RT，小弟由于刚接触VB不久，用VB6.0与FX2N通讯，向PLC的D写入值老是不对，不知道是不是格式不对，我是利用MSComm控件通讯的。。。outstring = Chr(&O2) + "1" + CStr(qiuhe) + "02" + CStr(xieru) + Chr(&O3) + hejiaoyan

Private Sub Command1_Click()      '写入D0=0
Dim Address As String
Dim SenData As String

MSComm1.Settings = "9600,E,7,1"              
MSComm1.InputMode = comInputModeText

Address = "1" + "1000" + "02" + "0000" + Chr(3)
SenData = Chr(2) & Address & SumChk(Address)
MSComm1.PortOpen = True
MSComm1.Output = SenData
End Sub

Private Function SumChk(Dats$) As String                  'CheckSum
    Dim i&
    Dim CHK&
    For i = 1 To Len(Dats)
        CHK = CHK + Asc(Mid(Dats, i, 1))
    Next i
    SumChk = Right(Hex$(CHK), 2)
End Function

写入的数据16进制数据, 是先写低字节, .再写高字节.
因此如写"1"进去PLC, 应写成"0100", 写"255"进去PLC, 应写成"FF00"

‘可用数组变量
Dim strText(10) As String

Private Sub Form_Load()
For i = 0 To 10
    strText(i) = Text1.Text & i
    List1.AddItem strText(i)
Next i

End Sub