[stella] *Why* does the AtariVox work?

[Stephen Anthony]

On April 16, 2008 08:24:37 am Thomas Jentzsch wrote:
> Stephen wrote:
> > Yes, I know that seems like a strange question.  However, I don't
> > understand how writing SWACNT actually writes data to the
> > controller port.  I thought writing SWACNT only acted as a 'mask'
> > for further reads/writes done by SWCHA.  But it seems as if
> > actually setting SWACNT causes writes to be sent to the controller
> > port.  Is this correct?
>
> I don't think so. The code I have indicates that SWACNT is only used
> for masking. What makes you think that SWACNT causes writes?
>
> > I'm asking because the AtariVox support in Stella does just that;
> > any writes to SWACNT then also do writes to the controller port,
> > and these latter writes are what drives the AVox.
>
> That sounds correct to me.

OK, now I'm confused.  My first paragraph states that writing to SWACNT 
causes immediate writes to the controller port as well, and you don't 
agree.  But in the next paragraph I say the same thing, and now you do 
agree :)  Which is it?  As for the second part (about Stella doing it 
that way), it only does so because we added a hack for it; what I'm 
trying to figure out is what's really supposed to happen.

> > The overall point of the this question is to get AVox/Savekey
> > EEPROM emulation working, which is causing problems right now.
>
> I suppose your problems must be somewhere else then.

I'm not convinced just yet, since accessing the SpeakJet and EEPROM are 
in some ways similar (using SWACNT and SWCHA), and may be a symptom of 
the same problem.

Thanks,
Steve