[Coco] Coco-3 to the GBS-8220 upscaler interfacing

[Steven Hirsch]

On Wed, 4 Jun 2014, Kandur wrote:

> Thanks.
> This circuit seem to assume negative sync inputs,
> while the Coco-3 has positive sync outputs.

>From the web site:

<quote>
The sync signal combiner has a system to adjust to different sync 
polarities so that it always makes correct composite sync signals. VGA 
card uses different sync signal polarities to tell the monitor which 
resolution is used. This circuit adjusts to sync signal polarity changes 
in less than 200 milliseconds, which is faster than setting time of a 
normal VGA monitor in the display mode change.
</quote>

It's actually a very clever design.



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