Augmented Multimode Compactors for IC Test Compression
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Solution Overview
Problem
Current test response compression techniques for integrated circuits face challenges in reducing test data volume and test application time due to limitations in bandwidth and the presence of unknown values, leading to error masking and reduced diagnostic efficiency.
Innovation Solution
The development of augmented multimode compactors that divide scan chains into groups and partitions, using logic gates and output registers to selectively compress test responses, ensuring unique error signatures and minimizing the X-masking effect, thereby enhancing observability and diagnostic capabilities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If conventional test response compression techniques are used, then test data volume is reduced, but error masking occurs and diagnostic efficiency decreases
Solution Approach 1:
The patent segments scan chains into multiple groups and partitions, with each group assigned to specific output registers. This segmentation allows selective compression of different scan chain groups, enabling unique error signatures to be maintained while reducing overall test data volume. The segmented structure prevents error masking by ensuring that errors in different segments produce distinguishable compressed responses.
Solution Approach 2:
The patent applies local quality by assigning different compression characteristics to different scan chain groups. Each output register handles specific groups with tailored compression logic, allowing some groups to be compressed more aggressively while others maintain higher observability. This local differentiation enables error detection to be preserved in critical areas while achieving overall data volume reduction.
2Productivity
If scan chains are compressed to reduce test application time, then test coverage is improved, but unknown values cause X-masking effect
Solution Approach 1:
The patent introduces intermediary output registers as mediators between scan chains and the compression process. These output registers serve as buffer stages that can accommodate unknown values without propagating them directly into the compressed response. The intermediary registers allow the system to handle unknown values gracefully, maintaining compression benefits while reducing X-masking effects.
Solution Approach 2:
The patent implements dynamic mode selection where the compactor can adapt its compression behavior based on the presence of unknown values. When unknown values are detected in certain scan chain groups, the system can switch to alternative compression modes or skip compression for those groups, dynamically adjusting the compression strategy to minimize X-masking while maintaining overall test efficiency.
3Quantity of substance
If more scan chains are compressed to reduce test data volume, then bandwidth requirements are reduced, but unique error signature capability is compromised
Solution Approach 1:
The patent segments scan chains into distinct groups that are mapped to different output registers, creating independent compression channels. This segmentation ensures that errors in different segments produce unique signatures in different output registers, maintaining measurement precision even as overall data volume is reduced through compression of multiple segments.
Solution Approach 2:
The patent adds a dimensional aspect by introducing multiple output registers that process different scan chain groups simultaneously. This multi-dimensional approach allows the system to compress data across multiple dimensions (scan chain groups) while maintaining unique error signatures through the additional register dimension, effectively increasing the signature space without compromising precision.
Data Source
AI summary
Methods and apparatuses for synthesizing and/or implementing an augmented multimode compactor are described.