[time-nuts] DDS - Cosine v. Sine LUT

Luis Cupido cupido at mail.ua.pt
Tue Jun 21 19:18:19 UTC 2011

Hi Brent,

A quarter table cos is exactly the same as a quarter table sin.
Only backwards, and not telling which quarter it is makes it a
quarter of either sin or cos. For one single output becomes irrelevant
as you only need one.
So I think it is just a matter of taste the name to call it.

Luis Cupido.

On 6/21/2011 8:03 PM, KD0GLS wrote:
>> On Jun 21, 2011, at 13:39, Chris Albertson wrote:
>> I used only 90 degrees of the table.
> Yes, as did I and most implementations, but why a cosine quarter-table instead of the more common sine?  A quick look at the data sheets (and the waveforms in the theory-of-op sections) for the two devices suggests they are clearly calling out one or the other, but without rationale regarding the choice.
> .73,
> Brent, KD0GLS, Minneapolis
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