Video Life

; Disassembly of VidLife.bin
; Disassembled Thu Apr 14 19:12:06 2011
; Using DiStella v3.0

VSYNC   =  $00
VBLANK  =  $01
WSYNC   =  $02
RSYNC   =  $03
NUSIZ0  =  $04
NUSIZ1  =  $05
COLUP0  =  $06
COLUP1  =  $07
COLUPF  =  $08
COLUBK  =  $09
CTRLPF  =  $0A
REFP0   =  $0B
REFP1   =  $0C
PF2     =  $0F
RESP0   =  $10
RESP1   =  $11
RESM0   =  $12
RESM1   =  $13
RESBL   =  $14
AUDC0   =  $15
AUDC1   =  $16
AUDF0   =  $17
AUDF1   =  $18
AUDV0   =  $19
AUDV1   =  $1A
GRP0    =  $1B
GRP1    =  $1C
ENAM0   =  $1D
ENAM1   =  $1E
ENABL   =  $1F
HMP0    =  $20
HMP1    =  $21
HMBL    =  $24
HMOVE   =  $2A
HMCLR   =  $2B
INPT4   =  $3C
INPT5   =  $3D
SWCHA   =  $0280
SWCHB   =  $0282
INTIM   =  $0284
TIM8T   =  $0295
TIM64T  =  $0296

LF851   =   $F851
LF9A2   =   $F9A2
LFA51   =   $FA51
LFAA2   =   $FAA2
LFB51   =   $FB51
LFC51   =   $FC51
LFCA2   =   $FCA2
LFDA2   =   $FDA2
LFE00   =   $FE00
LFEA2   =   $FEA2
LFF00   =   $FF00
LFFA2   =   $FFA2

CursorX_Hex = $80
CursorY_Hex = $81
CursorX_BCD = $82
CursorY_BCD = $83
Retraces    = $90 ; (Shorter version)
CellLineBuffer = $bc
ZoomBuffer  = $e8
GRID_WIDTH  =  96
GRID_HEIGHT =  80
FontBuffer  = $01CA
CellRead1 = $f000
CellRead2 = $f051
CellRead3 = $f0a2
CellRead4 = $f100
CellRead5 = $f151
CellRead6 = $f1a2
CellRead7 = $f200
CellRead8 = $f251
CellRead9 = $f2a2
CellRead10 = $f300
CellRead11 = $f351
CellRead12 = $f3a2
CellWrite1 = $f400
CellWrite2 = $f451
CellWrite3 = $f4a2
CellWrite4 = $f500
CellWrite5 = $f551
CellWrite6 = $f5a2
CellWrite7 = $f600
CellWrite8 = $f651
CellWrite9 = $f6a2
CellWrite10 = $f700
CellWrite11 = $f751
CellWrite12 = $f7a2


