Microcontrollers are widely used on simple systems; thus, how to keep them operating with high robustness and low power consumption are the two most important issues. It is widely known that asynchronous circuit is the best solution to address these two issues at the same time. However, it’s not very easy to realize asynchronous circuit and certainly very hard to model processors with asynchronous pipeline. That’s why most processors are implemented with synchronous circuit. There are several ways to model asynchronous pipeline.