Three-Value Simulation of Combinational and Sequential Circuits and its Applications

Tasks of exact three-value simulation of combinational and sequential circuits, verification of circuits, construction of transition graph of a sequential circuit and transition sequences based on it are discussed. Different methods of finding state transitions of a sequential circuit are considered. Proposed methods of the exact three-value simulation (simulation in presence of unknown values) and the transition graph construction are based on these methods of finding state transitions of a circuit. Methods use ROBDDs and SAT solvers. The usage of binary and three-value simulation to reduce computations is also considered. In addition, the application of the exact three-value simulation for verification is considered.