On Jan 16, 3:58*am, blue39 <(E-Mail Removed)> wrote:

> I need to find the value of e^(-x/y); where y is the constant and x keepschanging.

>

> Does anyone know how to find this value on Xilinx FPGAs. Is there any core available for it? or any Algorithm would also do.

>

> Thanks in advance.

>
Like all things, having an idea of what X is: complex/real, fixed/

floating point, range & resolution, bandwith and allowable latency to

get the answer (and what is its kind/range/resolution?) are going to

impact the choice of method to do the calculation.

Also, is Y REALLY a constant, or is it a parameter that changes very

infrequently, but you don't want to have to re-synthesize, place &

route to change it?

Without knowing the above, and since you only have one real-time

input, I would hesitantly suggest a look-up table, and depending on

range/resolution of the input and the result, linear interpolation

between table entries. Depending on the target architecture (whether

block ROMs are available), you may be able to populate the table with

a VHDL initialization function for the constant array that is the

table.

Andy