Functional ECO using metal-configurable gate-array spare cells

Abstract

Metal-configurable gate-array spare cells, which have versatile functionality, are developed to overcome the inflexibility of standard spare cells used in conventional metal-only engineering change order (ECO). In this paper, we focus on functional ECO optimization using the new type of spare cells to fully exploit its strength. We observe that this functional ECO problem has the nature of dynamic logical and physical costs for selecting spare gate arrays. Unlike existing functional ECO works, which perform technology mapping based on ECO patches, we perform reverse mapping from spare gate arrays to handle these dynamic costs. We devise a spare array relation graph to record geometrical adjacency among spare gate arrays and interleave with the and-inverter network of ECO patches. To avoid redundant traversal and monitor the dynamic costs, we adopt A* search to simultaneously traverse and map between the logical ECO network and the physical spare array relation graph.