[Coco] Re: Re: [Color Computer] Re: Adapter from Coo3 to SVGA

[jdaggett at gate.net]

Rodney

Here is a better explanation.

When you write to $FF22 you will write to the GIME chip i nternal register at $FF22. 
Internal to the GIME this register is a write only register. So that the old Coco1/2 bits 
for mode control of the 6847 will be maintained. A read of that address address will 
actually read from the PIA chip. 

Thus PB3 to PB7 of the PIA chip can actually be used as general purpose inputs 
only. I was in error when I said that they could be used as general purpose I/O (input 
and/or output).

james

On 5 Apr 2005 at 21:57, Rodney V Hamilton wrote:

To:             	coco at maltedmedia.com
From:           	Rodney_Hamilton at GBRonline.com (Rodney V Hamilton)
Date sent:      	Tue, 5 Apr 2005 21:57:05 +0000 (UTC)
Subject:        	[Coco] Re: Re: [Color Computer] Re: Adapter from Coo3 to 
SVGA
Send reply to:  	CoCoList for Color Computer Enthusiasts 
<coco at maltedmedia.com>
	<mailto:coco-
request at maltedmedia.com?subject=unsubscribe>
	<mailto:coco-
request at maltedmedia.com?subject=subscribe>

> In article <42512D8A.18685.C5802A at localhost>, 
> jdaggett at gate.net said...
> >
> >Torsten
> >
> >Yes pin#10 from  the monitor connector goes to PB3 of IC4 
> >(68B21). PB4 to PB7 of that chip is also not used!!!
> >
> >These four pins can be used for a SPI, I2C, PWM, or general 
> >purpose I/O. These were the mode control pins that were used on the
> >Coco1 and Coco2. Only the Coco3 can use these pins for other
> >purposes. 
> >
> >PB3 to PB7 is not mirrored inside the GIME. 
> >
> >james
> 
> Are you sure about that, James?
> 
> You don't normally see it, but the GIME emulates the 6847T1 chip
> and uses these bits to control the "extra" display features.  If
> you change the control mask at &H95C9 from 7 to 255, you can see
> the effect of these bits.  BASIC normally masks them off when it
> returns to the OK prompt.
> 
> Here is what they control in the GIME:
>   ff22.3  CSS  color set select (try SCREEN 0,1)
>   ff22.4  LC   lowercase enable
>   ff22.5  INV  inverted video enable
>   ff22.6  BRD  border color enable
>   ff22.7  GFX  graphics mode enable
> 
> Normally, you would use a mask of 127 so that the screen
> always returns to text mode when the program exits.
> 
> Rodney
> 
> 
> 
> -- 
> Coco mailing list
> Coco at maltedmedia.com
> http://five.pairlist.net/mailman/listinfo/coco