Apparatus and method for decoding differential multi-level data with adaptive threshold control

A decoder for decoding, into a bilevel signal, a differential pair of multiple level signals including a primary multiple level signal and an inverted multiple level signal, the decoder comprising:

• a voltage biasing circuit for offsetting the primary multiple level signal and the inverted multiple level signal as an offset primary multiple level signal and an offset inverted multiple level signal, respectively, based on detected voltage characteristics of the primary multiple level signal and the inverted multiple level signal;
• a first comparator circuit configured for outputting a first comparison signal in response to the primary multiple level signal having a value greater than the offset inverted multiple level signal;
• a second comparator circuit configured for outputting a second comparison signal in response to the offset primary multiple level signal having a value greater than the inverted multiple level signal;
• a third comparator circuit configured for outputting a third comparison signal in response to the offset inverted multiple level signal having a value greater than the primary multiple level signal;
• a fourth comparator circuit configured for outputting a fourth comparison signal in response to the inverted multiple level signal having a value greater than the offset primary multiple level signal;
• edge detection circuits, each configured for detecting a prescribed edge transition in a corresponding one of the comparison signals;
• and
• edge decoding logic for outputting the bilevel signal in response to the detected edge transitions in the comparison signals.

A method for decoding a differential pair of multiple level signals, including a primary multiple level signal and an inverted multiple level signal, into a bilevel signal, the method comprising:

• generating an offset primary multiple level signal based on the inverted multiple level signal, and an offset inverted multiple level signal based on the primary multiple level signal;
• detecting first and second decoding points based on respective first and second intersection points between the primary multiple level signal and the offset inverted multiple level signal;
• detecting third and fourth decoding points based on respective third and fourth intersection points between the inverted multiple level signal and the offset primary multiple level signal;
• and
• generating the bilevel signal based on prescribed edge transitions in the primary multiple level signal, the offset inverted multiple level signal, the inverted multiple level signal and the offset primary multiple level signal coinciding with the first, second, third, and fourth decoding points, respectively.