Digital sensitivity: predicting signal interaction using functional analysis

Maintaining signal integrity in digital systems is becoming increasingly difficult due to the rising number of analog effects seen in deep submicron design. One such effect, the signal crosstalk problem, is now a serious design concern. Signals which couple electrically may not affect system behavior because of timing or function in the digital domain. If we can isolate observable coupling then we can constrain layout synthesis to eliminate them. In this paper, we find that it is possible to predict signal interaction by signal functionality alone, leading to a significant amount of robust switching isolation, independent of parasitics introduced by layout or semiconductor process. We introduce techniques to predict signal interaction using functional sensitivity analysis. In general sequential networks we find that significant switching isolation can be extracted with efficient sensitivity analysis algorithms, thus giving promise to the goal of synthesizing layout free from crosstalk effects.