Characterization of Interconnect Fault Effects in SRAM-based FPGAs

The configurable interconnect of SRAM-based FPGAs makes up a significant portion of their configuration, and thus exposes a large attack surface to single-event upsets. A better understanding of the behavior of FPGA interconnects under the presence of these faults may allow fault injection campaigns and reliability estimation techniques to treat some interconnect faults as more serious than others. This work proposes an approach to (1) analyze the interconnect configuration of a given FPGA technology to deduce the logical effects caused by single-bit flips and (2) to characterize the effects of such faults on routes implemented on a given FPGA technology. These approaches are illustrated in case studies on two FPGA technologies: Xilinx 7 Series and Lattice iCE40. Characterization of interconnect faults on these devices revealed that certain subcategories of interconnect fault types are far more critical than others, allowing more focused fault injection campaigns. Applying this knowledge to three benchmark designs implemented on a Xilinx 7 Series device shows that fault injection effort can be significantly reduced by skipping bits that are unlikely to critically impact the design.