typedef unsigned short TDS_CRC;
#define CRC_START_VAL ((TDS_CRC)-1)
#define CRC_TAB_SIZE  256 

TDS_CRC tGetBlockCrc(UINT8 * pBlockStart, UINT32 u32Length)
{
TDS_CRC tds_crc=CRC_START_VAL;
        while (0 < u32Length--)
        {
                tds_crc = dscrcbyte(tds_crc, *pBlockStart++);
        }
        return tds_crc;
}

#define dscrcbyte( Old_crc_us, New_dat_uc) \
                        (\
                          (\
                                        (TDS_CRC) (New_dat_uc ^ ((Old_crc_us & 0x00ff) << 8))\
                                )\
                                ^ \
                                (\
                                        (TDS_CRC) (Crc_tab[(Old_crc_us >> 8)])\
                                )\
                        )

const TDS_CRC Crc_tab[CRC_TAB_SIZE] ={//the table containing (0x1021) Generatorpolynom
        0x0000, 0x1021, 0x2042, 0x3063, 0x4084, 0x50a5, 0x60c6, 0x70e7, 0x8108, 0x9129,
        0xa14a, 0xb16b, 0xc18c, 0xd1ad, 0xe1ce, 0xf1ef, 0x1231, 0x0210, 0x3273, 0x2252,
        0x52b5, 0x4294, 0x72f7, 0x62d6, 0x9339, 0x8318, 0xb37b, 0xa35a, 0xd3bd, 0xc39c,
        0xf3ff, 0xe3de, 0x2462, 0x3443, 0x0420, 0x1401, 0x64e6, 0x74c7, 0x44a4, 0x5485,
        0xa56a, 0xb54b, 0x8528, 0x9509, 0xe5ee, 0xf5cf, 0xc5ac, 0xd58d, 0x3653, 0x2672,
        0x1611, 0x0630, 0x76d7, 0x66f6, 0x5695, 0x46b4, 0xb75b, 0xa77a, 0x9719, 0x8738,
        0xf7df, 0xe7fe, 0xd79d, 0xc7bc, 0x48c4, 0x58e5, 0x6886, 0x78a7, 0x0840, 0x1861,
        0x2802, 0x3823, 0xc9cc, 0xd9ed, 0xe98e, 0xf9af, 0x8948, 0x9969, 0xa90a, 0xb92b,
        0x5af5, 0x4ad4, 0x7ab7, 0x6a96, 0x1a71, 0x0a50, 0x3a33, 0x2a12, 0xdbfd, 0xcbdc,
        0xfbbf, 0xeb9e, 0x9b79, 0x8b58, 0xbb3b, 0xab1a, 0x6ca6, 0x7c87, 0x4ce4, 0x5cc5,
        0x2c22, 0x3c03, 0x0c60, 0x1c41, 0xedae, 0xfd8f, 0xcdec, 0xddcd, 0xad2a, 0xbd0b,
        0x8d68, 0x9d49, 0x7e97, 0x6eb6, 0x5ed5, 0x4ef4, 0x3e13, 0x2e32, 0x1e51, 0x0e70,
        0xff9f, 0xefbe, 0xdfdd, 0xcffc, 0xbf1b, 0xaf3a, 0x9f59, 0x8f78, 0x9188, 0x81a9,
        0xb1ca, 0xa1eb, 0xd10c, 0xc12d, 0xf14e, 0xe16f, 0x1080, 0x00a1, 0x30c2, 0x20e3,
        0x5004, 0x4025, 0x7046, 0x6067, 0x83b9, 0x9398, 0xa3fb, 0xb3da, 0xc33d, 0xd31c,
        0xe37f, 0xf35e, 0x02b1, 0x1290, 0x22f3, 0x32d2, 0x4235, 0x5214, 0x6277, 0x7256,
        0xb5ea, 0xa5cb, 0x95a8, 0x8589, 0xf56e, 0xe54f, 0xd52c, 0xc50d, 0x34e2, 0x24c3,
        0x14a0, 0x0481, 0x7466, 0x6447, 0x5424, 0x4405, 0xa7db, 0xb7fa, 0x8799, 0x97b8,
        0xe75f, 0xf77e, 0xc71d, 0xd73c, 0x26d3, 0x36f2, 0x0691, 0x16b0, 0x6657, 0x7676,
        0x4615, 0x5634, 0xd94c, 0xc96d, 0xf90e, 0xe92f, 0x99c8, 0x89e9, 0xb98a, 0xa9ab,
        0x5844, 0x4865, 0x7806, 0x6827, 0x18c0, 0x08e1, 0x3882, 0x28a3, 0xcb7d, 0xdb5c,
        0xeb3f, 0xfb1e, 0x8bf9, 0x9bd8, 0xabbb, 0xbb9a, 0x4a75, 0x5a54, 0x6a37, 0x7a16,
        0x0af1, 0x1ad0, 0x2ab3, 0x3a92, 0xfd2e, 0xed0f, 0xdd6c, 0xcd4d, 0xbdaa, 0xad8b,
        0x9de8, 0x8dc9, 0x7c26, 0x6c07, 0x5c64, 0x4c45, 0x3ca2, 0x2c83, 0x1ce0, 0x0cc1,
        0xef1f, 0xff3e, 0xcf5d, 0xdf7c, 0xaf9b, 0xbfba, 0x8fd9, 0x9ff8, 0x6e17, 0x7e36,
        0x4e55, 0x5e74, 0x2e93, 0x3eb2, 0x0ed1, 0x1ef0
};

