“Just what makes an FPGA so different from a microcontroller and yet so versatile? This article continues the exploration of FPGAs, focusing on the role of flip-flops and lookup tables (LUTs) in logic blocks. The fundamental building blocks inside of an FPGA are the flip-flop and the lookup table (LUT). These are combined to form what are referred to as logic blocks. The logic blocks connect to each other, and the outside world, through programmable interconnects. The flip-flops operate more or less like any flip-flop you may have stumbled upon over the years. LUTs, on the other hand, aren’t quite as universal a concept.”