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piecewise linear function

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mohammadyou

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hi
i want to implement this function
Y=1./(1+exp(-x));
in FPGA
i can convert this nonlinear function to linear
like the picture show

but i want to know
is any program or matlab command
that do it for me
(for example i give the number of piece and program estimate the best linear function for me)

thank you :roll:
 

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A complex function can best be implemented using a look-up table. If you don't need high resolution, try to linearize.

There might exist a function for that in matlab, but it's just basic math.
 

thank you for your reply
but I need to save my register because of that i think its better linearized the function and just input line equation in FPGA !!!

another question is
can i use block ram and split it to n bank
i want to know its possible to read more data in the same clock from block ram
if it is possible i can use look-up table and store in block ram

best wishes
 

Today it's still not possible to split block RAM in banks. However, you can assign a range of addresses to your lookup table and another range for storage. This will take two clock cycles. Remember that the RAM will lose it's contents when power switches off.

If you can linearize, it should be possible to make use of the DSP blocks in FPGA's. Depending on the input range a different parameter set (a, b) is loaded (y = a.x + b).

helpful?
 
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