Configuration and Reasoning Functions for Knowledge-based VLSI Pattern Design System

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We have conducted a research from a viewpoint that a knowledge-based system structure and intelligent functions based on that structure are required toward advanced VLSI-CAD systems. For the knowledge-based CAD system. automatic or semi-automatic synthesis functions are needed in addition to the analysis or verification functions explored so far in connection with existing knowledge systems. Although several approaches may be possible toward a knowledge-based LSI pattern design system, we have constructed a prototype system having a functional cell library as a kernel. The functional cell library is based on a knowledge structure and stores a set of intelligent cell data (components) to be combined in response to the request. Our LSI functional cell library system named OCLS can presently support NMOS artwork pattern design based on the Mead-Conway design methodology. A pattern description language has been developed, which is suitable for a hierarchical pattern description, expressing geometical patterns with using variables, and embedding related knowledge. The language supports necessary functions in the framework of object-oriented programming style based on Prolog. A design rule checker is also integrated in the system. For the users not enough familiar with the syntax of OCLS, a syntax-directed editor with graphics is provided. In our LSI design system, the design proceeds basically as sellecting necessary cells and combining them to produce larger patterns. The selection is done by the user at present with the help of a cell catalog desplay window. Since we consider that a hypothesis-based reasoning can be advantageously used for automating this selection process, we have exploited an enhanced knowledge representation and a learning mechanism for the knowledge-base performing hypothesis-based reasoning.