US STOCKS-Futures rise ahead of Yellen's speech,
May 22, 2015 at 07:30 AM EDT
May 22 (Reuters) - U.S. stock index futures were higher on Friday, a day after the S&P 500 ended at an all-time high and ahead of Federal Reserve Chair Janet Yellen's take on the economy that investors will peruse for clues on the timing of a rate hike.