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:
Jan. 31, 1989
Filed:
Jul. 29, 1986
Craig D Shaw, Austin, TX (US);
Motorola, Inc., Schaumburg, IL (US);
Abstract
Status flag handling method and apparatus for use in a digital data processing system provide error-resistant operation and simplicity. Two storage elements comprising one bit of a status register are operated such that: a reset places both elements in first predetermined states; a set flag operation places both elements in second predetermined states; a read flag operation alters the state of the second storage element; and a clear flag alters the state of the first storage element if and only if the state of the second storage element has previously been altered by a read flag operation. The flag output corresponds to the state of the first storage element. When implemented with single instructions, inadvertant flag negation and errors due to intervening interrupts are avoided. The read flag operation temporarily disables the set flag mechanism, protecting against setting the flag during a read operation. The flag is always read as asserted prior to being negated.