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https://github.com/deater/dos33fsprogs.git
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101 lines
1.3 KiB
ArmAsm
101 lines
1.3 KiB
ArmAsm
; scrolling boxes (57 bytes)
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; by deater (Vince Weaver) <vince@deater.net>
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; Lovebyte 2023
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; Zero Page
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GBASL = $26
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GBASH = $27
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X2 = $FB
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FRAME = $FC
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PAGE = $FD
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; Soft Switches
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FULLGR = $C052 ; Full screen, no text
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PAGE1 = $C054 ; Page1
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;PAGE2 = $C055 ; Page2
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LORES = $C056 ; Enable LORES graphics
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; ROM routines
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HGR2 = $F3D8
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GBASCALC= $F847 ;; take Y-coord/2 in A, put address in GBASL/H ( a trashed, C clear)
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SETGR = $FB40
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.zeropage
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.globalzp page_smc
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boxes:
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;===================
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; init screen
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jsr HGR2 ; set hires graphics
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; full screen, page2
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; A=0, Y=0
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bit LORES ; switch to lores
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boxes_forever:
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inc FRAME ; increment frame
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ldx #23 ; YPos in X (0..48)
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; flip page
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lda page_smc+1
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pha
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lsr
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lsr
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tay
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lda PAGE1,Y
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pla
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eor #$4
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sta page_smc+1
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yloop:
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txa
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jsr GBASCALC ; get graphics line in GBASL/H
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; YPOS/2 in A, C clear after
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lda GBASH ; adjust for page flip
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page_smc:
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adc #0 ; start at page0
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sta GBASH
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ldy #39 ; Xpos: 0..39
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xloop:
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; calculate color for each X
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; color = (XX-FRAME)^(A)
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sec ; subtract frame from Xpos in Y
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tya
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sbc FRAME
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sta X2
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txa
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and #$FC ; add border?
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eor X2 ; color in A
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sta (GBASL),Y ; plot pixel
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dey ; count down Xpos
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bpl xloop ; loop until done
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dex ; count down YPos
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bpl yloop ; loop until done
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bmi boxes_forever ; continue
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