[Coco] PAL Coco 1/2 schematics/timings
msmcdoug at iinet.net.au
Fri Sep 10 02:51:29 EDT 2010
On 10/09/2010 4:40 PM, Ciaran Anscomb wrote:
> As the PAL and NTSC line rates are nearly identical, the main clock
> stays the same (actually *some* Dragons *slightly* alter this to
> 14.218MHz, but not all). Extra circuitry (including another crystal) is,
> however, added to encode the colour information.
> PAL has 50 more lines per field, so some simple logic is included that
> stops the clock to the VDG at two points during every field and inserts
> 25 "fake" blank scanlines.
> Of course, PAL CoCos may well do things in a subtly different way (which
> would explain a lot...), but I've no schematic to prove that so if
> anyone can come up with something, I'd be just as interested!
Bob Devries was kind enough to send me a scan of the video portion of the
Coco 2 manual. And yes, this is exactly what the Coco 2 does as well!
Interesting, as I assumed that the PAL Coco used a different base clock. But
as it turns out, this makes things a lot easier for me! ;)
| Mark McDougall | "Electrical Engineers do it
| <http://members.iinet.net.au/~msmcdoug> | with less resistance!"
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