Routines
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49820: Scroll Screen Down
Used by the routine at HandleBackspaceKey.
Scrolls the screen down one character row.
ScrollScreenDown 49820 PUSH HL Keep the caller's registers and point HL at the screen address 20703.
49821 PUSH DE
49822 PUSH BC
49823 LD HL,20703
49826 LD DE,20735 Take the screen.
49829 LD A,8 Use 8.
ScrollScreenDown_Loop 49831 PUSH HL Take a length of 128 entries.
49832 PUSH DE
49833 LD BC,128
49836 LDDR Scroll 128 bytes of this screen third up one character row.
49838 POP DE Jump back to ScrollScreenDown_Loop while the count is not finished.
49839 POP HL
49840 INC H
49841 INC D
49842 DEC A
49843 JR NZ,ScrollScreenDown_Loop
49845 LD HL,20576 Jump back to PrintARowOfSpaces to scroll screen up.
49848 JR PrintARowOfSpaces
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