Re: [hatari-devel] falcon crossbar and ff8932

[Nicolas Pomarède <npomarede@xxxxxxxxxxxx>]

Le 22/09/2016 à 16:39, Nicolas Pomarède a écrit :
> Le 22/09/2016 à 10:25, Nicolas Pomarède a écrit :
> > Le 21/09/2016 à 22:20, Laurent Sallafranque a écrit :
> > > Hi,
> > >
> > > When I coded the crossbar, I used another file that describes the
> > > registers.
> > > I haven't got any official doc for this, I did it by guessing the
> > > behaviour and with the help of the hardware.txt file.
> > > I don't ever think I had a Falcon by the time.
> > >
> > > I don't think it is possible to disconnect completly the sound from the
> > > crossbar, I'll have to check this with my Falcon.
> > >
> > > If you look at the compendium, it gives another mapping for this
> > > register (which seems to be wrong anyway).
> > >
> > > I'll do some tests.
> > >
> > > Laurent
> >
> > Teaser : based on this info (but not directly related), I should be able
> > to provide a fix to remove the noisy / random sound under Falcon
> > crossbar ;-)
>
> By the way, could you test on a real Falcon a call to xbios $8c with
> param=1 ?  (function sndstatus).
>
> This is supposed to reset the sound to some default values and to
> disconnect the crossbar matrix.
>
> Can you read the crossbard registers af $ff89xx after this call, to see
> what are those default values ?
>
> eg :
>
> move.w    #1,-(sp)
> move.w    #$8c,-(sp)
> trap      #14
> addq.l    #4,sp

Hi

Just for the record, I had a look at the TOS part to handle trap $8c and 
$8b (Devconnect) and from there it seems not possible to completely 
disconnect the DAC output from the crossbar : the DAC will always be 
connected to 1 of 4 possible sources.

For those interested in $ff8930/$ff8932 registers, you can have a look 
at $e066d0 and $e06504 for those 2 xbios calls. Unfortunatelly, some of 
the undocumented bits are not used by those 2 calls, so it's hard to get 
an authoritative meaning for all the falcon's sound registers.

Nicolas