Hardware-software codesign has been a research topic since the beginning of this decade (1990s), but only now are structured methods emerging that focus on automating design. Unfortunately, to date most codesign approaches leverage performance from individual hardware and software tools, rather than enforcing a structured integration of hardware and software systems simultaneously. A few frameworks have successfully done this integration and have the potential for significant benefits, including reduced time to market, smaller scale design, better likelihood of component reuse, and maximum use of processing power. The article describes a codesign approach that lets developers create models of a formal system representation independently of the hardware and software implementation. The authors' framework, which targets embedded systems, lets developers use simulation based modeling to explore the feasibility of virtual prototypes and then interactively map the specification onto a software-hardware architecture.