  This paper presents an I/O interface with Xtalk Minimizing Affine Signaling
(XMAS), which is designed to support high-speed data transmission in die-to-die
communication over silicon interposers or similar high-density interconnects
susceptible to crosstalk. The operating principles of XMAS are elucidated
through rigorous analyses, and its advantages over existing signaling are
validated through numerical experiments. XMAS not only demonstrates exceptional
crosstalk removing capabilities but also exhibits robustness against noise,
especially simultaneous switching noise. Fabricated in a 28-nm CMOS process,
the prototype XMAS transceiver achieves an edge density of 3.6TB/s/mm and an
energy efficiency of 0.65pJ/b. Compared to the single-ended signaling, the
crosstalk-induced peak-to-peak jitter of the received eye with XMAS is reduced
by 75% at 10GS/s/pin data rate, and the horizontal eye opening extends to 0.2UI
at a bit error rate < 10$^{-12}$.
