Efficient On-line Interconnect Testing in FPGAs with Provable Detectability for Multiple Faults

We present a very effective on-line interconnect built-in-self-test (BIST) method I-BIST for FPGAs that uses a combination of the following novel techniques: a track-adjacent and a switch-adjacent (also called "mirror adjacent") pairwise net comparison mechanism that achieves high detectability, a carefully designed set of only five net-configurations that cover all types and locations of wire-segment and switch faults, a 2-phase global-detailed testing approach, and a divide-and-conquer technique used in detailed testing to quickly narrow down the set of potential suspect interconnects that are then detail-diagnosed. These techniques result in I-BIST having provable detectability in the presence of an unbounded number of multiple faults, very high diagnosability of 99-100% even for high fault densities of up to 10% that are expected in emerging nano-scale technologies, and much lower test times or fault latencies than the previous best interconnect BIST techniques. In particular, for application to on-line testing, our method requires 2n roving-tester (ROTE) configurations to test an entire n times n FPGA, while the previous best online interconnect BIST technique requires n² configurations. Thus, I-BIST is an order of magnitude more time- as well as power-efficient, and scale well with rapidly increasing FPGA device sizes that are expected in emerging technologies