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- Exponential function in vhdl

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Altera_Forum

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08-26-2016
07:38 AM

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Exponential function in vhdl

hiii

I want to implement exp(x.^2) in VHDL for synthesis. Can any one suggest how to do it. Here x is in signed format and i want result in fixed point arithmatic i.e. without rondoff operation. Is there any instruction like in MATLAB 'exp' is there . Thanks and regards!Link Copied

8 Replies

Altera_Forum

Honored Contributor I

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08-26-2016
09:49 AM

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For exponential, you will need to create a look up table filled with all the results.

The address input of the LUT is x and the output is your function.
Altera_Forum

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08-26-2016
11:27 AM

450 Views

Altera_Forum

Honored Contributor I

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08-26-2016
12:04 PM

450 Views

Altera_Forum

Honored Contributor I

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08-26-2016
09:15 PM

450 Views

Altera_Forum

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08-27-2016
06:59 AM

450 Views

Altera_Forum

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08-27-2016
07:06 AM

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If not function then should I write any package for exp. Sorry I havent written any lookup table before so I dont know. And actually I want to design a Gaussian filter with variable window size & sigma value. For that I am using two 1D gaussian.

So the part I want to impliment is Gauss= exp^(-(x^2)/2*(sigma)^2); here sigma will vary from 0.1 to 5. and x is a vector =[-2 -1 0 1 2] for length equal to 5. I want to vary length also. How to do it.please help me with this. If you know any book for these type of operation then please suggest.
Altera_Forum

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08-27-2016
07:57 AM

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I highly suggest you learn about digital design. What you are going to create is a ROM - a read only memory. This can be done in VHDL using a constant which can be initialised from a function, a specified constant or a .mif file. you can have matlab generate the values to go into the constant.

There are plenty of examples out on the web.
Altera_Forum

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08-27-2016
07:57 AM

450 Views

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