[Coco] ML Question: Hi Res Text Screen

[William Mikrut]

Hello Robert!

With the advance of support for the CoCo I have definitely renewed my
interest in software development. Right now I am working on an easy project
as a starter to get something out there.

Once I am down I will upload it to colorcomputerarchive and go on from
there!
Thank you so much for the info.. I will start going through everything
again.

I remember back in 2008 or so I was flipping screens with ease.. it's just
moved out of my memory.





On Wed, Feb 11, 2015 at 5:24 PM, Robert Gault <robert.gault at att.net> wrote:

> 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
>
>
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