PLC与PC机通讯的VB源程序大体如下：我采用的是FX232BD通讯模块，协议就是FX通讯协议。
强制PLC为RUN
Private Sub command1_Click()
Dim dat As String
commli.OutBufferCount = 0
commli.InBufferCount = 0
dat = "01FFRR0"
commli.Output = Chr$(5) + dat + SumChk(dat)
End Sub
强制PLC为STOP
Private Sub command2_Click()
Dim dat As String
commli.OutBufferCount = 0
commli.InBufferCount = 0
dat = "01FFRS0"
commli.Output = Chr$(5) + dat + SumChk(dat)
End Sub
强制Y0为1
Private Sub command3_Click()
Dim dat As String
commli.OutBufferCount = 0
commli.InBufferCount = 0
commli.Output = “01FFBW0Y001011”
End Sub
强制Y0为0
Private Sub command3_Click()
Dim dat As String
commli.OutBufferCount = 0
commli.InBufferCount = 0
commli.Output = “01FFBW0Y001010”
End Sub
设置电脑通信参数
Private Sub Commlis()
If commli.PortOpen = True Then
commli.PortOpen = False
End If
If Not commli.PortOpen Then
commli.CommPort = 1 ''通信口
commli.Settings = "9600,N,8,1"
commli.Handshaking = 0
commli.InputLen = 0
commli.OutBufferCount = 0
commli.InBufferCount = 0
commli.PortOpen = True
End If
Exit Sub
End Sub
Private Function SumChk(Dats$) As String
Dim i&
Dim CHK&
For i = 1 To Len(Dats)
CHK = CHK + Asc(Mid(Dats, i, 1))
Next i
SumChk = Right(Hex$(CHK), 2)
End Function