MBIST Runtime March Testing for Continuous Memory Access
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Solution Overview
Problem
Conventional memory self-tests, such as March tests, are typically performed during system power-up or power-down, disrupting normal data access and can lead to unpredictable behavior or system crashes if not managed carefully, and existing runtime tests like ECC/EDC schemes increase memory size with redundant bits or have reduced diagnostic coverage.
Innovation Solution
A built-in self-test (BIST) system configured to operate in startup and runtime modes, performing March B tests during startup and March X or March Y tests during runtime intervals like vertical blanking intervals, ensuring memory integrity without additional overhead.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If March tests are performed during system power-up or power-down, then memory integrity can be thoroughly tested, but normal data access is disrupted and system behavior becomes unpredictable
Solution Approach 1:
The patent implements dynamic test selection based on operational context. The MBIST unit automatically adapts its behavior: performing comprehensive March A/B tests during startup/power-down phases when disruption is acceptable, and switching to lightweight March X/Y tests during runtime when data access continuity is critical. This dynamic adaptation resolves the contradiction by making the testing approach contingent on system state.
Solution Approach 2:
The patent employs periodic runtime testing during idle intervals (VBHANK/HBANK) rather than continuous testing. The MBIST unit monitors processor activity and triggers abbreviated March X/Y tests during these periodic idle windows, ensuring memory integrity verification occurs regularly without continuously disrupting normal data access operations.
2Reliability
If comprehensive March tests are performed during runtime, then memory faults can be detected timely, but system performance degrades due to extensive read and write operations
Solution Approach 1:
The patent applies partial action by selecting abbreviated March X/Y test algorithms for runtime testing instead of comprehensive March A/B tests. These abbreviated tests perform essential fault detection (stuck-at, transition, and coupling faults) with reduced read/write operations, achieving adequate fault coverage during runtime while minimizing performance impact. The test selection is partial rather than exhaustive, matching the runtime context.
Solution Approach 2:
The patent schedules runtime memory tests to occur periodically during processor idle intervals (VBHANK/HBANK) rather than continuously. This periodic execution ensures fault detection capability is maintained at appropriate intervals while allowing normal high-performance data access to continue during active periods, thus resolving the performance contradiction.
3Reliability
If ECC/EDC schemes are used for runtime testing, then memory reliability is improved, but memory size increases due to redundant bits
Solution Approach 1:
The patent implements self-service through the MBIST unit, which is a dedicated test execution engine integrated into the memory system. This self-contained test capability performs comprehensive March A/B tests during startup and abbreviated March X/Y tests during runtime without requiring external test equipment or additional redundant storage bits. The MBIST unit generates test patterns, executes tests, and reports faults autonomously, eliminating the need for ECC/EDC overhead while maintaining reliability.
4Reliability
If March A or March B tests are performed during startup, then thorough memory testing is achieved, but test execution time is extended
Solution Approach 1:
The patent performs comprehensive March A/B tests during the startup phase before the system enters normal operation. This preliminary action ensures thorough memory testing is completed upfront when the system is initializing, allowing detection of manufacturing defects and early degradation. By concentrating comprehensive testing at startup, the patent accepts the time cost during initialization in exchange for ensuring memory reliability before production use begins.
Data Source
AI summary
The disclosure provides a method for performing self-test on a memory. The method can include determining an operation mode of a memory built-in self-test (MBIST) unit based on status of the memory; in response to the operation mode being a startup mode, configuring the MBIST unit to perform a memory self-test of a first type; and in response to the operation mode being a runtime mode, configuring the MBIST unit to periodically perform a memory self-test of a second type.