193 lines
2.8 KiB
ArmAsm
193 lines
2.8 KiB
ArmAsm
; Moving
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; moving, orange and green
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; zero page
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GBASL = $26
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GBASH = $27
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YY = $69
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ROW_SUM = $70
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HGR_X = $E0
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HGR_XH = $E1
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HGR_Y = $E2
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HGR_COLOR = $E4
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HGR_PAGE = $E6
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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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HGR2 = $F3D8
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HPOSN = $F411 ; (Y,X),(A) (values stores in HGRX,XH,Y)
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;================================
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; Clear screen and setup graphics
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;================================
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oval:
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jsr HGR2 ; set hi-res 140x192, page2, fullscreen
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; A and Y both 0 at end
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;==================
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; create sinetable
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;ldy #0 ; Y is 0
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sinetable_loop:
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tya ; 2
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and #$3f ; wrap sine at 63 entries ; 2
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cmp #$20
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php ; save pos/negative for later
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and #$1f
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cmp #$10
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bcc sin_left ; blt
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sin_right:
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; sec carry should be set here
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eor #$FF
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adc #$20 ; 32-X
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sin_left:
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tax
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lda sinetable_base,X ; 4+
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plp
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bcc sin_done
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sin_negate:
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; carry set here
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eor #$ff
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; adc #0 ; FIXME: this makes things off by 1
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sin_done:
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sta sinetable,Y
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iny
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bne sinetable_loop
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; NOTE: making gbash/gbasl table wasn't worth it
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;============================
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; main loop
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;============================
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draw_oval:
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inc FRAME
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lda #191 ; YY
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create_yloop:
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; HGR_Y (YY) is in A here
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; ldx #39 ; X is don't care?
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; ldy #0 ; Y is also don't care?
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jsr HPOSN ; (Y,X),(A) (values stores in HGRX,XH,Y)
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; restore values
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lda HGR_Y ; YY
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tax
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calcsine_div4:
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lsr
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lsr ; 2
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sec
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sbc FRAME
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tay
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lda sinetable,y
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sta row_sum_smc+1
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; ldx HGR_Y ; YY
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ldy #39 ; XX
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create_xloop:
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;=====================
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; critical inner loop
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; every cycle here is 40x192 cycles
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;=====================
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clc
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tya
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adc FRAME
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tax
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lda sinetable,X
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adc sinetable,Y ; 4+
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row_sum_smc:
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adc #$dd ; row base value ; 2
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lsr ; double colors ; 2
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; also puts bit in carry
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; which helps proper color gen
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and #$7 ; 2
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tax ; 2
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lda colorlookup,X ; lookup in table ; 5
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ror_nop_smc:
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ror ; $6A/$EA ; 2
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sta (GBASL),Y ; 6
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lda ror_nop_smc ; toggle ror/nop ; 4
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eor #$80 ; 2
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sta ror_nop_smc ; 4
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dey ; 2
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bpl create_xloop ; 2/3
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dec HGR_Y
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lda HGR_Y
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cmp #$ff ; blah want to draw line 0
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bne create_yloop
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flip_pages:
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; Y should be $FF here
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lda HGR_PAGE ; will be $20/$40
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cmp #$20
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bne done_page
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dey
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done_page:
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ldx PAGE1-$FE,Y ; set display page to PAGE1 or PAGE2
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eor #$60 ; flip draw page between $2000/$4000
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sta HGR_PAGE
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bne draw_oval ; bra
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colorlookup:
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.byte $22,$aa,$ba,$ff,$ba,$aa,$22 ; use 00 from sinetable
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;.byte $00
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;.byte $11,$55,$5d,$7f,$5d,$55,$11 ; use 00 from sinetable
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;.byte $00
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;sinetable_base = $F5BA
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sinetable_base:
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; this is actually (32*sin(x))
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.byte $00,$03,$06,$09,$0C,$0F,$11,$14
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.byte $16,$18,$1A,$1C,$1D,$1E,$1F,$1F
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.byte $20
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; for bot
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; 3F5 - 7d = 378
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; jmp oval
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sinetable=$6000
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