Enhanced Functional Fault Model for Micro Operation Faults

Sequential test generation becomes very time consuming when the circuit-under-test has many hard-to-test faults. This happens in cyclic sequential circuit. Design-for-testability method is applied on such circuit in order to speed up test generation time. However, this introduces huge area overhead. Alternatively, functional test generation is used to generate test sequences. In this option, stuck-at fault model alone is not sufficient. Functional test generation works based on functional fault model. Several functional fault models have been introduced and few of them have been shown to have high correlation with stuck-at fault model through experiment. However, not all the stuck-at faults are considered in the experiment. One of the fault categories which were out of consideration is stuck-at faults in the arithmetic modules. This is because there is no functional fault model correlating well with stuck-at faults in the arithmetic modules. In this work, we refine the functional fault model for arithmetic operations and show the superiority of our extended functional fault model to other functional fault model theoretically and experimentally. Keywords— functional fault model, fault coverage, arithmetic operations.