Synthesis of Legacy Real-Time Ada Software to FPGA

Automatic system synthesis techniques prevalent in the hardware / software codesign community have typically focussed upon relatively small self-contained systems that contain little or no legacy software. In many domains that can benefit from the concepts of codesign, the systems are much larger, with considerable legacy software that must be re-used in any future design. This paper considers the use of codesign techniques in large real-time safety related embedded systems that contain large amount of legacy Ada software, e.g. avionics and aerospace systems. Such systems are usually developed with an early (manual) hardware / software split, but need to continually evolve their functionality throughout the lifetime. This is usually achieved by expanding software functionality, with minimal architectural or hardware changes. The paper argues that codesign techniques should be utilised during system evolution to rapidly search for system architectures and software configurations that can be mapped to a flexible target hardware architecture, ensuring that all non-functional requirements (safety, real-time, etc.) for the system are met. Specifically, the paper considers the case of legacy Ada, showing how it can be mapped to a flexible FPGA based architecture, as part of a codesign process that allows easy re-mapping should the Ada code evolve.