1、加入CRC校验的发送帧

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Private Sub Timer1_Timer()                                 '发送数据

Dim longCRC As Long                                     '定义校验变量

Dim aa(7) As Byte                                         '定义动态数组

      aa(0) = &H1                                        '地址

      aa(1) = &H3                                        '功能码 读

      aa(2) = &H0                                        '起始地址

      aa(3) = &HA

      aa(4) = &H0                                        '数据点数

      aa(5) = &H8

 longCRC = CRC16(aa)                                    'CRC校验

 aa(UBound(aa) - 1) = longCRC Mod 256

 aa(UBound(aa)) = longCRC \ 256

 MSComm1.OutBufferCount = 0                             '清空输出寄存器

 MSComm1.Output = aa                                    '发送

End Sub

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2，CRC校验程序

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Function CRC16(Coun() As Byte) As Long

Dim intBit, intTemp As Integer

Dim lonCRC As Long

lonCRC = &HFFFF&