Finite state machines with input multiplexing (FSMIMs) have been proposed in previous works as a technique for efficient mapping FSMs into ROM memory. In this paper, we propose a new architecture for implementing FSMIMs, called FSMIM with state-based input selection, whose goal is to achieve a further reduction in memory usage. This paper also describes in detail the algorithms for generating FSMIMs used by the tool FSMIM-Gen, which has been developed and made available on the Internet for free public use. A comparative study in terms of speed and area between FSMIM approaches and other field programmable gate array-based techniques is presented. The results show that the FSMIM approaches obtain huge reductions in the look-up table (LUT) usage by using a small number of embedded memory blocks. In addition, speed improvements over conventional LUT-based implementations have been obtained in many cases.Index Terms-Embedded memory blocks (EMBs), finite state machine (FSM), field programmable gate array (FPGA), logic synthesis, ROM.

This work presents a technique for the resource optimization of input multiplexed ROM-based Finite StateMachines. This technique exploits the don't care value of the inputs to reduce the memory size as well as multiplexer complexity. This technique has been applied to a publicly available FSM benchmarks and implemented in a low-cost FPGA. Results have been compared with tools supported ROM and standard logic cells implementations. In a significant number of test cases, the proposed technique is the best design alternative, both in resource requirements and speed.

Finite State Machines with Input Multiplexing (FSMIMs) were proposed in previous work as a technique for efficient mapping Finite State Machines (FSMs) into ROM memory. In this paper, we present new contributions to the optimization process involved in the implementation of FSMIMs in Field Programmable Gate Array (FPGA) devices. This process consists of two stages: (1) the simplification of the bank of input selectors of the FSMIM, and (2) the reduction of the depth of the ROM. This has a significant impact both on the number of used Look-Up Tables (LUTs) and on the number of the Embedded Memory Blocks (EMBs) required by the ROM. For the first stage, we present two approaches to optimize FSMIM implementations based on the Minimum Maximal k-Partial Matching (MMKPM) problem: one of them applies the greedy algorithm for the MMKPM problem, and the other based on a new multiobjetive variant of the MMKPM and its corresponding Integer Linear Programing formulation. We also propose a modification of the second stage, in which the characteristics of EMBs are taken into account to improve implementation results. The new optimization process significantly reduces the number of used FPGA resources with respect to the previous one. In addition, the proposed approaches achieve an adequate trade-off between the usage of EMBs and LUTs with respect to conventional FSM implementations based on ROM and to those based on LUT.

This work is focused on the problem of designing efficient reconfigurable multiplexer banks for RAM-based implementations of reconfigurable state machines. We propose a new architecture (called combination-based reconfigurable multiplexer bank, CRMUX) that use multiplexers simpler than that of the state-of-the-art architecture (called variation-based reconfigurable multiplexer bank, VRMUX). The performance (in terms of speed, area and reconfiguration cost) of both architectures is compared. Experimental results from MCNC finite state machine (FSM) benchmarks show that CRMUX is faster and more area-efficient than VRMUX. The reconfiguration cost of both multiplexer banks is studied using a behavioral model of a reconfigurable state machine. The results show that the reconfiguration cost of CRMUX is lower than that of VRMUX in most cases.

A new approach for ROM implementation of finite state machines (FSMs) is proposed, based on the selection of a subset of inputs in each state using multiplexers. This technique has been applied to different FSM standard benchmarks and very good results have been obtained.