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Coco background. Color


MrDave

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On 12/24/2019 at 7:35 AM, MrDave said:

Does anyone know if the screen color can be changed in the color basic rom ? I can easily reprogram the rom..

I was under the impression that the text (and background) colour was fixed by the 6847 video chip. I have never seen any software that changes the standard BASIC/OS screen colour.

 

There is a software way to switch the screen to an orange colour; it is used in the cartridge game Poltergeist. Alas, I have long since forgotten the details. 

 

It is also possible to force inverted video (light green text on a darker green background), but that requires a hardware modification.

 

If you look at some of the few other applications of the 6847 video chip (including a prototype computer adapter for the Atari 2600!), they all have the same 32x16 green screen with black text. 

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Funny from basic i can poke at ff22 to change modes to real lower case.. orange background  orange or green outside border and inverse the screen too ! It looks like orange on dark red really cool.. but as soon as basic tried to print it put it back to green lol. If i cant find it in rom i may hardware attack the vid chip !

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Ok so I have this figured out now

On alot of coco2's even in xroar ( coco2b mode)

Poke &H0167,&H39

Poke &HFF22,&H78

The first command locks out basic from resetting the vdg the second is a poke into the vdg the 7 can be a 7,6,5,4,3,2,1,0 and the second digit an 8 for orange or 0 for green

The top bits are for wideScreen..inverse,,lowercase. Try it out !

20200104_184910.jpg

Edited by MrDave
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On 1/4/2020 at 6:42 PM, MrDave said:

 

20200104_184910.jpg

 

Was there any commercial (or even amateur) software that used this mode? 

 

I am unsure if I like it more or less than the standard green screen. Neither is choice is great. 

 

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On 12/28/2019 at 5:53 PM, MrDave said:

Ahh i seen you on cocotalk.. i'm dave of dave & sharron. Lol i suppose if i really wanna play with the roms i could swap in a static ram to figure everything out by trial.. but someone must have done it already...

Thanks

 

Yep, that's me...   One of the CoCoTALKers that's been there since the First Show...  ;)

 

The Tandy CoCo Discord Server is https://discord.gg/4J5nHXm

 

MarkO

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On 1/4/2020 at 5:42 PM, MrDave said:

Ok so I have this figured out now

On alot of coco2's even in xroar ( coco2b mode)

Poke &H0167,&H39

Poke &HFF22,&H78

The first command locks out basic from resetting the vdg the second is a poke into the vdg the 7 can be a 7,6,5,4,3,2,1,0 and the second digit an 8 for orange or 0 for green

The top bits are for wideScreen..inverse,,lowercase. Try it out !

 

 

Good Information....

 

MarkO

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