;       ORG $F800

RenderTheScreen:
       INC    Retraces
       BNE    LF80A
       LDA    $86
       BMI    LF80A
       INC    $86
LF80A: LDA    Retraces
       AND    #$01
       BEQ    LF887
       LDA    #$80
       STA    HMP0
       STA    HMP1
       STA    WSYNC
       STA    HMOVE
LF81A: STA    WSYNC
       LDA    #$00
       STA    PF2
       TXA
       LSR    A
       TAY
       LDA    CellRead2,X
       STA    GRP0
       LDA    CellRead4,X
       STA    GRP1
       LDA    CellRead6,X
       STA    GRP0
       LDA    CellRead8,X
       STA    GRP1
       LDA    CellRead10,X
       STA    GRP0
       LDA    CellRead12,X
       STA    GRP1
       LDA    FontBuffer,Y
       STA    PF2
       CPX    CursorY_Hex
       BNE    LF84E
       LDA    #$FF
       STA    ENABL
LF84E: STA    WSYNC
       LDA    #$00
       STA    PF2
       TXA
       LSR    A
       TAY
       LDA    CellRead2,X
       STA    GRP0
       LDA    CellRead4,X
       STA    GRP1
       LDA    CellRead6,X
       STA    GRP0
       LDA    CellRead8,X
       STA    GRP1
       LDA    CellRead10,X
       STA    GRP0
       LDA    CellRead12,X
       STA    GRP1
       LDA    FontBuffer,Y
       STA    PF2
       LDA    #$00
       INX
       CPX    #$50
       STA    ENABL
       BNE    LF81A
       STA    WSYNC
       BEQ    LF8F2
LF887: STA    WSYNC
LF889: STA    WSYNC
       STA    PF2
       TXA
       LSR    A
       TAY
       LDA    CellRead1,X
       STA    GRP0
       LDA    CellRead3,X
       STA    GRP1
       LDA    CellRead5,X
       STA    GRP0
       LDA    CellRead7,X
LF8A2: STA    GRP1
       LDA    CellRead9,X
       STA    GRP0
       LDA    CellRead11,X
       STA    GRP1
       LDA    FontBuffer,Y
       STA    PF2
       CPX    CursorY_Hex
       BNE    LF8BB
       LDA    #$FF
       STA    ENABL
LF8BB: LDA    #$00
       STA    WSYNC
       STA    PF2
       TXA
       LSR    A
       TAY
       LDA    CellRead1,X
       STA    GRP0
       LDA    CellRead3,X
       STA    GRP1
       LDA    CellRead5,X
       STA    GRP0
       LDA    CellRead7,X
       STA    GRP1
       LDA    CellRead9,X
       STA    GRP0
       LDA    CellRead11,X
       STA    GRP1
       LDA    FontBuffer,Y
       STA    PF2
       LDA    #$00
       INX
       CPX    #$50
       STA    ENABL
       BNE    LF889
       STA    WSYNC
LF8F2: STA    GRP0
       STA    PF2
       STA    GRP1
       STA    WSYNC
       LDX    #$C5
       BIT    $86
       BPL    :+
LF900: LDX    Retraces
:      LDY    #$02
       STA    WSYNC
       STX    COLUBK
       STA    NUSIZ0
       STA    COLUP0
       STY    ENAM0
       STA    NUSIZ1
       STA    COLUP1
       STY    ENAM1
       LDA    #$3C
       STA    TIM64T
       RTS

WaitTimer1:
       LDA    INTIM ;F91A
       BNE    WaitTimer1
       LDA    #$2A
       STA    WSYNC
       STA    VBLANK
       STA    VSYNC
       STA    TIM8T
       RTS

WaitTimer2:
       LDA    INTIM ;F92B
       BNE    WaitTimer2
       STA    WSYNC
       STA    VSYNC
       LDA    #$30
       STA    TIM64T
       RTS

CopyCellLineToBuffer: ; see also: CopyBufferToCellLine
; Inputs:
; X -  Location of buffer in zeropage
; Y -  Row you want
       LDA    CellRead1,Y
       STA    $0,X
       LDA    CellRead2,Y
       STA    $1,X
       LDA    CellRead3,Y
       STA    $2,X
       LDA    CellRead4,Y
       STA    $3,X
       LDA    CellRead5,Y
LF951: STA    $4,X
       LDA    CellRead6,Y
       STA    $5,X
       LDA    CellRead7,Y
       STA    $6,X
       LDA    CellRead8,Y
       STA    $7,X
       LDA    CellRead9,Y
       STA    $8,X
       LDA    CellRead10,Y
       STA    $9,X
       LDA    CellRead11,Y
       STA    $a,X
       LDA    CellRead12,Y
       STA    $b,X
       RTS

ToggleCellUnderCursor: ; plays a sound too!
       LDY    CursorY_Hex
       LDX    #CellLineBuffer
       JSR    CopyCellLineToBuffer
       LDA    CursorX_Hex ; get index into CellLineBuffer (X/8)
       LSR    A
       LSR    A
       LSR    A
       TAX
       LDA    CursorX_Hex ; get bit number of the byte (X&7)
       AND    #$07
       TAY
       LDA    BitSelectTable,Y
       EOR    CellLineBuffer,X
       STA    CellLineBuffer,X
       LDX    #$08  ; make a different sound depending on if we're turning a bit on or off
       AND    BitSelectTable,Y
       BNE    :+
         LDX    #$10
:      STX    AUDF0
       LDY    CursorY_Hex
       LDX    #CellLineBuffer
       STX    AUDV0
CopyBufferToCellLine: ; see also: CopyCellLineToBuffer
; Inputs:
; X -  Location of buffer in zeropage
; Y -  Row you want
       LDA    0,X
       STA    CellWrite1,Y
       LDA    1,X
       STA    CellWrite2,Y
       LDA    2,X
       STA    CellWrite3,Y
       LDA    3,X
       STA    CellWrite4,Y
       LDA    4,X
       STA    CellWrite5,Y
       LDA    5,X
       STA    CellWrite6,Y
       LDA    6,X
       STA    CellWrite7,Y
       LDA    7,X
       STA    CellWrite8,Y
       LDA    8,X
       STA    CellWrite9,Y
       LDA    9,X
       STA    CellWrite10,Y
       LDA    10,X
       STA    CellWrite11,Y
       LDA    11,X
       STA    CellWrite12,Y
       RTS

