This paper addresses design methods for SoC-based HW/SW systems using reconfigurable architectures. The emphasis is the development of a method to enhance the reusability of HW and SW in the co-design process using proven languages like ANSI-C and VHDL. We distinguish between three abstraction layers for design modules consisting of both HW and SW. This approach benefits the reuse of HW sources as well as SW sources for different applications as well as on different devices. We utilize the reconfigurable SoC Atmel FPSLIC for experimental tests and obtain a significant reuse ratio.