Logic Synthesis by Signal-Driven Decomposition

This chapter investigates some restructuring techniques based on decomposition and factorization, with the objective to move critical signals toward the output while minimizing area. A specific application is synthesis for minimum switching activity (or high performance), with minimum area penalty, where decompositions with respect to specific critical variables are needed (the ones of highest switching activity for example). In order to reduce the power consumption of the circuit, the number of gates that are affected by the switching activity of critical signals is maintained constant. The chapter describes new types of factorization that extend Shannon cofactoring and are based on projection functions that change the Hamming distance among the original minterms to favor logic minimization of the component blocks. Moreover, the proposed algorithms generate and exploit don't care conditions in order to further minimize the final circuit. The related implementations, called P-Circuits, show experimentally promising results in area with respect to classical Shannon cofactoring.