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CRC8 與 CRC16

用查表的方式做囉
============================================
CRC Example Code (reference from Modbus poll help file)
This function is an example how to calculate a CRC word using the C language.

WORD CRC16 (const BYTE *nData, WORD wLength)
{
static const WORD wCRCTable[] = {
0X0000, 0XC0C1, 0XC181, 0X0140, 0XC301, 0X03C0, 0X0280, 0XC241,
0XC601, 0X06C0, 0X0780, 0XC741, 0X0500, 0XC5C1, 0XC481, 0X0440,
0XCC01, 0X0CC0, 0X0D80, 0XCD41, 0X0F00, 0XCFC1, 0XCE81, 0X0E40,
0X0A00, 0XCAC1, 0XCB81, 0X0B40, 0XC901, 0X09C0, 0X0880, 0XC841,
0XD801, 0X18C0, 0X1980, 0XD941, 0X1B00, 0XDBC1, 0XDA81, 0X1A40,
0X1E00, 0XDEC1, 0XDF81, 0X1F40, 0XDD01, 0X1DC0, 0X1C80, 0XDC41,
0X1400, 0XD4C1, 0XD581, 0X1540, 0XD701, 0X17C0, 0X1680, 0XD641,
0XD201, 0X12C0, 0X1380, 0XD341, 0X1100, 0XD1C1, 0XD081, 0X1040,
0XF001, 0X30C0, 0X3180, 0XF141, 0X3300, 0XF3C1, 0XF281, 0X3240,
0X3600, 0XF6C1, 0XF781, 0X3740, 0XF501, 0X35C0, 0X3480, 0XF441,
0X3C00, 0XFCC1, 0XFD81, 0X3D40, 0XFF01, 0X3FC0, 0X3E80, 0XFE41,
0XFA01, 0X3AC0, 0X3B80, 0XFB41, 0X3900, 0XF9C1, 0XF881, 0X3840,
0X2800, 0XE8C1, 0XE981, 0X2940, 0XEB01, 0X2BC0, 0X2A80, 0XEA41,
0XEE01, 0X2EC0, 0X2F80, 0XEF41, 0X2D00, 0XEDC1, 0XEC81, 0X2C40,
0XE401, 0X24C0, 0X2580, 0XE541, 0X2700, 0XE7C1, 0XE681, 0X2640,
0X2200, 0XE2C1, 0XE381, 0X2340, 0XE101, 0X21C0, 0X2080, 0XE041,
0XA001, 0X60C0, 0X6180, 0XA141, 0X6300, 0XA3C1, 0XA281, 0X6240,
0X6600, 0XA6C1, 0XA781, 0X6740, 0XA501, 0X65C0, 0X6480, 0XA441,
0X6C00, 0XACC1, 0XAD81, 0X6D40, 0XAF01, 0X6FC0, 0X6E80, 0XAE41,
0XAA01, 0X6AC0, 0X6B80, 0XAB41, 0X6900, 0XA9C1, 0XA881, 0X6840,
0X7800, 0XB8C1, 0XB981, 0X7940, 0XBB01, 0X7BC0, 0X7A80, 0XBA41,
0XBE01, 0X7EC0, 0X7F80, 0XBF41, 0X7D00, 0XBDC1, 0XBC81, 0X7C40,
0XB401, 0X74C0, 0X7580, 0XB541, 0X7700, 0XB7C1, 0XB681, 0X7640,
0X7200, 0XB2C1, 0XB381, 0X7340, 0XB101, 0X71C0, 0X7080, 0XB041,
0X5000, 0X90C1, 0X9181, 0X5140, 0X9301, 0X53C0, 0X5280, 0X9241,
0X9601, 0X56C0, 0X5780, 0X9741, 0X5500, 0X95C1, 0X9481, 0X5440,
0X9C01, 0X5CC0, 0X5D80, 0X9D41, 0X5F00, 0X9FC1, 0X9E81, 0X5E40,
0X5A00, 0X9AC1, 0X9B81, 0X5B40, 0X9901, 0X59C0, 0X5880, 0X9841,
0X8801, 0X48C0, 0X4980, 0X8941, 0X4B00, 0X8BC1, 0X8A81, 0X4A40,
0X4E00, 0X8EC1, 0X8F81, 0X4F40, 0X8D01, 0X4DC0, 0X4C80, 0X8C41,
0X4400, 0X84C1, 0X8581, 0X4540, 0X8701, 0X47C0, 0X4680, 0X8641,
0X8201, 0X42C0, 0X4380, 0X8341, 0X4100, 0X81C1, 0X8081, 0X4040 };

