Re: [hatari-devel] TT palette bankswitching should be supported

[Eero Tamminen <oak@xxxxxxxxxxxxxx>]

Hi,

Ah, so this isn't about ST<->TT color palette mapping,
but about e.g. 16/4/2 color modes.   Both TT and ST modes?


	- Eero


On 02/20/2016 04:45 PM, Roger Burrows wrote:
> Hi Eero,
> On 20 Feb 2016 at 11:37, Eero Tamminen wrote:
> > Bank number is taken into account in the ST & TT color register writes.
> Looking at my previous message, I can see that I did not explain the situation
> clearly enough.  If you switch banks (by writing to the TT shifter), the
> display screen does not switch to the new palette corresponding to the changed
> bank number.  It does on real hardware.  On Hatari, the displayed palette
> remains the same as before the switch.
>
> I have a very simple program that uses bank switching and works on my real TT
> but not on Hatari.  I can post it if necessary.
>
> Roger
> > On 02/19/2016 08:05 PM, Roger Burrows wrote:
> > > When running in ST Low, ST medium, or TT medium, the TT video hardware
> > supports
> > > bankswitching for the palette: the part of the TT palette that maps to the
> > > STe-compaitble palette can be changed, by changing the "bank number" in the
> > TT
> > > shifter.
> > >
> > > After power-on reset, the bank number is the set to zero, which causes the
> > > first 16 TT palette registers to map to the STe palette registers.  If you
> > set
> > > the bank number to N, then TT palette registers 16*N to 16*N+15 are mapped
> > > instead.  There is even a special TOS3 XBIOS call, EsetBank(), to do this.
> > >
> > > Hatari does not support this.
> > >
> > > In video.c, function Video_TTShiftMode_WriteWord(), I think that there needs
> > to
> > > be a check for bank number, which would then be used (I don't want to
> > guess
> > > where) to do the mapping.
> > >
> > > Tested on a real TT, and documented in "Atari TT030 Hardware Reference
> > Manual".
> > > Roger