Its shares slumped 2.2 percent to 254 yen, even as the Nikkei stock index <.N225> rose 1.7 percent.

Toshiba's board will meet on Friday to approve plans to make its chip business a separate company and hopes to raise more than 200 billion yen ($1.76 billion) by selling a 20 percent stake in it, a person with direct knowledge of the matter said.

The sale is part of its efforts to brace itself for an upcoming multi-billion dollar writedown on its U.S. nuclear business, a charge that other sources have said may exceed $4.4 billion.

(Reporting by Tokyo markets team; Editing by Stephen Coates)

Stocks treated in this article : Nikkei 225, Toshiba Corp