A "soft++" eFPGA physical design approach with case studies in 180nm and 90nm

Our recent work in embedded FPGAs has been focused on a soft IP approach where programmable fabrics are described at the RTL level and implemented using the ASIC digital flow and generic standard cells. Early results showed significant penalties in area, delay, and power overhead. However, using tactical standard cells and a structured physical design approach within such a flow, we were able to obtain large savings in area and delay. We defined this new approach as soft++ eFPGA. This paper provides details of the physical design flow, with particular emphasis on floor-planning, interconnect-planning, and clock tree synthesis. The advantages of our approach in handling larger circuits are demonstrated on a set of realistic benchmark circuits implemented in 180nm and 90nm CMOS process technology