242 lines
2.8 KiB
ArmAsm
242 lines
2.8 KiB
ArmAsm
; dots
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; based on Second Reality Dots code
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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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DRAW_PAGE = $E0
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OUTL = $FC
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OUTH = $FD
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INL = $FE
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INH = $FF
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; soft-switches
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FULLGR = $C052
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PAGE1 = $C054
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PAGE2 = $C055
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; ROM routines
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PLOT = $F800 ;; PLOT AT Y,A
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SETGR = $FB40
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WAIT = $FCA8 ;; delay 1/2(26+27A+5A^2) us
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dots:
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jsr SETGR
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bit FULLGR
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init_vars:
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lda #0
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sta DRAW_PAGE
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;===============================
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; setup
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lda #<dot_data
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sta INL
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lda #>dot_data
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sta INH
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main_loop:
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; FIXME: draw once offscreen and do a fast copy
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draw_background:
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ldx #11
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draw_sky_outer_loop:
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lda gr_offsets_l,X
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sta GBASL
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lda gr_offsets_h,X
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clc
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adc DRAW_PAGE
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sta GBASH
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lda #0
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ldy #39
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draw_sky_inner_loop:
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sta (GBASL),Y
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dey
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bpl draw_sky_inner_loop
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dex
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bpl draw_sky_outer_loop
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ldx #23
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draw_ground_outer_loop:
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lda gr_offsets_l,X
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sta GBASL
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lda gr_offsets_h,X
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clc
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adc DRAW_PAGE
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sta GBASH
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lda #$55 ; grey
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ldy #39
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draw_ground_inner_loop:
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sta (GBASL),Y
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dey
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bpl draw_ground_inner_loop
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dex
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cpx #11
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bne draw_ground_outer_loop
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jmp decode_loop
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;===============================
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decode_next:
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inc INL
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bne decode_loop
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inc INH
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decode_loop:
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ldy #0
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lda (INL),Y
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cmp #$FF
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bne check_shadow
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jmp done
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check_shadow:
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cmp #$FE
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bne check_balls
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lda #$00
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sta COLOR
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beq done_frame
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check_balls:
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cmp #$FD
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bne check_row
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lda #$66
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sta COLOR
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bne decode_next
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check_row:
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tax
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and #$C0
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bne check_dot_both
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; row value
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txa
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and #$1F
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tax
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lda gr_offsets_l,X
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sta OUTL
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lda gr_offsets_h,X
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clc
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adc DRAW_PAGE
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sta OUTH
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bne decode_next
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check_dot_both:
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cmp #$C0
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bne check_dot_top
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draw_dot_both:
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txa
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and #$3f
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tay
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lda COLOR
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sta (OUTL),Y
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jmp decode_next
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;==================
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check_dot_top:
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cmp #$80
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bne check_dot_bottom
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draw_dot_top:
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txa
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and #$3f
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tay
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lda COLOR
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and #$0F
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sta MASK
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lda (OUTL),Y
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and #$F0
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ora MASK
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sta (OUTL),Y
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jmp decode_next
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check_dot_bottom:
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draw_dot_bottom:
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txa
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and #$3f
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tay
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lda COLOR
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and #$F0
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sta MASK
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lda (OUTL),Y
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and #$0F
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ora MASK
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sta (OUTL),Y
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jmp decode_next
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done_frame:
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inc INL
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bne done_frame_noinc
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inc INH
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done_frame_noinc:
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; switch pages
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lda DRAW_PAGE
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beq switch_to_draw_page2
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bit PAGE2
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lda #0
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beq done_switch_page
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switch_to_draw_page2:
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bit PAGE1
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lda #$4
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done_switch_page:
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sta DRAW_PAGE
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; delay 143000us
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; delay 1/2(26+27A+5A^2) us
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; ~236
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lda #236
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jsr WAIT
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jmp draw_background
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done:
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jmp done
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gr_offsets_h:
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.byte >$400,>$480,>$500,>$580,>$600,>$680,>$700,>$780
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.byte >$428,>$4a8,>$528,>$5a8,>$628,>$6a8,>$728,>$7a8
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.byte >$450,>$4d0,>$550,>$5d0,>$650,>$6d0,>$750,>$7d0
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gr_offsets_l:
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.byte <$400,<$480,<$500,<$580,<$600,<$680,<$700,<$780
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.byte <$428,<$4a8,<$528,<$5a8,<$628,<$6a8,<$728,<$7a8
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.byte <$450,<$4d0,<$550,<$5d0,<$650,<$6d0,<$750,<$7d0
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dot_data:
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.incbin "out2.128.7fps",0,36000
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