43 lines
829 B
Plaintext
43 lines
829 B
Plaintext
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!src "cartheader.acme"
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!address {
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Temp = $02
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}
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Start:
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sei ; turn off interrupts
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ldy #0
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Loop:
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lda Message,y ; load message byte
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beq EOM ; 0 = end of string
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clc
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adc #$40
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sta $400+41,y ; store to screen
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iny
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bne Loop ; next character
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EOM:
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Wait1:
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lda $d011
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bmi Wait1 ; wait for line < 256
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Wait2:
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lda $d012 ; get current scanline
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Wait3:
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cmp $d012
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beq Wait3 ; wait for scanline to change
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lsr ; divide by 2
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lsr ; divide by 2
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clc
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adc Temp ; add to frame counter
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sta $d020 ; set border color
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lda $d011 ; get status bits
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bpl Wait2 ; repeat until line >= 256
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sty $d020 ; reset border color
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dec Temp ; change frame counter
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jmp Wait1 ; endless loop
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Message:
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!scr "HELLO WORLD", 0
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