Selective shielding: a crosstalk-free bus encoding technique

With CMOS process technology scaling to deep submicron level, propagation delay across long on-chip buses is becoming one of the main performance limiting factors in high-performance designs. Propagation delay is very significant when adjacent wires are transitioning in opposite direction (i.e., crosstalk transitions) as compared to transitioning in the same direction. As crosstalk transitions have significant impact on propagation delay, several bus encoding techniques have been proposed in literature to eliminate such transitions. In this work, we propose a technique, namely, selective shielding, to eliminate crosstalk transitions. Compared to the conventional shielding technique, our technique significantly reduces the number of extra wires. We give a lower bound on the number of wires required to encode n-bit data using the selective shielding technique. We show that our technique achieves better energy savings and requires less area as compared to the other techniques.