A Decoder – Look up Tables for FPGAs

The FPGA (Field-Programmable Gate Array) has recently become the popular hardware and so-called LUTs (Look up Tables) are the basic of the FPGAs logic. For example, n-LUT is the MOS pass transistors multiplexer 2n-1 which input data receive SRAM cells logic function configuration (user’s projects Truth Table). Address inputs of the LUT are the variables. Therefore, we get one n-arguments logic function for the actual FPGA configuration. To get m functions (even with the same n-arguments) we should take m LUT. Authors propose a novel Decoder n-LUT (n-DC LUT), which makes possible to get m functions with the same n-arguments, like in Program Logic Array (PLA) CPLD (Complex Programmable Logic Device). DC LUT activates one of the 2n product terms outputs. Combined with OR product terms we can get m functions with the same n-arguments. To do this option we can use, for example, FPGAs typical connections units. The restriction of Meade-Conway for the FPGAs allows n=3 in one tree. Two 3-LUTs with one 1-LUTs form 4-LUT. Modern Adaptive Logic Modules (ALM) have n=8, but not all possible functions are implemented. The article deals with the design and investigation of some variants 3-DC LUT: with pull up output resistors, with orthogonal output circuits, with orthogonal transistors for each pass transistor. Simulation confirms the feasibility of the proposed method and shows that DC LUT with orthogonal output circuits is better variant of the systems realization in terms of current consumption and time delay at large n. A further development of the ALM concept may be the introduction of adaptive DC LUT, which, by tuning, can calculate single LUT function or 2n decoder functions. The proposed elements allow to increase the functionality of the FPGAs.

SELF-TIMED LOOK UP TABLE FOR ULAs AND FPGAs

Context. Self-Timed Circuits, proposed by D. Muller on the rise of the digital era, continues to excite researchers’ minds. These circuits started with the task of improving performance by taking into account real delays. Then Self-Timed Circuits have moved into the field of green computing. At last, they are currently positioned mainly in the field of fault tolerance. There is much redundancy in Self-Timed Circuits. It is believed that Self-Timed Circuits approaches will be in demand in the nano-circuitry when a synchronous approach becomes impossible. Strictly Self-Timed Circuits check transition process completion for each gate’s output. For this, they use so-called D. Muller elements (C-elements, hysteresis flip-flops, G-flip-flops). Usually, Self-Timed Circuits are designed on Uncommitted Logic Array. Now an extensive base of Uncommitted Logic Array Self-Timed gates exists. It is believed that SelfTimed Circuits are not compatible with FPGA technology. However, attempts to create self-timed FPGAs do not stop. The article proposes a Self-Timed Lookup Table for the Self-Timed Uncommitted Logic Array and the Self-Timed FPGA, carried out either by constants or utilizing additional memory cells. Authors proposed 1,2 – Self-Timed Lookup Table and described simulation results. Objective. The work’s goal is the analysis and design of the Strictly Self-Timed universal logic element based on Uncommitted Logic Array cells and pass-transistors circuits. Methods. Analysis and synthesis of the Strictly Self-Timed circuits with Boolean algebra. Simulation of the proposed element in the CAD “ARC”, TRANAL program, system NI Multisim by National Instruments Electronics Workbench Group, and layout design by Microwind. The reliability theory and reliability calculations in PTC Mathcad. Results. Authors designed, analyzed, and proved the Self-Timed Lookup Table’s workability for the Uncommitted Logic Arrays and FPGAs. Layouts of the novel logic gates are ready for manufacturing. Conclusions. The conducted studies allow us to use proposed circuits in perspective digital devices.

Design and Construction of 3 x 3 Bits Programmable Logic Array (PLA) Circuit

A programmable logic array (PLA) is a kind of programmable logic device used to implement combinational logic circuits. The PLA has a set of programmable AND gate planes, which link to a set of programmable OR gate planes, which can then be conditionally complemented to produce an output. It has 2N AND gate s for N input variables and for M outputs from PLA, there should be M OR gates, each with programmable inputs from all of the AND gates. This layout allows for many logic functions to be synthesized in the sum of products canonical forms. The Programmable Logic Array (PLA) has a programmable AND array followed by a programmable OR array. Programmable Logic Array (PLA) circuit is built by using AND gates and OR gates. The 3x 4 bits data can be stored in this circuit. The large storage data bits of PLA circuit store by a using large AND-OR array with lots of inputs and product terms, and programmable connections. Programmable Logic Array circuit functions as ROM circuit.

Design and Implementation of Programmable Logic Array Using Quantum Dot Cellular Automata

Quantum Dot Cellular Automata (QCA) is an alternative to CMOS technology. The other technologies proposed by researchers are FINFET, CNTs and MTJ to reduce scalability of CMOS devices. Using Quantum Dot Cellular Automata, the low power, extremely dense circuits are designed. QCA cell is the fundamental unit in building logic gates. These cells are powered using specific clock. QCA cells are used to design basic gates and to realize Boolean expressions. QCA Designer tool is used to carry out simulations. The simulation results are same as theoretical results. The complexity and size of circuits are reduced using QCA. The paper includes design of Programmable Logic Array (PLA).