Configurable Mux-D Scan Flip-Flop Design for Flexible Observability
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Solution Overview
Problem
Current electrical circuit design techniques lack the ability to implement an observe-only scan mode for flip-flops in scan chains, limiting the flexibility and effectiveness of testing and functionality analysis.
Innovation Solution
A method and apparatus that include a selector load input to enable an observe-only scan mode in a scan chain, utilizing a first scan chain multiplexor and storage element to selectively control and observe storage elements, allowing for flexible scan chain implementation without the need for additional shadow elements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a fully scannable scan chain configuration is used, then each flip-flop is controllable and observable during testing, but the configuration does not allow for observation-only flip-flops in scan mode
Solution Approach 1:
The scan chain configuration is made dynamic by introducing a mode selector input that allows flip-flops to switch between fully scannable mode and observation-only mode. This dynamic reconfiguration enables the same hardware to adapt to different testing requirements without physical changes to the circuit structure.
Solution Approach 2:
The scan chain elements are designed to perform multiple functions: they can operate as fully controllable and observable flip-flops during normal scan mode, and as observation-only elements when the mode selector is activated. This multi-functionality eliminates the need for separate shadow flip-flops while maintaining both testing capabilities.
2Measurement precision
If shadow flip-flops are used to hold input of non-scannable flip-flops, then observation capability is provided, but additional circuitry is required
Solution Approach 1:
The existing scan chain flip-flops are made multi-functional by adding a mode selector input. When configured for observation-only mode, these same flip-flops provide the observation capability that previously required separate shadow flip-flops, thereby eliminating additional circuitry while maintaining measurement precision.
Solution Approach 2:
The observation function that was previously implemented through separate shadow flip-flops is merged into the existing scan chain elements. The mode selector input enables the same physical flip-flop to serve both as a scannable element and an observation-only element, consolidating functionality and reducing overall circuit complexity.
Data Source
AI summary
A method, computer program storage device and apparatus are provided for flexible observability during a scan. In one aspect of the present invention, a method is provided. The method includes providing a selector load input to at least a portion of a scan chain, selecting an observe-only scan mode for the at least a portion of the scan chain based at least upon the selector load input, and providing a data input to a storage element in the scan chain based at least upon the observe-only scan mode. The apparatus includes a first scan chain multiplexor comprising a selector input, a first input terminal, a second input terminal and an output terminal. The apparatus also includes a first scan chain storage element comprising an input terminal and an output terminal, where the input terminal of the first scan chain storage element is communicatively coupled to the output terminal of the first scan chain multiplexor. The apparatus further recites that the output terminal of the first scan chain storage element is communicatively coupled to the first input terminal of the first scan chain multiplexor. The computer program storage device adapts a manufacturing facility to create the apparatus.