ROM Non Stuck-At Fault Detection via Golden Value Comparison
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Solution Overview
Problem
Current memory testing methods, particularly for non stuck-at faults in read-only memories, face challenges such as limited control during external testing, high complexity, and issues like aliasing and error cancellation due to the use of multiple input shift registers, leading to increased time and memory consumption.
Innovation Solution
A method and system that generate a golden value for a victim cell, apply a fault-specific pattern, and compare it with a test reading to identify non stuck-at faults, eliminating the need for multiple input shift registers and reducing memory overhead by dynamically computing the golden value.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple input shift registers are used to generate signatures for fault detection, then the ability to detect non stuck-at faults is improved, but memory consumption and device complexity increase
Solution Approach 1:
The patent extracts the signature generation function from the traditional MISR approach and implements it through a simplified comparator circuit that directly compares test data with expected values. This removes the need for complex shift register-based signature generation, reducing memory requirements while maintaining fault detection capability.
Solution Approach 2:
Instead of using a complex MISR to generate a compressed signature, the patent creates a simplified copy of the expected value pattern and directly compares it with the test data. This copying approach eliminates the need for shift register operations and reduces the memory footprint significantly.
2Reliability
If multiple input shift registers are used for fault detection, then detection capability is improved, but diagnosis time increases
Solution Approach 1:
The patent extracts the time-consuming signature generation process from the testing sequence and replaces it with direct comparison operations. By removing the MISR-based signature computation, the diagnosis time is significantly reduced while maintaining the same fault detection capability.
Solution Approach 2:
The patent skips the intermediate signature generation step and goes directly to the comparison phase. By rushing through the diagnostic process without the overhead of MISR operations, the overall diagnosis time is reduced while still achieving accurate fault detection.
3Reliability
If multiple input shift registers are used to generate signatures, then fault detection is improved, but aliasing and error cancellation occur
Solution Approach 1:
The patent extracts the problematic signature compression function from the testing methodology and replaces it with direct pattern matching. This removes the source of aliasing and error cancellation while preserving the ability to detect non stuck-at faults accurately.
Solution Approach 2:
The patent uses a direct copy of the expected value pattern for comparison, eliminating the need for MISR-based signature generation. This copying approach avoids the aliasing and error cancellation problems inherent in compressed signature methods while maintaining detection accuracy.
Data Source
AI summary
A method for identifying non stuck-at faults in a read-only memory (ROM) includes generating a golden value of a victim cell, providing a fault-specific pattern through an aggressor cell, generating a test reading of the victim cell in response to the provided fault-specific pattern, and determining whether the ROM has at least one non stuck-at fault. The determination is based on a comparison of the golden value and the test reading of the victim cell.