BitSelectTable:
       .byt $01,$02,$04,$08,$10,$20,$40,$80

START: SEI
       CLD
       LDA    #$00
       TAX
:      STA    0,X          ; seems to clear memory but is kind of wacky
       TXS
       STX    CursorY_Hex
       INX
       BNE    :-
       STA    WSYNC
       LDX    #$04
:      DEX
       BNE    :-
       STA    RESM0
       LDX    #$0B
       STA    WSYNC
:      DEX
       BNE    :-
       STA    RESM1
       LDX    #$07
       STA    WSYNC
:      DEX
       BNE    :-
       STA    RESBL
       STA    $84
       STA    $87
       STA    $88
       LDA    #$C5
       STA    $F2
       LDA    #$08
       STA    AUDC1
       STA    REFP0
       STA    REFP1
       JSR    LFE96
       LDA    #$43
       JSR    LFEC4
       LDA    #$0F
       STA    AUDV1
LFA2C: INC    CursorY_Hex
       JSR    PrepareAndRenderThenWait
       JSR    PrepareAndRenderThenWait
       LDA    CursorY_Hex
       CMP    #$20
       BPL    LFA3C
       STA    AUDF1
LFA3C: CMP    #$25
       BMI    LFA2C
       LDA    #$37
       STA    CursorX_BCD
       STA    CursorY_BCD
       LDA    #$55
       STA    $F2
       LDA    #$00
       STA    AUDC1
       STA    $AE
:      JSR    PrepareAndRenderThenWait
       INC    $AE
       BPL    :-
       LDA    #$49
       JSR    LFEC4
       LDA    #$FE
       STA    $85
       BNE    LFA8F
LFA62: JSR    LFE96
       LDA    #$00
       STA    $87
       STA    $88
       STA    $86

