Integrated Circuit Mode Locking via Signature Comparison

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Solution Overview

Problem

Existing integrated circuits face challenges in definitively selecting an operating mode without fuses or anti-fuses, which can re-form, leading to loss of programming state and increased power consumption due to required power elements and limited manufacturing processes, especially in ferromagnetic memory circuits.

Innovation Solution

A device using a non-volatile memory with initial and current content signatures to determine the operating mode, where the difference between these signatures deactivates the mode selection signal if greater than a threshold, ensuring a definitive lock without fuses or anti-fuses, and utilizing a programmable memory that can only be written in the reserved mode.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a fuse is used to lock the operating mode, then the mode selection is definitive, but the fuse may re-form under certain conditions causing loss of programming state

Engineering Contradiction:

Improvemode selection stabilityVSAvoidprogramming state loss

Core Design Contradiction:

ReliabilityVSLoss of information

Solution Approach 1:

The patent creates a copy of the initial memory content (first signature) and stores it separately. By comparing the current memory content (second signature) with the stored first signature, the system verifies whether the memory has been modified. This copying approach allows definitive mode locking without using fuses that can re-form, as the integrity check is performed through signature comparison rather than physical fuse state.

Inventive Principle:

Principle #26Copying

Solution Approach 2:

The patent replaces the mechanical/physical fuse-based locking mechanism with an information-based signature comparison mechanism. Instead of relying on the physical state of a fuse that can re-form, the system uses digital signatures stored in non-volatile memory to verify whether the operating mode selection has been definitively made. This substitution eliminates the re-forming issue inherent in fuse-based systems.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Reliability

If a fuse is used for mode selection, then the circuit can be locked, but controlling the melting of the fuse requires significant power and increases circuit size

Engineering Contradiction:

Improvemode locking capabilityVSAvoidpower consumption

Core Design Contradiction:

ReliabilityVSUse of energy by moving object

Solution Approach 1:

The patent replaces the high-power fuse melting mechanism with a low-power signature comparison mechanism. Instead of requiring significant power to melt a fuse and control power elements, the system uses minimal power to read memory content, calculate signatures, and compare them. This substitution dramatically reduces power consumption while maintaining reliable mode locking capability.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent extracts the power-consuming fuse and power element components from the circuit and replaces them with a signature-based verification system. By taking out the fuse mechanism entirely and using only memory storage and comparison logic, the circuit eliminates the need for significant power elements, thereby reducing both power consumption and circuit size.

Inventive Principle:

Principle #2Taking out (Extraction)

3Reliability

If a fuse is used for mode selection, then the circuit can be locked, but the fuse formation requires certain manufacturing steps not available in all processes

Engineering Contradiction:

Improvemode locking capabilityVSAvoidmanufacturing process compatibility

Core Design Contradiction:

ReliabilityVSAdaptability or versatility

Solution Approach 1:

The patent uses a non-volatile memory component that can be programmed after manufacturing to store the first signature. This memory-based approach is universal and can be implemented in various manufacturing processes including ferromagnetic memory, unlike fuse formation which requires specific processes like tunnel oxide deposition. The signature comparison mechanism works across different memory technologies, providing manufacturing process compatibility while maintaining mode locking capability.

Inventive Principle:

Principle #6Universality (Multi-functionality)

4Ease of operation

If a fuse is used for mode selection, then the reserved mode can be accessed initially, but the fuse increases circuit surface area

Engineering Contradiction:

Improveinitial reserved mode accessVSAvoidcircuit surface area

Core Design Contradiction:

Ease of operationVSArea of stationary object

Solution Approach 1:

The patent extracts the fuse component and its associated power elements from the circuit, replacing them with a compact signature storage and comparison mechanism implemented in non-volatile memory. This removal of the fuse takes out the space-consuming elements while maintaining the ability to provide initial reserved mode access through the same memory-based verification system.

Inventive Principle:

Principle #2Taking out (Extraction)

Data Source

PatentUS7325181B2Method and device for selecting the operating mode of an integrated circuit

Publication Date: 2008.01.29 STMICROELECTRONICS FRANCE

AI summary

A device for selecting an operating mode of an integrated circuit, including a non-volatile memory programmable after manufacturing exhibiting prior to any programming an initial content, means for storing a first signature representative of the initial content of the memory, means for calculating a second signature representative of a current content of the memory, and means for evaluating a difference between the first and second signatures and for deactivating an operating mode selection signal when the difference is greater than a predetermined threshold.