Segmented Decompressor Routing Congestion Reduction
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Solution Overview
Problem
Existing test compression techniques face severe routing congestion due to centralized decompressors driving thousands of scan chains, which is exacerbated by the lack of layout information during design, leading to inefficiencies in test data distribution and potential sacrifices in test coverage or data volume.
Innovation Solution
The implementation of a segmented decompressor design, where the decompressor is partitioned into multiple segments, each driving a subset of scan chains, with injection points assigned based on life span values and predetermined requirements to optimize encoding capacity and reduce routing congestion, using a ring generator and phase shifters with XOR gates to distribute test stimuli effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a centralized decompressor is used to drive thousands of scan chains, then test compression capability is improved, but routing congestion increases severely
Solution Approach 1:
The decompressor is divided into multiple segments, where each segment drives a subset of scan chains. This segmentation reduces routing congestion by distributing the decompression functionality across multiple smaller units rather than using a single centralized decompressor that would require extensive routing to reach thousands of scan chains.
Solution Approach 2:
The patent introduces a two-dimensional map to organize injection points and scan chains, transforming the routing problem from a one-dimensional centralized approach to a two-dimensional distributed architecture. This dimensional change allows for more efficient spatial distribution of routing resources.
2Adaptability or versatility
If injection points are assigned without layout information, then design flexibility is maintained, but test data distribution efficiency decreases
Solution Approach 1:
The patent performs preliminary assignment of injection points to input channels based on lifespan values before final layout implementation. This preliminary action establishes an optimized mapping that can later be adapted to specific layout constraints, maintaining design flexibility while ensuring efficient test data distribution.
Solution Approach 2:
The patent uses lifespan values as a key parameter to optimize injection point assignment. By calculating and utilizing lifespan values for each injection point, the system dynamically adjusts the assignment to maximize test data distribution efficiency while maintaining adaptability to different design scenarios.
Data Source
AI summary
A circuit comprises: a register configured to be a linear finite state machine and comprising storage elements, injection devices, one or more input channels for injecting variables using the injection devices, and one or more feedback devices; a plurality of phase shifters, each of the plurality of phase shifters configured to receive signals from a unique segment of the register; scan chains, serial inputs of the scan chains configured to receive signals from outputs of the plurality of phase shifters, wherein the one or more input channels are coupled to the injection devices at injection points in the register, each of the injection points being assigned to one of the one or more input channels based on lifespan values for the injection points, the injection points being determined based on one or more predetermined requirements.