[time-nuts] DDS'ery

[John Miles]

Correct, CORDIC doesn't require a multiplier, only adds and shifts.  That's
the whole idea.

-- john, KE5FX

> -----Original Message-----
> From: time-nuts-bounces at febo.com [mailto:time-nuts-
> bounces at febo.com] On Behalf Of lists at lazygranch.com
> Sent: Monday, June 20, 2011 5:24 PM
> To: Discussion of precise time and frequency measurement
> Subject: Re: [time-nuts] DDS'ery
> 
> I don't have the algorithm in front of me, but I don't recall any
> multiplication, just addition and magnitude comparison.
> -----Original Message-----
> From: Jim Lux <jimlux at earthlink.net>
> Sender: time-nuts-bounces at febo.com
> Date: Mon, 20 Jun 2011 17:14:44
> To: Discussion of precise time and frequency measurement<time-
> nuts at febo.com>
> Reply-To: Discussion of precise time and frequency measurement
> 	<time-nuts at febo.com>
> Subject: Re: [time-nuts] DDS'ery
> 
> On 6/20/11 12:17 PM, lists at lazygranch.com wrote:
> > Just a FYI, you don't have to use sine lookup tables. You can generate
sine
> and cosine on the fly with a coordic. Perhaps not easy at RF speed, but
very
> common in audio DSP.
> >
> 
> It's a tradeoff..  To do CORDIC you need four multiplies and 2 adds,
> which might be a lot of gates, if you have a fair number of bits,
> compared to an adder and some lookup tables.
> 
> If you have a fast multiply instruction on a processor, then CORDIC gets
> very attractive.
> 
> The other problem with CORDIC is that roundoff errors accumulate, the
> longer you run the generator for, because it's basically a difference
> equation/numerical integration sort of scheme.
> 
> That said, some of AD's latest DDSes use a monolithic CORDIC generator.
> 
>