Const Crc16Tab : Array[0..255] of Word = (
$0000, $1021, $2042, $3063, $4084, $50a5, $60c6, $70e7,
$8108, $9129, $a14a, $b16b, $c18c, $d1ad, $e1ce, $f1ef,
$1231, $0210, $3273, $2252, $52b5, $4294, $72f7, $62d6,
$9339, $8318, $b37b, $a35a, $d3bd, $c39c, $f3ff, $e3de,
$2462, $3443, $0420, $1401, $64e6, $74c7, $44a4, $5485,
$a56a, $b54b, $8528, $9509, $e5ee, $f5cf, $c5ac, $d58d,
$3653, $2672, $1611, $0630, $76d7, $66f6, $5695, $46b4,
$b75b, $a77a, $9719, $8738, $f7df, $e7fe, $d79d, $c7bc,
$48c4, $58e5, $6886, $78a7, $0840, $1861, $2802, $3823,
$c9cc, $d9ed, $e98e, $f9af, $8948, $9969, $a90a, $b92b,
$5af5, $4ad4, $7ab7, $6a96, $1a71, $0a50, $3a33, $2a12,
$dbfd, $cbdc, $fbbf, $eb9e, $9b79, $8b58, $bb3b, $ab1a,
$6ca6, $7c87, $4ce4, $5cc5, $2c22, $3c03, $0c60, $1c41,
$edae, $fd8f, $cdec, $ddcd, $ad2a, $bd0b, $8d68, $9d49,
$7e97, $6eb6, $5ed5, $4ef4, $3e13, $2e32, $1e51, $0e70,
$ff9f, $efbe, $dfdd, $cffc, $bf1b, $af3a, $9f59, $8f78,
$9188, $81a9, $b1ca, $a1eb, $d10c, $c12d, $f14e, $e16f,
$1080, $00a1, $30c2, $20e3, $5004, $4025, $7046, $6067,
$83b9, $9398, $a3fb, $b3da, $c33d, $d31c, $e37f, $f35e,
$02b1, $1290, $22f3, $32d2, $4235, $5214, $6277, $7256,
$b5ea, $a5cb, $95a8, $8589, $f56e, $e54f, $d52c, $c50d,
$34e2, $24c3, $14a0, $0481, $7466, $6447, $5424, $4405,
$a7db, $b7fa, $8799, $97b8, $e75f, $f77e, $c71d, $d73c,
$26d3, $36f2, $0691, $16b0, $6657, $7676, $4615, $5634,
$d94c, $c96d, $f90e, $e92f, $99c8, $89e9, $b98a, $a9ab,
$5844, $4865, $7806, $6827, $18c0, $08e1, $3882, $28a3,
$cb7d, $db5c, $eb3f, $fb1e, $8bf9, $9bd8, $abbb, $bb9a,
$4a75, $5a54, $6a37, $7a16, $0af1, $1ad0, $2ab3, $3a92,
$fd2e, $ed0f, $dd6c, $cd4d, $bdaa, $ad8b, $9de8, $8dc9,
$7c26, $6c07, $5c64, $4c45, $3ca2, $2c83, $1ce0, $0cc1,
$ef1f, $ff3e, $cf5d, $df7c, $af9b, $bfba, $8fd9, $9ff8,
$6e17, $7e36, $4e55, $5e74, $2e93, $3eb2, $0ed1, $1ef0
);

Function TForm3.GenerateCRC16(Var s1:String):Word;
Var crc16:Word; i:Integer;
Begin
  crc16 := 0;
  For i := 1 to Length(s1) do Begin
    Crc16 := Crc16Tab[((Crc16 shr 8 ) xor Ord(s1[i])) and $ff] xor ((Crc16 shl 8) and $FFFF);
  End;
  Result := crc16;
End;

Procedure TForm3.Button1Click(Sender: TObject);
Var crc16:Word; s1:String;
Begin
  s1 := '274545957911547';

    crc16 := GenerateCRC16(s1);
    Memo1.Lines.Add(IntTostr(crc16));

End;