A new initialization technique for asynchronous circuits

Both fault-free and faulty sequential circuits may start in an arbitrary state during the powering up and testing of circuits. Initialization is the process of driving the state signals in the circuit to known states. Therefore, the first important step in the test generation of sequential circuits is initialization. The easiest way to make a circuit initializable is to change the design so that it uses a flip-flop with a master reset or clear input signal which can set it to a 0 state asynchronously. This modification requires a dedicated external pin on the circuit for initialization and it costs excessive time for re-designing and verification. We provide a new Design-for-Testability (DFT) initialization technique which has little overhead and can often be simplified. This technique does not change the complexity and hazard characteristics of the circuit since we do not redesign it.