why Timer always reload updatepanel, is it right?

I tried to use timer to reload updatepanel, code like this

<atlas:TimerControl runat="server" ID="timer" Interval="5000"/>

<atlas:UpdatePanel ID="UpdatePanel1" runat="server">
<ContentTemplate>
my controls...

</ContentTemplate>
</atlas:UpdatePanel>

right, I don't define trigger there. But even with code like that, the updatepanel still reload every 5 seconds, why it works this way?

thanks

I think I have found answer.

hello.

well, as you might have guesses by know, you have to set the mode property of the panel to conditional.