Because domino logic design offers smaller area and higher speed than complementary CMOS design, it has been very popularly used to design high-performance processors. However, domino logic suffers from several design problems and one of the most notable ones is the charge-sharing problem. Charge sharing may degrade output voltage level or even cause erroneous output value (named as charge-sharing fault). In this work, we find that charge-sharing faults are extremely resistant to scan test. In fact, charge-sharing faults occurring at the border gates cannot be detected by any scan method, due to the missing error caused by early signal arrival time. Further, we show that killing error might happen in charge-sharing fault detection for both border gates and non-border gates because of the low-speed testing problem caused again by scan test. We thoroughly investigate both test errors and propose two design-for-testability techniques to efficiently eliminate both problems.
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