mirror of
https://github.com/deater/dos33fsprogs.git
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120 lines
1.3 KiB
ArmAsm
120 lines
1.3 KiB
ArmAsm
; parallax hgr
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; by deater (Vince Weaver) <vince@deater.net>
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; Zero Page
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GBASL = $26
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GBASH = $27
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H2 = $2C
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COLOR = $30
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HGR_X = $E0
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HGR_Y = $E2
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HGR_COLOR = $E4
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HGR_HORIZ = $E5
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HGR_PAGE = $E6
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X2 = $FB
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FRAME = $FC
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; Soft Switches
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KEYPRESS= $C000
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KEYRESET= $C010
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SET_GR = $C050 ; Enable graphics
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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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HGR = $F3E2
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HGR2 = $F3D8
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HCLR = $F3F2
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HPLOT0 = $F457 ;; plot at (Y,X), (A)
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WAIT = $FCA8 ;; delay 1/2(26+27A+5A^2) us
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HPOSN = $F411 ; (Y,X),(A) (values stores in HGRX,XH,Y)
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boxes:
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;===================
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; init screen
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jsr HGR2
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boxes_forever:
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inc FRAME
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; flip page
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lda HGR_PAGE ; $40 or $20
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pha
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asl
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asl
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rol
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tay
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lda PAGE1,Y
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pla
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eor #$60 ; flip draw_page
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sta HGR_PAGE
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ldx #191 ; init Y
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yloop:
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txa
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pha
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jsr HPOSN
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pla
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tax
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ldy #39 ; 2
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xloop:
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; calculate color
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; color = (XX-FRAME)^(YY)
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lda #$00
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sta COLOR
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sec ; subtract frame from 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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lsr
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lsr
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eor X2
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and #$04
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beq no_color
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lda #$ff
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sta COLOR
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no_color:
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lda COLOR
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sta (GBASL),Y
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dey ; 1
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bpl xloop ; 2
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dex ; 1
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cpx #$ff
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bne yloop ; 2
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beq boxes_forever ; 2
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; for bot
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; jmp boxes
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