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. 30, 1985
Filed:
Sep. 20, 1982
Terutaka Tateishi, Kawasaki, JP;
Kazuyuki Shimizu, Machida, JP;
Fujitsu Limited, Kawasaki, JP;
Abstract
In a system which is provided with a key storage having stored therein main storage keys respectively corresponding to pages into which a main storage is split, each main storage key having at least a reference bit indicating whether the corresponding page is being accessed and a change bit indicating whether information has been written in the page, and in which a parity bit is added to each of the reference bits and the change bits to form the main storage key. There are provided a detecting device for detecting a parity error in a pair of the reference bit and the parity bit and a pair of the change bit and the parity bit when the main storage key is read out, and a device for rewriting the main storage key after setting the reference bit to a '1' indicating the corresponding page is being accessed and adding a new parity bit '0' to the reference bit when a parity error is detected by the detecting device in the pair of the reference bit and the parity bit and after setting the change bit to a '1' indicating a write in the corresponding page and adding an new parity bit '0' to the change bit when a parity error is detected in the pair of the change bit and the parity bit, thereby controlling the saving of the pages of the main storage into external storage.