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waterfall: even/odd now possible

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This commit is contained in:
Vince Weaver 2018-08-03 10:48:38 -04:00
parent 7149077cf3
commit c8014274af
1 changed files with 67 additions and 33 deletions
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100
waterfall/waterfall.s
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@ -201,7 +201,7 @@ loopB:
display_loop:
inc FRAME ; 5
lda FRAME ; 3
lda #$0 ; 2
and #$10 ; 2
beq even
; 2
lda FRAME ; (nop) ; 3
@ -469,38 +469,6 @@ gr_offsets:
.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
;=================================
@ -564,3 +532,69 @@ page0_loop_even: ; delay 115+(7 loop)+4 (bit)+4(extra)
bne outer_loop_even ; 2/3
rts ; 6
.align $100
;=================================
; Display Odd
;=================================
; 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_odd:
odd_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_odd:
bit PAGE1 ; 4
ldx #12 ; 65 cycles with PAGE0 ; 2
page1_loop_odd: ; delay 61+bit
dex ; 2
bne page1_loop_odd ; 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_odd: ; delay 115+(7 loop)+4 (bit)+4(extra)
dex ; 2
bne page0_loop_odd ; 2/3
dey ; 2
bne outer_loop_odd ; 2/3
rts ; 6