CRC-16 X25 und XMODEM Berechnung mit CRC-Modul von dsPIC33EP

unsigned char messageString[8] = {0x01,0x02,0x03,0x04,0x05,0x06,0x07,0x08};

     // CRC-16 X-25, geht nicht und liefert ein Wert von 0x8DDF soll aber 0x6DD4

crcResult = CRC_ChecksumByte( messageString, 8, 0xFFFF, 0xFFFF, 1, 1);

      // CRC-16 XMODEM, funktioniert  CRC=0x76AC

crcResult = CRC_ChecksumByte( messageString, 8, 0x0000, 0x0000, 0, 0);

unsigned int CRC_ChecksumByte( unsigned char *data, unsigned char Number_of_bytes, unsigned int initCRC,  unsigned int xorOut, unsigned int refIn, unsigned int refOut)

{

    unsigned char  volatile    *dest = ( unsigned char * ) &CRCDATL;

    unsigned int crc = 0; unsigned char c = 0;

    CRCWDATL = initCRC;

    IFS4bits.CRCIF=0;                //CRC status Flag is Cleared

    CRCCON1bits.CRCGO = 1;

    do

    {

       while(1 != CRCCON1bits.CRCMPT);

       while( (0 == CRCCON1bits.CRCFUL) && (0 < Number_of_bytes) )

        {

            c = (unsigned char)*data++;

            if (refIn==1) {c = reflect(c, 8);}          

            *dest = c;

            Number_of_bytes--;

        }

    } while( 0 < Number_of_bytes );

  while(!IFS4bits.CRCIF)

        Nop();

 CRCDATL = 0x0000;   /* Do this to shift the last word out of the CRC shift register */

  while( CRCCON1bits.CRCFUL == 1 );

  while(CRCCON1bits.CRCMPT!=1);  

  CRCCON1bits.CRCGO=0;

  crc = CRCWDATL;

  if (refOut==1) {crc=reflect(crc, 16);}

  return ( crc ^ xorOut);

}

unsigned int reflect (unsigned int crc, int bitnum) {

    // reflects the lower 'bitnum' bits of 'crc'

    unsigned int i, j=1, crcout=0;

    for (i=(unsigned int)1<<(bitnum-1); i; i>>=1) {

        if (crc & i) crcout|=j;

        j<<= 1;

    }

    return (crcout);

}