Optimization of the Microprogram Mealy Machine Circuit Based on LUT and EMB

Abstract

Introduction. A digital system is a collection of combinational and sequential blocks. Sequential blocks can be divided into library and non-standard classes. The first class includes, for example, counters or shift registers. To implement the circuits of such blocks, standard CAD programs are used. And for the second class, which is the control unit (CU), there are no standard library solutions. This explains the relevance of methods for synthesis and optimization of circuits of non-standard sequential blocks, such as CU. When synthesizing a finite state machine (FSM) circuit, a number of optimization problems arise that are aimed at improving CU characteristics. Methods for solving these problems depend on elemental base characteristics. This paper discusses the implementation of the FSM circuit on a FPGA (field-programmable logic array) basis. The main FPGA blocks that are used for FSM circuit implementation are LUT (look-up table) elements and EMB (embedded memory blocks) elements. Therefore, to solve optimization problems while developing an FSM circuit, it is necessary to reduce the number of these elements. The purpose of the article. This work presents an approach to lower hardware costs in the FSM Mile technique, which uses FPGA for implementation. The method is based on the extended coding of micro-operation sets, in which the set code also includes the transition state code. The state code is partial since it is determined for a set of states upon transition, from which this set is formed. To implement part of the FSM circuit, the built-in memory block EMB is used. If EMB capabilities are not enough to implement the circuit, then part of the circuit is implemented on LUT elements. It is proposed to implement part of the output signals (micro-operations) on EMB. An example of the synthesis of an FSM circuit using the proposed method is given. Results. To study the effectiveness of the proposed method, a comparison was made between the control unit of the known structure (U5) and the control unit obtained using the proposed method (U7). In this case, standard benchmarks from a well-known library were used. Research has shown that U7 can reduce the number of LUTs by 28 % of all benchmarks, and U5 only by 9 %. It is important to note that when implementing the entire 64 % standard MPA circuit, one EMB block is sufficient. Conclusions. The proposed method allows for a reduction in hardware costs (the number of LUT elements). The article shows the conditions for applying the proposed method. Results of experiments examining the effectiveness of the suggested approach to automata implementation with Virtex-7 family chips and the Vivado industrial package are given Keywords: Mili FSM, synthesis, FPGA, EMB, LUT, extended codes of micro-operation sets.