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循环冗余码校验原理分析..

循环冗余码校验原理分析..

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   Dim CRC16Lo As Byte, CRC16Hi As Byte   'CRC寄存器
   Dim CL As Byte, CH As Byte        '多项式码&HA001
   Dim SaveHi As Byte, SaveLo As Byte
   Dim i As Integer
   Dim Flag As Integer
   CRC16Lo = &HFF
   CRC16Hi = &HFF
   CL = &H1
   CH = &HA0
   For i = 0 To UBound(data)
    CRC16Lo = CRC16Lo Xor data(i) '每一个数据与CRC寄存器进行异或
    For Flag = 0 To 7
     SaveHi = CRC16Hi
     SaveLo = CRC16Lo PLC
     CRC16Hi = CRC16Hi \ 2      '高位右移一位
     CRC16Lo = CRC16Lo \ 2      '低位右移一位
     If ((SaveHi And &H1) = &H1) Then '如果高位字节最后一位为1
      CRC16Lo = CRC16Lo Or &H80   '则低位字节右移后前面补1
     End If              '否则自动补0
     If ((SaveLo And &H1) = &H1) Then '如果LSB为1,则与多项式码进行异或
      CRC16Hi = CRC16Hi Xor CH
      CRC16Lo = CRC16Lo Xor CL

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