On signal transition causality for self-timed implementation of Boolean functions

The authors discuss the two-rail, two-phase self-timed implementation of Boolean functions which interacts with its environment on the delay-insensitive model with the isochronic-forks assumption. The transition causality of a self-timed implementation is defined as a set of causal relations that hold among signal transitions on the primary input, the primary output, and the internal gates. The authors observe that the transition causalities for most self-timed implementations so far proposed are more that what is truly required. Based on the observation, a new self-timed implementation is presented which achieves a maximum parallelism, and therefore has the potential of operating at the highest possible average speed on the delay-sensitive circuit-environment model.