Protected Memory System for Flight Data Survivability
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Solution Overview
Problem
As lithographies shrink, solid-state memory devices in crash-protected memories for flight data recorders face reduced data retention at high temperatures due to diminished guard-bands, leading to random bit failures and data corruption, and the addition of Error Correcting Code (ECC) circuitry exacerbates thermal management issues.
Innovation Solution
A protected memory system with a memory array of separately located modules and a memory controller that stores identical data copies across multiple modules, allowing error detection and replacement, thereby maintaining data integrity without relying on ECC circuitry.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If SLC NAND Flash memory devices use smaller lithographies to meet manufacturing price targets and yields, then manufacturing cost and yield are improved, but data retention at high temperatures deteriorates due to reduced guard-bands
Solution Approach 1:
The memory system is divided into multiple independently located memory modules (first memory module, second memory module, etc.) that are physically separated. Each module stores copies of the same data packets, and they are spaced far enough apart that thermal effects from a crash-induced fire cannot simultaneously affect all modules. This segmentation allows the system to maintain data retention reliability even when using smaller lithographies with reduced guard-bands.
Solution Approach 2:
The system stores identical copies of data packets in corresponding memory locations across multiple separate memory modules. When data is written to the first memory module, corresponding copies are simultaneously written to the second and subsequent memory modules. This redundancy through copying ensures that if one module suffers thermal damage, the data can be recovered from another module, thereby maintaining data retention at high temperatures despite using smaller lithographies.
2Reliability
If Error Correcting Code (ECC) circuitry is added to maintain data integrity, then data integrity is improved, but power consumption increases and thermal management issues worsen
Solution Approach 1:
The invention extracts the error protection function from the traditional ECC circuitry approach and relocates it to the physical layout and redundancy structure of the memory system. Instead of using active ECC circuits that consume power to detect and correct errors, the system uses passive geographic separation and data copying across multiple modules. The error protection is achieved through the system architecture itself rather than through additional active circuitry, thereby maintaining data integrity without increasing power consumption.
3Reliability
If multiple separate memory modules are used to store identical data copies, then data integrity after crash events is improved, but device complexity increases
Solution Approach 1:
The invention combines multiple functions into the memory module structure: each module serves as both a data storage unit and an error protection unit through geographic separation. The memory controller integrates the functionality of writing to multiple modules, reading from multiple modules, detecting errors, and replacing corrupted data. By merging these functions into the existing memory architecture and controller, the system achieves improved crash survivability without proportionally increasing overall device complexity.
Data Source
AI summary
Systems and a method for storing data are provided. The protected memory system includes a memory array including a plurality of memory modules each separately located with respect to each other and a memory controller configured to receive data to be stored from the data acquisition unit, store the received data in corresponding memory locations in each of the plurality of memory modules wherein the stored data including error checking information, read data from a first one of the plurality of memory modules until a data error is detected at a first memory location, read data from a second memory location of a second one of the plurality of memory modules wherein the data read from the second memory location corresponds to the data read from the first memory location, and replace the data read from the first memory location with the data read from the second memory location.