mirror of
https://github.com/deater/dos33fsprogs.git
synced 2024-11-18 21:06:31 +00:00
131 lines
1.8 KiB
ArmAsm
131 lines
1.8 KiB
ArmAsm
;=========================================================
|
|
; gr_twoscreen_scroll, 40x48 version
|
|
;=========================================================
|
|
; offset is in BG_SCROLL, must be multiple of 2
|
|
;
|
|
; two screens, top is at $1000, bottom at $BC00
|
|
; copy lines Y-48 from $1000 to $c00
|
|
; copy lines 0 - (48-y) from $BC00 to $c00
|
|
|
|
gr_twoscreen_scroll:
|
|
|
|
lda #0
|
|
sta TEMPY ; dest
|
|
|
|
ldy BG_SCROLL
|
|
cpy #48
|
|
beq gr_twoscreen_bottom ; no top to draw
|
|
|
|
gr_twoscreen_top:
|
|
|
|
; calculate source
|
|
|
|
lda gr_offsets+1,Y
|
|
clc
|
|
adc #($10-4)
|
|
sta gr_twoscreen_smc_src+2
|
|
lda gr_offsets,Y
|
|
sta gr_twoscreen_smc_src+1
|
|
tya
|
|
pha
|
|
|
|
; calculate destination
|
|
|
|
lda TEMPY
|
|
tay
|
|
lda gr_offsets+1,Y
|
|
clc
|
|
adc #($c-4)
|
|
sta gr_twoscreen_smc_dst+2
|
|
lda gr_offsets,Y
|
|
sta gr_twoscreen_smc_dst+1
|
|
|
|
ldx #0
|
|
gr_twoscreen_line_loop:
|
|
|
|
gr_twoscreen_smc_src:
|
|
lda $1000,X
|
|
gr_twoscreen_smc_dst:
|
|
sta $c00,X
|
|
|
|
inx
|
|
cpx #40
|
|
bne gr_twoscreen_line_loop
|
|
|
|
|
|
inc TEMPY
|
|
inc TEMPY
|
|
|
|
pla
|
|
tay
|
|
|
|
iny
|
|
iny
|
|
|
|
cpy #48
|
|
|
|
bne gr_twoscreen_top
|
|
|
|
|
|
;===============================
|
|
; now copy the bottom from $BC00
|
|
|
|
lda BG_SCROLL
|
|
beq done_twoscreen_bottom ; if 0, no bottom
|
|
|
|
gr_twoscreen_bottom:
|
|
|
|
ldy #0
|
|
|
|
gr_twoscreen_bottom_loop:
|
|
|
|
; calculate source
|
|
|
|
lda gr_offsets+1,Y
|
|
clc
|
|
adc #($bc-4)
|
|
sta gr_twoscreen_bottom_smc_src+2
|
|
lda gr_offsets,Y
|
|
sta gr_twoscreen_bottom_smc_src+1
|
|
tya
|
|
pha
|
|
|
|
; calculate destination
|
|
|
|
lda TEMPY
|
|
tay
|
|
lda gr_offsets+1,Y
|
|
clc
|
|
adc #($c-4)
|
|
sta gr_twoscreen_bottom_smc_dst+2
|
|
lda gr_offsets,Y
|
|
sta gr_twoscreen_bottom_smc_dst+1
|
|
|
|
ldx #0
|
|
gr_twoscreen_bottom_line_loop:
|
|
|
|
gr_twoscreen_bottom_smc_src:
|
|
lda $BC00,X
|
|
gr_twoscreen_bottom_smc_dst:
|
|
sta $c00,X
|
|
|
|
inx
|
|
cpx #40
|
|
bne gr_twoscreen_bottom_line_loop
|
|
|
|
|
|
inc TEMPY
|
|
inc TEMPY
|
|
|
|
pla
|
|
tay
|
|
|
|
iny
|
|
iny
|
|
|
|
cpy BG_SCROLL
|
|
|
|
bne gr_twoscreen_bottom_loop
|
|
done_twoscreen_bottom:
|
|
rts ; 6
|