(*****************************************************************************
 *                      SAMPLE3.C : COUNTER/TIMER                            *
 *                                                                           *
 *  This program will set counter 0 to output 10,000 Hz, counter 1           *
 *  to output 1000 Hz, and will set counter 2 to output 100 Hz.              *
 *                                                                           *
 *****************************************************************************)
program sample3;
uses crt;

const
  DEFAULT_ADDRESS='340';
  COUNTER_OFFSET =$0C;

  procedure CtrMode(addr : word; cntr, mode:byte);
  var ctrl:byte;
  begin
      ctrl := (cntr shl 6) or $30 or (mode shl 1);
      port[addr+3] := ctrl;
  end;

  procedure CtrLoad(addr : word; c, val:word);
  begin
      port[addr+c] := lo(val);
      port[addr+c] := hi(val);
  end;

  function CtrRead(addr : word; c : integer) : word;
  var
    temp : word;
  begin
      port[addr+3] := c shl 6;
      temp := port[addr+c];
      CtrRead := temp + (port[addr+c] shl 8);
  end;

  function AskForBaseAddress(OldOne : String) : Word;
  const
     Msg : string[4] = '0';
  var
     NewOne, Success, Dummy, Error : Word;
     AddrInputPosX, AddrInputPosY : Word;
  begin
     if (OldOne = 'OLD') then OldOne := Msg;
     WriteLn('Please enter the Base Address (0000-FFFF) for your card (in hex)');
     WriteLn('or press ENTER for ', OldOne, '.  ');
     Write('>');
     AddrInputPosX := WhereX; AddrInputPosY := WhereY;
     Success := 0;
     repeat
        GotoXY(AddrInputPosX, AddrInputPosY);
        ClrEol;
        Readln(Msg);
        Val('$' + Msg, NewOne, Error);
        if (error=0) then begin
           Success := 1;
           Dummy := NewOne;
        end else if (Msg = '') then begin
           GotoXY(AddrInputPosX, AddrInputPosY);
           WriteLn(OldOne);
           Msg := OldOne;
           Success := 1;
           Val('$' + Msg, Dummy, Error);
        end;
     until (Success = 1);
     AskForBaseAddress := Dummy;
  end;


var
  base:integer;
  temp, control : word;
BEGIN

   ClrScr;
   WriteLn('Sample 3');
   WriteLn;
   WriteLn('This sample loads all three counters and continuously displays');
   WriteLn('the values that are currently in them.');
   WriteLn;

   base:= AskForBaseAddress( DEFAULT_ADDRESS);

   { Turn off interrupt request generation and set the A/DC trigger
     to software only.}
   temp:=port[base];                    { read the status reg., clr IRQ}
   { set to software start conversion, disabled irqs, read of base+3 to start
     conversions, enable internal clock, counter 1, and counter 2 }
   port[ base]:=$DF;

   CtrMode( base+COUNTER_OFFSET, 0, 3);
   CtrMode( base+COUNTER_OFFSET, 1, 3);
   CtrMode( base+COUNTER_OFFSET, 2, 3);

   CtrLoad( base+COUNTER_OFFSET, 0, 100);
   CtrLoad( base+COUNTER_OFFSET, 1, 1000);
   CtrLoad( base+COUNTER_OFFSET, 2, 10);

   clrscr;
   gotoxy(1, 15);
   writeln('Press a key to exit...');

   while( not keypressed) do
   begin
      gotoxy( 1,4);
      writeln('decrementing between 100 and 0');
      writeln('counter 0 = ', CtrRead( base+COUNTER_OFFSET, 0):7);

      gotoxy( 1,7);
      writeln('decrementing between 1000 and 0');
      writeln('counter 1 = ', CtrRead( base+COUNTER_OFFSET, 1):7);

      gotoxy( 1,10);
      writeln('decrementing between 10 and 0');
      writeln('counter 2 = ', CtrRead( base+COUNTER_OFFSET, 2):7);

      delay(250);
   end;
   GotoXY(1, 20);
END.