[Coco] Last video I promise... :)

[Luis Antoniosi (CoCoDemus)]

I needed a framebuffer because I couldn't make it to work without it. The
GIME clock gets out of the sync with the VGA timing and I ended up having a
rolling screen.

The pixel clocks are not mutiple. While the GIME pixel clock is 14.318Mhz,
the VGA pixel clock is 25.175Mhz

My converter needs a pixel perfect representation of the screen in order to
reconstruct the artifact modes. If I sample the screen using a different
clock pixel than a NTSC multiple I get a pixelated screen that is not
possible to make any artifact.

Having a framebuffer in the middle gives me freedom to each component to
work at their own speeds. Also, this solves the problem to convert from
50Hz to VGA 60Hz. I have a french coco2 peritel that does RGB SCART in 50Hz
and a MSX computer that can operate in 50Hz NTSC.


Luis Felipe Antoniosi



On Wed, Nov 12, 2014 at 1:45 AM, Mark McDougall <msmcdoug at iinet.net.au>
wrote:

> On 12/11/2014 12:06 PM, Luis Antoniosi (CoCoDemus) wrote:
>
>  top_generic is the general version and top_coco3 is the customized version
>>
>
> Why do you need a frame buffer?
>
> Regards,
>
> --
> |              Mark McDougall              | "Electrical Engineers do it
> |  <http://members.iinet.net.au/~msmcdoug> |   with less resistance!"
>
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