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:
Apr. 26, 2005
Filed:
May. 22, 2002
Tetsuya Kaneko, Chiba, JP;
Hiroaki Wake, Chiba, JP;
Youichi Endo, Chiba, JP;
Seiko Instruments Inc., Chiba, JP;
Abstract
A semiconductor memory device reliably protects data written once into a non-volatile memory and exhibits high EEPROM data security functionality. The device has a user memory area to which a user can write freely chosen data, and a write-information storage memory area for storing information indicating whether or not data has been written into the user memory area. A control logic circuit analyzes whether to execute a write command from a user and outputs a write-prohibition signal if data is already written into the user memory area. The control logic circuit may include a password authentication circuit for authenticating a user-inputted password by comparing it with a password maintained inside the control logic circuit. The frequency of a changeable clock may be used to perform password authentication.