[A83] TCPA's Scrolling Routine - Vertical Scrolling Without Looping
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[A83] TCPA's Scrolling Routine - Vertical Scrolling Without Looping
In a program, I am using TCPA's Scrolling Routine to scroll the screen, and I
stopped the looping for the horizontal scrolling by inserting:
or a
to the normal scroll routine: (I'm just using left as an example)
Scroll_Left:
ld hl, Plotsscreen-1
ld de, 12
ld b, 64
Left_Carry:
inc hl
ld a, (hl)
and %10000000
add hl, de
sub %10000000
CCF
ld c, b
ld b, 12
; I added or a right here
Left_Loop:
dec hl
RL (hl)
djnz Left_Loop
ld b, c
dec hl
add hl, de
djnz Left_Carry
jp ionFastCopy
That works. Now, I want to make it so the vertical scrolling does not loop.
Here is the up scrolling routine:
Scroll_Up:
ld hl, Plotsscreen
ld de, OP1
ld bc, 12
LDIR
ld hl, Plotsscreen+12
ld de, Plotsscreen
ld bc, 756
LDIR
ld hl, OP1
ld de, Plotsscreen+756
ld bc, 12
LDIR
jp ionFastCopy
Could someone please modify this short routine so the scrolling doesn't loop?
Thanks,
Colin Hart
darkfire139@aol.com
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