Ok, I misunderstood before.
FYI, I've been refering to lines by their number starting at 1, not 0,
because that's how the z26 trace log does it.
>From: Chris Wilkson <ecwilkso@xxxxxxx>
>Reply-To: stella@xxxxxxxxxxxxxxxxxx
>To: <stella@xxxxxxxxxxxxxxxxxx>
>Subject: RE: [stella] 262 scanline kernel is rolling
>Date: Sat, 26 Mar 2005 21:17:50 -0500
>
>Wait...
>
>What I meant was you should turn on VSYNC 3 lines after you turn on VBLANK.
>So when are you turning on VSYNC? Assuming you're numbering your lines so
>that the first line of VSYNC is line 0, (that's what most of the docs
>around
>here say to do) then you should turn on VBLANK at the beginning of line
>259.
>It would then be on for lines 259, 260, and 261. Then VSYNC comes on at
>the
>beginning of line 0 (= line 262) and turns off at the beginning of line 3.
>
>Is this equivilent to what you meant?
>
>-Chris
>
>On Sat, 26 Mar 2005, Zach M wrote:
>
> > I just tested a few minutes ago, and the screen does not roll anymore. I
>had
> > made the changes Dennis suggested, and also turned on VBLANK at line 261
>as
> > Chris had recommended. So it is hard to say exactly what the problem
>was.
> > The reason I suspect it had something to do with writing 8 to VBLANK is
> > because an earlier version of the kernel did not roll, and there #$42
>was
> > written to VBLANK (just like in"Our First Kernel"). The "lda #$42" line
> > before "sta VBLANK" was inadvertenly removed at some point.
> >
> > I might do more experiments with writing 8 to VBLANK if there is enough
> > interest.
> >
> > >From: "Dennis Debro" <dennis@xxxxxxxxxxxxxxx>
> > >Reply-To: stella@xxxxxxxxxxxxxxxxxx
> > >To: <stella@xxxxxxxxxxxxxxxxxx>
> > >Subject: RE: [stella] 262 scanline kernel is rolling
> > >Date: Sat, 26 Mar 2005 14:49:35 -0500
> > >
> > >Hi there,
> > >
> > > > Right now you're writing 0 at the start of vertical blank
> > > > and 8 at the start of overscan.
> > >
> > >That is strange. As Thomas said, D1 of VBLANK only controls the TIA
>output.
> > >At least as documented by the programming manual. So writing 8 to the
> > >register is essentially the same as writing 0 (i.e. enabling TIA
>output).
> > >
> > >I don't have my hardware setup at the moment to play with this. Was
>this
> > >truly the problem? What happens if you used other values or ignored
>VBLANK
> > >altogether? By the values you were entering this should have been
> > >simulated.
> > >Are there other bits used by VBLANK that we don't know about?
> > >
> > >Take care,
> > >Dennis
> >
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