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2002-12-29 09:28

Cybernator

Registered: Jun 2002
Posts: 154

VIC interrupts

Can anyone tell me: In which cycle the VIC is, when a raster interrupt occurs? (on normal line, badline, if there're sprites...)

Any help is appreciated.

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2002-12-30 17:01

CyberBrain
Administrator

Posts: 392

@cybernator: damn, i must have messed those 2 up then. It's been too long.. Gotta check my sources.

2002-12-31 12:24

Stryyker

Registered: Dec 2001
Posts: 466

I never thought of using $D011 method. The DMA delay issue doesn't always happen as easy as it seems. I had to do it in a FLD gap (idle gfx state). Another method is to use the CIA timer registers. I haven't figured out how they get it started. Lightpen X register can be used. It got messed up if space was pressed. Maybe some DDR of $DD02/$DD03 might fix that. I use the simpler double interrupt with first padded with NOPs.

With 8 sprites on screen check the timing charts - you need to simply shift the read forward some bytes. C= Hacking has it. I think 64doc or some other Marko text had it. I did plan to do this in a disk magazine but the coder who was to write about the methods I don't know has been very busy. I know in the past some writes to memory have made getting an interrupt stable a nightmare. Some effort and it'll all work out fine. Don't try to be too complex. If Singles Collection volume 2 was released then you would see a very simple double interrupt with $D012 comparing for the scroller stretcher.

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