Vehicle Control Device Memory Protection Unit Access Authority Management
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Solution Overview
Problem
Existing vehicle control systems face difficulties in implementing Freedom From Interference (FFI) due to limitations in the number of access control registers, making it challenging to comply with functional safety standards when the number of access authorities exceeds the number of registers.
Innovation Solution
The vehicle control device allocates storage devices for access authority definitions both fixedly and dynamically within the memory protection unit, allowing for a number of access authority definitions that is not less than the number of access control registers, by using a combination of dedicated and shared registers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the number of access control registers is increased to define more access authorities, then the number of access authority definitions increases, but the device complexity and cost increase
Solution Approach 1:
The patent combines multiple access authority definitions into a single access control register by storing definition data (such as access authority tables or configuration data) in memory. The memory protection unit dynamically loads and applies different access authority definitions from memory to the same register, allowing one register to serve multiple access authority roles without requiring multiple physical registers.
Solution Approach 2:
The patent creates virtual copies of access control registers by storing duplicate access authority definition data in memory. Multiple software groups can reference the same physical register through different definition data stored in memory, effectively creating virtual register instances that can be configured independently without duplicating hardware registers.
2Reliability
If the number of access control registers is increased to comply with functional safety standards, then Freedom From Interference is improved, but the device cost and complexity increase
Solution Approach 1:
The patent introduces dynamic configuration capability to the memory protection unit, allowing access authority definitions to be changed at runtime through software control. The system can dynamically load different access authority definitions from memory into the access control register based on which software group is currently executing, enabling flexible isolation of multiple safety-critical software groups using a single register.
Solution Approach 2:
The patent introduces memory as an intermediary layer between the software groups and the access control register. Instead of directly mapping each software group to a separate register, the system uses memory-stored definition data as an intermediary that can be selectively applied to the single access control register, providing the necessary isolation without requiring multiple registers.
3Adaptability or versatility
If access authority definitions are stored in memory instead of registers, then more definitions can be stored, but the access control speed may decrease
Solution Approach 1:
The patent pre-loads access authority definition data into memory before execution. The definition data is prepared and stored in advance in a structured format, allowing the memory protection unit to quickly retrieve and apply the appropriate definition when a software group needs access control, minimizing runtime overhead.
Solution Approach 2:
The patent optimizes the memory storage structure by placing access authority definition data in specific memory locations that are easily accessible to the memory protection unit. The system uses dedicated memory regions or cache areas for storing frequently accessed access authority definitions, ensuring that the most critical definitions are stored in the fastest-accessible memory locations.
Data Source
AI summary
The present invention provides a vehicle control device capable of realizing access authority definitions by the number equal to or greater than the number of access control registers provided in a memory protection device. In the vehicle control device according to the present invention, the whole or a part of a storage device that stores the access authority definitions used by the memory protection device to control the access authorities, is allocated fixedly to a memory area in advance and the rest is allocated dynamically.