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waterfall: re-achieved vapor lock

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This commit is contained in:
Vince Weaver 2018-08-03 10:43:24 -04:00
parent 77d19ad466
commit 7149077cf3
1 changed files with 124 additions and 35 deletions
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159
waterfall/waterfall.s
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@ -46,6 +46,9 @@ TEXT = $FB36 ;; Set text mode
HOME = $FC58 ;; Clear the text screen
WAIT = $FCA8 ;; delay 1/2(26+27A+5A^2) us
; location we don't care about
DUMMY = $300
waterfall_demo:
@ -60,6 +63,7 @@ waterfall_demo:
lda #0
sta BIRD_DIR
sta BIRD_STATE
sta FRAME
lda #4
sta DRAW_PAGE
@ -188,61 +192,49 @@ loopB:
; Vertical blank = 4550 cycles (70 scan lines)
; Total of 17030 cycles to get back to where was
; We want to alternate between page1 and page2 every 65 cycles
; vblank = 4550 cycles to do scrolling
; if even, 10 + 9 + display_even + 2 (balance) = 21+display_even
; if odd 10 + 8 + display_odd + 3 (balance) = 21+display_odd
; 2 + 48*( (4+2+25*(2+3)) + (4+2+23*(2+3)+4+5)) + 9)
; 48*[(6+125)-1] + [(6+115+10)-1]
; we have 3 (the jmp) + 6 (the rts) - 1 (fallthrough)
; = 8 cycles that need to be eaten by the vblank
display_loop:
ldy #96 ; 2
outer_loop:
bit PAGE0 ; 4
ldx #12 ; 65 cycles with PAGE0 ; 2
page0_loop: ; delay 61+bit
dex ; 2
bne page0_loop ; 2/3
; bit(4) -1(fallthrough) + loop*5 -1(fallthrouh)+4 extra = 61
; 5L = 55
bit PAGE1 ; 4
ldx #11 ; 65 cycles with PAGE1 ; 2
;
page1_loop: ; delay 115+(7 loop)+4 (bit)+4(extra)
dex ; 2
bne page1_loop ; 2/3
dey ; 2
bne outer_loop ; 2/3
inc FRAME ; 5
lda FRAME ; 3
lda #$0 ; 2
beq even
; 2
lda FRAME ; (nop) ; 3
jsr display_odd ; 6
jmp vblank ; 3
even:
; 3
nop ; (nop) ; 2
jsr display_even ; 6
jmp vblank ; 3
vblank:
;======================================================
; We have 4550 cycles in the vblank, use them wisely
;======================================================
; do_nothing should be 4550
; +1 fallthrough from above
; -2 display loop setup
; -6 jsr to do_nothing
; -8 letfover from HBLANK code
; -49 check for keypress
; -2252 copy screen
; -2231 draw sprite
; =============
; 11 cycles
; 10 cycles
; jsr do_nothing ; 6
; 17 cycles
inc YPOS ; 5
inc YPOS ; 5
inc YPOS ; 5
nop ; 2
; inc YPOS ; 5
; nop ; 2
; nop ; 2
;=========================
@ -475,3 +467,100 @@ gr_offsets:
.align $100
.include "tfv_sprites.inc"
.align $100
;==========================================
; DISPLAY ODD
display_odd:
ldy #96 ; 2
outer_loop_odd:
bit PAGE0 ; 4
ldx #12 ; 65 cycles with PAGE0 ; 2
page0_loop_odd: ; delay 61+bit
dex ; 2
bne page0_loop_odd ; 2/3
; bit(4) -1(fallthrough) + loop*5 -1(fallthrouh)+4 extra = 61
; 5L = 55
bit PAGE1 ; 4
ldx #11 ; 65 cycles with PAGE1 ; 2
;
page1_loop_odd: ; delay 115+(7 loop)+4 (bit)+4(extra)
dex ; 2
bne page1_loop_odd ; 2/3
dey ; 2
bne outer_loop_odd ; 2/3
rts
;=================================
; Display Even
;=================================
; we have 65 cycles per line
; the first 25 are in hblank
; we come in already 21 cycles into things
; so the first scanline is a loss (but that's OK)
; first scanline: 21+ 2 (from ldy) so need to kill 65-23 = 42
; second scanline, again kill so 65 killed
display_even:
even_first_line:
ldy #95 ; 2
asl DUMMY ; 6
asl DUMMY ; 6
asl DUMMY ; 6
asl DUMMY ; 6
asl DUMMY ; 6
asl DUMMY ; 6
asl DUMMY ; 6
asl DUMMY ; 6
asl DUMMY ; 6
asl DUMMY ; 6
asl DUMMY ; 6
asl DUMMY ; 6
asl DUMMY ; 6
asl DUMMY ; 6
asl DUMMY ; 6
asl DUMMY ; 6
asl DUMMY ; 6
lda YPOS ; 3
nop ; 2
outer_loop_even:
bit PAGE1 ; 4
ldx #12 ; 65 cycles with PAGE0 ; 2
page1_loop_even: ; delay 61+bit
dex ; 2
bne page1_loop_even ; 2/3
; bit(4) -1(fallthrough) + loop*5 -1(fallthrouh)+4 extra = 61
; 5L = 55
bit PAGE0 ; 4
ldx #11 ; 65 cycles with PAGE1 ; 2
;
page0_loop_even: ; delay 115+(7 loop)+4 (bit)+4(extra)
dex ; 2
bne page0_loop_even ; 2/3
dey ; 2
bne outer_loop_even ; 2/3
rts ; 6