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

RJRTTY at aol.com RJRTTY at aol.com
Tue Apr 5 02:28:56 EDT 2005

In a message dated 4/4/05 8:56:20 AM Eastern Daylight Time, 
Torsten at Dittel.info writes:

<< Isn't there a normally unused (input) pin at the CoCo's RGB connector, 
 which was planned to be used for RGB monitor detection? AFAIR (don't 
 have the Service Manual here) it is connected to a PIA and might be 
 programmed as an output to replace the cassette cable solution...

      You know I think that can work !!!!   Both the coco3 and the
converter could syncronize to the vertical sync signal using it as
the I2C clock.   The PIA line could do full duplex by programming
the PIA bit 3 in the register at &HFF22 for input or output on the fly
as needed for the data signal.

         You see?   That's what I like about this group.    Good ideas
abound and flow freely for anyone to use.
         I will look into this now and after the fest.   If it does work
and it doesn't take too long to impliment, I will use it.    The only
problem I can see is that I wont be able to use the "standard"
monitor cable people may already have (and you can get from
cloud nine).   Not enough pins.  Cable has 6 pins and we
need 7 unless someone knows how I could multiplex the PIA
signal with one of the RGB signals.

    Hmmmm,   let me think about this for awhile and we'll see.

<< By the way, is there a picture visible without running any software 
 before? I guess the software is just to modify e.g. the gamma curves...
 Torsten >>

     The display is there after power up when you hit the reset button
 on the coverter but it does not give a readable display, just a green "blob".
Programming is necessary  because the default values
for the registers in the video chips aren't compatible with
the coco3's video output.

If  you have to have a readable display on start up you could use a small
submonitor connected to the RF or composite video input I guess.
You could also use a short and easy to input filename for the
initialization routine when using RS basic or put it in a startup
file for Nitros9.   I don't have any trouble executing the initialization
file "blind" under RS basic.


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