Re: [Discuss-gnuradio] TX modulator shadow?

[Eric Blossom]

On Sat, Feb 24, 2007 at 08:42:35PM -0500, George Nychis wrote:
> Hey all,
> 
> I was wondering what the following does when initializing the host end of 
> the transmit chain:
> 
>   for (int i = 0; i < MAX_CHAN; i++){
>     d_tx_modulator_shadow[i] = (TX_MODULATOR_DISABLE_NCO
>         | TX_MODULATOR_COARSE_MODULATION_NONE);
>     ...
>   }
> 
> Thanks :)
> 
> - George

It keeps us from having to make a round-trip to the AD9862 over the
USB when we need to know the current contents of a particular
register.  The registers in question contain info that may come from
different sources.  In this particular case, AD9862 register 20
contains bits for "Negative Fine Tune", "Fine Mode", "Real Mix",
"Negative Coarse Tune", and "Coarse Modulation".

We want to be able to do a "read-modify-write" without having to pay
the overhead for the read.

Eric