The application of knowledge-based systems to design verification

As a circuit design proceeds, it is continually checked by the designer for errors, by visual inspection, by simulation, or by using other verification tools (such as electrical rule checkers). Before most designs can proceed to fabrication, they must go through a formal design review where other designers analyze the design and look for errors. Errors found during the verification process range from easily recognizable problems, such as a power supply short, to a CMOS static gate having N and P cores that are not logical duals, to hard-to-recognize problems, such as those dealing with charge sharing and race-conditions. A circuit critic is a tool that finds errors in a circuit design and may recommend corrections. There are three main uses of a circuit critic: finding errors not easily found by other verification tools (e.g. timing, charge sharing), finding errors for novices, and checking design style compliance. There are many errors that novice designers can make as they do circuit designs. Novices learn the circuit configurations that lead to these errors by experience. A circuit critic can have the patterns that describe these errors in it and the novice can use the critic to check the circuit. Many design styles have a set of rules, that if followed will produce a "correct" design. A circuit critic can check for compliance with these rules. The work presented in this dissertation focuses on exploring the ideas of technology independence of critics, tight integration with a sc CAD system, and the representation of knowledge for the critic. To explore these ideas a test-bed, called Critic, was developed. Critic reads a description of the technology and design style to be used in the check and is tightly integrated into the Berkeley Design Environment, both in terms of the data input to the system and the control of Critic. An example of the use of Critic and the results of using Critic are presented.