The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Jul. 17, 1990
Filed:
Jul. 10, 1989
Toshio Sasaki, Tokyo, JP;
Masakazu Aoki, Tokorozawa, JP;
Masashi Horiguchi, Kokubunji, JP;
Yoshinobu Nakagome, Hachioji, JP;
Shinichi Ikenaga, Kokubunji, JP;
Toshiaki Masuhara, Tokyo, JP;
Hitachi, Ltd., Tokyo, JP;
Abstract
In a defect relieving technology which replaces defective memory cells of a semiconductor memory device by spare memory cells, use is made of an associative memory. Address information of a defective memory cell is stored as a reference data of the associative memory, and new address information of a spare memory cell is written down as output data of the associative memory. A variety of improvements are made to the associative memory. For instance, a plurality of coincidence detection signal lines of the associative memory are divided into at least two groups, and one group among them is selected by switching means. Reference data of the associative memory comprises three values consisting of binary information of '0' and '1', and don't care value 'X'. The associative memory further includes a plurality of electrically programable non-volatile semiconductor memory elements.