A Highly Routable ULM Gate Array and Its Automated Customizaton

This paper describes the design of a new functional-cell gate-array with inherently high routability, and its automated customization software which achieves 100 percent first-time routing. Emphasis is placed upon the considerations which influence the selection of a functional array primitive. A highly structured interconnection architecture will be described, which employs interdigitating cell terminals in a polycell-like wiring channel topology to simplify the routing procedure for the array. The detailed structure and operation of an automatic customization software package is discussed. This package, developed specially for the array, utilizes the structured topology to achieve track densities which are comparable with those produced by state-of-the-art algorithms. This array has been fabricated, in a CMOS technology, as a test-vehicle for both the unusual topology and the unique functional cells. Throughout the study, emphasis has been placed on achieving a coherent strategy for producing efficiently routed gate-arrays with the minimum of sophisticated design tools. Examples will be cited to show that this methodology is economical both in the rapidity with which finished designs may be produced, and in its utilization of silicon-area.