base:detect_pal_ntsc
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base:detect_pal_ntsc [2020-11-10 21:51] – [Short PAL/NTSC detection] copyfault | base:detect_pal_ntsc [2020-11-10 21:56] – [Source Code] copyfault | ||
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- | ==== Source Code ==== | + | === Source Code === |
< | < | ||
chk: | chk: | ||
- | ldx #$aa //TAX | + | ldx #$aa //$aa = TAX |
lda $d012 | lda $d012 | ||
bne chk+1 | bne chk+1 | ||
Line 861: | Line 861: | ||
This routine continuously checks $D012==0 while saving the last read $D012-value in X and repeats the whole procedure when the value stored in X has the MSB set. This luckily suffices to distinguish the case "last line was $ff" from "last line was the last one of the frame", | This routine continuously checks $D012==0 while saving the last read $D012-value in X and repeats the whole procedure when the value stored in X has the MSB set. This luckily suffices to distinguish the case "last line was $ff" from "last line was the last one of the frame", | ||
- | Why that [ldx #TAX]? There' | + | Why that ['' |
base/detect_pal_ntsc.txt · Last modified: 2020-11-11 01:49 by copyfault