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Dr. Jay
Account closed
Registered: Jan 2003
Posts: 32 |
Stable rasters
Was going through some of the old code I wrote, back when I knew how to progam on the C=64, and found this routine. I think it works great. Too bad it's not precise enough (I think) to open the side borders, but it does help with stable rasters. I've seen people do these huge loops with nop / incrementing dummy locations / etc. which I think works great for timing necessary like side borders, and I've also seen code like Xbows where there are actual subroutines that are timed perfect ... anyway, my simple little routine works for rasters:
1. Get a stable raster, either with the sprite method, double interrupt, etc. Then, simply:
ldy #$00
loop lda colors,y
ldx timing,y
synch dex
bne synch
sta $d020
sta $d021
iny
cpy #16 ; number of rasters in table
bne loop
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TDJ
Registered: Dec 2001
Posts: 1879 |
Groepaz, could you post that link here? Saves me the trouble of typing it in myself. Thank you. |
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chatGPZ
Registered: Dec 2001
Posts: 11386 |
http://www.google.com/search?q=c64%20stable%20raster%20source&s..
0> i feel lucky <O
source for that standard double irq thing on c64, and the hcl-preferred double-timer thing for the vic-20 (its very much the same on c64 though, disasm some hcl code :0)).
marko even explains it well as far as i remember...however the link to c=hacking issue with all the info is second or third hit.
eh. you lazy bastard. :o) |
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TDJ
Registered: Dec 2001
Posts: 1879 |
Why didn't you make it a link? Now I have to cut & paste it .. bastard .. |
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Zodiac
Account closed
Registered: Jan 2004
Posts: 1 |
I remember using NOP to stabalize the rasters! Boy that brings back the memories... |
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waffieblaffie
Account closed
Registered: Apr 2004
Posts: 1 |
Back in the 80's we used some routine called 'waitlin' to stabilize rasters. It didn't rely on double ints or sprite irq's or any other funny stuff. Just plain and simple code. It worked by testing $d012 at the right sideborder. It needed about 3 or 4 rasterlines to get the raster stable. Unfortunatly I lost the source. Does anybody know what I'm talking about :)
WaffieBlaffie. |
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Graham
Account closed
Registered: Dec 2002
Posts: 990 |
3 to 4 lines is too much anyway, less than 2 lines and we're talking. |
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