98 lines
1.5 KiB
ArmAsm
98 lines
1.5 KiB
ArmAsm
;================================
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; HGR logo vscroll
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;================================
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; image to scroll in is in $4000
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;
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hgr_logo_vscroll:
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ldx #191 ; 2
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stx SCROLL ; SCROLL = 0 ; 3
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vscroll_loop:
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;====================
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; draw bottom part
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lda #0 ; 2
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sta SCROLL_OFFSET ; offset in logo ; 3
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ldx SCROLL ; offset in screen ; 3
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vscroll_bottom:
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cpx #192 ; 2
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bcc regular_scroll ; 2/3
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lda #$20
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sta vscroll_in_smc+2
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sta vscroll_out_smc+2
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lda #$00
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sta vscroll_in_smc+1
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sta vscroll_out_smc+1
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beq done_scroll_setup
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regular_scroll:
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ldy SCROLL_OFFSET ; 3
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lda hposn_high,Y ; 4
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eor #$60 ; $20->$40 ; 2
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sta vscroll_in_smc+2 ; INH ; 4
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lda hposn_low,Y ; 4
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sta vscroll_in_smc+1 ; INL ; 4
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;====
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; 21
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lda hposn_high,X ; 4
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sta vscroll_out_smc+2 ; OUTH ; 4
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lda hposn_low,X ; 4
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sta vscroll_out_smc+1 ; OUTL ; 4
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;====
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; 21
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done_scroll_setup:
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inc SCROLL_OFFSET ; 5
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ldy #39 ; 2
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vscroll_bottom_line:
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vscroll_in_smc:
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lda $A000,Y ; 4
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vscroll_out_smc:
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sta $2000,Y ; 5
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dey ; 2
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bpl vscroll_bottom_line ; 2/3
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;=====
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; 2+40*(14)-1
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; 561
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inx ; 2
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txa
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sec
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sbc SCROLL
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cmp #58
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bcc vscroll_bottom
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;==========
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;5+96*(42+561+7)-1
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; 58564
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done_scroll:
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;=====================
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; exit early if keypress
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lda KEYPRESS
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bmi vscroll_early_exit
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;=====================
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; scroll whole screen
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dec SCROLL
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bne vscroll_loop
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vscroll_early_exit:
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bit KEYRESET
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rts
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