[Coco] ML Question: Hi Res Text Screen

[Robert Gault]

William Mikrut wrote:
> It's been a long, lone time since I have been down this path.
>
> Years ago I was working with Robert Gault and others and was able to
> initialize and load graphic screens and the high res text screens from
> assembly.
>
> I know I can JSR to $F679 to set the default 80 column mode.
>
> I know to manipulate registers FFB8-FF9E  for foreground colors and
> FFB0-FFB6 for foreground (text) colors.
>
> What I cannot remember, for the life of me, is which register controls the
> top/bottom borders of the page?
>

Well it can be more complicated depending if you are using the ROMs or have a 
completely independent ml program, but $FF98 and $FF99 control the number of 
lines per character and number of lines per screen respectively.

$FF99 bits 5&6(0-7) are the lines per field.
0,0 192
0,1 200
1,0 undefined and produces weird results
1,1 225

However, if you are using the SECB ROM, it will reset the above values unless 
you change the tables at $E032. Study "Super Extended Basic Unravelled" which 
can be found on the Internet.

Changing the top and bottom screen boarders may also involve changing the delay 
after a VSYNC if the above does not do the job.

Robert