IC Bus Access Control Across Functional Safety Domains
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Solution Overview
Problem
In integrated circuits, a hardware unit in a functional safety level domain of low safety level can cause a hardware unit in a functional safety level domain of high safety level to fail due to unauthorized access requests, compromising the normal operation and safety requirements of the high safety level domain.
Innovation Solution
Implement a method and apparatus in the integrated circuit that includes a controller to determine access permissions based on safety levels, controlling the transmission of access requests through a bus using mechanisms like firewall, bandwidth limiting, hang detection, and hang protection to prevent faults from spreading across different safety level domains.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If hardware units in different functional safety level domains are allowed to access each other through a bus, then communication between domains is enabled, but faults from low safety level domains can spread to high safety level domains causing operational failures
Solution Approach 1:
The integrated circuit is divided into multiple functional safety level domains with different safety levels. Each domain is segmented to have independent access control, preventing fault propagation while allowing controlled communication. The bus access mechanism is segmented into permission checking and controlled transmission stages.
Solution Approach 2:
An access permission checking mechanism acts as an intermediary between hardware units in different safety level domains. This intermediary verifies access permissions before allowing bus transmission, blocking potentially harmful access requests from low safety level domains while permitting legitimate communications.
2Reliability
If access permission checking is implemented for all hardware units, then fault propagation is prevented, but system complexity and access control overhead increase
Solution Approach 1:
Different safety level domains are assigned different access permissions based on their specific safety requirements. High safety level domains have restricted access from low safety level domains, while low safety level domains can access high safety level domains only under specific conditions. This local quality differentiation reduces overall system complexity by applying appropriate control only where needed.
Solution Approach 2:
Access permissions are determined and configured in advance before actual bus access operations. The system pre-establishes which hardware units can access which domains under what conditions, so that during operation, only permission verification is needed rather than complex real-time decision-making, reducing operational overhead.
Data Source
AI summary
A method for access through a bus in an integrated circuit includes generating, through a first hardware unit in a first functional safety level domain, a first request for access; determining, based on the first request for access, a first identification of the first hardware unit; reading, from a register, first configuration information corresponding to a second hardware unit in a second functional safety level domain, the first configuration information including a second identification of a target hardware unit, the target hardware unit being in a functional safety level domain of a safety level higher than a safety level of the second functional safety level domain; determining, based on the first identification and the second identification, an access permission the first hardware unit has to the second hardware unit; controlling, based on the access permission, transmission of the first request for access from a bus to the second hardware unit.