; could be the main loop
LFA6D: STA    $85
LFA6F: JSR    PrepareAndRender
       JSR    RenderThreeNumbers
       JSR    WaitTimer1
       JSR    WaitTimer2
       JSR    LFB92
       JSR    PrepareAndRenderThenWait
       LDX    #$00
       STX    AUDV0
       LDA    SWCHB
       LSR    A
       BCC    LFA62
       LDA    INPT5
       BMI    LFA92
LFA8F: JMP    LFD03
LFA92: LDA    SWCHA   ; get keys?
       ORA    #$0F
       LDY    INPT4   ; button on the controller
       BPL    :+
         STX    $84
         AND    #$FE
         CMP    #$FE
:      BEQ    LFA6D   ; no keys pressed, TRY AGAIN
       ; keys pressed, so process them
       STX    $86
       CMP    $85
       STA    $85
       BNE    LFAB1
       LSR    $8F            ; if
       BNE    LFA6F
       BEQ    LFAB5
LFAB1: LDA    #$40           ; else
       STA    $8F
LFAB5: LDA    $85            ; end
       AND    #$01
       BEQ    :+
       LDA    $84
       BNE    :+
       INC    $84
       JSR    ToggleCellUnderCursor
:      LDA    $85
       AND    #$F0
       CMP    #$F0
       BEQ    LFA6F
       LDX    #$00
       STX    $84
       AND    #$40
       BNE    CheckPressingUp
       LDA    CursorX_Hex
       BNE    DontNeedWrapLeft
       LDX    #$0B
       STA    WSYNC
LFADC: DEX
       BNE    LFADC
       STA    RESBL
       LDA    #$5F
       STA    CursorX_Hex
       LDA    #$95
       STA    CursorX_BCD
       LDA    #$20
       BNE    WrappedAroundLeft
DontNeedWrapLeft:
         DEC    CursorX_Hex
         SED
         SEC
         LDA    CursorX_BCD
         SBC    #$01
         STA    CursorX_BCD
         CLD
         LDA    #$10
WrappedAroundLeft:
       STA    HMBL
       STA    WSYNC
       STA    HMOVE
LFB00: STA    WSYNC   ; label not referenced anywhere?
       STA    HMCLR
CheckPressingUp:
       LDA    $85             ; Pressing up?
       AND    #$10
       BNE    CheckPressingRight
       LDA    CursorY_Hex
       BNE    :+
         LDA    #$4F
         STA    CursorY_Hex
         LDA    #$79
         STA    CursorY_BCD
         BNE    CheckPressingRight
:      DEC    CursorY_Hex
       SED
       SEC
       LDA    CursorY_BCD
       SBC    #$01
       STA    CursorY_BCD
       CLD
CheckPressingRight:
       LDA    $85             ; Pressing right?
       AND    #$80
       BNE    CheckPressDown
       LDA    CursorX_Hex     ; Do we need to wrap the cursor around?
       CMP    #GRID_WIDTH-1
       BNE    :+
         STA    WSYNC
         STA    RESBL
         LDA    #$00
         STA    CursorX_Hex
         STA    CursorX_BCD
         LDA    #$80
         BNE    WrappedAroundRight
:      INC    CursorX_Hex
       SED
       CLC
       LDA    CursorX_BCD
       ADC    #$01
       STA    CursorX_BCD
       CLD
       LDA    #$F0            ; move the ball cursor
WrappedAroundRight:
       STA    HMBL            ;
       STA    WSYNC           ;
       STA    HMOVE           ; update ball X position
       STA    WSYNC
       STA    HMCLR
CheckPressDown:
       LDA    $85             ; Pressing down?
       AND    #$20
       BNE    DownNotPressed
       LDA    CursorY_Hex     ; Do we need to wrap the cursor around?
       CMP    #GRID_HEIGHT-1
       BNE    :+
         LDA    #$00
         STA    CursorY_Hex
         STA    CursorY_BCD
         BEQ    WrappedAroundDown
:      INC    CursorY_Hex
       SED
       CLC
       LDA    CursorY_BCD
       ADC    #$01
       STA    CursorY_BCD
       CLD
DownNotPressed:
WrappedAroundDown:
       JMP    LFA6F

LFB76: .byte $F3
LFB77: .byte $F0,$F0,$F0,$F1,$F1,$F1,$F2,$F2,$F2,$F3,$F3,$F3,$F0
LFB84: .byte $A2
LFB85: .byte $00,$51,$A2,$00,$51,$A2,$00,$51,$A2,$00,$51,$A2,$00

LFB92: LDA    CursorY_Hex
       CMP    #$4B
       BMI    :+
         SEC
         SBC    #$50
:      CLC
       ADC    #$05
       STA    $92
       LDA    CursorX_Hex
LFBA2: CLC
       ADC    #$05
       TAY
       AND    #$07
       STA    $99
       TYA
       LSR    A
       LSR    A
       LSR    A
       TAY
       LDA    LFB76,Y
       STA    $95
       ORA    #$04
       STA    $A3
       LDA    LFB84,Y
       STA    $94
       STA    $A2
       LDA    LFB77,Y
       STA    $97
       ORA    #$04
       STA    $A5
       LDA    LFB85,Y
       STA    $96
       STA    $A4
       LDA    #$09
       STA    $93
       LDA    SWCHB
       BPL    MakeZoomBuffer
       LDA    SWCHA   ; pressing anything?
       AND    #$0F
       CMP    #$0F
       BEQ    LFC2A   ; exit mystery routine
       LDA    INPT4
       BMI    LFC2A   ; exit mystery routine
       LDA    #$FF
       STA    $B1
       LDA    #$00
       LDX    $99
       SEC
       BEQ    LFBF6
:      ROL    A
       ROL    $B1
       DEX
       BNE    :-
LFBF6: STA    $B0
LFBF8: LDA    $92
       BPL    :+
         CLC
         ADC    #$50
:      TAY
LFC00: LDA    #$00
       STA    $AF
       LDX    $93
       LDA    ZoomBuffer,X
       LDX    $99
       BEQ    LFC12
LFC0C: ASL    A
       ROL    $AF
       DEX
       BNE    LFC0C
LFC12: STA    $AE
       LDA    ($94),Y
       AND    $B0
       ORA    $AE
       STA    ($A2),Y
       LDA    ($96),Y
       AND    $B1
       ORA    $AF
       STA    ($A4),Y
       DEC    $92
       DEC    $93
       BPL    LFBF8
LFC2A: RTS

