Reading of the state of a non-volatile storage element

Abstract

A method for reading of the state of a non-volatile memory element including conditioning the frequency of a first oscillator to the state of this element, and comparing the frequency of the first oscillator with the predetermined frequency of a second oscillator, selected between two possible frequency values for the first oscillator, according to the state of the storage element.

Description

CROSS REFERENCE TO RELATED APPLICATIONS[0001]This application is a division of prior application Ser. No. 11 / 662,995, filed Mar. 15, 2007 entitled “Reading Of The State Of A Non-Volatile Storage Element” which application is a U.S. National Stage filing of International application Serial No. PCT / FR2005 / 050738, filed on Sep. 13, 2005, entitled “Reading Of The State Of A Non-Volatile Storage Element” which application claims the priority benefit of French patent application number 04 / 52058, filed on Sep. 15, 2004, entitled “entitled “Reading Of The State Of A Non-Volatile Storage Element” which applications are hereby incorporated by reference to the maximum extent allowable by law.BACKGROUND OF THE INVENTION[0002]1. Field of the Invention[0003]The present invention generally relates to the reading of the state of a non-volatile storage element and more specifically to the reading of the programmed or unprogrammed state of such an element.[0004]An example of application of the presen...

AI Technical Summary

Benefits of technology

This approach reduces the integration area required, is insensitive to manufacturing dispersions, and enhances security by making the stored state undetectable without reading, while providing a reliable and efficient means to determine the programming state of the storage element.

Problems solved by technology

A disadvantage is that it is then necessary to have accurate and stable current and / or voltage references, and the corresponding generation circuits take up space on an integrated circuit.

Another disadvantage is that current and / or voltage measurements are often sensitive to technological and integrated circuit manufacturing dispersions, and undergo drifts along the circuit lifetime.

Another disadvantage of non-volatile (reversible or not) storage element read systems is that the measurement of the current or of the voltage (more specifically its comparison with a threshold) requires a synchronization with respect to a triggering signal, and thus a synchronous operation.

This results in a risk of modification of the comparison result after modification of the clock synchronizing the measurement.

Such a disadvantage is particularly disturbing in so-called security applications, for example, when the content in the storage element conditions aspects of access authorization to certain functions of the component or the data encryption (key).

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