U.S. semiconductor manufacturers yesterday gave a mixed review to the first year of a landmark semiconductor trade agreement with Japan, saying that "serious violations" by the Japanese have continued despite sanctions imposed by President Reagan in April.

Semiconductor Industry Association President Andrew A. Procassini, in a letter to Reagan reporting on the results of the pact, recommended that Reagan continue the trade sanctions "until consistent and full compliance ... has been achieved."

The industry assessment generally coincides with the opinion of the Reagan administration, which lifted a small portion of the sanctions imposed on $300 million of Japanese imports during June's economic summit but has refused since then to remove the rest of the punitive duties.

The trade agreement was considered vital to U.S. high-technology production. Semiconductors, also known as chips, are key components of high-technology products, such as computers and sophisticated weapons, and are being used increasingly in everyday products, such as home appliances.

Procassini said the Japanese have complied with one part of the agreement to stop dumping memory chips in the United States at below their production cost. Since the penalty duties were applied in April, moreover, the Japanese have "gradually reduced" their dumping of semiconductors in other countries, the SIA head said.

But he said Japan has failed to open its markets to U.S. chips despite a year of increased efforts by American companies to gain sales in what has become the largest semiconductor market in the world.

Procassini said that the U.S. share of Japanese semiconductor purchases -- which has hovered around the 10 percent mark since 1982 compared with its market share of about 50 percent in countries where U.S. suppliers compete head-to-head with Japan -- have actually dropped since the SIA filed an unfair trade complaint in June 1985. That complaint charged Japan with protecting its home markets by refusing to buy American-made products.

At that time, the U.S. share of Japanese semiconductor sales was 9.4 percent. Its share, however, dropped to 9 percent in the second three months of this year.

"If steady progress were being made toward full access to the Japanese semiconductor market," Procassini wrote Reagan, "it is reasonable to expect that U.S. companies would have sold an additional $162.6 million {worth} of semiconductors in Japan over the last year. These additional sales would have meant 1,500 additional jobs in the U.S. semiconductor industry."

Although neither the United States nor the Japanese ever said what the U.S. share of the market should be, it was understood by industry analysts that both sides had expected sales to increase steadily and gradually to about 20 percent of the sales in Japan.

To double American access, U.S. manufacturers called for Japan to "implement a detailed action program" leading to more sales.

In addition, Procassini said the Japanese government, through its guidance to manufacturers, has "disrupted the supply of key semiconductor products" to American users by limiting production and setting floor prices, mechanisms that were specifically rejected by the Reagan administration during the long negotiations leading to the agreement.