以前的ajax调用不会中止数据表

Question

     var oTable;            
      $(document).ready(function() {
            oTable = $('#example').dataTable( {
                "bProcessing": true,
                "bServerSide": true,
                "sAjaxSource": "module/parents/calendar/file_proc.php",
                "fnServerData": function ( sSource, aoData, fnCallback, oSettings ) {

                                  oSettings.jqXHR = $.ajax( {
                                    "dataType": 'json',
                                    "type": "GET",
                                    "url": sSource,
                                    "data": aoData,
                                    "success": fnCallback
                                  } );
                                   if (typeof $ !== "undefined" && $.fn.dataTable) {
            var all_settings = $($.fn.dataTable.tables()).DataTable().settings();
            for (var i = 0, settings; (settings = all_settings[i]); ++i) {
                //alert(676);
                if (settings.jqXHR)
                    settings.jqXHR.abort();
            }
        }
                },
                "aoColumns": [
                   { "sWidth": "320px"},
                   { "sWidth": "70px"},
                   { "sWidth": "100px"},
                   { "sWidth": "180px"},                      
                    { "bVisible":    false },                            
                ],                                                          
                "aaSorting": [[2, 'desc']]
            });

        });
    </script>

我在旧网站上使用jquery dataTable 1.6.2。当用户在datatables插件中搜索搜索框中的内容时，它会在每次按键后加载ajax请求。我搜索了谷歌并实施了代码，用于中止以前的ajax请求，但它无效。

搜索字段ID html标记为

<input id="tt" type="text">