Diagnosis-Aware Scan Chain Stitching for High Resolution
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Solution Overview
Problem
Current scan chain fault diagnosis techniques face challenges in achieving high diagnostic resolution due to high costs and hardware overhead in tester-based methods, and limited effectiveness in software-based methods without careful scan chain design.
Innovation Solution
The development of diagnosis-aware scan chain stitching techniques that analyze the potential logic relationship and layout information of scan cells to form or modify scan chains, optimizing the number and distribution of sensitive cells for improved diagnostic resolution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If tester-based diagnosis techniques are used, then diagnostic resolution is improved, but cost and diagnostic time increase
Solution Approach 1:
The patent applies preliminary action by pre-forming scan chains with optimized structures before actual diagnosis is needed. The scan chains are designed in advance to include specific sensitive cells and follow particular stitching patterns that enable high-resolution diagnosis without requiring expensive tester equipment during the actual fault detection process.
Solution Approach 2:
The patent uses software-based simulation and analysis to create virtual copies of the diagnosis process. By modeling the scan chain behavior and simulating fault detection algorithms, the system can perform diagnosis without physical tester equipment, thereby reducing cost and time while maintaining diagnostic resolution.
2Measurement precision
If hardware-based diagnosis techniques are used, then faulty scan cells can be identified, but hardware overhead increases
Solution Approach 1:
The patent replaces hardware-based diagnosis mechanisms with software-based algorithms. Instead of adding physical diagnostic circuits and hardware resources to identify faulty scan cells, the system uses computational algorithms that analyze scan chain responses through software processing, thereby eliminating the need for additional hardware overhead while maintaining fault identification capability.
Solution Approach 2:
The patent makes the existing scan chain structure multi-functional by designing it to serve both normal circuit operation and diagnostic purposes. The scan chains are configured with sensitive cells and stitching patterns that enable them to perform both their original function and fault detection without requiring separate dedicated diagnostic hardware.
3Device complexity
If software-based diagnosis techniques are used, then hardware overhead is reduced, but diagnostic resolution becomes problematic
Solution Approach 1:
The patent applies local quality by creating specific localized structures within the scan chains, namely sensitive cells with particular fan-in cone characteristics. These localized regions are specifically designed to provide diagnostic information, while the rest of the scan chain maintains its normal functionality. This localized optimization enables high diagnostic resolution without requiring the entire system to be complex.
Solution Approach 2:
The patent changes key parameters of the scan chain structure, including the distribution and positioning of sensitive cells, the stitching patterns connecting scan cells, and the fan-in cone configurations. By optimizing these parameters during the design phase, the system achieves high diagnostic resolution through software analysis of the modified scan chain parameters without requiring additional hardware.
4Ease of manufacture
If scan chains are not carefully designed, then implementation is simpler, but diagnostic resolution is compromised
Solution Approach 1:
The patent segments the scan chain into distinct functional components, particularly identifying and isolating sensitive cells from other scan cells. This segmentation allows the sensitive cells to be strategically positioned and connected through specific stitching patterns, enabling optimized diagnostic resolution while maintaining relatively simple implementation through modular design principles.
Data Source
AI summary
Aspects of the invention relate to techniques for determining scan chains that could be diagnosed with high resolution. A circuit design and the information of scan cells for the circuit design are analyzed to determine information of potential logic relationship between the scan cells. The information of potential logic relationship between the scan cells may comprise information of fan-in cones for the scan cells. Based at least in part on the information of potential logic relationship between the scan cells, scan chains may be formed. The formation of scan chains may be further based on layout information of the circuit design. The formation of scan chains may be further based on compactor information of the circuit design.