A Scalable and Area-Efficient Configuration Circuitry for Semi-Custom FPGA Design

Configuration circuitry is an essential component of a field-programmable gate array (FPGA) fabric, which enables the configuration of each programmable logic and takes over 40% of the FPGA chip area. Following the recent trends of automated custom FPGA design, it is essential to study the impact on the area and power of the configuration circuitry. This study compares the performance of different configuration circuitries using a strictly automated and complete standard cell-based semi-custom design methodology. We leverage an open-source framework, OpenFPGA, and extended it to support two configuration protocols: shift-register-based configuration (SRC) and memory-bank-based configuration (MBC) circuitries and their variants. We proposed area optimization strategies to improve the physical implementation of each configuration circuitry. Our results show that compared with naive SRC implementation, the proposed optimization strategies minimize the area overhead by more than 30% and power dissipation during programming by 20%. Whereas compared with MBC implementation, the optimized SRC implementation requires approximately a similar area. However, considering the more practical implementation of MBC with the write-verify functionality with optimized SRC implementation, the MBC implementation requires an 11% higher area and 30% higher routing wirelength, but results in a 62% reduction in the power dissipation during programming.