The inexorable march of Japan Inc into the heartlands of US high tech industry took another big step forward yesterday as National Semiconductor Corp announced that it had now got to the letter of intent stage with Matsushita Electronics Corp for sale of its chip plant in Puyallup, up in Washington state. Matsushita agreed to pay $86m in cash for the facility and will assume some financial liabilities associated with the plant. The transaction is expected to close in the first quarter of 1991. Matsushita gets the two buildings, 92 acres of land, and some manufacturing equipment, but there will be no transfer of technologies, products or processes: Matsushita intends to make dynamic RAMs and MOS logic at the plant. The sale enables National to reduce its excess capacity that resulted from its decision to withdraw from statics.