LDA #$50
STA $44
loop1: ;Move the screen up a line;
LDA #$C0 ;$19C0 The first line of the screen.
STA $40
LDA #$19
STA $41
LDA #$D4 ;$19D4 The second line of the screen.
STA $42
LDA #$19
STA $43
LDX #$00
loop2: ;Move a line up.
LDY #$00
LDA ($42),Y
STA ($40),Y
INY
CPY #$14
BCC loop2 ;If y<#$14 then goto loop2.
CLC ;$40+#$14 Next line.
LDA $40
ADC #$14
STA $40
LDA $41
ADC #$00
STA $41
CLC ;$42+#$14 Next line.
LDA $42
ADC #$14
STA $42
LDA $43
ADC #$00
STA $43
INX
CPX #$50
BCC loop2 ;If x<#$50 then goto loop1
DEC $44
BNE loop1
RTS
[此贴子已经被作者于2004-11-29 13:06:07编辑过]
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