Boolean Analysis of MOS Circuits

The switch-level model represents a digital metal-oxide semiconductor (MOS) circuit as a network of charge storage nodes connected by resistive transistor switches. The functionality of such a network can be expressed as a series of systems of Boolean equations. Solving these equations symbolically yields a set of Boolean formulas that describe the mapping from input and current state to the new network states. This analysis supports the same class of networks as the switch-level simulator MOSSIM II and provides the same functionality, including the handling of bidirectional effects and indeterminate (X) logic values. In the worst case, the analysis of an n-node network can yield a set of formulas containing a total of O(n /sup 3/) operations. However, all but a limited set of dense, pass-transistor networks give formulas with O(n) total operations. The analysis can serve as the basis of efficient programs for a variety of logic design tasks, including logic simulation (on both conventional and special-purpose computers), fault simulation, test generation, and symbolic verification.