[Coco] Re: CoCo Monitor

Kevin Diggs kevdig at hypersurf.com
Thu Jun 24 18:20:51 EDT 2004


	What are "artifact colors"? Does this have anything to do with
the 555 timer chip that is hooked to one of the color lines from the
6847 in my deuce?


KnudsenMJ at aol.com wrote:
> In a message dated 6/23/04 1:37:38 PM Eastern Daylight Time,
> alsplace at pobox.com writes:
> > What is the connection between the CoCo's RGB-A outputs, and
> >  TV/composite?  Is there some reason a TV monitor would sync to 15khz?
> The vertical and horizontal sweep rates are the same from the Coco,
> regardless of composite versus RGB-A.
> The Coco's rates are the same as North American broadcast TV, so any TV
> monitor works fine with a Coco 3, or a 1/2 with a little internal hacking.
> In composite video, all three colors plus both syncs are crammed into one 4
> MHz bandwidth, so the video will be too smeared to read 80-column text or busy
> graphics, but 40-columns will read fine.
> Artifact colors won't work in RGB-A mode.
> >  Anyone care to refresh my memory on the technical aspects of CoCo video
> >  out?
> Well I got it off to a good start.
>  Thing to remember is, any TV set or composite monitor contains circuits that
> convert composite video into RGB-A.  Every TV set ends up RGB-A at the three
> guns of the color CRT.  Given the schematics for a color TV, you could figure
> out how to feed Coco RGB-A into the right places for a crisp picture.
> Same applies to the two syncs, hor and vert.
> Though a TV's CRT will not have fine enough dot pitch for 80-column text,  In
> fact, Tandy's CM-8 barely qualifies.
> --Mike K.
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