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fsphil/gist:05deaa06804b9b2054260b616cafed4b

Created August 13, 2019 11:28
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gistfile1.txt
ov = $90 ; == $40, initial value for the overflow counter
ct = $D5 ; == $27 / 39, number of passes. Decrementing, finished at -1
sp = $D1 ; == $07C0, pointer to the bottom line (only set after scolling)
* = $02E5
scroll: jsr $E8EA
loop: ldy ct
lda #$A0
sta $D020, y
p1: sta $07C0
sta (sp), y
inc p1 + 1
adc ov
sta ov
dec ct
bmi *
bcc loop
jmp scroll
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