Testing and diagnosis of interconnect faults in cluster-based FPGA architectures

As IC densities are increasing, cluster-based field programmable gate arrays (FPGA) architectures are becoming the architecture of choice for major FPGA manufacturers. A cluster-base architecture is one in which several logic blocks are grouped together into a coarse-grained logic block. While the high-density local interconnect often found within clusters serves to improve FPGA utilization, it also greatly complicates the FPGA interconnect testing problem. To address this issue, we have developed a hierarchical approach to define a set of FPGA configurations which enable interconnect fault detection and diagnosis. This technique enables the detection of bridging faults involving intracluster interconnect and extracluster interconnect. The hierarchical structure of a cluster-based tile is exploited to define intracluster configurations separately from extracluster configurations, thereby improving the efficiency of the configuration definition process. The cornerstone of this work is the concise expression of the detectability conditions of each fault and the distinguishability conditions of each fault pair. By guaranteeing that both intracluster and extracluster configurations have several test transparency properties, hierarchical fault detectability is ensured.