Auto-detection between referenceless and reference clock mode of operation
US6831523B1 · kind B1 · utility
Assignee
Inventors
Key dates
| Filing date | Apr 24, 2002 |
| Grant date | Dec 14, 2004 |
| Priority date | — |
| Expiry date | May 10, 2022 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04L7/0004
- WIPO fieldBasic communication processes
- WIPO sectorElectrical engineering
Abstract
An internal frequency reference, such as a VCO used in a PLL, having a free-running frequency fairly well controlled within a predictable range, is used to determine which of two possible modes of operation, a referenceless or reference clock mode of operation, is used based on a detected frequency of an externally-provided frequency reference signal. The frequency is detected without any additional externally provided signal to indicate the mode of operation or the frequency of the reference clock. If the frequency detection circuit detects a frequency below a predetermined threshold, referenceless mode of operation is indicated. Otherwise, reference clock mode of operation is indicated. In referenceless mode of operation such operations as frequency acquisition and lock detect are performed without the use of a reference clock. In reference clock mode the reference clock is used for such operations as frequency acquisition and lock detect.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.