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:
Nov. 23, 1993
Filed:
Aug. 29, 1990
Kevin S Saldanha, Ft. Collins, CO (US);
Allen J Piepho, Ft. Collins, CO (US);
Hewlett-Packard Company, Palo Alto, CA (US);
Abstract
An apparatus and method for allowing writable, magneto-optic (MO) data storage media to be defined as read-only. Because the MO media specification is compatible with WORM media, each sector of the media contains an error recovery section, called the defect management pointer (DMP). In MO media, error recovery information is stored at a common location, so the DMP of each sector is used to indicate the state of the sector--writable or read-only. A special data pattern is used to indicate whether the sector is blank or contains user data. With the DMP information set in the writable state, the sector can be written, however, the process of writing the sector also sets the DMP information to the data pattern that indicates that the sector is now in a read-only state. Once the storage state has been changed to the read-only state, the drive will no longer write data into this sector. The drive will also not allow the state to be changed from the read-only state back to the writable state. For data security purposes, data on media must sometimes be written over, or obliterated. After this process, the invention places a special pattern in the DMP, and thereafter, the drive can detect whether a sector contains user data, is blank, or has been obliterated.