more of process, voltage or temperature; wherein the variable oscillator provides a signal that causes a count of the first counter to change at rate proportional to an oscillation frequency of the variable oscillator; wherein the second counter is operable to receive a reference clock signal that has an oscillation time period that substantially does not vary with variations in one or more of process, time or voltage and that causes a count of the second counter to change at a rate proportional to an oscillation frequency of the received clock signal; and wherein the first counter is operable to count a reference count interval; wherein the second counter is operable to count beginning from a start value while the first counter counts the reference count interval; wherein the start value and the reference count interval are selected so that a count value produced by the second counter produces a value indicative of variable oscillator speed at or about the moment when the count of the first counter finishes counting the reference count interval; and further including, a circuit operable to determine when the first counter has counted the reference count interval.