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:
Oct. 27, 1987
Filed:
Dec. 18, 1985
Takao Nishida, Kokubunji, JP;
Toru Hiyama, Atsugi, JP;
Kaoru Moriwaki, Hadano, JP;
Shun Ishiyama, Hadano, JP;
Shunsuke Miyamoto, Tokyo, JP;
Hitachi, Ltd., Tokyo, JP;
Abstract
A logic circuit having a diagnostic function is disclosed in which each of first latches for applying data to combinational circuits included in the logic circuit and/or receiving data from the combinational circuits is provided with a second latch and a selector for selecting the output of the first latch in a first mode and for selecting the output of the second latch in a second mode. In a regular operation, the output of the first latch is never transferred through the second latch, and the selector is operated in the first mode. Accordingly, the output of the first latch is supplied directly to a succeeding combinational circuit, and thus the delay caused by the second latch in the prior art can be eliminated. Although the delay caused by the selector is unavoidable, this delay can be made far smaller than the delay caused by the second latch. In a diagnostic operation, the output of the first latch is transferred through the second latch, and the selector is operated in the second mode, in order to perform the diagnostic operation stably even when data is transferred between first latches having the same phase, or the logic circuit includes a one-latch loop.