VB FX1N通讯数据丢失[求助]

我的程序代码如下，显示时有时数据为空。
Private Sub Timer1_Timer()
 Label1.Caption = Word_Read(MSComm1, FindAddrWord("D130"))
 Label2.Caption = Word_Read(MSComm1, FindAddrWord("D131"))
 Label3.Caption= Word_Read(MSComm1, FindAddrWord("D132"))
 Label4.Caption = Word_Read(MSComm1, FindAddrWord("D133"))
 Label5.Caption = Word_Read(MSComm1, FindAddrWord("D134"))
End Sub

Public Function FindAddrWord(sName As String) As String
 Dim strTagType As String
 Dim strTmp As String

 strTagType = Left$(sName, 1)
 strTmp = Right$(sName, Len(sName) - 1)
 Select Case UCase(strTagType)
   Case "C"
     FindAddrWord = "0" + Hex(Val(strTmp) * 2 + 2560)
   Case "T"
     FindAddrWord = "0" + Hex(Val(strTmp) * 2 + 2048)
   Case "D"
     FindAddrWord = Hex(Val(strTmp) * 2 + 4096)
 End Select
 Exit Function
End Function