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. 05, 1990
Filed:
Jun. 09, 1989
Mark W McDermott, Austin, TX (US);
Antone L Fourcroy, Austin, TX (US);
Motorola, Inc., Schamburg, IL (US);
Abstract
A microprocessor or other integrated circuit including a clock generator circuit which is dependent on an externally-provided reference signal includes the capability of detecting the loss of this externally-provided reference signal and producing an alternate clock signal despite the loss of the reference. In a particular embodiment, the clock generator comprises a phase locked loop frequency synthesizer which normally relies on an external crystal oscillator for its reference frequency signal. The generator includes a circuit for detecting abnormalities in the crystal signal and switching the voltage controlled oscillator of the frequency synthesizer to an internally-generated reference voltage. In the particular embodiment, the clock generator is also capable of producing a reset signal in response to the loss of the reference signal.