Comparing the Reliability of PLA and Custom Logic Implementations of a QCA Adder

Assuming that nanoelectronic systems will face a large number of defective devices resulting in numerous computational faults, defect and/or fault tolerance will be necessary in these systems. However, multiple methods exist for providing this tolerance; in particular, many nanoelectronic systems are considering the use of reprogrammable logic or circuit redundancy. One decision point that may aid in determining which approach should be favored is whether the circuits to be implemented are more reliable when they are implemented in custom logic or in a regular logic array such as a PLA. In this paper, we consider the simple case of an adder circuit implemented in both logic types. We consider the use of QCA devices since both regular and custom logic designs are possible with QCA. We show that, when the components used to build each circuit are faulty, custom logic is preferable to regular logic since the component requirements are significantly smaller for custom logic.