[Coco] Q: CoCo2 border

[jdaggett at gate.net]

Alex

The MC6847 chip is noninterlace.The chip is doing 262 vertical 
lines. One field per frame. Therefore the frame rate is ~ 60 frames 
per second. Well above the flicker rate. Movie projectors are 24 
frames per second. 

Per the 6847 spec

13 vertical blanking
26 top border
192 visable
25 bottom border
6 vertical retrace.


james
 

On 11 Jan 2004 at 10:36, Alex wrote:

From:           	Theodore (Alex) Evans 
<alxevans at concentric.net>
Subject:        	Re: [Coco] Q: CoCo2 border
Date sent:      	Sun, 11 Jan 2004 10:36:02 -1000
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> 
> On Jan 11, 2004, at 6:57 AM, jdaggett at gate.net wrote:
> 
> > Torsten
> >
> > Top border is 25 lines and bottom border is 26 lines. The right and
> > left borders in pixel count are more dependant on the pixel clock
> > frequency.
> 
> That just doesn't add up.  I frame of NTSC video has 525 lines 
> consisting of two fields of 262.5 lines each.  CoCo video uses 192
> lines per field leaving a total of 70.5 lines unused.  It is possible
> that the CoCo colors only 51 of these lines, and in fact a certain
> number of these must be maintained as black in order to avoid extra
> lines being drawn during retrace, but they are still there.
> 
> 
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