PLC Shared Memory Interface for Asynchronous Access
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Solution Overview
Problem
Current programmable logic controllers (PLCs) lack flexible and asynchronous memory access methods, limiting third-party devices and software to synchronous data transfer, which restricts access to PLC memory and requires physical proximity.
Innovation Solution
An Open Development Kit (ODK) interface is introduced, enabling external applications to access PLC memory through a shared dual-port random access memory area, allowing asynchronous and on-demand access to input and output memories, even from remote locations, using a handle for communication and supporting various data types.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If synchronous data transfer method is used, then data transfer is simple and reliable, but memory access flexibility and asymptotic access capability are limited
Solution Approach 1:
A shared memory interface acts as an intermediary between the PLC and external applications, enabling asynchronous access without requiring complex custom interface development. The shared memory serves as a mediator that allows external applications to read/write PLC memory directly, resolving the contradiction between access flexibility and interface complexity.
Solution Approach 2:
The shared memory interface provides universal access capability that works across multiple applications and platforms. Instead of creating specialized interfaces for each application, the system uses a universal shared memory mechanism that can be accessed by any external application, thereby improving adaptability without proportionally increasing complexity.
2Speed
If synchronous data transfer is used, then data consistency is maintained, but access speed and responsiveness to external requests are reduced
Solution Approach 1:
The system dynamically switches between synchronous and asynchronous access modes. The shared memory interface allows asynchronous operations for improved speed, while maintaining data consistency through proper synchronization mechanisms when needed, thus resolving the contradiction between access speed and data consistency.
3Adaptability or versatility
If physical connection is required for memory access, then system reliability is high, but remote access capability is limited
Solution Approach 1:
The shared memory interface serves as an intermediary that enables remote applications to access PLC memory without requiring direct physical connections. The interface abstracts the physical connection requirements, allowing remote access through standard communication protocols while maintaining system reliability.
4Adaptability or versatility
If third-party applications are restricted from direct memory access, then PLC security is maintained, but application functionality and integration are limited
Solution Approach 1:
The shared memory interface acts as a controlled intermediary that allows third-party applications to access PLC memory in a secure manner. Instead of completely restricting access or allowing unrestricted access, the interface provides controlled access mechanisms that maintain security while enabling application integration.
Data Source
AI summary
A system for providing an application with a plurality of methods for accessing memory of a programmable logic controller includes an application, an interface for establishing communication between the application and a programmable logic controller, and a shared memory area initiated by the application or the programmable logic controller. The shared memory area includes an input memory and an output memory. The application is enabled by the interface to write to the input memory and to read from the output memory.