MakeZoomBuffer:
       LDA    $92
       BPL    :+
       CLC
       ADC    #$50
:      TAY
       LDA    ($96),Y
       STA    $AE
       LDA    ($94),Y
       LDX    $99
       BEQ    LFC43
:      LSR    $AE
       ROR    A
       DEX
       BNE    :-
LFC43: LDX    $93
       STA    ZoomBuffer,X
       DEC    $92
       DEC    $93
       BPL    MakeZoomBuffer
       RTS

RenderThreeNumbers:
       LDA    #$00
       STA    $A1
       LDX    #$04
:      STA    $CA,X   ; seems to clear out the generations count
       DEX
       BPL    :-
; Render three numbers
       LDX    #$DA
       LDA    CursorX_BCD
       JSR    RenderNumber
       LDX    #$E1
       LDA    CursorY_BCD
       JSR    RenderNumber
       LDX    #$CA
       LDA    $88
       BEQ    :+
       JSR    RenderNumber
:      LDA    $88
       STA    $A1
       LDX    #$D0
       LDA    $87
RenderNumber: ;Renders BCD-coded number A to zeropage at address X
       STA    $92     ; store number to render for later
       AND    #$0F
       TAY            ; render the low nybble
       LDA    #$F0
       STA    $A0
       LDA    #$00    ; clear out the render area
       STA    0,X
       STA    1,X
       STA    2,X
       STA    3,X
       STA    4,X
       JSR    RenderNybble
       LDA    $92     ; get stored number from last time
       AND    #$F0    ; check if top nybble is zero,
       BNE    :+      ; if it isn't, go on with drawing it!
         LDY    $A1
         BEQ    ExitNumberRenderer ; otherwise don't draw it
:      LSR    A
       LSR    A
       LSR    A
       LSR    A
       TAY             ; render high nybble
       LDA    #$0F     ; store to top
       STA    $A0
RenderNybble:          ; $A0=Digit mask ($F0 or $0F), X=A to render to, Y=Digit to render
       LDA    Font1,Y
       AND    $A0
       ORA    0,X
       STA    0,X
       LDA    Font2,Y
       AND    $A0
       ORA    1,X
       STA    1,X
       LDA    Font3,Y
       AND    $A0
       ORA    2,X
       STA    2,X
       LDA    Font4,Y
       AND    $A0
       ORA    3,X
       STA    3,X
       LDA    Font5,Y
       AND    $A0
       ORA    4,X
       STA    4,X
ExitNumberRenderer:
       RTS

; Font! High and low nybbles are the same
; so it can mask off one of them and OR with
; the font buffer for the top and low nybbles
Font1: .byte $22,$22,$77,$77,$55,$77,$77,$77,$77,$77
Font2: .byte $55,$22,$44,$44,$55,$11,$11,$44,$55,$55
Font3: .byte $55,$22,$77,$77,$77,$77,$77,$44,$77,$77
Font4: .byte $55,$22,$11,$44,$44,$44,$55,$44,$55,$44
Font5: .byte $22,$22,$77,$77,$44,$77,$77,$44,$77,$77

