Automatic generation of FPGA routing architectures from high-level descriptions

Abstract

In this paper we present a `high-level' FPGA architecture description language which lets FPGA architects succinctly and quickly describe an FPGA routing architecture. We then present an `architecture generator' built into the VPR CAD tool that converts this high-level architecture description into a detailed and completely specified flat FPGA architecture. This flat architecture is the representation with which CAD optimization and visualization modules typically work. By allowing FPGA researchers to specify an architecture at a high-level, an architecture generator enables quick and easy `what-if' experimentation with a wide range of FPGA architectures. The net effect is a more fully optimized final FPGA architecture. In contrast, when FPGA architects are forced to use more traditional methods of describing an FPGA (such as the manual specification of every switch in the basic tile of the FPGA), far less experimentation can be performed in the same time, and the architectures experimented upon are likely to be highly similar, leaving important parts of the design space completely unexplored. This paper describes the automated routing architecture generation problem, and highlights the two key difficulties - creating an FPGA architecture that matches all of an FPGA architect's specifications, while simultaneously determining good values for the many unspecified portions of an FPGA so that a high quality FPGA results. We describe the method by which we generate FPGA routing architectures automatically, and present several examples.