SCAN-BASED TRANSITION TEST

Skewed-load transition test is a form of scan-based transition test where the second vector of the delay test pair is a one bit shift over the first vector in the pair. This situation occurs when testing the combinational logic residing between scan chains. In the skewed-load test protocol, in order not to disturb the logic initialized by the first vector of the delay test pair, the second vector of the pair (the one that launches the transition) is required to be the next (i.e., one bit-shift) pattern in the scan chain. Although a skewed-load transition test is attractive from a timing point of view, there are various problems that may arise if this strategy is used. This paper investigates several issues of skewed-load transition test. Issues such as transition test calculus, detection probability of transition faults, transition fault coverage, and enhancement of transition test quality are thoroughly studied.