LFD03: LDX    #$AF
       LDY    #$00
       STY    $86
       STY    $91
       JSR    CopyCellLineToBuffer
       LDA    #$0C
       STA    AUDC0
       LDA    $AF
       STA    $BB
       LDA    $BA
       STA    $AE
       LDY    #$50
       JSR    CopyBufferToCellLine
       LDX    #$A1
       LDY    #$4F
       STY    AUDV0
       JSR    CopyCellLineToBuffer
       LDA    $A1
       STA    $AD
       LDA    $AC
       STA    $A0
       LDA    #$01
       STA    $8F
LFD34: LDA    #$0A
       JSR    LFF67
       LDX    #$0D
       LDY    #$00
:      LDA    $A0,X
       STA    $92,X
       LDA    $AE,X
       STA    $A0,X
       STY    CellLineBuffer,X
       DEX
       BPL    :-
       LDY    $8F
       LDX    #$AF
       JSR    CopyCellLineToBuffer
LFD51: LDA    $AF
       STA    $BB
       LDA    $BA
       STA    $AE
       LDA    #$00
       STA    $8A
       LDA    $9F
       LSR    A
       ROL    $8A
       LDA    $BB
       LSR    A
       ROL    $8A
       LDA    $AD
       LSR    A
       ROL    $8A
       LDX    #$0C
       STX    $8E
       LDY    #$00
       BEQ    LFDA9
LFD74: TYA
       ASL    A
       ASL    A
       ASL    A
       AND    #$38
       ORA    $8A
       TAY
       LDA    #$00
       ASL    $8B
       ROL    A
       ASL    $8C
       ROL    A
       ASL    $8D
       ROL    A
       TAX
       STX    $8A
       LDA    LFE56,Y
       AND    BitSelectTable,X
       BEQ    LFD9B
       ASL    $89
       INC    $89
       BCC    LFD74
       BCS    LFD9F
LFD9B: ASL    $89
       BCC    LFD74
LFD9F: LDX    $8E
       LDA    $89
       ASL    A
       ROL    $BE,X
       LSR    A
       STA    $BD,X
LFDA9: LDA    #$0A
       JSR    LFF67
       LDX    $8E
       BEQ    LFDC5
       TYA
       AND    #$07
       ORA    $8A
       ORA    $92,X
       ORA    $AE,X
       ORA    $A0,X
       BNE    LFDC5
       STA    $89
       DEC    $8E
       BPL    LFD9F
LFDC5: LDA    $92,X
       STA    $8B
       LDA    $AE,X
       STA    $8C
       LDA    $A0,X
       STA    $8D
       LDA    #$01
       STA    $89
       DEC    $8E
       BPL    LFD74
       TYA
       ASL    A
       ASL    A
       ASL    A
       AND    #$38
       ORA    $8A
       TAY
       LDA    #$00
       ASL    $8B
       ROL    A
       ASL    $8C
       ROL    A
       ASL    $8D
       ROL    A
       TAX
       LDA    LFE56,Y
       AND    BitSelectTable,X
       CLC
       BEQ    :+
       SEC
:      ROL    $BD
       LDY    $8F
       DEY
       LDX    #$BD
       JSR    CopyBufferToCellLine
       INC    $8F
       CPY    #$4F
       BEQ    LFE0B
       JMP    LFD34
LFE0B: LDA    INTIM
       ORA    #$08
       STA    AUDF0
LFE12: LDA    #$FF
       JSR    LFF67
       LDA    $91
       BEQ    LFE12
       SED
       CLC
       ADC    $87
       STA    $87
       LDA    #$00
       ADC    $88
       STA    $88
       CLD
       BCS    LFE4F
       JSR    RenderThreeNumbers
       JSR    WaitTimer1
       JSR    WaitTimer2
       JSR    LFB92
       JSR    PrepareAndRenderThenWait
       JSR    PrepareAndRenderThenWait
       JSR    PrepareAndRenderThenWait
       LDA    SWCHA
       CMP    #$FF
       BNE    LFE4F
       LDA    SWCHB
       LSR    A
       BCC    LFE4F
       JMP    LFD03

LFE4F: LDA    #$05
LFE51: STA    AUDC0
       JMP    LFA6F

; could possibly have something to do with grid calculation
LFE56: .byt $80,$E8,$68,$7E,$68,$7E,$16,$17,$68,$7E,$16,$17,$16,$17,$01,$01
       .byt $68,$7E,$16,$17,$16,$17,$01,$01,$16,$17,$01,$01,$01,$01,$00,$00
       .byt $68,$7E,$16,$17,$16,$17,$01,$01,$16,$17,$01,$01,$01,$01,$00,$00
       .byt $16,$17,$01,$01,$01,$01,$00,$00,$01,$01,$00,$00,$00,$00,$00,$00

