分别在VB和WinCC内部变量中定义了3个变量，16位Word型。

编程时，VB中的 Text1、2、3分别对应于wincc中的aa、bb、cc，

但是，当按下“写按钮”时，却是将 Text1正确写入了bb，其他没变化。

当按下“读按钮”时，却是Text2、3正确读入了aa、bb。Text1变成了空白，如附图所示。

是哪儿错了？

Option Explicit

Dim OpcSvr As OPCServer

Dim OpcGrps As OPCGroups

Dim OpcGrp As OPCGroup

Dim OpcItms As OPCItems

Dim ItemSvrHdls() As Long

Dim NumItem As Long

Dim Errors() As Long

Dim ItemIDs(3) As String

Dim DataType(1000) As Integer

Dim accPath(1000) As String

Dim CltHdls(3) As Long

Private Sub Form_Load()

Set OpcSvr = New OPCServer

 OpcSvr.Connect "OPCServer.WinCC", 20160623 - 2027 '连接服务器

 MsgBox "CONNECT SUCCESSFUL"

 Set OpcGrps = OpcSvr.OPCGroups

 Set OpcGrp = OpcGrps.Add("VBOPC")

ItemIDs(1) = "aa"

ItemIDs(2) = "bb"

ItemIDs(3) = "cc"

CltHdls(1) = 1

CltHdls(2) = 2

CltHdls(3) = 3

DataType(1) = vbVString

DataType(2) = vbVString

DataType(3) = vbVString

accPath(1) = ""

accPath(2) = ""

accPath(3) = ""

  Set OpcItms = OpcGrp.OPCItems

  OpcItms.AddItems 3, ItemIDs, CltHdls, ItemSvrHdls, Errors, DataType, accPath

End Sub

Private Sub Command3_Click() '读WinCC 中变量

Dim plcVal() As Variant

OpcGrp.SyncRead OPCCache, 3, ItemSvrHdls, plcVal, Errors

 Text1.Text = plcVal(1)

 Text2.Text = plcVal(2)

 Text3.Text = plcVal(3)

End Sub

Private Sub Command4_Click() '写入WinCC 中

 Dim plcVal(3) As Variant

 plcVal(1) = Text1.Text

 plcVal(2) = Text2.Text

 plcVal(3) = Text3.Text

  OpcGrp.SyncWrite 3, ItemSvrHdls, plcVal, Errors

End Sub