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Altera_Forum
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18 years ago

FIR coefficient reloading problem

I have a simple single rate FIR filter (StratixII, fully parallel, coef storage in M512, signed binary, 12 bit input data, 12 bit coefficient). I calculated a low pass with an external software, ...
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Altera_Forum
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18 years ago

Hi nemo,

I have some news. I decreased the number of coefficients from 51 to 3 and everything was fine. So I increased the coefficients to 31 and also, everything is fine. As I have a logic analyzer on the coef_in port I'm sure that I'm loading all data, with 31 coeffs as well as with 51 coeffs.

I suppose that coef_seq.exe has a bug. I tried to understand the source coef_seq.cpp but it is difficult. When having less or equal 31 coefficients, I always get a number of values from coef_seq.exe which are a power of 2 (4, 64, 128). With 51 coefs I get 192.

As I already mentioned, when loading the coefficients with the GUI, it's OK. I think they will use coef_seq.exe also inside the GUI when transforming the coefficients!?!

I'm trying to get an answer from ALTERA support because I can do nothing at the time because I don't know anything about the function of coef_seq.exe.