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61 lines
1.3 KiB
ArmAsm
61 lines
1.3 KiB
ArmAsm
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; Oliver Schmidt, 2020-06-14
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;
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; void waitvsync (void);
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;
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.ifdef __APPLE2ENH__
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.constructor initvsync
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.export _waitvsync
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.import _get_ostype
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.include "apple2.inc"
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.segment "ONCE"
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initvsync:
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jsr _get_ostype
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sta ostype
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rts
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.code
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_waitvsync:
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bit ostype
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bmi iigs ; $8x
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bvs iic ; $4x
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: bit RDVBLBAR
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bpl :- ; Blanking
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: bit RDVBLBAR
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bmi :- ; Drawing
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rts
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; Apple IIgs TechNote #40, VBL Signal
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iigs: bit RDVBLBAR
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bmi iigs ; Blanking
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: bit RDVBLBAR
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bpl :- ; Drawing
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rts
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; Apple IIc TechNote #9, Detecting VBL
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iic: sei
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sta IOUDISOFF
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lda RDVBLMSK
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bit ENVBL
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bit PTRIG ; Reset VBL interrupt flag
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: bit RDVBLBAR
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bpl :-
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asl
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bcs :+ ; VBL interrupts were already enabled
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bit DISVBL
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: sta IOUDISON ; IIc Tech Ref Man: The firmware normally leaves IOUDIS on.
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cli
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rts
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.segment "INIT"
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ostype: .res 1
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.endif ; __APPLE2ENH__
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