Crosstalk based Fine-Grained Reconfiguration Techniques for Polymorphic Circuits

Truly polymorphic circuits, whose functionality/circuit behavior can be altered using a control variable, can provide tremendous benefits in multi-functional system design and resource sharing. For secure and fault tolerant hardware designs these can be crucial as well. Polymorphic circuits work in literature so far either rely on environmental parameters such as temperature, variation etc. or on special devices such as ambipolar FET, configurable magnetic devices, etc., that often result in inefficiencies in performance and/or realization. In this paper, we introduce a novel polymorphic circuit design approach where deterministic interference between nano-metal lines is leveraged for logic computing and configuration. For computing, the proposed approach relies on nano-metal lines, their interference and commonly used FETs. For polymorphism, it requires only an extra metal line that carries the control signal. In this paper, we show a wide range of crosstalk polymorphic logic gates and their evaluation results. We also show an example of a large circuit that performs both the functionalities of multiplier and sorter depending on the configuration signal. A comparison is made with respect to other existing approaches in literature, and transistor count is benchmarked. For crosstalk-polymorphic circuits, the transistor count reduction range from 25% to 83% with respect to various other approaches. For example, polymorphic AOI21-OA21 cell show 83%, 85% and 50% transistor count reduction, and Multiplier-Sorter circuit show 40%, 36% and 28% transistor count reduction with respect to CMOS, genetically evolved, and ambipolar transistor based polymorphic circuits, respectively.