modbus.bas

这是modbus的应用。觉得这讲的很清楚

Attribute VB_Name = "Module1"
Function CRC16(Data() As Byte, no As Integer, CRC16Lo As Byte, CRC16Hi As Byte) As String
    
      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 no - 1

        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

          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

          End If

        Next Flag

      Next i

      Dim ReturnData(1) As Byte

      ReturnData(0) = CRC16Hi              'CRC高位

      ReturnData(1) = CRC16Lo              'CRC低位

      CRC16 = ReturnData

    End Function

'CRC低位字节值表
Function GetCRCLo(ind As Long) As Byte
 
 GetCRCLo = Choose(ind + 1, &H0, &HC1, &H81, &H40, &H1, &HC0, &H80, &H41, &H1, &HC0, _
                            &H0, &HC1, &H81, &H40, &H0, &HC1, &H81, &H40, &H1, &HC0, _
                           &H80, &H41, &H1, &HC0, &H80, &H41, &H0, &HC1, &H81, &H40, _
                           &H0, &HC1, &H81, &H40, &H1, &HC1, &H80, &H41, &H0, &HC1, _
                           &H81, &H40, &H1, &HC0, &H80, &H41, &H1, &HC0, &H80, &H41, _
                           &H0, &HC1, &H81, &H40, &H1, &HC0, &H80, &H41, &H0, &HC1, _
                           &H81, &H40, &H0, &HC1, &H81, &H40, &H1, &HC0, &H81, &H41, _
                           &H0, &HC1, &H81, &H40, &H1, &HC0, &H80, &H41, &H1, &HC0, _
                           &H80, &H41, &H0, &HC1, &H81, &H40, &H0, &HC1, &H81, &H40, _
                           &H1, &HC0, &H80, &H41, &H1, &HC0, &H80, &H41, &H0, &HC1, _
                           &H81, &H40, &H1, &HC0, &H80, &H41, &H0, &HC1, &H81, &H40, _
                           &H0, &HC1, &H81, &H40, &H1, &HC0, &H80, &H41, &H1, &HC0, _
                           &H80, &H41, &H0, &HC1, &H81, &H40, &H0, &HC1, &H81, &H40, _
                           &H1, &HC0, &H80, &H41, &H0, &HC1, &H81, &H40, &H1, &HC0, _
                           &H80, &H41, &H1, &HC0, &H80, &H41, &H0, &HC1, &H81, &H40, _
                           &H0, &HC1, &H81, &H40, &H1, &HC0, &H80, &H41, &H1, &HC0, _
                           &H80, &H41, &H0, &HC1, &H81, &H40, &H1, &HC0, &H80, &H41, _
                           &H0, &HC1, &H81, &H40, &H0, &HC1, &H81, &H40, &H1, &HC0, _
                           &H80, &H41, &H0, &HC1, &H81, &H40, &H1, &HC0, &H80, &H41, _
                           &H1, &HC0, &H80, &H41, &H0, &HC1, &H81, &H40, &H1, &HC0, _
                           &H80, &H41, &H0, &HC1, &H81, &H40, &H0, &HC1, &H81, &H40, _
                           &H1, &HC0, &H80, &H41, &H1, &HC0, &H80, &H41, &H0, &HC1, _
                           &H81, &H40, &H0, &HC1, &H81, &H40, &H1, &HC0, &H80, &H41, _
                           &H0, &HC1, &H81, &H40, &H1, &HC0, &H80, &H41, &H1, &HC0, _
                           &H80, &H41, &H0, &HC1, &H81, &H40)

End Function

'CRC高位字节值表
Function GetCRCHi(ind As Long) As Byte
 GetCRCHi = Choose(ind + 1, &H0, &HC0, &HC1, &H1, &HC3, &H3, &H2, &HC2, &HC6, &H6, &H7, &HC7, &H5, &HC5, &HC4, &H4, &HCC, &HC, &HD, &HCD, _
                           &HF, &HCF, &HCE, &HE, &HA, &HCA, &HCB, &HB, &HC9, &H9, _
                           &H8, &HC8, &HD8, &H18, &H19, &HD9, &H1B, &HDB, &HDA, &H1A, _
                           &H1E, &HDE, &HDF, &H1F, &HDD, &H1D, &H1C, &HDC, &H14, &HD4, _
                           &HD5, &H15, &HD7, &H17, &H16, &HD6, &HD2, &H12, &H13, &HD3, _
                           &H11, &HD1, &HD0, &H10, &HF0, &H30, &H31, &HF1, &O33, &HF3, _
                           &HF2, &H32, &H36, &HF6, &HF7, &H37, &HF5, &H35, &H34, &HF4, _
                           &H3C, &HFC, &HFD, &H3D, &HFF, &H3F, &H3E, &HFE, &HFA, &H3A, _
                           &H3B, &HFB, &H39, &HF9, &HF8, &H38, &H28, &HE8, &HE9, &H29, _
                           &HEB, &H2B, &H2A, &HEA, &HEE, &H2E, &H2F, &HEF, &H2D, &HED, _
                           &HEC, &H2C, &HE4, &H24, &H25, &HE5, &H27, &HE7, &HE6, &H26, _
                           &H22, &HE2, &HE3, &H23, &HE1, &H21, &H20, &HE0, &HA0, &H60, _
                           &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