BCAM Error Detection via Data Signatures and Cross-Bank Replication
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Solution Overview
Problem
Binary content addressable memory (BCAM) systems face high soft error rates due to errors introduced by ionizing radiation, exceeding acceptable limits, especially with large numbers of bits stored, which existing technologies fail to effectively detect and correct in real-time.
Innovation Solution
The implementation of data signature circuitry and/or duplicate entries within BCAMs allows for real-time error detection and correction by analyzing data signatures during compare operations and using error correction circuitry to identify and correct errors without external data retrieval, employing error correcting codes like Hamming codes to detect and correct single or multiple bit errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If BCAM stores large numbers of bits to increase storage capacity, then the storage capacity is improved, but the soft error rate increases beyond acceptable limits
Solution Approach 1:
The patent divides the BCAM into multiple banks, with each bank containing a subset of the total bits. This segmentation isolates errors to specific banks, preventing errors from propagating across the entire memory system. The segmentation allows the system to maintain high storage capacity while limiting the impact of soft errors to manageable portions.
Solution Approach 2:
The patent implements duplicate entries and cross-bank replication of data. By storing copies of data in multiple banks, the system can detect and correct errors by comparing identical data across different banks. This copying mechanism enables error correction without sacrificing storage capacity, as the redundant copies are used solely for error detection and correction purposes.
2Reliability
If error correction circuitry is added to detect and correct errors in real-time, then the reliability is improved, but the device complexity increases
Solution Approach 1:
The patent combines error detection and correction functions with the existing BCAM compare operations. The error correction circuitry is integrated into the memory structure itself, utilizing the same data paths and control logic already present in the BCAM. This merging approach enables real-time error correction without adding separate complex external correction systems.
Solution Approach 2:
The BCAM system performs self-diagnosis and self-correction by comparing data across multiple banks and using embedded duplicate entries. The system automatically detects errors through cross-bank comparison and corrects them using the redundant copy data, without requiring external intervention or complex external correction circuitry. This self-service mechanism reduces overall system complexity.
3Reliability
If duplicate entries are used for error detection, then the reliability is improved, but the storage capacity is reduced
Solution Approach 1:
The patent implements duplicate entries selectively in specific banks rather than throughout the entire memory system. Each bank contains duplicate entries for its portion of the data, creating local redundancy where it is most needed for error detection. This local quality approach provides sufficient error detection capability while minimizing the overall impact on storage capacity.
Solution Approach 2:
The patent organizes duplicate entries in a cross-bank dimension rather than simply replicating them within the same bank. By distributing duplicates across multiple banks in a dimensional arrangement, the system achieves error detection capability while optimizing the use of storage space. This dimensional organization allows efficient error detection with reduced redundancy overhead.
Data Source
AI summary
A binary content addressable memory (BCAM) is disclosed. The BCAM includes a memory array, data signature circuitry, and a data match module and compare circuitry. The memory array is configured to store a data entry for a data word and a corresponding data signature for the data entry. The data signature circuitry is configured to calculate the data signature for the data entry and to calculate the data signature for an input word. The data match module compares the data entry to the input word to produce a content match output, and compares the data signature for the data entry to the data signature of the input word to produce a signature match output. The compare circuitry compares the content match output and the data signature match output.