But given 2-inputs, there’s lots of possible output combinations, which all must be possible to satisfy given a 2-input LUT. The above examples show a 2-input LUT that has been configured to be an AND gate and an OR gate. If it's for a single prototype, just use the biggest FPGA you can afford. A Look-Up Table (LUT) is how any arbitrary Boolean logic gets implemented inside your FPGA.
#6 input lut upgrade
I suggest you choose your vendor, port enough of your design to get an idea of how big a FPGA you need and choose a FPGA with an upgrade path (if you want to market). The same design on two different foundries should have similar system gates number, as waste is not really an issue for ASIC. I want to put a design with approx 4 times more LUTs onto an FPGA. System gates is a common measure of ASIC design complexity. Hi We build designs with very high logic cell count and interconnect density - but relatively low usage of registers, dsp, block ram etc. Consider an example of MUX consisting of 4 bit input and 2 bit sel line and is implemented in HDL as, Then the Schematic would look like as depicted by below illustration. Same with fast-carry logic, I don't know if they count that in equivalent gate number, but be advised that number is inflated. A single LUT6 contains 6 input pins and a output pin, which can be used to implement a 4:1 MUX (where 4 inputs + 2 select lines 6 inputs).
A Xilinx FPGA should fit 1.5 times the logic of an Altera FPGA, since it's LUT have 6 instead of 4, right? Well, it largely depends on the design, if the design can't use 6-inputs much, the unused ones are wasted. They are aggregated in logic blocks which has other features like fast-carry chain, registers and distributed memory.Ĭonverting to system gates is useful, but don't forget it's also a marketing war. In their most recent architecture, Xilinx use 6-input LUT and altera 4-input LUT. Xilinx has adopted a different approach to design a CLB that contains the two slices each slice has four 6-input LUTs as shown in Figure 5 with two outputs and integrated with fast look-ahead carry logic and provide with better routing switches.
#6 input lut code
Although code targeting 4-input LUT architectures compiles successfully for 6-input. For many years 4-input LUT is the traditional LUT architecture design in practice. Take advantage of this feature by restructuring your code for better performance.
In Intel FPGA device families with 6-input LUT in their basic logic structure, ALMs can simultaneously add three bits. Xilinx use LUT, Altera LE, microsemi/lattice possibly something else. Architectures with 6-Input LUTs in Adaptive Logic Modules. LUT, Logic Cell and Logic Element are all the same to me: the most basic FPGA general logic primitive.
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