[Coco] Text/Background Screen Inversion

[Brendan Donahe]

Michael,

While what Alex describes is certainly the most straightforward approach,
I'd think it would also be possible to (on a 64k CoCo 1 or 2, at least), be
able to patch a copy of the BASIC ROM in RAM for use within all your
BASIC-only programs.  I'm not sure which system(s) you're targeting or in
what software you want to preserve your reverse-video.  The problem is that
even with a BASIC patch, other ML software you might launch from BASIC
likely overwrites that video mode setting and would not preserve the bit
change you wrote to the VDG control register.  $FF22 bit 5, in particular,
would be of interest to you - see page 50 of
https://www.lomont.org/software/misc/coco/Lomont_CoCoHardware.pdf.

If you want it permanent without copying the ROM to RAM and patching BASIC
or in various software packages, a hardware solution would be best.
Assuming we're talking about the CoCo 1 or 2, you can invert the sense of
the INV pin on the 6847 VDG with a hardware hack.  This was a common
modification back-in-the-day.

Hope this helps,
Brendan

On Sat, Jan 29, 2022 at 6:47 PM Alex Evans <varmfskii at gmail.com> wrote:

> Not really. When the CoCo is at the Ok prompt, it resets the display
> features.
> You can poke to invert the colors and/or switch to orange instead of green,
> and it will stay that way as long as your program is running.
>
>
> On Sat, Jan 29, 2022 at 3:14 PM <michaelkline704 at gmail.com> wrote:
>
> > Is there a poke(s) or a ML programme that would invert the screen
> > background
> > and text colours to a dark green background / light green text and leave
> it
> > that way until you power cycled?
> >
> >
> >
> > Michael
> >
> >
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