22 lines
524 B
ArmAsm
22 lines
524 B
ArmAsm
; wait for VBLANK
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; no way to do this on II/II+ short of vapor lock / floating bus
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; IIe you can read $C019 (in VBLANK when top bit 0)
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; IIc you can also read $C019 (also can setup interrupt)
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; IIgs you can read $C019 but reverse of IIe (in VBLANK when top bit 1)
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VBLANK = $C019 ;
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; wait for vblank on IIe
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; positive? during vblank
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wait_vblank_iie:
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lda VBLANK
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bmi wait_vblank_iie ; wait for positive (in vblank)
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wait_vblank_done_iie:
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lda VBLANK ; wait for negative (vlank done)
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bpl wait_vblank_done_iie
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rts
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