Synthesizable Standard Cell FPGA Fabrics Targetable by the Verilog-to-Routing CAD Flow

Abstract

In this article, we consider implementing field-programmable gate arrays (FPGAs) using a standard cell design methodology and present a framework for the automated generation of synthesizable FPGA fabrics. The open-source Verilog-to-Routing (VTR) FPGA architecture evaluation framework [Rose et al. 2012] is extended to generate synthesizable Verilog for its in-memory FPGA architectural device model. The Verilog can subsequently be synthesized into standard cells, placed and routed using an ASIC design flow. A second extension to VTR generates a configuration bitstream for the FPGA, where the bitstream configures the FPGA to realize a user-provided placed and routed design. The proposed framework and methodology makes possible the silicon implementation of a wide range of VTR-modeled FPGA fabrics. In an experimental study, area and timing-optimized FPGA implementations in 65nm TSMC standard cells are compared to a 65nm Altera commercial FPGA. In addition, we consider augmenting the generic standard-cell library from TSMC with a manually designed and laid-out FPGA-specific cell. We demonstrate the utility of the custom cell in reducing the area of the synthesized FPGA fabric.