MBIST Adaptive Port for Non-Destructive In-Field Testing
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Solution Overview
Problem
Current memory testing technologies, such as MBIST, cannot be performed in-field during operational mode due to the time required for testing exceeding acceptable windows and the destructive nature of writing to memory locations, which disrupts operational data.
Innovation Solution
A BIST adaptive port (BAP) interface enables non-destructive in-field memory testing by storing operational data in registers during testing, allowing periodic testing without disrupting system functionality, and includes predictive error detection and repair capabilities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If MBIST testing is performed on memory locations, then memory faults can be detected, but operational data in the memory is destroyed due to writing test patterns
Solution Approach 1:
The memory testing process is segmented into distinct phases: data saving phase, testing phase, and data restoration phase. During the testing phase, only specific memory segments are tested while other segments continue to operate normally. The BAP interface segments the data path by providing separate channels for test data and operational data, allowing simultaneous testing and operation without data loss.
Solution Approach 2:
Before MBIST testing begins, the BAP interface performs preliminary actions by saving operational data from memory locations to be tested into temporary storage buffers. This preliminary data preservation ensures that when test patterns are written to memory, the original operational data is already secured and can be restored after testing completes, preventing any loss of operational information.
2Reliability
If complete memory testing is performed, then all memory faults are detected, but the testing time exceeds acceptable operational windows
Solution Approach 1:
Memory testing is implemented as periodic action rather than continuous operation. The MBIST controller periodically initiates testing sequences during idle periods or low-utilization windows, while the system continues normal operations. The BAP interface enables this periodic testing by quickly saving and restoring data, allowing testing to occur in discrete time intervals without halting system operation, thus fitting testing within acceptable time windows.
Solution Approach 2:
The system performs partial testing actions during operational periods, testing a subset of memory locations during each testing window rather than attempting to test the entire memory space in one continuous operation. The BAP interface facilitates this by enabling rapid data save/restore operations that allow multiple partial testing passes to collectively cover the full memory space over time, achieving complete fault detection without requiring excessive continuous testing time.
3Adaptability or versatility
If MBIST testing is performed during operational mode, then in-field testing is enabled, but system operation is disrupted due to memory writing
Solution Approach 1:
The BAP interface acts as an intermediary between the MBIST controller and the memory array. It mediates the conflict between testing operations and operational data by intercepting test write operations, redirecting them through protected data paths, and ensuring original data is preserved. This intermediary layer allows MBIST testing to proceed during operational mode without directly disrupting system operations, as the BAP absorbs and manages the data protection overhead.
Solution Approach 2:
The system applies local quality protection by selectively saving and protecting only the specific memory locations that are currently being tested, rather than protecting the entire memory space. The BAP interface implements local quality control by maintaining small buffers for tested locations and restoring only those specific locations after testing. This localized approach minimizes the impact on system operation while enabling in-field testing capability.
Data Source
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AI summary
A BIST (built-in self-test) adaptive port (BAP) interface enables an in-field MBIST (memory BIST). The BAP enables non-destructive testing of the memory locations. The BAP includes registers to store contents of the memory device during the in-field MBIST on the memory device. The BAP can store the starting address of the next infield periodic testing and operational data from a selected memory address in the registers while the MBIST controller performs the test on the memory address. The system can then restore the operational contents of the memory after the test is complete.