In this paper, we propose an approach to test pattern generation for Speed-Independent (SI) asynchronous control circuits. Test patterns are generated based on a specified sequence, which is derived from the specification of a target circuit in the form of a Signal Transition Graph (STG). Since the sequence represents the behavior of a circuit only with stable states, the state space of the circuit can be represented as reduced one. A product machine, which consists of a fault-free circuit and a faulty circuit, is constructed and then the specified sequence is applied sequentially to the product machine. A fault is detected when the product machine produces inconsistency, i.e., output values of a fault-free circuit and a faulty circuit are different, and the sequentially applied part of the sequence becomes a test pattern to detect the fault. We also propose a test generation method using an undetectable fault identification as well as the specified sequence. Since the reduced state space is a subset of that of a gate level implementation, test patterns based on a specification cannot detect some faults. The proposed method identifies those faults with a circuit topology in advance. BDD is used to implement the proposed methods efficiently, since the proposed methods have a lot of state sets and set operations. Experimental results show that the test generation using a specification achieves high fault coverage over single stuck-at fault model for several synthesized SI circuits. The proposed test generation using a circuit topology as well as a specification decreases execution time for test generation with negligible cost retaining high fault coverage.

In this paper, we have proposed an efficient high-level test generation method for asynchronous circuits. The test generation is based on specification level, especially on Signal Transition Graph (STG), which is a kind of specification method for asynchronous circuits. We define a high-level fault model, called a single State Transition Fault (STF) model on STG. Test patterns for STFs are generated based on Stable State Graph (SSG), which can be derived from STG directly. The state space explored in test generation is greatly reduced and hence the test generation cost is small in terms of execution time. To enhance the fault coverage at gate-level, we have also proposed an extended STF (ESTF) model with additional gate-level information. Experimental results show that the generated test for STFs achieves high fault coverage with low cost for single stuck-at faults of its corresponding synthesized gate-level circuit. The generated test for ESTFs attains higher fault coverage with same benchmark in cost of longer execution time. Further, we have also proposed a 3-phase test generation based on the above proposed methods. An effective test generation is implemented by 3-phase: 1) test generation for STFs, 2) test generation for ESTFs, and 3) test generation using an asynchronous product machine traversal method. Experimental results also show that the proposed 3-phase test generation achieves higher fault coverage in cost of longer execution time.