U.S. stock index futures were flat on Tuesday as investors digested the latest round of corporate profits.

Texas Instruments Inc fell 2.3 percent to $34 in premarket trading after the chip maker warned of slower-than-usual quarterly sales growth. As Texas Instruments scrambles to restart production after Japan's earthquake, the company said it was unclear when the supply of the silicon and wafers it needs will return to normal.

Goldman Sachs is expected to report sharply lower quarterly earnings due to weak trading and a charge for buying back preferred stock from Warren Buffett's Berkshire Hathaway . Analysts surveyed by Thomson Reuters on average expect Goldman to post first-quarter earnings of 82 cents per share, down from $5.59 a year earlier.

Bank of New York Mellon , one of the world's largest custody banks, said first-quarter profit rose 4 percent, helped by an increase in assets under custody and fee revenue.

Companies scheduled to report quarterly results on Tuesday include Intel Corp , International Business Machines Corp , Johnson & Johnson , Yahoo Inc and CSX Corp .

S&P 500 futures added 0.1 point and were slightly above value, a formula that evaluates pricing by taking into account interest rates, dividends and time to expiration on the contract. Dow Jones industrial average futures gained 8 points and Nasdaq 100 futures fell 2 points.

Economic indicators on tap include March housing starts at 8:30 a.m..

Seagate Technology Plc posted a third-quarter profit below market expectations on lower hard-drive shipments and also announced a deal to buy Samsung Electronics Co's <005930.KS> hard disk business for $1.4 billion in cash and stock.

Citigroup Inc said it has been selling a $12.7 billion portfolio of toxic assets that led to some of its losses during the financial crisis, in a bid to mitigate the impact of new global capital rules for banks.

Research In Motion's PlayBook, the long-awaited response to Apple's iPad, goes on sale in the United States and Canada on Tuesday. RIM hopes the product will win over consumers.

European shares rallied as fund managers said strong earnings would support markets in the short term, overshadowing economic risks, with LVMH and Burberry results' beating forecasts. <.EU>

Asian stocks slid, falling further from a three-year high hit last week as investors took profits on risks of a Greek debt restructuring in Europe and the long-term threat of a U.S. government debt downgrade.

Wall Street fell more than 1 percent on Monday as sovereign debt fears on both sides of the Atlantic and China's monetary tightening hurt the outlook for global economic growth.

(Reporting by Chuck Mikolajczak; Editing by Kenneth Barry)