CS4210 datasheet(32/102 Pages) NSC

32 / 102 page

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Operational Description (Continued)

Figure 3-1. CRC1 and CRC2 Sample Code

ff ff ff ff ff ff ff ff -> CRC1 = feh, CRC2 = 70h

01 23 45 67 89 ab cd ef -> CRC1 = 19h, CRC2 = 07h

00 00 00 00 00 00 00 00 -> CRC1 = bfh, CRC2 = f4h

#include <stdio.h>

typedef unsigned char uchar_t;

typedef unsigned short ushort_t;

typedef unsigned long long_t;

ushort_t calc_crc(ushort_t r, uchar_t d);

ushort_t rev16(ushort_t src);

/* main routine */

int main(int argc, char *argv[])

{

ushort_t residual = 0xffff;

int din;

uchar_t byte;

uchar_t crc1, crc2;

while(scanf("%2x", &din ) != EOF ) {

byte = din;

printf("%2.2x ", byte);

residual = calc_crc(residual, byte);

};

printf("\n");

residual = rev16(residual);

crc1 = ~(residual & 0x00ff);

crc2 =

~(residual>>8);

printf("CRC1 = %2.2hxh\n", crc1);

printf("CRC2 = %2.2hxh\n", crc2);

return(0);

/* calc_crc - apply a byte of data to the 16-bit CRC */

}

ushort_t calc_crc(ushort_t r, uchar_t d)

{

ushort_t bit_in;

int i;

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

bit_in = (d>>i) & 0x0001;

if((r>>15) ^ bit_in)

r = (((r<<1) & 0x7ffb) | ((r>>15 ^ ((r>>14)&0x0001) ^ bit_in) << 15) |

((r>>15 ^ ((r>>1)&0x0001) ^ bit_in) << 2) | 0x0001 );

else

r<<= 1;

}

return(r);

}

ushort_t rev16(ushort_t src)

{

return(

((src&0x0001)<<15) |

((src&0x0002)<<13) |

((src&0x0004)<<11) |

((src&0x0008)<<9) |

((src&0x0010)<<7) |

((src&0x0020)<<5) |

((src&0x0040)<<3) |

((src&0x0080)<<1) |

((src&0x0100)>>1) |

((src&0x0200)>>3) |

((src&0x0400)>>5) |

((src&0x0800)>>7) |

((src&0x1000)>>9) |

((src&0x2000)>>11) |

((src&0x4000)>>13) |

((src&0x8000)>>15);

}

CS4210 датащи(PDF) 32 Page - National Semiconductor (TI)

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