CRC校验的实施

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//CRC初始值

#define        BOOT_CRC_DATA_INIT            0xFFFF


/* CRC16 余式表 */
u16 g_au16CRC16Table[256]={
    0x0000, 0x1021, 0x2042, 0x3063, 0x4084, 0x50a5, 0x60c6, 0x70e7,
    0x8108, 0x9129, 0xa14a, 0xb16b, 0xc18c, 0xd1ad, 0xe1ce, 0xf1ef,
    0x1231, 0x0210, 0x3273, 0x2252, 0x52b5, 0x4294, 0x72f7, 0x62d6,
    0x9339, 0x8318, 0xb37b, 0xa35a, 0xd3bd, 0xc39c, 0xf3ff, 0xe3de,
    0x2462, 0x3443, 0x0420, 0x1401, 0x64e6, 0x74c7, 0x44a4, 0x5485,
    0xa56a, 0xb54b, 0x8528, 0x9509, 0xe5ee, 0xf5cf, 0xc5ac, 0xd58d,
    0x3653, 0x2672, 0x1611, 0x0630, 0x76d7, 0x66f6, 0x5695, 0x46b4,
    0xb75b, 0xa77a, 0x9719, 0x8738, 0xf7df, 0xe7fe, 0xd79d, 0xc7bc,
    0x48c4, 0x58e5, 0x6886, 0x78a7, 0x0840, 0x1861, 0x2802, 0x3823,
    0xc9cc, 0xd9ed, 0xe98e, 0xf9af, 0x8948, 0x9969, 0xa90a, 0xb92b,
    0x5af5, 0x4ad4, 0x7ab7, 0x6a96, 0x1a71, 0x0a50, 0x3a33, 0x2a12,
    0xdbfd, 0xcbdc, 0xfbbf, 0xeb9e, 0x9b79, 0x8b58, 0xbb3b, 0xab1a,
    0x6ca6, 0x7c87, 0x4ce4, 0x5cc5, 0x2c22, 0x3c03, 0x0c60, 0x1c41,
    0xedae, 0xfd8f, 0xcdec, 0xddcd, 0xad2a, 0xbd0b, 0x8d68, 0x9d49,
    0x7e97, 0x6eb6, 0x5ed5, 0x4ef4, 0x3e13, 0x2e32, 0x1e51, 0x0e70,
    0xff9f, 0xefbe, 0xdfdd, 0xcffc, 0xbf1b, 0xaf3a, 0x9f59, 0x8f78,

    0x9188, 0x81a9, 0xb1ca, 0xa1eb, 0xd10c, 0xc12d, 0xf14e, 0xe16f,
    0x1080, 0x00a1, 0x30c2, 0x20e3, 0x5004, 0x4025, 0x7046, 0x6067,
    0x83b9, 0x9398, 0xa3fb, 0xb3da, 0xc33d, 0xd31c, 0xe37f, 0xf35e,
    0x02b1, 0x1290, 0x22f3, 0x32d2, 0x4235, 0x5214, 0x6277, 0x7256,
    0xb5ea, 0xa5cb, 0x95a8, 0x8589, 0xf56e, 0xe54f, 0xd52c, 0xc50d,
    0x34e2, 0x24c3, 0x14a0, 0x0481, 0x7466, 0x6447, 0x5424, 0x4405,
    0xa7db, 0xb7fa, 0x8799, 0x97b8, 0xe75f, 0xf77e, 0xc71d, 0xd73c,
    0x26d3, 0x36f2, 0x0691, 0x16b0, 0x6657, 0x7676, 0x4615, 0x5634,
    0xd94c, 0xc96d, 0xf90e, 0xe92f, 0x99c8, 0x89e9, 0xb98a, 0xa9ab,
    0x5844, 0x4865, 0x7806, 0x6827, 0x18c0, 0x08e1, 0x3882, 0x28a3,
    0xcb7d, 0xdb5c, 0xeb3f, 0xfb1e, 0x8bf9, 0x9bd8, 0xabbb, 0xbb9a,
    0x4a75, 0x5a54, 0x6a37, 0x7a16, 0x0af1, 0x1ad0, 0x2ab3, 0x3a92,
    0xfd2e, 0xed0f, 0xdd6c, 0xcd4d, 0xbdaa, 0xad8b, 0x9de8, 0x8dc9,
    0x7c26, 0x6c07, 0x5c64, 0x4c45, 0x3ca2, 0x2c83, 0x1ce0, 0x0cc1,
    0xef1f, 0xff3e, 0xcf5d, 0xdf7c, 0xaf9b, 0xbfba, 0x8fd9, 0x9ff8,
    0x6e17, 0x7e36, 0x4e55, 0x5e74, 0x2e93, 0x3eb2, 0x0ed1, 0x1ef0,
};



/************************************************************************
函 数 名:servCRC16Table
描    述:CRC校验函数1
输入参数:
          参数名称            参数类型             参数说明
          u16CrcInit          u16                  CRC初始值
          pu8Buf              u8*                  要进行CRC校验的数据
          u32Len              u32                  要进行CRC校验的数据长度
输出参数:无
返 回 值:无
说    明:内部函数
************************************************************************/
u16 servCRC16Table(u16 u16CrcInit, u8 *pu8Buf, u32 u32Len)
{


    u8   u8CrcReg;
    u16  u16CRC = u16CrcInit;


    while(u32Len--)
    {
        u8CrcReg = u16CRC >> 8;
        u16CRC <<= 8;
        u16CRC ^= g_au16CRC16Table[u8CrcReg ^ *pu8Buf++];
    }
    return(u16CRC);
}


        /************************************************************************
        函 数 名:updateCrcGenerate
        描    述:CRC校验函数2
        输入参数:
                  参数名称            参数类型             参数说明
                  au8DataBuf           u8[]                要校验的数据缓冲区
                  u32Cnt               u32                 数据字节数
                  u16CrcInit           u16                 CRC校验初始值,默认为0xFFFF
        输出参数:无
        返 回 值:CRC校验码
        说    明:内部函数
        ************************************************************************/
        public u16  updateCrcGenerate(u8[]  au8DataBuf, u32  u32Cnt, u16 u16CrcInit)
        {
            u8 u8CrcReg;
            u16 u16CRC = u16CrcInit;
            u32 u32i;


            for (u32i = 0; u32i < u32Cnt; u32i++)
            {
                u8CrcReg = (u8)(u16CRC >> 8);
                u16CRC <<= 8;
                u16CRC ^= g_au16CRC16Table[u8CrcReg ^ au8DataBuf[u32i]];
            }
            return (u16CRC);
        }

//比较前后的crc值

if (u16CrcOld != u16CrcNew)

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

        //CRC 计算
        public void GetCRC(byte[] message, ref byte[] CRC)
        {
            //Function expects a modbus message of any length as well as a 2 byte CRC array in which to 
            //return the CRC values:
            ushort CRCFull = 0xFFFF;
            byte CRCHigh = 0xFF, CRCLow = 0xFF;
            char CRCLSB;


            for (int i = 0; i < (message.Length) - 2; i++)
            {
                CRCFull = (ushort)(CRCFull ^ message[i]);


                for (int j = 0; j < 8; j++)
                {
                    CRCLSB = (char)(CRCFull & 0x0001);
                    CRCFull = (ushort)((CRCFull >> 1) & 0x7FFF);


                    if (CRCLSB == 1)
                        CRCFull = (ushort)(CRCFull ^ 0xA001);
                }
            }
            CRC[1] = CRCHigh = (byte)((CRCFull >> 8) & 0xFF);
            CRC[0] = CRCLow = (byte)(CRCFull & 0xFF);
        }


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