Optimization of a Mealy Automaton Circuit in a Mixed Element Basis

Abstract

Introduction. The control device is one of the most important blocks of any digital system. The main function of the control device is to coordinate the interaction of the remaining units of the system. Therefore, the characteristics of the control device circuit have a significant impact on the quality of the overall system. To represent the law of functioning of the control device, the models of the microprogrammed automaton (MPA) by Moore and Mealy are used. When synthesizing MPA circuits, it is necessary to solve a number of optimization problems: reducing hardware costs, increasing performance, minimizing power consumption, and jointly optimizing hardware-time characteristics. Methods for solving these problems largely depend on the elemental basis used. Currently, one of the main bases in which modern digital systems are implemented is the FPGA. The main blocks in the FPGA are configurable logic blocks, a programmable interconnect matrix, a timing tree, and programmable inputs and outputs. To implement MPA schemes, two types of configurable logic blocks can be used: tabular logic elements (TLE) and built-in memory blocks (VBP), which have the property of reconfiguration. However, VBPs are widely used to implement various operating blocks of digital systems. Therefore, the controller circuit designer can use a limited number of such memory blocks. Purpose of the article. The article deals with the issues of MPA synthesis when there are a limited number of "free" blocks of EBP. In this case, the microprogram automaton circuit is represented by a network consisting of VBP and TLE blocks. A method for the synthesis of a microprogram automaton with optimization of the number of TLEs is proposed when only one VBP can be used in the microprogram automaton circuit. The proposed method is based on the use of a built-in memory block that performs the replacement of input variables and the coding of the automaton outputs. Results. Studies of the effectiveness of the proposed method were carried out on standard machines. FPGAs of the Virtex-7 family from Xilinx were used as the elemental basis. To implement the proposed MPA, the Vivado package was used. The results of the research showed that the use of the VBP block made it possible to reduce the number of SLE blocks by an average of 14 % – 18 % compared to schemes consisting only of SLE. For the Virtex-7 family FPGA, the number of TLE inputs Io= 6 was sufficient for a single-level implementation of the output system. Conclusions. The effectiveness of the proposed method makes it possible to recommend it for use in the synthesis of microprogram automata under conditions of an extremely limited number of BVPs. Keywords: Mealy automaton, synthesis, coding of inputs, coding of sets of outputs.