[Coco] Re: CoCo Monitor

KnudsenMJ at aol.com KnudsenMJ at aol.com
Wed Jun 23 23:11:46 EDT 2004

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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