mirror of
https://github.com/deater/dos33fsprogs.git
synced 2024-10-30 02:26:58 +00:00
478 lines
8.9 KiB
ArmAsm
478 lines
8.9 KiB
ArmAsm
; Lo-res cycle-counting water transparency hack
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; by deater (Vince Weaver) <vince@deater.net>
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; Zero Page
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FRAMEBUFFER = $00 ; $00 - $0F
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YPOS = $10
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YPOS_SIN = $11
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CH = $24
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CV = $25
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GBASL = $26
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GBASH = $27
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BASL = $28
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BASH = $29
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MASK = $2E
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COLOR = $30
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FRAME = $60
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BIRD_STATE = $E0
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BIRD_DIR = $E1
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DRAW_PAGE = $EE
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LASTKEY = $F1
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PADDLE_STATUS = $F2
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XPOS = $F3
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TEMP = $FA
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TEMPY = $FB
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INL = $FC
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INH = $FD
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OUTL = $FE
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OUTH = $FF
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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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PAGE0 = $C054 ; Page0
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PAGE1 = $C055 ; Page1
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LORES = $C056 ; Enable LORES graphics
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PADDLE_BUTTON0 = $C061
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PADDL0 = $C064
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PTRIG = $C070
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; ROM routines
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TEXT = $FB36 ;; Set text mode
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HOME = $FC58 ;; Clear the text screen
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WAIT = $FCA8 ;; delay 1/2(26+27A+5A^2) us
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waterfall_demo:
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;===================
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; init screen
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jsr TEXT
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jsr HOME
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bit PAGE0
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;===================
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; init vars
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lda #0
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sta BIRD_DIR
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sta BIRD_STATE
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lda #4
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sta DRAW_PAGE
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sta XPOS
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;=============================
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; Load foreground to graphic page1 (apple page2)
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lda #$0c
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sta BASH
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lda #$00
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sta BASL ; load image to $c00
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lda #<waterfall_page1
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sta GBASL
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lda #>waterfall_page1
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sta GBASH
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jsr load_rle_gr
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jsr gr_copy_to_current ; copy to page1
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;=============================
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; Load bg to memory
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lda #$0c
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sta BASH
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lda #$00
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sta BASL ; load image to $c00
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lda #<waterfall_page2
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sta GBASL
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lda #>waterfall_page2
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sta GBASH
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jsr load_rle_gr
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;==============================
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; setup graphics for vapor lock
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;==============================
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; Clear Page0
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lda #$0
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sta DRAW_PAGE
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lda #$44
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jsr clear_gr
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; Make screen half green
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lda #$11
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ldy #24
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jsr clear_page_loop
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;=====================================================
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; attempt vapor lock
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; by reading the "floating bus" we can see most recently
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; written value of the display
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; we look for $55 (which is the grey line)
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;=====================================================
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; See:
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; Have an Apple Split by Bob Bishop
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; Softalk, October 1982
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; Challenges: each scan line scans 40 bytes.
