Motorola MCPN750A Benutzerhandbuch

5-12

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Remote Start Via the PCI Bus

/*

 * srom_crc - generate CRC data for the passed buffer

 * description:

 *This function’s purpose is to generate the CRC for thepassed 

buffer.

 * call:

 *argument #1 = buffer pointer

 *argument #2 = number of elements

 * return:

 *CRC data

 */

unsigned int

srom_crc(elements_p, elements_n)

register unsigned char *elements_p;/* buffer pointer */

register unsigned int elements_n;/* number of elements */

{

   register unsigned int crc;

   register unsigned int crc_flipped;

   register unsigned char cbyte;

   register unsigned int index, dbit, msb;

   crc = 0xffffffff;

   for (index = 0; index < elements_n; index++) {

      cbyte = *elements_p++;

      for (dbit = 0; dbit < 8; dbit++) {

 msb = (crc >> 31) & 1;

 crc <<= 1;

 if (msb ^ (cbyte & 1)) {

    crc ^= 0x04c11db6;

    crc |= 1;

}

 cbyte >>= 1;

}

}

crc_flipped = 0;

for (index = 0; index < 32; index++) {