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NCO DESIGN

Hi everybody,

I would like to implement a NCO (Numerical Controlled Oscillator).

The output is a square wave. The reference clock is 352 MHz.
I want the output varies by step of 2,841ns around a 22MHz square signal.

What is the simplest way to implement it :

if rising_edge(clk_ref) then
  count <= count + 1 + in;
end;

if (count>=16) then 
  output <= 1;
  count <= 0;
else
  output <= 0;
end;
0
patrick
5/5/2004 1:48:56 PM
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patrick.melet@dmradiocom.fr (Patrick) wrote in message news:<54b3002.0405050548.40d8eb56@posting.google.com>...
> Hi everybody,
> 
> I would like to implement a NCO (Numerical Controlled Oscillator).
> 
> The output is a square wave. The reference clock is 352 MHz.
> I want the output varies by step of 2,841ns around a 22MHz square signal.
> 
> What is the simplest way to implement it :
> 
> if rising_edge(clk_ref) then
>   count <= count + 1 + in;
> end;
> 
> if (count>=16) then 
>   output <= 1;
>   count <= 0;
> else
>   output <= 0;
> end;

I am no expert on NCOs, but here is a good website for the basic
theory of operation.  It will not tell you the best way to implement a
VHDL design.  I expect this depends on your target device.  You can
also download a simulator if you wish.

Charles

http://www.geocities.com/CapeCanaveral/5611/dds.html
0
charles
5/10/2004 12:24:55 PM
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