VB与AB的PLC之间通讯.doc

VB与AB的PLC之间通讯VB与ABPLC之间通讯 AB系列PLC一般都有专用驱动程序用于实现PLC和计算机之间通讯，如RSLINX就是专门用于做这项工作，但使用RSLINX也具有一定局限性，这里提供一个使用VB编程实现PLC和计算机之间通讯程序，使用协议是DF1，可以支持Micrologix、SLC500等系列PLC。使用代码如下： Option Explicit Dim tns%, comunicating Private Sub Command1_Click() ReDim tb%(10) Dim st If ReadTable(0, tb%() Then For st = 0 To 9 显示结果 Text1.SelText = Str(tb%(st) + Chr(32) Next st Text1.SelText = Chr(13) + Chr(10) End If End Sub Private Sub Command2_Click() ReDim tm%(5) tm%(0) = Rnd * 32768 tm%(1) = Rnd * 32768 tm%(2) = Rnd * 32768 tm%(3) = Rnd * 32768 tm%(4) = Rnd * 32768 If Not WriteTable(4, tm%() Then Text1.SelText = 写入错误！ End Sub Private Sub Exit_Click() Unload Me End End Sub Private Sub Form_Load() Comm1.PortOpen = True End Sub Private Sub Form_Unload(Cancel As Integer) Comm1.PortOpen = False End Sub Private Sub CalcCRC(mes$) Dim byt%, res& 对消息进行crc校验，然后将结果添加到消息结尾。 byt% = 3 Do res& = res& Xor Asc(Mid(mes$, byt%, 1) rotate res& If Asc(Mid(mes$, byt%, 1) = 16 Then mes$ = Left$(mes$, byt%) + Chr(16) + Right$(mes$, Len(mes$) - byt%) byt% = byt% + 1 End If byt% = byt% + 1 Loop While (byt% Timer And Form1.Comm1.InBufferCount 2 从缓冲中移除确认 Form1.Comm1.InputLen = 2 com$ = Form1.Comm1.Input If com$ Chr(16) + Chr(6) Then comunicating = False Exit Function End If st = Timer 等待应答 Do DoEvents Loop While st + 3 Timer And Form1.Comm1.InBufferCount 12 + (UBound(n%) * 2) 超时则退出 If Form1.Comm1.InBufferCount 12 + (UBound(n%) * 2) Then comunicating = False Exit Function End If 发送确认 Form1.Comm1.Output = Chr(16) + Chr(6) 到应答 Form1.Comm1.InputLen = 0 com$ = Form1.Comm1.Input st = 3 Do If Mid(com$, st, 1) = Chr(16) Then com$ = Left(com$, st) + Right(com$, Len(com$) - 1 - st) End If st = st + 1 Loop While st Timer And Form1.Comm1.InBufferCount 2 Form1.Comm1.InputLen = 2 com$ = Form1.Comm1.Input If com$ Chr(16) + Chr(6) Then comunicating = False Exit Function End If st = Timer Do DoEvents Loop While st + 3 Timer And Form1.Comm1.InBufferCount 12 Form1.Comm1.Output = Chr(16) + Chr(6) If Form1.Comm1.InBufferCount 12 Then comunicating = False Exit