Structural Decomposition in FSM Design: Roots, Evolution, Current State—A Review

The review is devoted to methods of structural decomposition that are used for optimizing characteristics of circuits of finite state machines (FSMs). These methods are connected with the increasing the number of logic levels in resulting FSM circuits. They can be viewed as an alternative to methods of functional decompositions. The roots of these methods are analysed. It is shown that the first methods of structural decomposition have appeared in 1950s together with microprogram control units. The basic methods of structural decomposition are analysed. They are such methods as the replacement of FSM inputs, encoding collections of FSM outputs, and encoding of terms. It is shown that these methods can be used for any element basis. Additionally, the joint application of different methods is shown. The analysis of change in these methods related to the evolution of the logic elements is performed. The application of these methods for optimizing FPGA- based FSMs is shown. Such new methods as twofold state assignment and mixed encoding of outputs are analysed. Some methods are illustrated with examples of FSM synthesis. Additionally, some experimental results are represented. These results prove that the methods of structural decomposition really improve the characteristics of FSM circuits.

A Lithography-Free and Field-Programmable Photonic Metacanvas

The unique correspondence between mathematical operators and photonic elements in wave optics enables quantitative analysis of light manipulation with individual optical devices. Phase-transition materials are able to provide real-time reconfigurability of these devices, which would create new optical functionalities via (re)compilation of photonic operators, as those achieved in other fields such as field-programmable gate arrays (FPGA). Here, by exploiting the hysteretic phase transition of vanadium dioxide, an all-solid, rewritable metacanvas on which nearly arbitrary photonic devices can be rapidly and repeatedly written and erased is presented. The writing is performed with a low-power laser and the entire process stays below 90 °C. Using the metacanvas, dynamic manipulation of optical waves is demonstrated for light propagation, polarization, and reconstruction. The metacanvas supports physical (re)compilation of photonic operators akin to that of FPGA, opening up possibilities where photonic elements can be field programmed to deliver complex, system-level functionalities.

Programmable resistive-switch nanowire transistor logic circuits

Programmable logic arrays (PLA) constitute a promising architecture for developing increasingly complex and functional circuits through nanocomputers from nanoscale building blocks. Here we report a novel one-dimensional PLA element that incorporates resistive switch gate structures on a semiconductor nanowire and show that multiple elements can be integrated to realize functional PLAs. In our PLA element, the gate coupling to the nanowire transistor can be modulated by the memory state of the resistive switch to yield programmable active (transistor) or inactive (resistor) states within a well-defined logic window. Multiple PLA nanowire elements were integrated and programmed to yield a working 2-to-4 demultiplexer with long-term retention. The well-defined, controllable logic window and long-term retention of our new one-dimensional PLA element provide a promising route for building increasingly complex circuits with nanoscale building blocks.