DataSource Controls :: Binding Getting Refreshed At Page Half Refresh

yes i know half post ack occurs but it does occur right?so why doesnt the dropdownlist get refreshed when the timer ticks on?. for alternative i tried manually clicking a button to create postback but still no refresh of connection of th list

<asp:ScriptManager ID="ScriptManager1" runat="server">
</asp:ScriptManager>
<br />
<asp:UpdatePanel ID="UpdatePanel2" runat="server">
<ContentTemplate>
<asp:Label ID="Label1" runat="server" Text="Status"></asp:Label>
<asp:Timer ID="Timer1" runat="server" Interval="6000">
</asp:Timer>
<asp:GridView ID="GridView1" runat="server"
AutoGenerateColumns="False" DataKeyNames="Username"
DataSourceID="SqlDataSource1">
<Columns>
<asp:BoundField DataField="Username"
HeaderText="Username" ReadOnly="True" SortExpression="Username" />
<asp:BoundField DataField="Password"
HeaderText="Password" SortExpression="Password" />
<asp:BoundField DataField="Code" HeaderText="Code"
SortExpression="Code" />
<asp:BoundField DataField="Validated"
HeaderText="Validated" SortExpression="Validated" />
<asp:BoundField DataField="Silenced"
HeaderText="Silenced" SortExpression="Silenced" />
<asp:BoundField DataField="Full_Name"
HeaderText="Full_Name" SortExpression="Full_Name" />
<asp:BoundField DataField="Batch" HeaderText="Batch"
SortExpression="Batch" />
<asp:BoundField DataField="Department"
HeaderText="Department" SortExpression="Department" />
<asp:BoundField DataField="abuse" HeaderText="abuse"
SortExpression="abuse" />
<asp:BoundField DataField="Status" HeaderText="Status"
SortExpression="Status" />
<asp:CommandField ShowDeleteButton="True"
ShowEditButton="True" ShowHeader="True" ShowInsertButton="True"
ShowSelectButton="True" />
</Columns>
</asp:GridView>
<br />
<asp:DropDownList ID="DropDownList1" runat="server"
DataSourceID="SqlDataSource2" DataTextField="Username"
DataValueField="Username">
</asp:DropDownList>
<br />
</ContentTemplate>
</asp:UpdatePanel>