' Six bars - use ATM88 or above

' 0x3C = Block
' 0x3E = Half block

$crystal = 20000000
$BAUD = 0

' Reserve screen variable area at start of RAM

' Assembler interrupt code has two byte variables IN BETWEEN two word variables
Dim ScreenAddr1 as word at $100
Dim RAMVar1 as byte at $102
Dim RAMVar2 as byte at $103
Dim ScreenAddr2 as word at $104

Dim ScreenRAM(600) as byte AT $106

Dim Addr As Word
Dim NumChar as byte
Dim MaxBar as byte
Dim Bar as byte
Dim I as byte
Dim Colour as byte

On Oc2a Tvinterrupt Nosave
Goto Main
!.org $100
$inc Tvinterrupt , Nosize , "tvinc.bin"
Return


Main:
' Set up clock division - only need to do this if DIV8 fuse not set, as default fuse setting is div. by 8
Config Clockdiv = 1
'        CLKPR=$80
'        CLKPR=0
' Setup timer 2
        TCCR2B=$02
        OCR2A=158
        OCR2B=160
        TIMSK2=&b00000110
' Now set up sleep mode [SMCR = Sleep Mode Control Register] - must be enabled or TV code cannot work accurately
        SMCR=1
' Set PORTB to all outputs for video signal
        DDRB=$FF
' Enable & config SPI
        SPCR=$54
        SPSR=1
' Init RAM variables for interrupt code
        RAMVar1=0
        RAMVar2=0
        ScreenAddr1=$106
        ScreenAddr2=$106

        ENABLE OC2A
'        ENABLE OC2B
        ENABLE INTERRUPTS
' Now continue with user code


Do

        Addr=1        ' Set Addr to address of first screen location
        NumChar=$30     ' ASCII value for 0

' Display three sets of alternately coloured bars
        GoSub TwoBars
        GoSub TwoBars
        GoSub TwoBars

        Incr Addr
        ScreenRAM(Addr)=13

' Decimal {012} = $0C = END OF LINE MARKER
' Decimal {013} = $0D = END OF SCREEN MARKER

' Decimal {017} = $11 = Green on black
' Decimal {019} = $13 = Cyan on blue
' Decimal {020} = $14 = Yellow on red
' Decimal {022} = $16 = White on magenta

        Wait 1
Loop

TwoBars:
        Incr NumChar
        Colour=19
        GoSub DisplayBar
        Incr NumChar
        Colour=20
        GoSub DisplayBar
        Return

DisplayBar:
        ScreenRAM(Addr)="B"
        Incr Addr
        ScreenRAM(Addr)="a"
        Incr Addr
        ScreenRAM(Addr)="r"
        Incr Addr
        ScreenRAM(Addr)=" "
        Incr Addr
        ScreenRAM(Addr)=NumChar
        Incr Addr
        ScreenRAM(Addr)=":"
        Incr Addr
        ScreenRAM(Addr)=12
        Incr Addr
' Display row of bar characters plus an end of line char
MaxBar=45
Bar=RND(MaxBar)
Incr Bar
' Make sure Bar is not zero, between 1 and 46

        ScreenRAM(Addr)=Colour
        Incr Addr        
For I=1 to Bar                  ' Write a bar character for each unit in "Bar"
        ScreenRAM(Addr)=$3C
        Incr Addr
Next I

        ScreenRAM(Addr)=" "     ' Write a space
        Incr Addr
        Incr Bar

        ScreenRAM(Addr)=17      ' Write a green on black command to end bar
        Incr Addr      
        Incr Bar

For I=Bar to 50                 ' Write number of spaces to make bars all the same length (makes screen steady)
        ScreenRAM(Addr)=" "
        Incr Addr
Next I

        ScreenRAM(Addr)=12      ' Write end of line character
        Incr Addr

Return

End