exp(-x) function

I'm new to math function on FPGA, but I need to calculate exp(-x) wit a Spartan3 in fixed point 16bit numbers. How can i do that? What's th best way? Can someone hel me?[size=24:ae1f1145a8][/size:ae1f1145a8

Reply to
andpaoli
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Depends on what is the range of parameters. Your statement "fixed point 16bit numbers" doesn't help much, because it doesn't specify any particular encoding -- is it 8 bits for the integral part and 8 bits for fractions or only 16 bits of fraction, which describe a number in the range of (-1,1) or something else?

As I said, it depends.

Best regards Piotr Wyderski

Reply to
Piotr Wyderski

I've posted on this subject before (search google using andraka and exp) here is one such posting that is probably the closest to what you want:

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--Ray Andraka, P.E.
President, the Andraka Consulting Group, Inc.
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Ray Andraka

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Most likely that's the way to do it. An alternative would be a hyperbolic CORDIC, also explained by Ray:

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Kolja Sulimma

Reply to
Kolja Sulimma

If I needed high precision or for some reason could not use reasonably sized look-up tables, I'd consider a hybrid of these two, replacing the look-up with a CORDIC exp(x) after performing the normalize to strip off the integer part. The look up method I described in my prior post will get you plenty of precision for most applications.

--
--Ray Andraka, P.E.
President, the Andraka Consulting Group, Inc.
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Reply to
Ray Andraka

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