U.S. makers of computer chips ended the year with their first increase in market share in more than a decade, halting at least temporarily a trend that has pushed most of the business into the hands of Japanese competitors.

Japanese producers lost ground in 1990 for the first time since 1982, according to a report to be released today by Dataquest Inc., a San Jose market research firm. But the report shows that the Japanese still remain the leading producers of semiconductor chips, the circuits whose widespread use in electronic products make their sales an important indicator of economic health.

Japanese firms' slip last year can be attributed to the same factor that caused their surge in the mid-1980s -- their heavy dependence on the manufacture of dynamic random access memory chips, or DRAMs, which store data inside computers and other electronic gear. As the market became glutted, memory-chip prices plummeted in 1990.

U.S. manufacturers excel at making the complex circuitry that handles calculations -- microprocessors and other so-called logic chips. Those markets remained strong last year, helping to fill the coffers of Motorola Inc. and of Intel Corp., which jumped from eighth to fifth place in the worldwide ranking of chipmakers.

Japanese firms still retained six of the Top 10 slots, with NEC Corp., Toshiba Corp. and Hitachi Ltd. in the top three positions, Dataquest said.

Overall, U.S. firms eked out a gain of 1.6 percentage points last year, the first yearly increase since 1979. That brought their share to 36.5 percent of the $58.4 billion worldwide semiconductor market. European firms gained 1 percentage point, while the share held by Japanese producers fell 2.6 percentage points to 49.5 percent, in what was mostly a flat global market.

The U.S. market share gain is just one piece of a somewhat brighter competitive picture for the U.S. high-technology industry. Exports of virtually all types of electronic goods, from computers to medical equipment, have been growing steadily, prompting the American Electronics Association to project recently that the nation's 1990 electronics trade deficit will have narrowed by 80 percent from 1989. Trade in semiconductors is expected to reverse from a deficit to a surplus.

U.S. semiconductor firms continued to gain ground in Japan, thanks in part to a 1986 trade pact and Japanese government pressure on its own manufacturers to buy U.S.-made chips. U.S. makers now claim 12 percent of Japan's market, up from 10.2 percent in 1988, according to the Semiconductor Industry Association, a trade group.

Industry observers caution against celebration, however. In the U.S. chip industry, "things are beginning to look a little better, but don't get carried away," said John M. Geraghty, an analyst with First Boston Corp.

Orders from U.S. buyers slipped markedly in November, the latest month for which figures are available, and analysts say the outlook for the worldwide chip industry remains uncertain. Estimates for 1991 range from a 2 percent drop in industry size to a 12 percent gain. In 1990, the industry grew only 2 percent worldwide, the lowest rate since 1985, Dataquest said.

Meanwhile, although Japanese producers may suffer for a year or two because of their dependence on DRAMs, they are likely to profit again when the highly cyclical memory market turns around, analysts say. "The one given is that it is going to swing back," said Jerry Banks, a Dataquest analyst.