LFE96: JSR    PrepareAndRenderThenWait
       LDX    #$0D
LFE9B: LDA    #$00
       STA    $92,X
       LDA    #$FF
       STA    $A0,X
       DEX
       BPL    LFE9B
:      LDY    $92
       LDX    #$A1
       JSR    CopyBufferToCellLine
       JSR    PrepareAndRenderThenWait
       JSR    PrepareAndRenderThenWait
       LDY    $92
       LDX    #$93
       JSR    CopyBufferToCellLine
       INY
       STY    $92
       CPY    #$50
       BMI    :-
       JMP    PrepareAndRenderThenWait

LFEC4: STA    $B4
       LDA    #$00
       STA    $B3
       LDA    LFF1C
       STA    $AE
       LDA    LFF1D
       STA    $AF
       LDA    #$19
       STA    $B0
       LDA    #$1C
       STA    $B1
LFEDC: JSR    PrepareAndRenderThenWait
       LDA    CursorY_Hex
       PHA
       LDY    $B3
       LDA    ($AE),Y
       LSR    A
       LSR    A
       LSR    A
       LSR    A
       CMP    #$08
       BMI    LFEF0
       ORA    #$F0
LFEF0: CLC
       ADC    $B0
       STA    $B0
       STA    CursorX_Hex
       LDA    ($AE),Y
       AND    #$0F
       CMP    #$08
       BMI    LFF01
       ORA    #$F0
LFF01: CLC
       ADC    $B1
       STA    $B1
       STA    CursorY_Hex
       JSR    ToggleCellUnderCursor
       PLA
       STA    CursorX_Hex
       STA    CursorY_Hex
       JSR    PrepareAndRenderThenWait
       INC    $B3
       LDA    $B3
       CMP    $B4
       BNE    LFEDC
       RTS

LFF1C: .byt $1E
LFF1D: .byt $FF,$00,$20,$21,$12,$20,$10,$1F,$0F,$FF,$E1,$01,$03,$02,$02,$02
       .byt $02,$02,$01,$F1,$EF,$FF,$1F,$20,$21,$21,$20,$1F,$0D,$01,$13,$2F
       .byt $2F,$1F,$1F,$1E,$0E,$0E,$FE,$F0,$01,$02,$02,$02,$04,$02,$02,$12
       .byt $2F,$0E,$FE,$FE
LFF51: .byt $30,$20,$20,$1F,$1F,$0E,$EF,$F1,$01,$02,$02,$01,$11,$20,$2F,$2F
       .byt $08,$0F,$1F,$01,$10,$01

LFF67: CMP    INTIM
       BCC    LFF9F
       STY    $8B
       LDA    $91
       BNE    LFF95
       LDA    SWCHB
       AND    #$40
       BNE    :+
       JSR    PrepareAndRender
       INC    $91
       BNE    LFF9D
:      LDA    INTIM
       BNE    :-
       LDX    #$02
LFF87: STA    WSYNC
       DEX
       BPL    LFF87
       INC    $91
       LDA    #$FF
       STA    TIM64T
       BNE    LFF9D
LFF95: JSR    WaitTimer1
       JSR    WaitTimer2
       DEC    $91
LFF9D: LDY    $8B
LFF9F: RTS

PrepareAndRender:
       LDA    INTIM   ; wait until the timer is empty
       BNE    PrepareAndRender
       ; A is now zero
       STA    WSYNC
       STA    VBLANK
       LDY    #$17
       BIT    $86
       BPL    :+
         LDY    Retraces
:      STY    COLUPF
       LDY    #$06
       STA    WSYNC
       STA    RESP0
       LDX    #$04    ; delay
:      DEX
       BNE    :-
       STA    RESP1
       LDA    #$90
       STA    HMP0
       LDA    #$80
       STA    HMP1
       LDX    #$00
       LDA    $F2
       BIT    $86
       BPL    :+
         LDA    Retraces
         EOR    #$FF
         AND    #$FD
         TAX
         LDA    Retraces
:      STA    WSYNC
       STA    HMOVE
       STX    COLUBK
       STX    ENAM0
       STX    ENAM1
       STY    NUSIZ0
       STY    NUSIZ1
       STA    COLUP0
       STA    COLUP1
       LDX    #$00
       JMP    RenderTheScreen

PrepareAndRenderThenWait:
       JSR    PrepareAndRender
       JSR    WaitTimer1
       JSR    WaitTimer2
       RTS

LFFFA: ;.byte $E6,$F9,$E6,$F9,$E6,$F9
       .addr START, START, START