[Coco] CoCo 3 Prototype - Reverse Engineered

[Robert Gault]

brian palmer wrote:
> Hi Robert.
> 
> I'm curious to know If you tried setting Text Characters to the strange mode I found RG. Since I did find that normal Palette Control was inactive except for $FFB0 and that the HEVEN Reg was also not being used or not accessible. So I'm curious to know if maybe this strange mode is a very odd form of Semi-graphics by some chance, I'm going to attempt placing Characters on the screen, Since the strange mode does give you 28rows if you set 011, or 25rows if you use 100 since these settings are Text based bits. The hard part will be learning how semi-graphics characters were placed on the display screen. I'm hoping maybe you have already attempted this Robert.
> 
> Another thing I did manage to get the Hack to start running from $FEXX thru to the end of the $FE69 area, And when you set the Text based bits, 101 would give you a perfect 20rows, And I'm sure another bit setting gives you 25rows.
> 
> Next course of action if Text based Charcters have not been attempted is to try and set up text characters to this mode. Btw the reserved bits in normal text modes were they usable or did they not work correctly. Since I did find that the hack using Text modes the reserved Lines Per Row settings give you a nice clean Text mode.
> 
> laters
> 
> Briza
> 
> 
> 
> 
>

I've not tried to use these modes as activated in your test program. As 
for semi-graphics, they are placed on the screen for the most part just 
as letters are.

I'd suggest that you try initiating these unsanctioned modes without 
using special memory locations for your code, involving the timer, or 
changing the screen at each interrupt. If what you are seeing represents 
new useful if unsanctioned screen modes, then they should be completely 
stable in normal use.
One way to try this would be to modify the tables at $E032- and the 
hires print routines to reflect any changes in character height. Then 
just see if Basic runs.