Integrated circuit with clock generator
US4931748A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Jun 9, 1989 |
| Grant date | Jun 5, 1990 |
| Priority date | — |
| Expiry date | Jun 9, 2009 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG06F1/04
- WIPO fieldMeasurement
- WIPO sectorInstruments
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.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.