Basic Raster

Leeeeee · Post by **Leeeeee** » Mon Mar 30, 2009 5:21 am

Line 27 waits for near the end of frame so that the effect doesn't retrigger prematurely.

Line 28 positions the effect in the new frame.

IF PEEK(W)<>V GOTO can take too long to execute to wait for a particular line.

Lee.

Mike · Post by **Mike** » Mon Mar 30, 2009 7:36 am

carlsson wrote:Unless I'm totally confused, it means $9004 will become 0..4 twice per frame in NTSC, 0..55 in PAL [...]

There's no ambiguity here: $9004 contains bits 1..8 of the current raster line, i.e. there's a granularity of two raster lines. Bit 0 is stored within bit 8 of $9003.

Michael

nippur72 · Post by **nippur72** » Mon Mar 30, 2009 7:51 am

Leeeeee wrote:Line 27 waits for near the end of frame so that the effect doesn't retrigger prematurely.

I can't see how it could retrigger (other than basic code being executed within the same two rasterlines, but it's not the case). Am I missing something?

carlsson · Post by **carlsson** » Tue Mar 31, 2009 3:58 am

Mike wrote:$9004 contains bits 1..8 of the current raster line, i.e. there's a granularity of two raster lines. Bit 0 is stored within bit 8 of $9003.

Ah, ok. Without looking it up, I thought it was the other way around with MSB in $9003.