This paper presents an approach for abstract modeling of hardware/software architectures using Hierarchical Colored Petri Nets. The approach is able to capture complex behavioral characteristics often seen in software and hardware architectures, thus it is suitable for high level codesign issues such as performance estimation. In this paper, the development of a model of the ARM7 processor [5] is described to illustrate the full potential of the modeling approach. To further illustrate the approach, a cache model is also described. The approach and related tools are currently being implemented in the LYCOS system [12]. Details and the basic characteristics of the approach can be found in [8].