Patent ID: 7612622

Claim:
A device comprising: a ring oscillator having an odd number of ordered inverting elements, wherein each of said inverting elements has an input port, an output port, and an enable port, and wherein said inverting elements are arranged in a ring, and wherein at least one of said inverting elements is an inverting memory element; an inverter to form an inverted periodic signal from a periodic signal; a switch to operably connect said periodic signal to each of said inverting elements' enable port in a first state and to operably connect said inverted periodic signal to each of said inverting elements' enable port in a second state; a starter to start oscillations of said output ports of said inverting elements during said first state and during said second state; and a counter to count a first number of oscillations of one of said inverting elements' output port in said first state and a second number of oscillations of said one of said inverting elements' output port in said second state, wherein the difference between said first number and said second number is proportional to a duty cycle offset of said periodic signal.