[Coco] Hi! I'm new here!

[Robert Gault]

Hugo Dufort wrote:

><snip>
> Reading the documentation, I can't even figure out how to initialize
> the high-res graphics. I would like to first test the functionalities in Basic
> (init graphics using pokes/peeks, vertical/horizontal scrolling, memory copy, etc.)
>
> Right now I'm trying to figure out the high-res graphics using memory addresses
> FF90 to FF9F. I also want to understand how to set & move the graphic port
> adress in memory (MMU banks?) I'd go with 256x200x16 and try the scrolling
> pokes. By the way, is anyone using the 320x225 or 256x225 modes? Are they
> useful? Thanks.
>
> Hugo
>

Greetings and I hope you enjoy this listserver!

To turn on the Coco3 hi-res screens from Basic, there are two simple methods. 
The easiest uses the hi-res text screens which can be turned on with a command.
WIDTH40    you get a 40 column text screen
WIDTH80    you get an 80 column text screen

You can turn on the hi-res graphic screens with simple commands but they will 
not stay turned on unless a program is running. HSCREEN mode   is the command 
needed. The modes are
mode          screen type
0               revert to low-res PMODE
1               320x192,  4 color
2               320x192, 16 color
3               640x192,  2 color
4               640x192,  4 color

You can't arbitrarily alter the formats of these screens as they will be reset 
by Basic. However, you can make changes within ml programs or you can patch 
Basic to force changes in the screen formats.
All Coco3 units run in full RAM mode, that means you can POKE changes to the ROM 
code. You will want to find the Coco3 Service Manual and the "Unravelled" series 
of books on-line for complete discussions and listing of the ROM code.
The screen formats are controlled by two tables at
$E032-E04C  text screens
$E070-$E081 graphic screens
If you change the bytes corresponding to $FF98-$FF99, then you can alter the 
number of rows per text letter and the horizontal and vertical screen size.

I normally run OS-9 (NitrOS-9) with 80x225 text screens. There is not much point 
in trying to change the Basic graphic/text screens as the ROM code does not 
support 225 lines. If you patch the ROM code, then you can use the larger screens.
There has been some experimentation with unsupported screen settings and you can 
find discussions at
http://www.tandycoco.com/forum/         limited activity
and
http://www.coco3.com/community/         essentially inactive

To understand the use of $FF90-$FF9F, you should study the Coco3 service manual 
and the code in the Unravelled series. Ask specific questions and you will get 
answers on the listserver.

Robert