mirror of
https://github.com/deater/dos33fsprogs.git
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266 lines
4.3 KiB
ArmAsm
266 lines
4.3 KiB
ArmAsm
;==============================
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; setup graphics for vapor lock
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;==============================
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vapor_lock:
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; Clear Page0
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lda #$0
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sta DRAW_PAGE
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lda #$ff ; full screen dark green $44
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jsr clear_gr
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lda #$aa
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ldy #24
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jsr clear_page_loop ; make top half red $11
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ldy #00 ; 0
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sty $728+20
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iny ; 1
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sty $728+21
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iny ; 2
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sty $728+22
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iny ; 3
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sty $728+23
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iny ; 4
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sty $728+24
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iny ; 5
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sty $728+25
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iny ; 6
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sty $728+26
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iny ; 7
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sty $728+27
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iny ; 8
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sty $728+28
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iny ; 9
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sty $728+29
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iny ; a
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sty $728+30
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iny ; b
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sty $728+31
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iny ; c
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sty $728+32
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iny ; d
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sty $728+33
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iny ; e
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sty $728+34
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iny ; f
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sty $728+35
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iny ; 10
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sty $728+36
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iny
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sty $728+37
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iny
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sty $728+38
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iny
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sty $728+39
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;btt:
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; jmp btt
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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 $55 (which is the grey line)
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;=====================================================
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; See:
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; Have an Apple Split by Bob Bishop
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; Softalk, October 1982
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; Challenges: each scan line scans 40 bytes.
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; The blanking happens at the *beginning*
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; So 65 bytes are scanned, starting at adress of the line - 25
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; the scan takes 8 cycles, look for 4 repeats of the value
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; to avoid false positive found if the horiz blanking is mirroring
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; the line (max 3 repeats in that case)
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vapor_lock_loop:
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; first make sure we have a full line of red
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; we can only read every
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lda #$aa ; 2
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zxloop:
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ldx #$04 ; 2
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wiloop:
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cmp $C051 ; read the floating bus ; 4
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bne zxloop ; if not red, start from scratch ; 2/3
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dex ; we were red, dec ; 2
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bne wiloop ; if not 4 of them, restart ; 3/2
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; if we get here we read 4 proper pixels, 11 apart
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; X X X X
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; X X X X
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; X X X X
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; X X X X
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; X X X X
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; X X X X
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; X X X X
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; 0123456789012345678901234 0123456789012345678901234567890123456789
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; 1 2 1 2 3
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; hsync pixels
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; XXXXXXXXXXXXXXXXXXXXXXXXX 4444444444444444444444444444440123456789
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; now look for the color change that
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; happens at line 12*8 = 96
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lda #$ff ; 2
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zloop:
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ldx #$04 ; 2
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qloop:
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cmp $C051 ; read floating bus ; 4
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bne zloop ; 2/3
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dex ; 2
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bne qloop ; 3/2
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;============
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; 11
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; delay 65 *1
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inc $0
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inc $0
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inc $0
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inc $0
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inc $0
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inc $0
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inc $0
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inc $0
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inc $0
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inc $0
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inc $0
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inc $0
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inc $0
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; delay 65 *1
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inc $0
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inc $0
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inc $0
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inc $0
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inc $0
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inc $0
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inc $0
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inc $0
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inc $0
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inc $0
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inc $0
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inc $0
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inc $0
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; delay 65 *1
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inc $0
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inc $0
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inc $0
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inc $0
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inc $0
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inc $0
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inc $0
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inc $0
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inc $0
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inc $0
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inc $0
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inc $0
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inc $0
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; delay 65 *1
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inc $0
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inc $0
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inc $0
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inc $0
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inc $0
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inc $0
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inc $0
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inc $0
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inc $0
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inc $0
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inc $0
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inc $0
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inc $0
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; delay 65 *1
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inc $0
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inc $0
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inc $0
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inc $0
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inc $0
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inc $0
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inc $0
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inc $0
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inc $0
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inc $0
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inc $0
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inc $0
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inc $0
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; delay 65 *1
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inc $0
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inc $0
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inc $0
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inc $0
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inc $0
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inc $0
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inc $0
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inc $0
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inc $0
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inc $0
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inc $0
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inc $0
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inc $0
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; delay 65 *1
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inc $0
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inc $0
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inc $0
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inc $0
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inc $0
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inc $0
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inc $0
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inc $0
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inc $0
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inc $0
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inc $0
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inc $0
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inc $0
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; delay 65 *1
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inc $0
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inc $0
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inc $0
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inc $0
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inc $0
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inc $0
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inc $0
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inc $0
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inc $0
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inc $0
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inc $0
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lda $C051
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;kbb:
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; jmp kbb
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; we are in theory on line $728 = 14*8 = 112
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; so 112*65 = 7280 cycles from start
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; we are actualy 25+20+A pixels in
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; 7325+A
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; 114 is at 7410 cycles
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; 7410 - 7325 = 85
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; so kill 85-A cycles
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; -6 to do subtraction
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; -6 for rts
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; -25 for delay_a overhead
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eor #$ff ; 2
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sec ; 2
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adc #48 ; 2
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jsr delay_a ; should total 48 cycles
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done_vapor_lock:
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rts ; 6
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