Cable length estimation circuit using data signal edge rate detection and analog to digital conversion

A transmission line length estimation circuit for receiving an input signal provided through a transmission line and for providing a digital control signal to an equalizer, the equalizer also for receiving the input signal from the transmission line and restoring amplitude loss and phase delay to the input signal resulting from the transmission line based on the digital control signal, the transmission line length determination circuit comprising:

• an edge rate detection circuit comprising:
• an analog to digital (A/D) edge rate measurement circuit for receiving the input signal, and generating first digital signals representative of a rate of change in voltage with respect to time of the input signal at an output;
• and
• a sample and hold circuit having an input connected to the output of the A/D edge rate measurement circuit for receiving the digital signals from the A/D edge rate measurement circuit and providing second digital signals at an output for the edge rate detection circuit indicating the state of the first digital signals during transitions of the input signal, the output of the edge rate detection circuit being coupled to provide the digital control signal to the equalizer.