CRC校驗原理與程序設計――(RS485總線系統應用之1
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H61, HA1, H63, HA3, HA2, H62, H66, HA6, HA7, H67,_
HA5, H65, H64, HA4, H6C, HAC, HAD, H6D, HAF, H6F,_
H6E, HAE, HAA, H6A, H6B, HAB, H69, HA9, HA8, H68,_
H78, HB8, HB9, H79, HBB, H7B, H7A, HBA, HBE, H7E,_
H7F, HBF, H7D, HBD, HBC, H7C, HB4, H74, H75, HB5,_
H77, HB7, HB6, H76, H72, HB2, HB3, H73, HB1, H71,_
H70, HB0, H50, H90, H91, H51, H93, H53, H52, H92,_
H96, H56, H57, H97, H55, H95, H94, H54, H9C, H5C,_
H5D, H9D, H5F, H9F, H9E, H5E, H5A, H9A, H9B, H5B,_
H99, H59, H58, H98, H88, H48, H49, H89, H4B, H8B,_
H8A, H4A, H4E, H8E, H8F, H4F, H8D, H4D, H4C, H8C,_
H44, H84, H85, H45, H87, H47, H46, H86, H82, H42,_
H43, H83, H41, H81, H80, H40)
End Function
Function GetCRCLo(Ind As Long) As Byte ’CRC低位字節值表
GetCRCLo = Choose(Ind + 1,_
H00, HC1, H81, H40, H01, HC0, H80, H41, H01, HC0,_
H80, H41, H00, HC1, H81, H40, H01, HC0, H80, H41,_
H00, HC1, H81, H40, H00, HC1, H81, H40, H01, HC0,_
H80, H41, H01, HC0, H80, H41, H00, HC1, H81, H40,_
H00, HC1, H81, H40, H01, HC0, H80, H41, H00, HC1,_
H81, H40, H01, HC0, H80, H41, H01, HC0, H80, H41,_
H00, HC1, H81, H40, H01, HC0, H80, H41, H00, HC1,_
H81, H40, H00, HC1, H81, H40, H01, HC0, H80, H41,_
H00, HC1, H81, H40, H01, HC0, H80, H41, H01, HC0,_
H80, H41, H00, HC1, H81, H40, H00, HC1, H81, H40,_
H01, HC0, H80, H41, H01, HC0, H80, H41, H00, HC1,_
H81, H40, H01, HC0, H80, H41, H00, HC1, H81, H40,_
H00, HC1, H81, H40, H01, HC0, H80, H41, H01, HC0,_
H80, H41, H00, HC1, H81, H40, H00, HC1, H81, H40,_
H01, HC0, H80, H41, H00, HC1, H81, H40, H01, HC0,_
H80, H41, H01, HC0, H80, H41, H00, HC1, H81, H40,_
H00, HC1, H81, H40, H01, HC0, H80, H41, H01, HC0,_
H80, H41, H00, HC1, H81, H40, H01, HC0, H80, H41,_
H00, HC1, H81, H40, H00, HC1, H81, H40, H01, HC0,_
H80, H41, H00, HC1, H81, H40, H01, HC0, H80, H41,_
H01, HC0, H80, H41, H00, HC1, H81, H40, H01, HC0,_
H80, H41, H00, HC1, H81, H40, H00, HC1, H81, H40,_
H01, HC0, H80, H41, H01, HC0, H80, H41, H00, HC1,_
H81, H40, H00, HC1, H81, H40, H01, HC0, H80, H41,_
H00, HC1, H81, H40, H01, HC0, H80, H41, H01, HC0,_
H80, H41, H00, HC1, H81, H40)
End Function
3.2 用計算法求CRC函數的程序
計算法的優點是程序編碼量小，雖然比查表法速度偏慢，但當被校驗的數據量不大時并不明顯。
3.2.1 用VC編寫的程序
unsigned short CRC16(unsigned char buf[], int n)
{
unsigned short crc = 0xffff ;
for(i = 0; i n; i++)
{
crc ^ = buf[i] ;
for(b = 0; b 8; b++)
{
bool f = crc 1 ;
crc >> = 1 ;
if(f)
crc ^ = 0xa001 ;
}
}
return(crc) ;
}
3.2.2 用VB編寫的程序
Function CRC16(Data() As Byte, No As Integer, CRC16Lo As Byte, CRC16Hi As Byte) As String
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