[Isfet]

например - так

 
var repeat:uint = 1800;
			var t:Timer = new Timer(1000, repeat);
			var min:uint = 30;
			var sec:uint;
			t.addEventListener(TimerEvent.TIMER, f)
			t.start();
			function f(e:TimerEvent) {
 
				minutes.digit.text = String(uint(repeat / 60));
				seconds.digit.text = String(repeat%60);
				trace(uint(repeat / 60),repeat%60 );
				repeat--;
 
			}