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; The blanking happens at the *beginning*
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; So 65 bytes are scanned, starting at adress of the line - 25
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; the scan takes 8 cycles, look for 4 repeats of the value
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; to avoid false positive found if the horiz blanking is mirroring
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; the line (max 3 repeats in that case)
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vapor_lock_loop: ; first make sure we have all zeroes
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LDA #$11
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zxloop:
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LDX #$04
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wiloop:
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CMP $C051
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BNE zxloop
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DEX
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BNE wiloop
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LDA #$44 ; now look for our border color (4 times)
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zloop:
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LDX #$04
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qloop:
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CMP $C051
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BNE zloop
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DEX
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BNE qloop
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; found first line of black after green, at up to line 26 on screen
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; so we want roughly 22 lines * 4 = 88*65 = 5720 + 4550 = 10270
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; - 65 (for the scanline we missed) = 10205 - 12 = 10193
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jsr gr_copy_to_current ; 6+ 9292
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; 10193 - 9298 = 895
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; Fudge factor (unknown) -30 = 865
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; GR part
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bit LORES ; 4
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bit SET_GR ; 4
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bit FULLGR ; 4
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; Try X=88 Y=2 cycles=893 R2
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nop
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ldy #2 ; 2
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loopA:
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ldx #88 ; 2
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loopB:
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dex ; 2
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bne loopB ; 2nt/3
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dey ; 2
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bne loopA ; 2nt/3
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jmp display_loop
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.align $100
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;================================================
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; Display Loop
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;================================================
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; each scan line 65 cycles
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; 1 cycle each byte (40cycles) + 25 for horizontal
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; Total of 12480 cycles to draw screen
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; Vertical blank = 4550 cycles (70 scan lines)
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; Total of 17030 cycles to get back to where was
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; We want to alternate between page1 and page2 every 65 cycles
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; vblank = 4550 cycles to do scrolling
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; 2 + 48*( (4+2+25*(2+3)) + (4+2+23*(2+3)+4+5)) + 9)
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; 48*[(6+125)-1] + [(6+115+10)-1]
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display_loop:
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ldy #96 ; 2
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outer_loop:
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bit PAGE0 ; 4
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ldx #12 ; 65 cycles with PAGE0 ; 2
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page0_loop: ; delay 61+bit
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dex ; 2
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bne page0_loop ; 2/3
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; bit(4) -1(fallthrough) + loop*5 -1(fallthrouh)+4 extra = 61
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; 5L = 55
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bit PAGE1 ; 4
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ldx #11 ; 65 cycles with PAGE1 ; 2
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;
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page1_loop: ; delay 115+(7 loop)+4 (bit)+4(extra)
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dex ; 2
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bne page1_loop ; 2/3
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dey ; 2
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bne outer_loop ; 2/3
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;======================================================
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; We have 4550 cycles in the vblank, use them wisely
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;======================================================
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; do_nothing should be 4550
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; +1 fallthrough from above
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; -2 display loop setup
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; -6 jsr to do_nothing
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; -49 check for keypress
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; -2252 copy screen
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; -2231 draw sprite
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; =============
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; 11 cycles
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; jsr do_nothing ; 6
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; 17 cycles
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inc YPOS ; 5
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inc YPOS ; 5
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inc YPOS ; 5
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nop ; 2
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;=========================
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; Clear background
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;=========================
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jsr gr_copy_row22 ; 6+ 2246
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;=========
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; 2252
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;==========================
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; draw bird sprite
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;==========================
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; 8 prefix
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; bird_walk_right= 14 + 2175 2206 (need 17)
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; bird_stand_right= 13 + 2190 2206 (need 3)
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; bird_walk_left= 15 + 2175 2206 (need 16)
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; bird_stand_left= 14 + 2190 2206 (need 2)
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; call to sprite 17 postfix
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;====================================================
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; 2231
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lda BIRD_STATE ; 3
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and #1 ; 2
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ldx BIRD_DIR ; 3
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bne bird_left
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bird_right:
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; 2
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cmp #1 ; 2
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beq bird_walk_right
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; 2
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bird_stand_right:
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ldx #>bird_rider_stand_right ; 2
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ldy #<bird_rider_stand_right ; 2
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lda YPOS ; nop=3
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jmp draw_bird ; 3
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bird_walk_right:
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; 3
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ldx #>bird_rider_walk_right ; 2
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ldy #<bird_rider_walk_right ; 2
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jmp kill_less_time ; 3
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bird_left:
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; 3
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cmp #1 ; 2
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beq bird_walk_left
