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:
Jun. 04, 1991
Filed:
Mar. 30, 1988
Tsukasa Matoba, Kawasaki, JP;
Takeshi Aikawa, Tokyo, JP;
Mitsuyoshi Okamura, Tokyo, JP;
Ken-ichi Maeda, Kamakura, JP;
Mitsuo Saito, Yokosuka, JP;
Kabushiki Kaisha Toshiba, Kawasaki, JP;
Abstract
Each register of an internal register unit of a microprocessor has a pair of register cells consisting of first and second cells having the same register address. When one of these cells is selected, the other cell non-selected serves as a 'back-up cell' for the selected cell. Each register of the register unit has a flag bit for storing a selector flag representing which cell of the pair of cells of the register is currently selected, and a flag bit for storing a change flag representing whether register information of the register is rewritten after a selected cell is changed between the first and second cells of the register. When the register information is stored in one of the pair of cells currently being selected of a certain register and is to be rewritten with another new information, the other cell of the register is selected to store the new information therein. The original register information is held in the first cell, thereby eliminating necessity of saving the original register information to a main memory at this stage. When the original register information is required again, the original register information can be rapidly restored, by only selecting the first cell again, in the corresponding register without executing save/restore processing between the register unit and the main memory.