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Ok I think i understand what you mean. But when I will initiate the ROM with some sort of funktion, i will need to use some other program to do that, right?
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Not necessarily. There is a cos function in VHDL that can be used to directly calculate the correct values.
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So say I use Excel to do my calculation and convert it to a *.mif file. How about the answers in the calculation? They are real numbers, will they automatic be converted?
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No, you will need to use excel functions to convert them to decimal or hexadecimal first.