We extended general-purpose RISC processor architecture and developed a new RISC core, Casablanca II, for supporting real-time processing in embedded systems. The processor core has multiple register-sets and achieves fast context-switching by automatically changing the active register-set and reducing overheads to save and restore the contents of the registers when exceptions or interruptions occur. In addition, the core has mechanisms for explicit data cache control, enabling data prefetching and fast DMA, which is invoked by executing extended instructions. In this paper, we describe the organization of Casablanca II developed by using an ASIC process and present preliminary evaluation of the processor.