QCA memory with parallel read/serial write: design and analysis

The authors present a novel memory architecture for quantum-dot cellular automata (QCA). The proposed architecture combines the advantage of reduced area of a serial memory with the reduced latency in the read operation of a parallel memory, hence its name is ‘hybrid’. This hybrid architecture utilises a novel arrangement in the addressing circuitry of the QCA loop for implementing the memory-in-motion paradigm. An evaluation of latency and area is pursued. It is shown that while for a serial memory, latency is O(N) (where N is the number of bits in a loop), a constant latency is accomplished in the hybrid memory. For area analysis, a novel characterisation that considers cells in the logic circuitry, interconnect in addition to the unused portion of the Cartesian plane (i.e. the whole geometric area encompassing the QCA layout), is proposed. This is referred to as the effective area. Different layouts of the hybrid memory are proposed to substantiate the reduction in effective area.