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:
May. 13, 1997
Filed:
Feb. 29, 1996
Youji Idei, Asaka, JP;
Katsuhiro Shimohigashi, Musashimurayama, JP;
Masakazu Aoki, Tokorozawa, JP;
Hiromasa Noda, Tokyo, JP;
Katsuyuki Sato, Akishima, JP;
Hidetoshi Iwai, Ome, JP;
Makoto Saeki, Ome, JP;
Jun Murata, Kunitachi, JP;
Yoshitaka Tadaki, Hannou, JP;
Toshihiro Sekiguchi, Hidaka, JP;
Osamu Tsuchiya, Hamura, JP;
Hitachi, Ltd., Tokyo, JP;
Abstract
A period pulse corresponding to the shortest information retention time of those of dynamic memory cells is counted to form a refresh address to be assigned to a plurality of word lines. A carry signal outputted from the refresh address counter is divided by a divider. For each of said plurality of word lines assigned with the refresh address, one of a short period corresponding to an output pulse of a timer or a long period corresponding to the divided pulse from the divider is stored in a storage circuit as refresh time setting information. A memory cell refresh operation to be performed by the refresh address is made valid or invalid for each word line according to the refresh time setting information stored in the storage circuit and the refresh time setting information itself is made invalid by the output pulse of the divider.