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46 lines
932 B
ArmAsm
46 lines
932 B
ArmAsm
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; 2016-02-28, Groepaz
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; 2017-06-19, Greg King
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;
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; char cpeekc (void);
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;
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.export _cpeekc
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.import CURS_X: zp, CharPtr: zp
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.include "cbm610.inc"
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_cpeekc:
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ldx IndReg
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ldy #$0F
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sty IndReg
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ldy CURS_X
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lda (CharPtr),y ; get char from system bank
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stx IndReg
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ldx #>$0000
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and #<~$80 ; remove reverse bit
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; Convert the screen code into a PetSCII code.
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; $00 - $1F: +$40
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; $20 - $3F
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; $40 - $5f: +$20
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; $60 - $7F: +$40
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cmp #$20
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bcs @sk1 ;(bge)
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ora #$40
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rts
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@sk1: cmp #$40
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bcc @end ;(blt)
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cmp #$60
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bcc @sk2 ;(blt)
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;sec
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adc #$20 - $01
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@sk2: ;clc ; both above cmp and adc clear carry flag
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adc #$20
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@end: rts
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