Shared Memory Access Control for Stable Industrial Controllers
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Solution Overview
Problem
Existing data sharing methods between control programs and data processing programs lack access right management, which can affect the operation of control programs when data processing programs transmit or receive data from external systems.
Innovation Solution
A controller with a shared memory and an access right management unit that determines and enforces access rights for the shared memory, ensuring that only authorized access is permitted, thereby preventing interference with control program operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If data processing programs are allowed to access shared memory without access right management, then data processing functionality is improved, but control program operation stability deteriorates
Solution Approach 1:
The shared memory access rights are segmented into different levels (read-only, read-write, execute) that are assigned to different program types. Control programs receive read-only access to ensure stability, while data processing programs can receive appropriate access rights based on their specific needs, thus resolving the contradiction between functionality and stability.
Solution Approach 2:
An access right management unit is introduced as an intermediary between programs and shared memory. This intermediary validates and controls access requests, ensuring that data processing programs can access shared memory when needed while preventing unauthorized or harmful access that would destabilize control program operations.
2Reliability
If access control mechanisms are implemented for shared memory, then control program stability is improved, but system complexity increases
Solution Approach 1:
The access right management unit performs multiple functions: it manages access rights for different program types, validates access requests, and enforces access control policies. By consolidating these functions into a single multi-functional component, the system achieves necessary stability without proportionally increasing complexity.
Solution Approach 2:
Access rights are represented as configurable parameters (read-only, read-write, execute) that can be assigned to different program types. This parameter-based approach allows flexible control over access permissions without requiring complex structural changes to the system architecture.
3Productivity
If multiple programs share the same memory space, then resource utilization is improved, but access conflicts increase
Solution Approach 1:
Access rights are dynamically assigned to programs based on their type and requirements. Control programs consistently receive read-only access rights, while data processing programs can be granted appropriate access rights when needed. This dynamic allocation allows multiple programs to share memory resources efficiently while preventing access conflicts through enforced access control policies.
Data Source
AI summary
In a controller that operates a control program which executes sequence control or the like together with a data processing program which executes a complex arithmetic operation or the like, I/O resource information is shared with a shared memory, and an access right to the I/O resource information by the data processing program is controlled using read-in prohibited information and write-in permitted information.