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Golara
Account closed
Registered: Jan 2018
Posts: 212 |
Black background when sideborder open
I've got this effect where I open almost the whole sideborder to show a "raster bar" go by the screen. Everything was working like normal until I replaced my macro loops with proper code generators. The effect is still working, but I've got a black background.
When you look at the normal view it looks like the sideborder is still closed but there's a sprite on top of it.
Any ideas ? |
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Raistlin
Registered: Mar 2007
Posts: 552 |
Judging from the screenshot, that just looks like they're changing $3fff on each rasterline. The value will repeat across the line and then be read again at HSYNC for the next line. |
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Oswald
Registered: Apr 2002
Posts: 5017 |
krill, cool workaround didnt think of that so far :D what I did sometimes is simply change ffff back and forth sometimes you can have that irq outside the display area. |
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ChristopherJam
Registered: Aug 2004
Posts: 1378 |
Quoting CompyxI always thought that was $F9FF ?
It is. EBCM zeros the address lines that would ordinarily select which quarter of a charset VIC is accessing, so in this instance it just shifts the ghost byte down from the end of the bank by 1536 bytes (3/4 of the 2k a charset occupies). |
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Krill
Registered: Apr 2002
Posts: 2839 |
Yes, $F9FF. Sorry, brainfart. :) |
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Krill
Registered: Apr 2002
Posts: 2839 |
Quoting RaistlinJudging from the screenshot, that just looks like they're changing $3fff on each rasterline. The value will repeat across the line and then be read again at HSYNC for the next line. It's read continually, actually. Changing the visible pattern mid-line is possible, so you can have $3FFF-splits. :) |
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oziphantom
Registered: Oct 2014
Posts: 478 |
with an REU you can change it per char to make a "picture" |
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Perplex
Registered: Feb 2009
Posts: 254 |
Quoting KrillYes, $F9FF. Sorry, brainfart. :)
A shame it's not $FAFF, that would be the perfect address for the idle byte. |
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Golara
Account closed
Registered: Jan 2018
Posts: 212 |
Quote: Quoting KrillYes, $F9FF. Sorry, brainfart. :)
A shame it's not $FAFF, that would be the perfect address for the idle byte.
why ? |
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Krill
Registered: Apr 2002
Posts: 2839 |
Wiktionary and Urban Dictionary are your friends. :) |
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Firehawk
Registered: Aug 2011
Posts: 31 |
@oziphantom: Yes, check out the QI demo where James did some exellent raster/3fff images. |
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