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CRC-16-DNP

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CRC-16-DNP is also an error detection scheme (similar to CRC-16-CCITT), which uses the polynomial:

x16 + x13 + x12 + x11 + x10 + x8 + x6 + x5 + x2 + 1


Source code for DNP CRC16 calculation:


static unsigned short dnpdnpCrcTable[256] = {

0x0000, 0x365e, 0x6cbc, 0x5ae2, 0xd978, 0xef26, 0xb5c4, 0x839a,

0xff89, 0xc9d7, 0x9335, 0xa56b, 0x26f1, 0x10af, 0x4a4d, 0x7c13,

0xb26b, 0x8435, 0xded7, 0xe889, 0x6b13, 0x5d4d, 0x07af, 0x31f1,

0x4de2, 0x7bbc, 0x215e, 0x1700, 0x949a, 0xa2c4, 0xf826, 0xce78,

0x29af, 0x1ff1, 0x4513, 0x734d, 0xf0d7, 0xc689, 0x9c6b, 0xaa35,

0xd626, 0xe078, 0xba9a, 0x8cc4, 0x0f5e, 0x3900, 0x63e2, 0x55bc,

0x9bc4, 0xad9a, 0xf778, 0xc126, 0x42bc, 0x74e2, 0x2e00, 0x185e,

0x644d, 0x5213, 0x08f1, 0x3eaf, 0xbd35, 0x8b6b, 0xd189, 0xe7d7,

0x535e, 0x6500, 0x3fe2, 0x09bc, 0x8a26, 0xbc78, 0xe69a, 0xd0c4,

0xacd7, 0x9a89, 0xc06b, 0xf635, 0x75af, 0x43f1, 0x1913, 0x2f4d,

0xe135, 0xd76b, 0x8d89, 0xbbd7, 0x384d, 0x0e13, 0x54f1, 0x62af,

0x1ebc, 0x28e2, 0x7200, 0x445e, 0xc7c4, 0xf19a, 0xab78, 0x9d26,

0x7af1, 0x4caf, 0x164d, 0x2013, 0xa389, 0x95d7, 0xcf35, 0xf96b,

0x8578, 0xb326, 0xe9c4, 0xdf9a, 0x5c00, 0x6a5e, 0x30bc, 0x06e2,

0xc89a, 0xfec4, 0xa426, 0x9278, 0x11e2, 0x27bc, 0x7d5e, 0x4b00,

0x3713, 0x014d, 0x5baf, 0x6df1, 0xee6b, 0xd835, 0x82d7, 0xb489,

0xa6bc, 0x90e2, 0xca00, 0xfc5e, 0x7fc4, 0x499a, 0x1378, 0x2526,

0x5935, 0x6f6b, 0x3589, 0x03d7, 0x804d, 0xb613, 0xecf1, 0xdaaf,

0x14d7, 0x2289, 0x786b, 0x4e35, 0xcdaf, 0xfbf1, 0xa113, 0x974d,

0xeb5e, 0xdd00, 0x87e2, 0xb1bc, 0x3226, 0x0478, 0x5e9a, 0x68c4,

0x8f13, 0xb94d, 0xe3af, 0xd5f1, 0x566b, 0x6035, 0x3ad7, 0x0c89,

0x709a, 0x46c4, 0x1c26, 0x2a78, 0xa9e2, 0x9fbc, 0xc55e, 0xf300,

0x3d78, 0x0b26, 0x51c4, 0x679a, 0xe400, 0xd25e, 0x88bc, 0xbee2,

0xc2f1, 0xf4af, 0xae4d, 0x9813, 0x1b89, 0x2dd7, 0x7735, 0x416b,

0xf5e2, 0xc3bc, 0x995e, 0xaf00, 0x2c9a, 0x1ac4, 0x4026, 0x7678,

0x0a6b, 0x3c35, 0x66d7, 0x5089, 0xd313, 0xe54d, 0xbfaf, 0x89f1,

0x4789, 0x71d7, 0x2b35, 0x1d6b, 0x9ef1, 0xa8af, 0xf24d, 0xc413,

0xb800, 0x8e5e, 0xd4bc, 0xe2e2, 0x6178, 0x5726, 0x0dc4, 0x3b9a,

0xdc4d, 0xea13, 0xb0f1, 0x86af, 0x0535, 0x336b, 0x6989, 0x5fd7,

0x23c4, 0x159a, 0x4f78, 0x7926, 0xfabc, 0xcce2, 0x9600, 0xa05e,

0x6e26, 0x5878, 0x029a, 0x34c4, 0xb75e, 0x8100, 0xdbe2, 0xedbc,

0x91af, 0xa7f1, 0xfd13, 0xcb4d, 0x48d7, 0x7e89, 0x246b, 0x1235

} ;

/*

Function = calcDnpCrc


params: buff - the buffer to be checked.

count - number of bytes in buffer


return: crc as as a 16 bit unsigned number


/


static unsigned short calcDnpCrc(unsigned char *p, UINT count )

{

UINT crc = 0 ;

while ( count-- ) crc = ( crc >> 8 ) ^ dnpCrcTable[( crc ^ *p++) & 0x00ff] ;

return( (unsigned short) ( ~crc ) ) ;

}

/*

Function = checkDnpCrc


params: buff - the buffer to be checked.

count - excludes the crc bytes in the buffer - ie count of all bytes up to but excluding the crc bytes.


return: 1 if crc is good else zero


/

unsigned short checkDnpCrc(unsigned char *buff, unsigned short count )

{

unsigned crc ;

count -= 2 ;

crc = calcDnpCrc( buff, count) ;

buff += count ;

if ( (*buff++ != ( crc & 0xff) ) || (*buff != ( crc >> 8 ) ) )

return( 1 ) ;

else

return( 0 ) ;

}