Testability Improvement by Branch Point Control for Conditional Staements With Multiple Branches

High-level test synthesis (HLTS) methodologies have attracted much many research interest in recent years as digital design has moved to higher levels of abstraction. Conditional statements in behavioral descriptions tend to produce testability problems and have to be taken care of in the early stage of the design cycle. In this paper, we present an HLTS methodology for the Built-In Self-Test (BIST) environment. Our methods modify conditional case statements in the original design so as to control the number of test patterns applied to modules being tested. As a result, the number of required test patterns can be greatly reduced. This method is especially useful when there is a wide variance in the number of random test patterns required for functional units. Experimental results show that our methods achieve a high degree of fault coverage with a much smaller number of test patterns while the area and time overheads are negligible.