38 lines
801 B
ArmAsm
38 lines
801 B
ArmAsm
;
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; 2016-02-28, Groepaz
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; 2017-08-17, Greg King
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;
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; char cpeekrevers (void);
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;
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.export _cpeekrevers
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.import ppubuf_waitempty
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.forceimport initconio
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.include "nes.inc"
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_cpeekrevers:
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; wait until all console data has been written
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jsr ppubuf_waitempty
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ldy SCREEN_PTR+1
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lda SCREEN_PTR
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; waiting for vblank is incredibly slow ://
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vwait:
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; ldx PPU_STATUS
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; bpl vwait
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ldx #>$0000
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sty PPU_VRAM_ADDR2
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sta PPU_VRAM_ADDR2
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lda PPU_VRAM_IO ; first read is invalid
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lda PPU_VRAM_IO ; get data
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stx PPU_VRAM_ADDR2
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stx PPU_VRAM_ADDR2
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and #<$80 ; get reverse bit
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rts
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