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waterfall: re-achieved vapor lock
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77d19ad466
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@ -46,6 +46,9 @@ 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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; location we don't care about
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DUMMY = $300
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waterfall_demo:
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@ -60,6 +63,7 @@ waterfall_demo:
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lda #0
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sta BIRD_DIR
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sta BIRD_STATE
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sta FRAME
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lda #4
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sta DRAW_PAGE
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@ -188,61 +192,49 @@ loopB:
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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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; if even, 10 + 9 + display_even + 2 (balance) = 21+display_even
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; if odd 10 + 8 + display_odd + 3 (balance) = 21+display_odd
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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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; we have 3 (the jmp) + 6 (the rts) - 1 (fallthrough)
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; = 8 cycles that need to be eaten by the vblank
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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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inc FRAME ; 5
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lda FRAME ; 3
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lda #$0 ; 2
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beq even
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; 2
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lda FRAME ; (nop) ; 3
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jsr display_odd ; 6
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jmp vblank ; 3
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even:
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; 3
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nop ; (nop) ; 2
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jsr display_even ; 6
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jmp vblank ; 3
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vblank:
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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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; -8 letfover from HBLANK code
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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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; 10 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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; inc YPOS ; 5
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; nop ; 2
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; nop ; 2
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;=========================
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@ -475,3 +467,100 @@ gr_offsets:
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.align $100
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.include "tfv_sprites.inc"
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.align $100
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;==========================================
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; DISPLAY ODD
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display_odd:
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ldy #96 ; 2
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outer_loop_odd:
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bit PAGE0 ; 4
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ldx #12 ; 65 cycles with PAGE0 ; 2
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page0_loop_odd: ; delay 61+bit
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dex ; 2
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bne page0_loop_odd ; 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_odd: ; delay 115+(7 loop)+4 (bit)+4(extra)
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dex ; 2
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bne page1_loop_odd ; 2/3
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dey ; 2
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bne outer_loop_odd ; 2/3
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rts
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;=================================
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; Display Even
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;=================================
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; we have 65 cycles per line
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; the first 25 are in hblank
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; we come in already 21 cycles into things
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; so the first scanline is a loss (but that's OK)
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; first scanline: 21+ 2 (from ldy) so need to kill 65-23 = 42
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; second scanline, again kill so 65 killed
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display_even:
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even_first_line:
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ldy #95 ; 2
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asl DUMMY ; 6
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asl DUMMY ; 6
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asl DUMMY ; 6
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asl DUMMY ; 6
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asl DUMMY ; 6
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asl DUMMY ; 6
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asl DUMMY ; 6
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asl DUMMY ; 6
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asl DUMMY ; 6
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asl DUMMY ; 6
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asl DUMMY ; 6
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asl DUMMY ; 6
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asl DUMMY ; 6
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asl DUMMY ; 6
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asl DUMMY ; 6
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asl DUMMY ; 6
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asl DUMMY ; 6
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lda YPOS ; 3
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nop ; 2
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outer_loop_even:
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bit PAGE1 ; 4
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ldx #12 ; 65 cycles with PAGE0 ; 2
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page1_loop_even: ; delay 61+bit
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dex ; 2
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bne page1_loop_even ; 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 PAGE0 ; 4
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ldx #11 ; 65 cycles with PAGE1 ; 2
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;
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page0_loop_even: ; delay 115+(7 loop)+4 (bit)+4(extra)
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dex ; 2
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bne page0_loop_even ; 2/3
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dey ; 2
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bne outer_loop_even ; 2/3
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rts ; 6
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