Programmable Logic Implemented Using Quantum-Dot Cellular Automata
The authors describe a geometric layout of quantum-dot cellular automata (QCA) cells and an associated set of clock signals that can be used to implement a programmable array of logic (PAL). PALs are an important category of programmable logic that can be programmed (typically once) to perform a particular sum-of-products Boolean operation. The particular device described has six inputs, four product terms, and one output. The connections between the inputs and the product terms are fully re-programmable, while the connections between the product terms and the output are hardwired. This device takes 22 clock cycles to load the connection data and then completes the calculation in 57 cycles. The connection data are preserved in memory, so additional calculations with the same set of connections can be performed in just 57 cycles each.