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| From: Crown (all posts)
Date: 1998-05-11
Subject: TED timing, Interlace
|
Hi dudes,
Lion, it looks ok, so I would say it's 100% ok.
I have only one addition, how this relates to the horizontal dot counter register ($ff1e). So in cycle 1, $ff1e contains $c4, in cycle 2 it contains $c6.
It increments by 2 at every cycle till it reaches $e2, this happens in cycle 16, in cycle 17 it is set to $0, then continues incrementing by 2, and in cycle 114 it is $c2.
This register reflects the actual dot position divided by 2.
It'is also writable, but you have to write negated value into it.
(This was used in my 42 char wide screen effect in Gotu Megadisk II.
Check it! :) )
Also note, that with these knowledges, it is possible to write exact positioning codes!
Interlace:
I've played a little, but with not much results yet. What I could achieve, that in the upper area of the screen, it was true interlace,
but in the lower areas of the screen it was again normal. I tried to delay the end of the vertical sync signal, by 1 line, and because of this delay-timed sync the raster line was moved, but the TV detects this, and tries to compensate, so at the time the electron beam reached the lower area it succeded. I haven't given up yet, so will check this further....
Tibor Biczo / Crown of GOTU
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