Guest Editor's Introduction Design Automation

T he Design Automation Conference has the reputation of bringing together practitioners in a variety of disciplines who share the common goal of using the computer to perform design tasks. Correspondingly, the design field's most significant development in recent years has been the integration of individual disciplines into systems that extend throughout the design process from conception to manufacture. These systems offer benefits that are due as much to the smooth flow of information between parts of the process as they are to the new capabilities the systems themselves provide. Sophisticated workstations and computer networks play as large a role in realizing these systems as improvements in algorithm programming. Thus, concepts and innovations that originated in universities and were shared in open forums like the DAC now influence product cost and development cycles for many manufacturers. The articles chosen for this special issue of Design & Test were originally presented at the 21st Design Automation Conference. Selected to represent key activities in the integration process, they illustrate the emphasis that is being placed on complete design systems and the languages used to communicate between the component parts of these systems. In addition, the quality of a design is being improved by providing enhanced tools for simulation and verification before a chip is fabricated. Lastly, they show how classical approaches to design and test are being augmented with knowledgebased systems that enable us to learn from our experience. Thus, the emphasis is on the specific design and synthesis task performed by the engineer and not on analysis tools that aid in this process. In the past, the design community was primarily concerned with processing large amounts of data in a reasonable time so that increasingly complex VLSI chips could be designed. Now, of equal concern is rapid experimentation and a comparison of alternatives so that final product performance is improved. The effect is a shift from the automation of an initial design to the management of the change process so that alternatives can be evaluated. The lead article, "The Magic VLSI Layout System," by John Ousterhout et al., illustrates the effect of taking an integrated approach to the design of a VLSI chip. Magic is a smart layout system for integrated circuits. The user interface combines the efficiency of mask-level design with the flexibility of symbolic representations. It provides a continuous design-rule checker that operates in the background to ensure that the changes that are made do not violate the underlying connectivity or the design rules that govern the processing technology. In addition, it provides the capability for interactively stretching and compacting the layout, routing around existing connections in channels, and hierarchical circuit extraction to verify that the correct design has been realized. The efficiency of the overall system is heavily dependent upon the data structure that was chosen to implement these operations. The second article, "Hierarchical Layout Verification," by Todd Wagner, illustrates the importance that must be placed upon automatic verification of the correctness of a system that designs extremely complex VLSI chips. The article describes how the comparison of the schematic to layout net list is performed and how the design-rule checking is carried out. The key to the system is a hierarchical cell structure that is flexible enough to handle the complexities of VLSI design and yet takes into account the restrictions that are necessary for practical fabrication of these chips. Thus, the system verifies that a chip is manufacturable as well logically correct.