Analyzing controllability of a hardware circuit for its reuse

In this paper, a scheme has been proposed to identify under what condition a circuit, capable of performing a given set of operations/functions, can be reused while designing another circuit. This is characterized by a concept called external controllability of a function. When a function is externally controllable, the circuit executing the function, can be reused subsequently. The concept of external controllability has been formalized around finite state machine model. Also, the algorithm to verify the external controllability has been proposed.