Implantable Backup Firmware Using Switched RAM Blocks
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Solution Overview
Problem
Existing implantable medical devices (IMDs) face challenges in mitigating adverse effects of memory failures during backup modes, particularly in Class III devices like pacemakers and ICDs, where RAM failures can disrupt essential functions and therapies.
Innovation Solution
Implementing a non-volatile memory (NVM) with multiple separate RAM blocks and a counter to selectively store variables in functional RAM blocks, using watchdogs to detect malfunctions and increment the counter to switch to a different RAM block upon failure, ensuring continuous operation in backup mode.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single RAM block is used to store variables during backup mode, then device complexity is reduced, but reliability deteriorates when RAM failure occurs
Solution Approach 1:
The patent divides the RAM into multiple separate RAM blocks (first RAM block, second RAM block, etc.) to segment the memory storage. This segmentation allows the system to isolate failures to specific blocks while maintaining operational capability through other blocks, thereby improving reliability without requiring complete redundancy of the entire memory system.
Solution Approach 2:
The patent introduces a counter that changes the operational parameter by selecting which RAM block is active based on failure detection. When a RAM block fails, the counter increments to switch to a different RAM block, dynamically changing the memory allocation parameter to maintain system reliability.
2Reliability
If multiple RAM blocks are implemented with counter selection, then reliability improves, but device complexity increases
Solution Approach 1:
The patent segments RAM into multiple blocks with a counter to track and select functional blocks. This segmentation approach improves reliability by isolating failures to specific blocks while the counter management keeps the complexity controlled through a simple selection mechanism rather than complex redundancy systems.
3Reliability
If RAM is used to store both firmware and variables in backup mode, then device complexity is reduced, but reliability deteriorates due to memory failures
Solution Approach 1:
The patent segments the memory function by using separate RAM blocks for storing variables during backup mode, while firmware is stored in non-volatile memory. This segmentation isolates the critical firmware storage from volatile memory failures, improving reliability without significantly increasing overall device complexity.
Solution Approach 2:
The patent introduces non-volatile memory as an intermediary storage for firmware during backup mode. This intermediary separates the firmware storage function from the variable storage function in volatile RAM, protecting the system from RAM failures while maintaining operational capability.
Data Source
AI summary
Embodiments described herein relate to an IMD operating in a backup mode in a manner that mitigates against adverse effects of a memory failure. The IMD includes a NVM that stores backup mode firmware, a RAM that includes multiple separate RAM blocks, a processor, and a counter. The processor executes the backup mode firmware to operate the IMD in accordance with a backup mode in response to detection of a malfunction that when detected should cause the IMD to operate in accordance with the backup mode. While the processor operates the IMD in accordance with the backup mode the processor stores and accesses variables in one of the RAM blocks. The counter is selectively incremented and used to select which one of the RAM blocks the variables are stored within while the processor executes the backup mode firmware to operate the IMD in accordance with the backup mode.