Hierarchical Test Development and Design-For for (a)synchronous Semi-Custom Asics.
The research, described in this thesis, deals in particular with several problems, which arise when trying to automate the process of testing low-volume semi-custom ASICs. For low-volume ASICs one of the major problems is the reduction of the test application costs. To reduce the costs of testing low-volume ASICs, the use of a semi -custom test method with associated design-for-testability techniques is proposed. To be able to start the detection and removal of testability problems during the design, a novel automated hierarchical test program development procedure is presented. It is shown how, by generating a test specification for each hierarchical module, the test program can be developed incrementally. As a result, the testability of each module becomes known and it circumvents the need to generate a complete new test program after changes. To reduce the ASIC test time, the hierarchical test development approach supports the synthesis of a reconfigurable scan path. Thereby, our novel scan path architecture circumvents the need to introduce explicit test controllers by simply loading the reconfiguration information through the scan path itself. Since the hierarchical ASIC test development method as well as the semi-custom test method requires that all test vectors can be applied through a synchronous (reconfigurable) scan path, it is also investigate how asynchronous control circuits can be designed in such a way that they are synchronously scan testable. An implementation model is presented, that uses an explicit stale register composed of SR flip-flops. It is shown that these controllers are synchronously testable and can be derived directly from a state diagram description. Finally, the possibility of using a dedicated test generation procedure is illustrated by showing how the test program for modules composed of a data path and a finite state machine controller can be derived by the use of a novel symbolic test assembly procedure. The automated hierarchical test development approach has been used for several industrial designs and the results shown the effectiveness of the presented techniques and the associated CAD tools.
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- Physics: Electricity and Magnetism