Delphi Modbus RTU CRC16校验码

function CheckCrc16(const ABuf; ALen: Integer): Boolean;
var
uwTemp: WORD;
i, j: BYTE;
P: PByte;
begin
  Result := False;

P := PByte(@ABuf);

uwTemp := $FFFF;
  for i := 1 to ALen do
  begin
    uwTemp := uwTemp xor P^;
    for j := 1 to 8 do
    begin
       if (uwTemp and 1) = 1 then
          uwTemp := (uwTemp shr 1) xor $A001
       else
          uwTemp := uwTemp shr 1
    end;
    Inc(P);
  end;

if P^ = BYTE(uwTemp) then
  begin
      Inc(P);
      if P^ = BYTE(uwTemp shr 8) then
      begin
         Result := True;
      end
   end
end;