(*****************************************************************************
 *                                                                           *
 *                     SAMPLE6.PAS : COUNTER/TIMER                           *
 *                                                                           *
 *  This program will acquire data at the rate input to pin 25.              *
 *                                                                           *
 *****************************************************************************)
program sample6;
uses crt;

const
  DEFAULT_ADDRESS='340';

(* returns the 'busy' bit, high = conversion in progress *)
function CheckForBusy(base : word) : boolean;
begin
    CheckForBusy := ((port[base+2] AND $80) = $80);
end;

(****************************************************************************
 *  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                                                  *
 ****************************************************************************)
var
   data:word;
   timeout:longint;
   chan:word;
   base:integer;
   ch:char;

BEGIN
   chan := 0;
   ClrScr;

   WriteLn('                     Pascal SAMPLE #6: SAMPLE6.PAS                ');
   WriteLn('                                                                  ');
   WriteLn('This program will read data from channel 0 on the A/D card');
   WriteLn('at the rate input to pin 25 (active low edge to start).');
   WriteLn('Therefore, to use this sample, a signal must be provided to this');
   WriteLn('pin.  It is possible to use the output of the counter, or any');
   WriteLn('frequency generator.');
   base:= AskForBaseAddress( DEFAULT_ADDRESS);

   port[base+2]:=chan; (* setup channel and gain (gain code 0, gain of 1) *)
   port[base+0]:=$F4;
   while not keypressed do begin
      timeout:=655354;
      (* wait for start of conversion *)
      while (NOT CheckForBusy(base) AND (timeout > 0)) do dec(timeout);
      (* wait for end of conversion *)
      while (CheckForBusy(base) AND (timeout > 0)) do dec(timeout);
      data:=(portw[base+6] SHR 4) AND $0FFF; (* read data from conversion *)
      gotoxy(10,12+chan);
      ClrEol;
      WriteLn('Channel: ',chan,'  Data Read: ',data);
      if (timeout = 0) THEN BEGIN WriteLn('A/D Timeout Error'); WriteLn; END
      else ClrEol;
      INC(chan);
      chan := chan MOD 8;
      port[base+2]:=chan;   (* setup next channel *)
   END;
   ch := readkey;
   gotoxy(1,20);
END.