A well-known challenge during processor design is to obtain the best possible results for a typical target application domain that is generally described as a set of benchmarks. Obtaining the best possible result in turn becomes a complex tradeoff between the generality of the processor and the physical characteristics. A custom instruction to perform a task can result in significant improvements for an application, but generally, at the expense of some overhead for all other applications. In the recent years, Application-Specific Instruction-Set Processors (ASIP) have gained popularity in production chips as well as in the research community. In this paper, we present a unique architecture and methodology to design ASIPs in the embedded controller domain by customizing an existing processor instruction set and architecture rather than creating an entirely new ASIP tuned to a benchmark.