Open-Source Bitstream Generation

Abstract

This work presents an open-source bitstream generation tool for Torc. Bitstream generation has traditionally been the single part of the FPGA design flow that could not be openly reproduced, but our novel approach enables this without reverse-engineering or violating End-User License Agreement terms. We begin by creating a library of “micro-bitstreams” which constitute a collection of primitives at a granularity of our choosing. These primitives can then be combined to create larger designs, or portions thereof, with simple merging operations. Our effort is motivated by a desire to resume earlier work on embedded bitstream generation and autonomous hardware. This is not feasible with Xilinx bitgen because there is no reasonable way to run an x86 binary with complex library and data dependencies on most embedded systems. Initial support is limited to the Virtex5, but we intend to extend this to other Xilinx architectures. We are able to support nearly all routing resources in the device, as well as the most common logic resources.