AngularJS, How to call a function in component from Directive? - angularjs

Question

Thanks in advance, Basically in app component a timer which should be start when I call from a directive, Please let me know how I can call? I tried some method but didn't helpful. I'm new in angular js Please guide me.Thanks Here is the Js File code.
var app = angular.module('quizApp', []);
app.directive('quiz', function (quizFactory) {
return {
restrict: 'AE',
scope: {},
templateUrl: '/Home/Dashboard',
link: function (scope, elem, attrs) {
//Calling function cmpTimer(); in Component
};
}
}
});
app.component('cmpTimer', {
bindings: {
cmpFrom: '<',
cmpUnit: '#'
},
template: '<div class="timer">{{$ctrl.timeRemaining}}</div>',
controller: function ($interval) {
var vm = this, ONE_SECOND = 1000, timerInterval;
function startTimer() {
var END_TIME = vm.getEndTime();
function update() {
vm.timeRemaining = moment((moment(END_TIME) - moment())).format("HH:mm:ss");
}
timerInterval = $interval(function () {
if (moment() > moment(END_TIME)) return vm.stopTimer();
update();
}, ONE_SECOND);
update();
}
vm.getEndTime = function () {
return moment().add(vm.cmpFrom, vm.cmpUnit);
}
vm.stopTimer = function () {
alert('Time\'s up!');
vm.$onDestroy();
}
vm.$onDestroy = function () {
$interval.cancel(timerInterval);
}
vm.$onInit = startTimer;
}
});