Method and apparatus for real time clock frequency error correction

US6304517A · kind A · utility

Assignee

• Telefonaktiebolaget LM Ericsson (Publ) · SE

Inventors

• Rolf Erik Ledfelt · Malmö, SE
• Anders Wilhelm Ostsjo · Ulricehamn, SE

Key dates

• Filing date: Jun 18, 1999
• Grant date: Oct 16, 2001
• Expiry date: Jun 18, 2019

Classification

• Technology area (CPC H): Electricity
• CPC primary: H03L1/00
• WIPO field: Measurement
• WIPO sector: Instruments

Abstract

A real time clock, suitable for use in mobile units in a radiocommunication system, is calibrated during production, and corrects for timing inaccuracies during normal operation. As a result, the accuracy of the real time clock's crystal oscillator is increased economically and efficiently. Frequency error correction is performed by periodically adjusting the frequency of the real time clock by a fixed amount once for every interval of time defined by an adjustment value. The adjustment value is determined by a calibration procedure performed during manufacture of the mobile unit.