Combining ESOP minimization with BDD-based decomposition for improved FPGA synthesis

This paper proposes a novel method to improve the utilization efficiency and performance of field-programmable gate arrays (FPGAs). The proposed method, ExorBDD, uses a stage of exclusive-sum-of-product (ESOP) minimization, followed by a stage of decomposition using binary decision diagrams (BDDs). For exclusive OR (XOR)-intensive circuits, experiments were conducted on 19 MCNC benchmark parity circuits (ranging from 5 to 25 inputs), as they are the most representative case of XOR-intensive circuits. The results using the proposed approach show significant improvements over Exorcism4, BDS, and commercial tools. On average, the new approach uses only 30.3% as many look-up tables as are used by Xilinx tools (and only 16.4% in comparison to Altera). On average, the new approach has a maximum combinational path delay of 89.2% compared to the delay with Xilinx tools (80.3% compared to Altera). Experiments were also conducted on non-XOR-intensive circuits. These results show that ExorBDD also performs well for arbitrary circuits.