' Serial input demo.
' NOTES:
' Uses an array of bytes for Screen RAM
' Uses Tilde char "~" = $7E for new screen
 
$crystal = 20000000
$BAUD = 19200
 
' 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
 
' Reserve Screen RAM - can reserve as much or as little as required
Dim ScreenRAM(600) as byte at $106
Dim Addr As Word
Dim CharIn as Byte
 
Const NewScreen = $7E
 
'Config Com1 = Dummy , Synchrone = 0 , Parity = None , Stopbits = 1 , Databits = 8 , Clockpol = 0
'Config is not needed unless settings differ from default
 
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
 
 
 
 
  Addr=1       ' Set Addr to address of first screen location
 
  Do
     CharIn=INKEY()
    If CharIn>0 then
        ScreenRAM(Addr)=CharIn
        Incr Addr
        ScreenRAM(Addr)=13     ' Make sure there is always an end of screen character
    End If
    If CharIn=NewScreen then
        Addr=1
        ScreenRAM(Addr)=13
    End If
    If Addr>599 then Addr=599       ' Make sure cannot write past end of screen Ram
  Loop
 
  ' 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
 
End