Test Generation for Path Delay Faults

Abstract

This chapter concentrates on multi-value systems and methods proposed for generating tests for single and multiple path delay faults. The robust, non-robust, validatable non-robust and functional sensitizable faults are considered as single path delay faults. These paths usually can be tested with many different tests, i.e., there are many different robust tests for a robust testable path, many different non-robust tests for a non-robust testable path, etc. Since robust tests are guaranteed to detect a faulty target path independent of whether or not there are delay faults on paths other than the target path, most test generators do not differentiate between robust tests for a given path. These test generators do not use any timing information. On the other hand, some non-robust tests have a higher probability of detecting a faulty non-robust testable path than other tests. Similar argument holds for the functional sensitizable tests. The higher quality non-robust and functional sensitizable tests can be found by including the timing information into the test generation process. This chapter presents test generation algorithms that can produce high quality tests based on using the timing information for the non-robust and functional sensitizable faults. A non-robust test for a given target path becomes invalid if certain other paths in the circuit are defective. If the faults that may invalidate the non-robust test for the target path can be robustly tested, those robust tests along with the non-robust test for the target path form a validatable non-robust test (VNR). An algorithm for automatic generation of validatable non-robust tests is outlined in this chapter.