Ordered ternary decision diagrams and the multivalued compiled simulation of unmapped logic

We describe a method for generating logic simulation code which correctly responds to any number of unde ned logic values at the code inputs. The method is based on our development of the Ordered Ternary Decision Diagram, itself based on Kleenean ternary logic, which explicitly and correctly manages the unknown logic value `U' in addition to the `1' and `0' of conventional OBDDs. We describe the OTDD and how to implement its reduction, application, and restriction operations. This method avoids expensive technology mapping, producing highly e cient `U'-correct compiled logic simulation code in seconds rather than in hours. Our experiments toward conrming the validity of the method are reported.