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32 lines
748 B
ArmAsm
32 lines
748 B
ArmAsm
;
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; Stefan Haubenthal, 2004-10-07
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; Based on code from Pu-239
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;
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; unsigned char get_tv (void);
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; /* Return the video mode the machine is using */
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;
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.include "vic20.inc"
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.include "get_tv.inc"
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;--------------------------------------------------------------------------
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; _get_tv
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.proc _get_tv
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NTSC_LINES = 261
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; detect the system
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lda #TV::NTSC
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tax
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@L0: ldy VIC_HLINE
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cpy #1
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bne @L0 ; wait for line 1
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@L1: ldy VIC_HLINE
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beq @L2 ; line 0 reached -> NTSC
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cpy #NTSC_LINES/2+2
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bne @L1
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lda #TV::PAL
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@L2: rts ; system detected: 0 for NTSC, 1 for PAL
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.endproc
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