Scan Chain Fault Diagnosis Using Path Control Flip-Flops
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing hardware-based scan chain fault diagnosis methods are inefficient for diagnosing multiple faults, requiring many test pins and degrading diagnostic resolution with increasing faults, leading to increased time and costs for physical analysis.
Innovation Solution
A scan device with path control scan flipflops connected in an array, allowing for controlled connection paths to reduce the fault range and detect fault positions, utilizing a first phase of flush tests and a second phase of path changes to diagnose single and multiple faults with high resolution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If additional hardware is used to maximize diagnostic resolution for fault diagnosis, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The scan chain is divided into multiple segments by inserting path control scan flipflops at specific positions. These flipflops can switch connection paths to isolate different segments, allowing faults to be localized to specific regions without requiring additional diagnostic hardware for each segment.
Solution Approach 2:
The path control scan flipflops serve multiple functions: they act as regular scan flipflops for normal operation and as diagnostic control elements for fault localization. By controlling connection paths, a single element performs both scanning and fault segmentation functions, eliminating the need for separate diagnostic hardware.
2Measurement precision
If multiple test pins are added for structural application to diagnose multiple faults, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The connection paths in the scan chain are made dynamically controllable through path control scan flipflops that can switch between different connection configurations. This dynamic path control allows the same hardware structure to adapt to different diagnostic scenarios, enabling multiple fault diagnosis without adding static test pins.
Solution Approach 2:
The system changes the connection path parameters controlled by path control scan flipflops to diagnose different fault scenarios. By varying the path configuration parameters rather than adding physical test pins, the system achieves multiple fault diagnosis capability with the existing hardware structure.
3Adaptability or versatility
If the number of faults in circuitry increases, then the scope of diagnosis is improved, but measurement precision degrades
Solution Approach 1:
When multiple faults are present, the path control scan flipflops segment the scan chain into isolated regions. By controlling connection paths to bypass faulty segments, the system can diagnose remaining faults with full resolution, preventing the degradation that would occur in a continuous scan chain with multiple faults.
Solution Approach 2:
The path control scan flipflops act as intermediary elements between faulty and non-faulty regions. They mediate the signal flow by switching paths to exclude faulty segments from the diagnostic process, allowing high-resolution diagnosis of remaining faults even when multiple faults are present in the circuitry.
4Measurement precision
If physical analysis is performed on fault candidate positions diagnosed later, then measurement precision is improved, but loss of time increases
Solution Approach 1:
The path control scan flipflops perform preliminary fault localization by segmenting and isolating fault regions during the scan operation itself. This preliminary action narrows down the fault candidate positions before physical analysis is required, significantly reducing the time needed for subsequent physical analysis while maintaining accurate fault position identification.
Data Source
AI summary
Provided are scan device and method of diagnosing scan chain fault. The scan device for diagnosing a fault includes a scan partition including a plurality of scan chains which include path control scan flipflops connected to scan flipflops in cascade. In the scan partition, connection paths of the scan flipflops are controllable. The connection paths of the path control scan flipflops are controlled to detect a position of a fault such that a fault range in the scan partition is reduced to diagnose the fault.