A development system for developing new peripheral software code for new peripheral hardware that will be used in a new integrated system. The development system includes a legacy, or preexisting, integrated system substantially the same as the new integrated system. A model of the new peripheral hardware is made. Each I/O register of the model is mapped into memory-mapped I/O space. Development code corresponding to the new peripheral software code is executed on the preexisting hardware so as to interact with the model via the memory-mapped I/O space. In one embodiment, the model is executed as an embedded model on the preexisting integrated system. In another embodiment, the model is executed as a non-embedded model on a hardware descriptive language simulator.