![]() The technology used was a 2 µm aluminum technology with 2 levels of metallization. This device had a maximum capacity of 800 logic gates. The best industrial and academic FPGA synthesis flows are around 70 times larger in terms of area on average and, in some cases, as much as 500 times larger on LEKU examples. The first commercial FPGA chip (XC2064) was introduced and delivered for the first time in 1985 by the American technology company (Xilinx). The LEKU circuits were constructed to show where the logic synthesis flow can be improved, while the LEKO circuits specifically deal with the performance of the technology mapping. Using these circuits and their derivatives (called Logic synthesis Examples with Known Optimal (LEKO) and Logic synthesis Examples with Known Upper bounds (LEKU), respectively), we show that although leading FPGA technology-mapping algorithms can produce close to optimal solutions, the results from the entire logic-synthesis flow (logicoptimization+mapping) are far from optimal. LUT-based obfuscation in FPGA In an FPGA solutions the hardware resources are are xed and is designed independent of a given netlist. These TTL chips were the mainstay of digital design throughout the 1960s and 1970s. These basic gates were provided in SSI chips using various technologies, the most popular being transistor-transistor logic (TTL). Because in Xilinx devices we have LUT1, LUT2, LUT3, LUT4, LUT5 and LUT6. LUT-BASED OBFUSCATION FOR ASIC AND FPGA A. circuit can be made using only NAND gates (or only NOR gates), where each NAND or NOR gate contains four transistors. Methods that inspect the subcircuit structure containing gates in ASIC netlists cannot be immediately ap-plied to FPGA netlists. In FPGAs, LUTs, carry modules and other combinational modules absorb considerable amount of logic. A rough estimate of the FPGA LUTs required for implementing ASIC gates is as follows. It says, 1 LUT 6 Two input NAND Gate equivalent (go try it) What I don't understand is what is meant by 'LUT'. of gate-level ASIC netlist reverse engineering, only a few techniques address FPGA designs. In this paper, we present a novel method for constructing arbitrarily large circuits that have known optimal solutions after technology mapping. Figure 1 shows a typical flow for prototyping ASICs using FPGAs. I know the > approximate conversion ratio between ASIC and FPGA gates is 1:5, but > way of identifying gates used in FPGA implementation is unknown > (atleast for the latest families to be implemented on ISE 10.1). Although there are many empirical studies that compare different FPGA synthesis/mapping algorithms, little is known about how far these algorithms are from the optimal (recall that both logic-optimization and technology-mapping problems are NP-hard, if we consider area optimization in addition to delay/depth optimization). It seems natural to then question whether the current logic-synthesis and technology-mapping algorithms for FPGA designs are producing near-optimal solutions. ![]() However, progress within the last few years has slowed considerably (with some notable exceptions). Field-programmable gate-array (FPGA) logic synthesis and technology mapping have been studied extensively over the past 15 years. ![]()
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