MULGA - An Interactive Symbolic Layout System for the Design of Integrated Circuits

Symbolic layout methodologies are a means of abstracting the detailed and often laborious task of mask design of integrated circuits. They offer the advantages of hand-packed mask design with regard to density of layout, while also having advantages over manual layout with respect to time to design a circuit and reduction in the number of manual errors introduced into a design. In essence, the use of symbology reduces the complexity of the ic design process, which in addition to the advantages mentioned above, allows experienced designers to undertake more complicated circuits than would otherwise be possible, and, more importantly, allows novice designers to complete designs with a high degree of confidence. This last point is regarded as * UNIX is a trademark of Bell Laboratories. 823 especially important as system designers move to use silicon as an implementation medium, rather than more conventional techniques. A particular ic design may be described in three domains, namely, the structural, physical and behavioral domains. Structurally, a design may be thought of as a graph where components are represented by nodes in the graph and their interconnection modeled by branches. The graph nodes may in turn be represented by subgraphs. The physical domain in an integrated circuit is typified by a collection of geometric areas defined on masks used in the various process steps used to fabricate the chip. Finally, the behavioral domain indicates how the design functions from the level of electrical circuit performance to possibly higher levels of architectural simulation.