Patent ID: 7893741

Claim:
A signal edge alignment apparatus comprising: multiple delay stages connected in series and each having a delay stage input and a delay stage output, wherein each delay stage of the multiple delay stages is characterized by an inherent delay, and each delay stage includes a delay line coupled to the delay stage input and adapted to receive an input signal, wherein the delay line includes a plurality of delay elements connected in series, and a plurality of taps associated with the plurality of delay elements, wherein the delay elements are adapted sequentially to apply fixed-width delays to the input signal in order to produce a plurality of delayed versions of the input signal at the taps, an interface circuit having an interface circuit input and an interface circuit output, wherein the interface circuit input is coupled with the taps, and the interface circuit is adapted to pass a delayed version of the input signal from one of the taps to the interface circuit output in response to a control signal, and wherein the inherent delay of the delay stage includes an inherent interface circuit delay between the interface circuit input and the interface circuit output, and a tap selection circuit coupled with the taps and with the interface circuit, wherein the tap selection circuit is adapted to identify a finally-identified tap of the plurality of taps by determining an initially-identified tap at which a delayed version of the input signal most closely has a desired alignment with the input signal, and by identifying the finally-identified tap in the control signal as a tap that occurs earlier in the delay line than the initially-identified tap in order to compensate for the inherent delay of the delay stage.