Method of automatically measuring the horizontal scan frequency of a composite synchronism signal, and an electronic circuit operating in accordance with the method

USRE36508E · kind E · reissue

Assignee

• SGS-Thomson Microelectronics S.A. · IT

Inventors

• Silvano Gornati · Casorezzo, IT
• Giorgio Betti · Milano, IT
• Fabrizio Sacchi · Valenza, IT
• Gianfranco Vai · Pavia, IT
• Maurizio Zuffada · Milano, IT

Key dates

• Filing date: Sep 17, 1997
• Grant date: Jan 18, 2000
• Expiry date: Sep 17, 2017

Classification

• Technology area (CPC —): General

Abstract

A method of automatically measuring the horizontal scan frequency of a composite synchronism signal, comprising horizontal synchronization impulses at line frequency, consists of first performing a count of a number of impulses having a repeat frequency higher than said line frequency, as intervening between two successive impulses at line frequency. The count value, corresponding to said number of impulses, is stored to obtain the line frequency of the signal, and thereafter, a series of down counts is effected, as initiated at predetermined times, until a change of frequency of the signal is detected.