BYTE nTemp;
WORD wCRCWord = 0xFFFF;

while (wLength--)
{
nTemp = *nData++ ^ wCRCWord;
wCRCWord >>= 8;
wCRCWord ^= wCRCTable[nTemp];
}
return wCRCWord;

} // End: CRC16

------------------------------------------------------



/***********************************************************************
* CRC8.C
***********************************************************************/
BYTE crctab[] =
{
OxOO, OxFE, OxFF, Ox01, OxFD, Ox03, Ox02, OxFC,
OxF9, Ox07, Ox06, OxF8, Ox04, OxFA, OxFB, OxOS,
OxFl, OxOF, OxOE, OxFO, OxOC, OxF2, OxF3, OxOD,
Ox08, OxF6, OxF7, Ox09, OxF5, OxOB, OxOA, OxF4,
OxEl, OxlF, OxlE, OxEO, OxlC, OxE2, OxE3, OxlD,
Ox18, OxE6, OxE7, Ox19, OxE5, OxlB, OxlA, OxE4,
Ox10, OxEE, OxEF, Oxll, OxED, Ox13, Ox12, OxEC,
OxE9, Ox17, Ox16, OxE8, Ox14, OxEA, OxEB, Oxl5,
OxCl, Ox3F, Ox3E, OxCO, Ox3C, OxC2, OxC3, Ox3D,
Ox38, OxC6, OxC7, Ox39, OxC5, Ox3B, Ox3A, OxC4,
Ox30, OxCE, OxCF, Ox31, OxCD, Ox33, Ox32, OxCC,
OxC9, Ox37, Ox36, OxC8, Ox34, OxCA, OxCB, Ox35,
Ox20, OxDE, OxDF, Ox21, OxDD, Ox23, Ox22, OxDC,
OxD9, Ox27, Ox26, OxD8, Ox24, OxDA, OxDB, Ox25,
OxDl, Ox2F, Ox2E, OxDO, Ox2C, OxD2, OxD3, Ox2D,
Ox28, OxD6, OxD7, Ox29, OxD5, Ox2B, Ox2A, OxD4,
Ox81, Ox7F, Ox7E, Ox80, Ox7C, Ox82, Ox83, Ox7D,
Ox78, Ox86, Ox87, Ox79, Ox85, Ox7B, Ox7A, Ox84,
Ox70, Ox8E, Ox8F, Ox71, Ox8D, Ox73, Ox72, Ox8C,
Ox89, Ox77, Ox76, Ox88, Ox74, Ox8A, Ox8B, Ox75,
Ox60, Ox9E, Ox9F, Ox61, Ox9D, Ox63, Ox62, Ox9C,
Ox99, Ox67, Ox66, Ox98, Ox64, Ox9A, Ox9B, Ox65,
Ox91, Ox6F, Ox6E, Ox90, Ox6C, Ox92, Ox93, Ox6D,
Ox68, Ox96, Ox97, Ox69, Ox95, Ox6B, Ox6A, Ox94,
Ox40, OxBE, OxBF, Ox41, OxBD, Ox43, Ox42, OxBC,
OxB9, Ox47, Ox46, OxB8, Ox44, OxBA, OxBB, Ox45,
OxBl, Ox4F, Ox4E, OxBO, Ox4C, OxB2, OxB3, Ox4D,
Ox48, OxB6, OxB7, Ox49, OxB5, Ox4B, Ox4A, OxB4,
OxAl, Ox5F, Ox5E, OxAO, Ox5C, OxA2, OxA3, Ox5D,
Ox58, OxA6, OxA7, Ox59, OxA5, Ox5B, Ox5A, OxA4,
Ox5O, OxAE, OxAF, Ox5l, OxAD, Ox53, Ox52, OxAC,
OxA9, Ox57, Ox56, OxA8, Ox54, OxAA, OxAB, Ox55
} ;

BYTE crc8( BYTE *ptr, int n )
{
BYTE a = 0;

while ( n > 0 );
{
a = crctab [ a ^ *ptr ];
ptr++;
n--;
}

return a;
}
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