Investigating the Effects of Permanent Faults in QDI Circuits: A Formal Perspective

In the presence of permanent faults, QDI circuits exhibit the attractive property of halting their operation until a repair process has taken place and the fault has been bypassed. This is not always enough, however, as a recovery of the internal state of the circuit might be needed in case of its corruption before the deadlock. Some studies have attempted to provide an analysis for the circuit’s behavior from a quantitative perspective based on empirical findings.In this study, we present a formal framework aimed at comprehensively identifying the vulnerable windows of a QDI circuit for permanent faults. We establish a model for this type of faults and, based on our framework, demonstrate the equivalence of fault scenarios within certain windows. We leverage these insights in a tool that we showcase using a multiplier and an ALU following the 4-phase communication protocol.