Read method
Description | This function makes a blocking call to the server to read the item. Read can be called with only a source (either OPC_DS_CACHE or OPC_DS_DEVICE) to refresh the item's value, quality, and timestamp properties. |
Syntax | Read (Source As Integer, Optional ByRef Value As Variant, Optional ByRef Quality As Variant, Optional ByRef TimeStamp As Variant)Source — Specifies readinf from cache (OPC_DS_CACHE) or from device (OPC_DS_DEVICE).Value (optional) — Returns the latest value read either from cache if OPC_DS_DEVICE is specified or from the server if OPC_DS_DEVICE is specified.Quality (optional) — Returns the latest quality read from the server.TimeStamp (optional) — Returns the latest timestamp read from the server. |
Example | Private Sub ReadButton_Click() Dim MyOPCItem as OPCItem Dim vValue As Variant Dim vQuality As Variant Dim vTimeStamp As Variant Set MyOPCItem = MyOPCGroup.OPCItems(txtValue(i)) '/* Read selected items value and quality MyOPCItem.Read OPC_DS_CACHE, vValue, vQuality, vTimeStamp '/* Display information txtValue = vValue txtQuality = vQuality txtTimeStamp = vTimeStamp End Sub |
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