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:
Mar. 17, 1992
Filed:
Aug. 13, 1990
Matthew K Adams, Dallas, TX (US);
Dallas Semiconductor Corporation, Dallas, TX (US);
Abstract
An adjunct chip, usable as a peripheral to a microprocessor, which detects power failure, and which puts the microprocessor into a known state upon power down. In order to reliably and stably put the microprocessor into a known state, several clocks are generated after the reset signal. However, since the power supply is falling, it is possible that the crystal-controlled oscillator may already have become unreliable. Therefore, a simple logic circuit (a ring oscillator, in the presently preferred embodiment) is used to generate the needed additional clocks at power-down. The switch from crystal-controlled oscillator to ring oscillator is stabilized by using a latched multiplexer to switch between the two oscillator inputs. The latch adds hysteresis to the switching characteristic, avoiding any problems of switching jitter.