<< Click to Display Table of Contents >> Manual > Server Creation Guide > Interface > IPLink-Interface > IPLinkClient Library > IPLinkClient Library Sample Collection > Loading data

overview

This sample is a sample program that reads tag values using the four methods explained in "Client Cache and Server Cache".

 

 

 

Download the sample

The creation examples shown on this page are provided with samples.

 

The sample can be downloaded from below.

 

Samples and detailed explanations will be provided in VB.NET2010.

 

 

Program Highlights

We will explain the main points of the program.

 

▪ValueChanged event
The ValueChanged event occurs when the tag value changes. The return value "Value" contains the value when communication is successful, so it is a reliable value.
 

'------------------------------------------
' Event - ValueChanged
'------------------------------------------
Private Sub AxIPLink1_ValueChanged(sender As Object, e As AxIPLINKLib6._DClientIPLinkEvents_ValueChangedEvent) Handles AxIPLink1.ValueChanged
    Select Case e.tagPath
        Case "U01.F01.T01"
            txtRead1.Text = CStr(e.value)
    End Select
End Sub

 
 

▪ReadVal(DataSource=0)
The value of the client cache is obtained by setting the third argument DataSource of the ReadVal method to 0. This method is the fastest way to obtain data, so use this method when quick response of ReadVal is required.
 

If Not AxIPLink1.ReadVal("U01.F01.T02", a, 0) Then
    txtError.Text = AxIPLink1.ErrMessage
    Exit Sub
End If

 
 

▪ReadVal(DataSource=1)
If you set the third argument DataSource of the ReadVal method to 1, the value in the server cache will be obtained. Since the value obtained is updated on the server side, there is no need for periodic automatic updates between the client and server, which has the effect of reducing the load between them. For this reason, this method is used when the network bandwidth is narrow.
 

If Not AxIPLink1.ReadVal("U01.F01.T03", a, 1) Then
    txtError.Text = AxIPLink1.ErrMessage
    Exit Sub
End If

 
 

▪ReadVal(DataSource=2)
Setting the third argument DataSource of the ReadVal method to 2 will retrieve the device value. This method requires the longest processing time and has the highest load, as it forcibly requests communication with the PLC. However, since the results of actual communication with the PLC are returned each time a request is made, it is possible to retrieve the most recent device value. This method is optimal when synchronization with PLC is required or when low-frequency data retrieval is not required, and processing is performed at regular intervals like batch processing.
 

If Not AxIPLink1.ReadVal("U01.F01.T04", a, 2) Then
    txtError.Text = AxIPLink1.ErrMessage
    Exit Sub
End If

 

 

Operation check

After going online, run the Visual Basic application. Check that the tag lights "T01" to "T03" are red, and "T04" is yellow.

 

Once you have confirmed that the communication connection is correct, click each read button to verify that the tag values are read correctly.