Patent ID: 7346119

Claim:
A communication system for providing data communication, the system comprises: a plurality of links, wherein each link includes: a backplane; transmitter circuitry, coupled to the backplane, to transmit a data stream in a 4-level Pulse Amplitude Modulation (PAM-4) format on the backplane, wherein the transmitter circuitry includes: PAM-4 encoding circuitry to encode a plurality of bits of data into a PAM-4 representation thereof; and output driver circuitry, coupled to the PAM-4 encoding circuitry, to output the data stream on the backplane; and wherein the transmitter maintains a running data sum (RDS), which is used to select which code in a balanced code pair is to be transmitted for a given bit pattern in order to drive the RDS value to zero; receiver circuitry, coupled to the backplane, to receive the data stream transmitted by the transmitter circuitry, wherein the receiver circuitry includes: adaptive slicer circuitry, coupled to the backplane, to generate slicer output signals, having discrete amplitudes, which are representative of the data stream received by the receiver circuitry; and PAM-4 decoding circuitry, coupled to the adaptive slicer circuitry, to decode the slicer output signals into a plurality of bits of data; and equalization circuitry, wherein the equalization circuitry is controlled via a back channel.