Efficient on-line testing of FPGAs with provable diagnosabilities

Abstract

We present novel and efficient methods for on-line testing in FPGAs. The testing approach uses a ROving TEster (ROTE), which has provable diagnosabilities and is also faster than prior FPGA testing methods. We present 1- and 2-diagnosable built-in self-tester (BISTer) designs that make up the ROTE, and that avoid expensive adaptive diagnosis. To the best of our knowledge, this is the first time that a BISTer design with diagnosability greater than one has been developed for FPGAs. We also develop functional testing methods that test PLBs in only two circuit functions that will be mapped to them (as opposed to testing PLBs in all their operational modes) as the ROTE moves across a functioning FPGA. Simulation results show that our 1-diagnosable BISTer and our functional testing technique leads to significantly more accurate (98% fault coverage at a fault/defect density of 10%) and faster test-and-diagnosis of FPGAs than achieved by previous work. The fault coverage of ROTE is also expected to be high at fault/defect densities of up to 25% using our 1-diagnosable BISTer and up to 33% using our 2-diagnosable BISTer. Our methods should thus prove useful for testing current very deep submicron FPGAs as well as future nano-CMOS and molecular nanotechnology FPGAs in which defect densities are expected to be in the 10% range.