Test-model based hierarchical DFT synthesis

With increasing design sizes and adoption of system on a chip (SoC) methodology, design synthesis and test automation tools are hitting capacity and performance bottlenecks. Currently, hierarchical synthesis flows for large designs lack complete design-for-test (DFT) support. With this paper, we address a solution, involving the introduction of test models in a traditional DFT synthesis flow, that we term hierarchical DFT synthesis (HDS). We discuss the use of core test language (CTL) based test models combined with physical and timing models to provide a complete flow for chip-level DFT. In doing so we address some challenges the new flow presents such as design rule checking (DRC), DFT architecting and optimization. We describe methods to overcome these challenges thereby presenting a new methodology to handle complex next generation designs.