Low pass MAC Filter incorrect response

Hi all, thanks to your help, I have managed to solve the JTAG problem on my 
XTREME DSP Development Kit.

However I had a response which attenuates all frequencies even though my 
design is low pass filter.. Anybody can help me with that because i checked 
through my design n it seems fine. It is a MAC based FIR 43 tap filter 
though. 

"Bryan" <sfoo@xilinx.com> writes:

> Hi all, thanks to your help, I have managed to solve the JTAG problem on my 
> XTREME DSP Development Kit.
>
> However I had a response which attenuates all frequencies even though my 
> design is low pass filter.. Anybody can help me with that because i checked 
> through my design n it seems fine. It is a MAC based FIR 43 tap filter 
> though. 

It's almost certainly a scaling problem. What are your coefficients and the
relevent wordlengths (input wordlength, coefficient wordlength, accumulator
wordlength, etc.)?
-- 
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%% Fuquay-Varina, NC            %  sliding, it's magic."
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http://home.earthlink.net/~yatescr

Bryan wrote:
> Hi all, thanks to your help, I have managed to solve the JTAG problem on my 
> XTREME DSP Development Kit.
> 
> However I had a response which attenuates all frequencies even though my 
> design is low pass filter.. Anybody can help me with that because i checked 
> through my design n it seems fine. It is a MAC based FIR 43 tap filter 
> though. 
> 
> 
Before you do anything else, try just passing your input signal to the 
output and see how loud it is -- once you have that for a baseline, then 
look at what's wrong with your filter.

-- 

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

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