Don't-care identification on specific bits of test patterns

Abstract

Given a test set for stuck-at faults, a primary input value may be changed to the opposite logic value without losing fault coverage. One can regard such a value as a don 't-care (X). The don't care values can be filled appropriately to achieve test compaction, test data compression, or power reduction during testing. Howevel; these uses are better served if the don't cares can be placed in desired/specific bit positions of the test patterns. In this papel; we present a methodfor maximally fixing Xs on specific bits of given test vectors. Experimental results on ISCAS benchmark circuits show how the proposed method can increase the number of Xs on specific bits compared with an earlier proposed method.

Distribution-Controlled X-Identification for Effective Reduction of Launch-Induced IR-Drop in At-Speed Scan Testing

“…We call a distribution of the percentages in a test cube set as "distribution of X-bits" in this paper. Although Specific Bits X-Identification [24] can minimally control X-bit distribution, its effect is relatively small and it is difficult to average the X-bit distribution since the framework is the same as that described in [17]. Figure 3 shows the typical distribution of X-bits identified by an existing X-identification method [17] for an industrial circuit shown in Sect.…”

“…Papers of [17], [18], [24] only consider stuck-at fault testing. In this paper, X-identification used is for transition delay fault testing with the LOC (Launch-Off-Capture) clocking scheme.…”

Test data compression technique using selective don't-care identification

“…In this paper, distinct internal scan vectors are referred to as simply "words" like those in dictionary-based compression In our method, don't-care identification is applied under conditions that each bit in frequent words is fixed to binary value (0 or 1), and cannot be replaced into don't-care value X. It is similar to don't-care identification for specific bits in [13]. This process is repeated through gradually increasing the number of binary-fixed words.…”

On combining pinpoint test set relaxation and run-length codes for reducing test data volume

“…A method for placing the Xs on a maximal number of specific bits of a test set has been proposed in [18]. The method allows a user to specify bits for the placement of Xs for each one of the given test vectors.…”

“…Before encoding given test patterns, we efficiently change values of some bits of the test patterns using a technique of don't-care identification [18]. This procedure retains the fault coverage of the test set.…”