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Shadow
Account closed
Registered: Apr 2002
Posts: 355 |
Forcing new charline every 4th rasterline?
OK, this might seem like something that every C64 coder should know, but I never was very good with the VIC timing stuff (or any good at all for that matter).
Now that I'm playing around with the DTV, I have come across some things where I think I need a bit of VIC trickery.
Say that we have a normal char screen
ABCDEF...
GHIJK...
LMNO..
...
Now, is it somehow possible to code a routine that display 4 lines from line 1, then (by triggering a badline?) makes it display 4 lines from line 2, then 4 lines later take data from line 3 etc.? (in essence compressing each line to only 4 lines, and thereby having a 50 lines -edit- ofcourse I don't mean 50 full lines, but 50 lines of upper-half chars -edit-)
If that is not possible, my second idea is to make a kind of 'FLI' approach, and add a second screen:
123456..
789012...
1234...
...
And have the routine trigger badlines and switch between these, so we got something like this
ABCDEF..
123456...
GHIJKL..
but with only 4 lines from each screen.
Also I would ideally want this IRQ-driven somehow, so I can have code running without having to cycle-exactly interleave it into the display code, but how the hell do you go about making an IRQ that is stable and nice and hits the right spot every 4th line? |
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hollowman
Registered: Dec 2001
Posts: 474 |
Using two screens and taking 4 lines from each row sounds like a 4x4 fli mode. Check cwiartki.asm in ftp://ftp.elysium.pl/gnu-generation/Brush/raster.zip |
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Shadow
Account closed
Registered: Apr 2002
Posts: 355 |
Thanks, yeah, I was pretty sure that was how 4x4 FLI was done, but just to make sure I tried to describe it in general terms.
I'd like really like to check that source out, but unfortunately it seems like I'm not elite enough to be able to access that FTP... :(
(530 access denied when I try anon login) |
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Shadow
Account closed
Registered: Apr 2002
Posts: 355 |
Found a mirror of the site. Time to start inspecting the code! |
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Oswald
Registered: Apr 2002
Posts: 5094 |
hmm someone can up a 4x4 src to codebase ? I only have ugly and slow sources in c64 tasm. (double irq method) |
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Radiant
Registered: Sep 2004
Posts: 639 |
Shadow: You can not compress a screen in the manner you want to, no. Using a second screen is the solution. Those pesky internal counters... |
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Ninja
Registered: Jan 2002
Posts: 411 |
Oswald: As far as I know, you have a lot of 4x4-source codes in AS-format ;) (which are not that ugly, I hope)
If someone is interested in putting it into codebase64, then I'll happily donate sources. |
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MagerValp
Registered: Dec 2001
Posts: 1078 |
Just paste them inside <code> tags and cleanup later? |
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Frantic
Registered: Mar 2003
Posts: 1648 |
I agree with mister Magervalp. |
