Study and Comparison of QDI Pipeline Components’ Sensitivity to Permanent Faults

Abstract

In the presence of permanent faults, QDI circuits exhibit the beneficial property of halting their operation until a repair procedure has been conducted. The state in which the circuit resides, however, does not always remain clean, i.e., a recovery process might be needed. This depends on how the circuit reacts in these situations. In this study, we investigate the effect a permanent fault has on the different components of the pipeline, the logic function unit and the butter. Our aim is to identify the weaknesses of each component and try to enhance each one accordingly. We perform extensive fault-injection simulations on different circuits following the famous 4-phase communication protocol, while varying the logic function and butter style for comparison. Our results show that the logic function does not affect the resilience of a specific butter type, and hence we can deduce which butter should perform better for a specific application based on parameters we extract from our experiments. On a parallel note, the implementation style of the logic also has an impact on the block’s ability to hold out against faults. We investigate two of these styles.