(****************************************************************************
 *                        PSAMPLE #4: SAMPLE4.PAS                           *
 *                                                                          *
 *  This sample will continuously read the digital input port and display   *
 *  the value bit by bit.                                                   *
 *                                                                          *
 ****************************************************************************)
program sample4;
uses dos,crt;

var bits:word;
    i:word;
    address:word;
    ch:char;


(****************************************************************************
 *  FUNCTION: AskForBaseAddress                                             *
 ****************************************************************************)
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;
   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;  { end of AskForBaseAddress }

(****************************************************************************
 *                                                                          *
 *  FUNCTION: main program - global routine                                 *
 *                                                                          *
 *     INPUT: None.                                                         *
 *                                                                          *
 *     CALLS: None.                                                         *
 *                                                                          *
 *    OUTPUT: None.                                                         *
 *                                                                          *
 ****************************************************************************)

begin
  clrscr;
  WriteLn('                     Pascal SAMPLE #4: SAMPLE4.PAS                        ');
  WriteLn('                                                                          ');
  WriteLn('  This sample will continuously read the digital input port and display   ');
  WriteLn('  the value bit by bit.                                                   ');
  WriteLn;
  WriteLn;
  Address := AskForBaseAddress('340');
  port[Address+1]:=$00;                     (* tristate the port and set to zero *)
  port[Address]:=$20;                     (* initialize the control register   *)
  while not keypressed do begin
    gotoxy(30,14);
    for i:=0 to 7 do begin
      write(ord((port[Address+1] and ($80 shr i))<>0),' ');
    end;{for}
  end;{while}
  ch := readkey;
end.