var stopscroll = false;
var scrollElem = document.getElementById("roll");
var marqueesHeight = scrollElem.style.height;
scrollElem.onmouseover = new Function('stopscroll = true');
scrollElem.onmouseout  = new Function('stopscroll = false');
var preTop = 0;
var currentTop = 0;
var stoptime = 0;
var leftElem = document.getElementById("roll_con");
scrollElem.appendChild(leftElem.cloneNode(true));
init_srolltext();
function init_srolltext(){
 scrollElem.scrollTop = 0;
 setInterval('scrollUp()',30);//数值越小,速度越快
}
function scrollUp(){
 if(stopscroll) return;
 currentTop += 2; //设为1,间歇式的滚动;设2,连续滚动
 if(currentTop == 19) {
  stoptime += 1;
  currentTop -= 1;
  if(stoptime == 180) {
   currentTop = 0;
   stoptime = 0;
  }
 }else{
  preTop = scrollElem.scrollTop;
  scrollElem.scrollTop += 1;
  if(preTop == scrollElem.scrollTop){
   scrollElem.scrollTop = 0;
   scrollElem.scrollTop += 1;
  }
 }
}