Re: [hatari-devel] Videl Emu and TimerB

[Laurent Sallafranque <laurent.sallafranque@xxxxxxx>]

Thanks Nicolas,

The first problem actually is that many code in mfp.c calls video_... 
functions
like video_get_position, video_getTimerBPos, ...

And as I don't want to call anything from video (which is no more 
initialized), it goes wrong.

Do you thing we should encapsulate every mfp.c functions with something 
like :
if (machine == falcon)
  do_ videl (or do_nothing)
else
  call video_...

What could explain that the mouse doesn't work anymore ?

Laurent



Le 07/03/2012 23:25, Nicolas Pomarède a écrit :
> On 07/03/2012 21:28, Laurent Sallafranque wrote:
> > Hi,
> >
> > I've given another try to handle all the HBL, VBL, ... into Videl and
> > stop using video.c for the Falcon)
> >
> > I manage to arrive to the desktop but with no mouse, because of timerB..
> >
> > The problem seems to be in void MFP_ActiveEdge_WriteByte(void)
> > At the end of the function, there's
> >
> > /* Timer B position changed, update the next interrupt */
> > if ( LineTimerBCycle_old != LineTimerBCycle )
> > Video_AddInterruptTimerB ( LineTimerBCycle );
> >
> > I'd like to recode this addInterruptTimerB into Videl, but I don't know
> > well what is the TimerB.
> >
> > Some doc or explanation is needed here.
> >
> > Regards
> >
> > Laurent
> Hello,
>
> this is strange, I don't recall timer B is used to drive the mouse on 
> a real ST (and I think it's the same on the falcon), I'm not sure this 
> is the cause of the problem.
>
> Basically, you need to emulate an interrupt that start when videl 
> starts displaying the right border. Forget all other code in video.c 
> (such as the one above), it's only STF/STE, for special corner cases.
>
> So, the "problem" is to compute the correct number of cycles to start 
> the timer B from the HBL interrupt so that the exception happens 
> roughly when videl will start drwaing the right border with color 0 
> (I'm not sure timer B is available in all the videl's video mode).
>
> A 1st approach to have a timer B is to call the timer B exception from 
> the HBL handler too, but only on visible line (not during top/bottom 
> boder). I think this would fix many demos that require timer B to do 
> rasters (color would not be changed at exactly the correct position 
> (maybe ~80-100 pixels too late), but that's a good base to start).
>
> Nicolas