On Close-to-Functional Test Sequences

Abstract

Close-to-functional broadside tests create close-to-functional operation conditions during the clock cycles where delay faults are detected in order to avoid overtesting. The requirement for functional operation conditions is relaxed in order to achieve the fault coverage of arbitrary (non-functional) broadside tests, and thus avoid test escapes. Existing procedures for computing close-to-functional broadside tests are based on limited information about the deviations that the tests create from functional operation conditions. Noting that functional broadside tests can be extracted from functional test sequences, this paper defines a new concept of a close-to-functional test sequence from which close-to-functional broadside tests can be extracted. For the resulting tests, the deviations from functional operation conditions are known, and can be bounded, over multiple clock cycles. The paper also describes a procedure for computing close-to-functional test sequences that are effective for the detection of transition faults. Experimental results demonstrate the deviations that need to be allowed in order to achieve the transition fault coverage of an arbitrary (non-functional) broadside test set.