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59 lines
630 B
ArmAsm
59 lines
630 B
ArmAsm
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; Ullrich von Bassewitz, 28.09.1998
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;
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; Write to the CRTC.
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;
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.export write_crtc, read_crtc
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.importzp crtc
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.include "cbm610.inc"
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.include "zeropage.inc"
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; Write a value to the CRTC. The index is in Y, the value in A
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.proc write_crtc
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sta sedt1
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lda IndReg
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pha
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lda #$0F
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sta IndReg
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tya
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ldy #$00
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sei
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sta (crtc),y
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iny
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lda sedt1
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sta (crtc),y
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cli
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pla
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sta IndReg
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lda sedt1
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rts
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.endproc
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.proc read_crtc
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sty sedt1
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lda IndReg
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pha
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lda #$0F
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sta IndReg
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lda sedt1
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ldy #$00
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sei
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sta (crtc),y
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iny
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lda (crtc),y
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cli
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tay
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pla
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sta IndReg
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tya
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ldy sedt1
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rts
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.endproc
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