Date of Original Version
Abstract or Description
A logic simulator can prove the correctness of a digital circuit if it can be shown that only circuits fulfilling the system specification will produce a particular response to a sequence of simulation commands.This style of verification has advantages over the other proof methods in being readily automated and requiring less attention on the part of the user to the low-level details of the design. It has advantages over other approaches to simulation in providing more reliable results, often at a comparable cost. This paper presents the theoretical foundations of several related approaches to circuit verification based on logic simulation. These approaches exploit the three-valued modeling capability found in most logic simulators, where the third-value X indicates a signal with unknown digital value. Although the circuit verification problem is NP-hard as measured in the size of the circuit description, several techniques can reduce the simulation complexity to a manageable level for many practical circuits.