# Reducing LUT Count for FPGA-Based Mealy FSMs
## 6 Experimental Results  
To investigate the efficiency of proposed method, we use standard benchmarks from the library [29]. The library includes 48 benchmarks taken from the design practice. The benchmarks are rather simple, but they are very often used by different researches to compare new and known results [9; 43]. The benchmarks are represented in KISS2 format. These benchmarks are Mealy FSMs, so we can directly use them in our research. The characteristics of these benchmark FSMs are shown in Table 4.  
The process of obtaining synthesis research results in Vivado [57] has been divided into two stages. The first stage was a generation of the VHDL code based on benchmarks saved in the KISS2 format. Each benchmark was generated by the tool K2F [35; 45] according to the given FSM model. It should be noted that generated code uses a specific Vivado code style [65] in order to provide the proper FSM extraction and fully synthesizable code. Then, in the next stage, the VHDL code was imported into Vivado (ver. 2019.1). The target device was the Xilinx Virtex 7 (XC7 VX690 TTFG1761) [66]. The chip includes LUTs with six inputs. The synthesis and optimization options were set to: _max_bram 0_, _opt_design -retarget -propconst -bram_power_opt_ and the selected FSM state encoding method one of the following: _auto, one_hot, sequential, johnson_ or _gray_. The final results presented in the tables are taken after the post-implementation. As we have found, our method can give economy in area if \(R+L>S_{L}\). We have divided the benchmarks into categories using the values of \(L+R\) and \(S_{L}\). If \(L+R\leq 6\), then benchmarks belong to category 0 (trivial FSMs); if \(L+R\leq 12\), then to category 1 (simple FSMs); if \(L+R\leq 18\), then to category 2 (average FSMs); if \(L+R\leq 24\), then to category 3 (big FSMs); otherwise, they belong to category 4 (very big FSMs). Obviously, there is no sense to apply our approach to FSMs belonging to category 0. As our researches show, the higher the category, the more saving the proposed approach gives. \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Benchmark** & **L** & **N** & **R+L** & **M/R** & **H** & **Category** \\ \hline bbara & 4 & 2 & 8 & 12/4 & 60 & 1 \\ bbsse & 7 & 7 & 12 & 26/5 & 56 & 1 \\ bbtas & 2 & 2 & 6 & 9/4 & 24 & 0 \\ beecount & 3 & 4 & 7 & 10/4 & 28 & 1 \\ cse & 7 & 7 & 12 & 32/5 & 91 & 1 \\ dk14 & 3 & 5 & 8 & 26/5 & 56 & 1 \\ dk15 & 3 & 5 & 8 & 17/5 & 32 & 1 \\ dk16 & 2 & 3 & 9 & 75/7 & 108 & 1 \\ dk17 & 2 & 3 & 6 & 16/4 & 32 & 0 \\ dk27 & 1 & 2 & 5 & 10/4 & 14 & 0 \\ dk512 & 1 & 3 & 6 & 24/5 & 15 & 0 \\ donfile & 2 & 1 & 7 & 24/5 & 96 & 1 \\ ex1 & 9 & 19 & 16 & 80/7 & 138 & 2 \\ ex2 & 2 & 2 & 7 & 25/5 & 72 & 1 \\ ex3 & 2 & 2 & 6 & 14/4 & 36 & 0 \\ ex4 & 6 & 9 & 11 & 18/5 & 21 & 1 \\ ex5 & 2 & 2 & 6 & 16/4 & 32 & 0 \\ ex6 & 5 & 8 & 9 & 14/4 & 34 & 1 \\ ex7 & 2 & 2 & 12 & 17/5 & 36 & 1 \\ keyb & 7 & 7 & 12 & 22/5 & 170 & 1 \\ kirkman & 12 & 6 & 18 & 48/6 & 370 & 2 \\ lion & 2 & 1 & 5 & 5/3 & 11 & 0 \\ lion9 & 2 & 1 & 6 & 11/4 & 25 & 0 \\ mark1 & 5 & 16 & 10 & 22/5 & 22 & 1 \\ mc & 3 & 5 & 6 & 8/3 & 10 & 0 \\ modulo12 & 1 & 1 & 5 & 12/4 & 24 & 0 \\ opus & 5 & 6 & 10 & 18/5 & 22 & 1 \\ planet & 7 & 19 & 14 & 86/7 & 115 & 2 \\ planet1 & 7 & 19 & 14 & 86/7 & 115 & 2 \\ pma & 8 & 8 & 14 & 49/6 & 73 & 2 \\ s1 & 8 & 7 & 14 & 54/6 & 106 & 2 \\ s1488 & 8 & 19 & 15 & 112/7 & 251 & 2 \\ s1494 & 8 & 19 & 15 & 118/7 & 250 & 2 \\ s1a & 8 & 6 & 15 & 86/7 & 107 & 2 \\ s208 & 11 & 2 & 17 & 37/6 & 153 & 2 \\ s27 & 4 & 1 & 8 & 11/4 & 34 & 1 \\ s386 & 7 & 7 & 12 & 23/5 & 64 & 1 \\ s420 & 19 & 2 & 27 & 137/8 & 137 & 4 \\ s510 & 19 & 7 & 27 & 172/8 & 77 & 4 \\ s8 & 4 & 1 & 8 & 15/4 & 20 & 1 \\ s820 & 18 & 19 & 25 & 78/7 & 232 & 4 \\ s832 & 18 & 19 & 25 & 76/7 & 245 & 4 \\ sand & 11 & 9 & 18 & 88/7 & 184 & 3 \\ shifreg & 1 & 1 & 5 & 16/4 & 16 & 0 \\ sse & 7 & 7 & 12 & 26/5 & 56 & 1 \\ styr & 9 & 10 & 16 & 67/7 & 166 & 2 \\ tma & 7 & 9 & 13 & 63/6 & 44 & 2 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Characteristics of Mealy FSM benchmarks.