252 lines
3.5 KiB
ArmAsm
252 lines
3.5 KiB
ArmAsm
; static
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; bring blue pages
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; by Vince `deater` Weaver (vince@deater.net) / dSr
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; with some help from qkumba
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; zero page
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GBASL = $26
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GBASH = $27
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MASK = $2E
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COLOR = $30
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;CTEMP = $68
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YY = $69
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FRAME = $FC
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SUM = $FD
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SAVEX = $FE
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SAVEY = $FF
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; soft-switches
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FULLGR = $C052
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PAGE1 = $C054
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; ROM routines
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PLOT = $F800 ;; PLOT AT Y,A
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PLOT1 = $F80E ;; PLOT at (GBASL),Y (need MASK to be $0f or $f0)
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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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SETCOL = $F864 ;; COLOR=A*17
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SETGR = $FB40
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;================================
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; Clear screen and setup graphics
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;================================
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static:
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jsr SETGR ; set lo-res 40x40 mode
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bit FULLGR ; make it 40x48
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draw_plasma:
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ldx #39
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create_yloop:
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ldy #47
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create_xloop:
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lda #128
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sta SUM
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txa
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adc FRAME
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jsr calcsine
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tya
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; adc FRAME
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jsr calcsine_div_2
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clc
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stx SAVEX
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tya
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adc SAVEX
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jsr calcsine
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stx SAVEX
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sty SAVEY
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; clc
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adc FRAME
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and #$7
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tax
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lda colorlookup,X
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jsr SETCOL
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ldy SAVEX
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lda SAVEY
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jsr PLOT ; PLOT Y,A
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ldx SAVEX
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ldy SAVEY
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dey
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bpl create_xloop
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dex
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bpl create_yloop
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; X and Y both $FF
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create_lookup_done:
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forever_loop:
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inc FRAME
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jmp draw_plasma
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; jmp forever_loop
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.if 0
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cycle_colors:
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; cycle colors
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; instead of advancing entire frame, do slightly slower route
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; instead now and just incrememnting the frame and doing the
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; adjustment at plot time.
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; increment frame
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inc frame_smc+1
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; set/flip pages
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; we want to flip pages and then draw to the offscreen one
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flip_pages:
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; ldy #0
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; iny ; y is $FF, make it 0
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lda draw_page_smc+1 ; DRAW_PAGE
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bne done_page
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dey
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done_page:
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; ldx PAGE1,Y ; set display page to PAGE1 or PAGE2
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ldx $BF56,Y ; PAGE1 - $FF
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eor #$4 ; flip draw page between $400/$800
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sta draw_page_smc+1 ; DRAW_PAGE
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; plot current frame
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; scan whole 40x48 screen and plot each point based on
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; lookup table colors
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plot_frame:
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ldx #47 ; YY=47 (count backwards)
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plot_yloop:
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txa ; get YY into A
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pha ; save X for later
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lsr ; call actually wants Ycoord/2
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php ; save C flag for mask handling
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; ugh can't use PLOT trick as it always will draw something
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; to PAGE1 even if we don't want to
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jsr GBASCALC ; point GBASL/H to address in (A is ycoord/2)
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; after, A is GBASL, C is clear
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lda GBASH ; adjust to be PAGE1/PAGE2 ($400 or $800)
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draw_page_smc:
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adc #0
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sta GBASH
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; increment YY in top nibble of lookup for (yy<<16)+xx
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; clc from above, C always 0
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lda plot_lookup_smc+1
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adc #$10 ; no need to mask as it will oflo and be ignored
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sta plot_lookup_smc+1
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;==========
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ldy #39 ; XX = 39 (countdown)
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; sets MASK by calling into middle of PLOT routine
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; by Y being 39 draw in a spot that gets over-written
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plp
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jsr $f806
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plot_xloop:
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tya ; get XX & 0x0f
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and #$f
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tax
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plot_lookup_smc:
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lda lookup,X ; load lookup, (YY*16)+XX
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clc
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frame_smc:
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adc #$00 ; add in frame
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and #$f
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lsr ; we actually only have 8 colors
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tax
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lda colorlookup,X ; lookup color
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sta COLOR ; each nibble should be same
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jsr PLOT1 ; plot at GBASL,Y (x co-ord goes in Y)
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dey
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bpl plot_xloop
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pla ; restore YY
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tax
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dex
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bpl plot_yloop
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bmi forever_loop
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.endif
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calcsine_div_8:
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lsr
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calcsine_div_4:
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lsr
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calcsine_div_2:
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lsr
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calcsine:
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stx SAVEX
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and #$f
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tax
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lda sinetable,X
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clc
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adc SUM
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sta SUM
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ldx SAVEX
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rts
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colorlookup:
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; blue
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.byte $55,$22,$66,$77,$ff,$77,$55,$00
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sinetable:
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; this is actually (32*sin(x))
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.byte $00,$0C,$16,$1D
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.byte $20,$1D,$16,$0C
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.byte $00,$F4,$EA,$E3
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.byte $E0,$E3,$EA,$F4
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entry:
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jmp static
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; want this to be at 3f5
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; Length is 116 so start at 384
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