Experimental Research On At-Speed Current Testing For Microprocessor

With the development of manufacturing technology of digital integrated circuit, the voltage test method based on stuck-at fault model can not detect all the faults in modern integrated circuit. In order to reducing the cost of test and improving the reliability of integrated circuit, current based test method arises at the historic moment. The current based test method can be divided into two categories, the one is quiescent current test (IDDQ testing) and the other is transient current test (IDDT testing). Quiescent current test method has been widely applied in IC industries already and transient current testing is still at the stage of studying due to its harsh requirement for apparatus and other technical problems. Focus on the reality that transient current testing overly relies on the test equipments, Professor Min Yinghua from Institute of Computing Technology of China Sicence academy proposed At-Speed current testing method (IDDA Testing) grounded on transient current testing. The feasibility of At-Speed current testing has already been verified in the simulative experiments. But At-Speed current testing is still need the support of practical test experiments.Microprocessor is one kind of comparatively special integrated circuit. It can run merely relying on the programs in its memory without any external stimuli. If taking programs in the memory as test stimulus, the course of testing microprocessor with At-speed current testing method can be carried out easily. In this paper we have proposed instruction level At-speed current testing method taking both the characteristics of microprocessor and At-speed current testing into account. We Hope to illustrate the feasibility of At-speed current testing method for microprocessor through the instance of microprocessor AT89C51. After detailed analysis of microprocessor AT89C51, we fixed a data path oriented scheme to test AT89C51 and in this paper we have given the test program generation procedure according to most data paths of AT89C51. To make the test process feasible, compile program are carefully generated to let them be able to execute repeatedly by the microprocessor, and the average current consumed by AT89C51 is then measured with a simple current meter. The experimental results indicate that it is feasible to applied At-speed current testing to AT89C51 microprocessor at instruction level. Through testing of data paths, we can not only detect the faults arose by data path, but also find the faults brought in by control parts.