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25 lines
452 B
ArmAsm
25 lines
452 B
ArmAsm
;;
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;; Kevin Ruland
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;;
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;; char cgetc (void);
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;;
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;; If open_apple key is pressed then the high-bit of the
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;; key is set.
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.export _cgetc
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.include "apple2.inc"
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_cgetc:
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lda KBD
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bpl _cgetc ; if < 128, no key pressed
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;; At this time, the high bit of the key pressed
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;; is set
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bit KBDSTRB ; clear keyboard strobe
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bit BUTN0 ; check if OpenApple is down
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bmi pressed
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and #$7F ; If not down, then clear high bit
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pressed:
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ldx #$00
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rts
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