[time-nuts] Re: pulling some crystals

[ghf at hoffmann-hochfrequenz.de]

Am 2023-12-18 16:14, schrieb Matt Huszagh via time-nuts:

> Don't forget that you can also use a lookup table implementation with
> interpolation between table entries. Often, a small table and simple
.......
> This probably goes without saying, but also don't forget that you don't
> need to store one full sine/cosine period! The only non-redundant part
> if you're computing just sine or just cosine is one quarter of the
> period. Or, if you're computing both simultaneously, just take 1/8 of a
> period. So, for the fixed-point implementation when computing both, 
> drop
> the 3 most significant bits for lookup in the table, then use those 3
...


I'd sign all of this.

I have published a Sine/cos table some 12 years ago in pure VHDL on
<  https://opencores.org/projects/sincos   > that does all the mirroring
and pipelining automagically and delivers sine AND cos at the same time
without doubling the resources. IIRC it ran at 200 MHz without tuning on 
a
Spartan 6 eval board. Completely portable, no Xilinx IP required. (but
synthesis-friendly). The delays of a CORDIC are highly unwelcome in an 
all-
digital PLL or Costas loop, and for mixed A/D systems, the DAC and its
reference voltage are usually the limit.

With hardwired carry chains, DSP-48 blocks and block rams, long word 
lengths
have lost their horror.

In 1985, I built this 200 MSPS signal averager. It took 8 pipelines in
parallel, each 2 dozen stages deep. We have come a long way since then.
<   
https://www.flickr.com/photos/137684711@N07/52758369518/in/dateposted-public/ 
     >
The board replaces everything blurred in the background.

Attila, if you see this, that was at Fraunhofer, 300 meters downhill
from where you work now.  :-)

regards, Gerhard