On reliable modular testing with vulnerable test access mechanisms

In modular testing of system-on-a-chip (SoC), test access mechanisms (TAMs) are used to transport test data between the input/output pins of the SoC and the cores under test. Prior work assumes TAMs to be error-free during test data transfer. The validity of this assumption, however, is questionable with the ever-decreasing feature size of today\´s VLSI technology and the ever-increasing circuit operational frequency. In particular, when functional interconnects such as network-on-chip (NoC) are reused as TAMs, even if they have passed manufacturing test beforehand, failures caused by electrical noise such as crosstalk and transient errors may happen during test data transfer and make good chips appear to be defective, thus leading to undesired test yield loss. To address the above problem, in this paper, we propose novel solutions that are able to achieve reliable modular testing even if test data may sometimes get corrupted during transmission with vulnerable TAMs, by designing a new "jitter-aware" test wrapper and a new "jitter-transparent" ATE interface. Experimental results on an industrial circuit demonstrate the effectiveness of the proposed technique.