On Monday 07 April 2003 02:59 am, Alan B. Pearce wrote:
> >But it seens there's no way for generating video with a good
> >resolution (say 160x128) with just a PIC solution. I think
> >there's some OSD generators that could be used for this.
>
> IIRC the Pong game uses an F84 at 4MHz. I suspect that you could
> probably do what you want with an 18F252 or 452, running at 40MHz.
>
> These chips also have the advantage that with the 4x internal PLL
> you can use an ordinary colour burst crystal for the particular
> video standard you are using, and achieve a respectable clock rate
> at close to the video rate specs, making it easier to insert into
> other video streams.

And you can do an Apple-like chroma phase shift to make colors. You
have to make the chroma burst appear during the "front porch" of the
H lines, though.

As I recall (this is entirely from Woz's description to me ca. 1975;
sorry if I'm fuzzy on the details) they used the chroma clock and
phase shifted it (whether using delays through gates/RC or a divider
or something, I don't recall).

They then used a gate or analog switch to route the proper phase (i.e.
color) chroma signal out to the video.

--
Ned Konz
http://bike-nomad.com
GPG key ID: BEEA7EFE

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