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. 27, 1995
Filed:
Jul. 01, 1993
Mizanur M Rahman, Cupertino, CA (US);
Fred C Sabernick, Sunnyvale, CA (US);
Jeff A Sprouse, Mountain View, CA (US);
Tandem Computers Incorporated, Cupertino, CA (US);
Abstract
A diagnostic system for diagnosing states of circuit elements is described, wherein scannable circuits can be scanned without disturbing the state of unscannable circuits or violating protocols of busses on which unscannable devices are attached. One unscannable device is a standardized microprocessor. A processor interface circuit is coupled between the microprocessor and scannable processor circuits, via a processor bus, to insulate the scannable processor circuits from the unscannable microprocessor. The processor interface circuit is also scannable, including memory elements which affect the bus, by preventing a scan when the bus is in use. A scan is prevented through the use of a maintenance request signal from a scan controller to the processor interface circuit, and one or more maintenance approval signals from the processor interface circuit to the scan controller.