Interfacing hardware and software using C++ class libraries

As chip capacity increases and system-on-a-chip becomes more than just a catch phrase, hardware and system design are being driven in new directions. Systems are designed not just as hardware, but as a tightly coupled combination of both hardware and software. C++, extended with class libraries, is emerging as the way to design such complex systems. This paper proposes methods to specify and refine designs from a purely software description at a functional level to a level where the hardware components are encapsulated as objects and their interfaces clearly defined. The entire system functionality is described in C++ using some of the commercially available class libraries like SystemC from Synopsys and Cynlib from CynApps. We propose a methodology where a designer can migrate software functionality. We also show that the software driver for the hardware device is generated as a side-effect of the interface refinement process. We demonstrate our methodology on the design of a fax machine from a purely software description of the system. We refine the design by implementing its decoder functionality in hardware and interfacing it with the software encoder.