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bird_stand_left:
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; 2
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ldx #>bird_rider_stand_left ; 2
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ldy #<bird_rider_stand_left ; 2
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nop ; nop=2
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jmp draw_bird ; 3
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bird_walk_left:
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; 3
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ldx #>bird_rider_walk_left ; 2
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ldy #<bird_rider_walk_left ; 2
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kill_time:
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nop ; 2 ; need to kill 16
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kill_less_time:
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lda YPOS ; nop=3 ; need to kill 14
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lda YPOS ; nop=3
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lda YPOS ; nop=3
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lda YPOS ; nop=3
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nop ; 2
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jmp draw_bird ; 3
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draw_bird:
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stx INH ; 3
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sty INL ; 3
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lda #22 ; 2
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sta YPOS ; 3
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jsr put_sprite ; 6
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;=========
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; 17 + 2190
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;====================
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; Handle keypresses
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; if no keypress, 9
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; if keypress, 6+43 = 49
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lda KEYPRESS ; 4
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bmi keypress
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; 2
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no_keypress:
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; kill 40 cycles
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ldx #0 ; 2
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inc YPOS,X ; 6
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inc YPOS,X ; 6
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inc YPOS,X ; 6
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inc YPOS,X ; 6
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inc YPOS,X ; 6
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inc YPOS,X ; 6
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nop ; 2
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jmp display_loop ; 3
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;===================================================
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; key was pressed handling takes 12 + 20 + 11 = 43
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keypress:
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; 1
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bit KEYRESET ; 4
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inc BIRD_STATE ; 5
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and #$5f ; mask keypress ; 2
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is_it_right:
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cmp #$15 ; right arrow ; 2
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bne is_it_left
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; 2
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inc XPOS ; 5
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lda #0 ; 2
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sta BIRD_DIR ; 3
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lda YPOS ; 3-cycle nop ; 3
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convoluted:
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jmp adjust_xpos ; 3 ; 20 if right
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is_it_left:
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; 5
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cmp #$8 ; left arrow ; 2
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beq is_left
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; 2
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nop ; 2
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lda YPOS ; 3-cycle nop
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jmp convoluted ; 3
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; ------ 20 if neither
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is_left:
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; 3
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dec XPOS ; 5 ; 20 if left
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lda #1 ; 2
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sta BIRD_DIR ; 3
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adjust_xpos:
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lda XPOS ; 3
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and #$1f ; keep in 0-31 range ; 2
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sta XPOS ; 3
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jmp display_loop ; 3
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;=================================
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; do nothing
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;=================================
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; and take 11-6 = 5 cycles to do it
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;do_nothing:
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; Try X=3 Y=1 cycles=22
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; nop ; 2
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; nop ; 2
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; ldy #1 ; 2
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;loop1:
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; ldx #3 ; 2
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;loop2:
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; dex ; 2
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; bne loop2 ; 2nt/3
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; dey ; 2
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; bne loop1 ; 2nt/3
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; rts ; 6
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;==================================
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; HLINE
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;==================================
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; Color in A
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; Y has which line
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hline:
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pha ; 3
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ldx gr_offsets,y ; 4+
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stx hline_loop+1 ; 4
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lda gr_offsets+1,y ; 4+
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clc ; 2
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adc DRAW_PAGE ; 3
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sta hline_loop+2 ; 4
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pla ; 4
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ldx #39 ; 2
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hline_loop:
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sta $5d0,X ; 38 ; 5
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dex ; 2
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bpl hline_loop ; 2nt/3
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rts ; 6
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;==========================
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; Clear gr screen
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;==========================
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; Color in A
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clear_gr:
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ldy #46
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clear_page_loop:
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jsr hline
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dey
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dey
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bpl clear_page_loop
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rts
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gr_offsets:
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.word $400,$480,$500,$580,$600,$680,$700,$780
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.word $428,$4a8,$528,$5a8,$628,$6a8,$728,$7a8
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.word $450,$4d0,$550,$5d0,$650,$6d0,$750,$7d0
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.include "../asm_routines/gr_unrle.s"
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.include "../asm_routines/keypress.s"
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.include "gr_copy.s"
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.include "gr_unrolled_copy.s"
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.include "put_sprite.s"
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.include "waterfall_page1.inc"
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.include "waterfall_page2.inc"
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.align $100
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.include "tfv_sprites.inc"
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