92 lines
1.4 KiB
ArmAsm
92 lines
1.4 KiB
ArmAsm
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;=======================================
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; hgr_vertical scroll
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;=======================================
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; scrolls from $6000 to page1
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; jumps increments of 8 for speed
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;=======================================
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; offset line in $6000 to copy in from in COUNT
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hgr_vertical_scroll_left:
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lda #0
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beq hgr_vertical_scroll_common
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hgr_vertical_scroll_right:
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lda #20
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hgr_vertical_scroll_common:
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sta vscroll_offset_smc+1
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hgr_vertical_scroll:
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ldx #0 ; start at top
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outer_vscroll_loop:
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lda hposn_low,X ; get page1 address
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sta OUTL ; set as output
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lda hposn_high,X
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sta OUTH
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txa ; get address of X+8
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clc ; and set as input
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adc #8
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tay
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lda hposn_low,y
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sta INL
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lda hposn_high,Y
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sta INH
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ldy #29 ; only scroll from 9..29
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inner_vscroll_loop:
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lda (INL),Y
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sta (OUTL),Y
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dey
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cpy #9
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bpl inner_vscroll_loop
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inx
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cpx #184
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bne outer_vscroll_loop
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;================================
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; copy in off screen
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; for now from 0..19
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hgr_vertical_scroll2:
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ldx #184 ; start 8 from bottom
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outer_vscroll_loop2:
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lda hposn_low,X
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clc
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adc #10 ; copy to middle of screen
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sta OUTL
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lda hposn_high,X
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sta OUTH
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ldy COUNT
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lda hposn_low,Y
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clc
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vscroll_offset_smc:
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adc #$0
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sta INL
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lda hposn_high,Y
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clc
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adc #$40 ; load from $6000
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sta INH
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ldy #19
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inner_vscroll_loop2:
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lda (INL),Y
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sta (OUTL),Y
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dey
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bpl inner_vscroll_loop2
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inc COUNT
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inx
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cpx #192
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bne outer_vscroll_loop2
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rts
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