Multi-level receiver circuit with digital output using a variable offset comparator

The receiver circuit of claim 2 wherein the offset control input of each comparator is to receive a multi-bit binary number.

An electronic system comprising:

• a printed wiring board on which a parallel bus is formed, an integrated circuit (IC) chip package being operatively installed on the board to communicate using the parallel bus, the package having an IC chip that includes a logic function section and an I/O section as an interface between the logic function section and the bus, the I/O section having a bus receiver in which there are a plurality of comparators each of which has an input coupled to receive a transmission line analog signal level, each comparator has substantially variable offset that is controllable to represent a respective variable reference level and without a separate input to receive a voltage reference level, an output of each comparator is to provide a value that represents a comparison between the transmission line analog signal level and the respective reference level,
• wherein the bus receiver further includes a reference calibration unit whose output is coupled to an offset control input of each conparator and whose input is coupled to the output of each comparator, the calibration unit being able to calibrate the respective reference level of each comparator by setting the variable offset of each comparator to represent a separate symbol level in a multi-level transmission line analog signal.

An article of manufacture comprising:

• a machine-readable medium having instructions stored thereon which, when executed by a processor, cause an electronic system to display a representation of a multi-level receiver in which there are a plurality of comparators each of which has an input coupled to receive a transmission line analog signal level, each comparator has substantially variable offset that is controllable to represent a respective variable reference level without a separate input to receive a voltage reference level, an output of each comparator is to provide a value that represents a comparison between the transmission line analog signal level and the respective reference level,
• a reference calibration unit whose output is coupled to an offset control input of each comparator and whose input is coupled to the output of each comparator, the calibration unit being able to calibrate the respective reference level of each comparator by setting the variable offset of each comparator to represent the midpoint between two adjacent symbol levels.