Merge pull request #26 from mintar/patch-2

README: from -> except
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Tim Ansell 2019-08-22 15:17:25 +02:00 committed by GitHub
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@ -64,7 +64,7 @@ To do this, we turn to a truth table:
| IO3 | 0 | 1 | 0 | 1 | 0 | 1 | 0 | 1 | 0 | 1 | 0 | 1 | 0 | 1 | 0 | 1 |
| O |_?_|_?_|_?_|_?_|_?_|_?_|_?_|_?_|_?_|_?_|_?_ |_?_ |_?_ |_?_ |_?_ |_?_ |
For example, to create a LUT that acted as an AND gate, we would define O to be 0 for everything except the last column. To create a NAND gate, we would define O to be 1 for everything from the last column.
For example, to create a LUT that acted as an AND gate, we would define O to be 0 for everything except the last column. To create a NAND gate, we would define O to be 1 for everything except the last column.
FPGA LUTs are almost always _n_-inputs to 1-output. The ICE family of FPGAs from Lattice have 4-input LUTs. Xilinx parts tend to have 5- or 6-input LUTs which generally means they can do more logic in fewer LUTs. Comparing LUT count between FPGAs is a bit like comparing clock speed between different CPUs - not entirely accurate, but certainly a helpful rule of thumb.