A 4.1pJ/b 16Gb/s coded differential bidirectional parallel electrical link

This paper introduces coded differential (CD) signaling for high-speed parallel electrical links. CD preserves the desirable properties of differential signaling while offering ISI mitigation that is superior to 1-tap decision feedback equalization (DFE) [1-2] at no loss in pin efficiency or throughput. Specifically, CD encodes two bits of data over four binary wires in such a way that post-cursor inter-symbol interference (ISI) is completely eliminated across the entire unit-interval (UI). CD signaling is NRZ on individual wires and is balanced across the bus, meaning over any UI half the four-wire set have a high signaling level while the other half have a low level. The balanced nature of signaling leads to low supply switching noise. Received data is detected differentially by discriminating the difference between the signals on wire pairs without the need for a fixed reference voltage.