PLC Symbol Table for Legacy Device Name Mapping
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Solution Overview
Problem
In industrial automation environments, programmable logic controllers (PLCs) executing high-level language programs face communication challenges with older peripheral equipment, as these controllers recognize variable names and memory addresses instead of device names, leading to incompatibility and the need for expensive middleware solutions.
Innovation Solution
A method is introduced to generate a symbol table that maps device names to their corresponding physical addresses, allowing PLCs to execute high-level language programs and communicate effectively with peripheral equipment by compiling and linking high-level language programs with an association table, enabling direct access to devices through the symbol table stored in the PLC's memory.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a PLC executes high-level language programs, then programming ease and maintainability are improved, but compatibility with legacy peripheral equipment deteriorates
Solution Approach 1:
The patent introduces a symbol table as an intermediary data structure that maps device names used by legacy peripheral equipment to memory addresses used by high-level language programs. This symbol table acts as a mediator between the two different communication paradigms, allowing PLCs to execute high-level language programs while maintaining compatibility with legacy equipment through the mapping relationships stored in the symbol table.
2Adaptability or versatility
If a PLC uses device names for communication, then compatibility with legacy equipment is maintained, but ability to execute high-level language programs deteriorates
Solution Approach 1:
The patent segments the communication interface into two distinct layers: the device name layer for legacy equipment compatibility and the memory address layer for high-level language program execution. The symbol table creates a clear separation between these two layers, allowing each to operate independently while maintaining their relationships through the mapping structure.
3Adaptability or versatility
If middleware is used to enable communication between high-level language PLCs and legacy equipment, then compatibility is achieved, but system complexity and cost increase
Solution Approach 1:
The patent extracts the compatibility functionality from a separate middleware component and integrates it directly into the PLC's memory structure through the symbol table. By taking out the mapping functionality from an external middleware and embedding it within the PLC's address space, the system eliminates the need for additional software layers while maintaining compatibility with legacy equipment.
Data Source
AI summary
A method of generating a symbol table for a programmable logic controller which executes high-level language program is provided. The method includes reading the high-level language program and an association table specifying relationship between devices controlled by the programmable logic controller and variable names in the high-level language program; compiling and linking the high-level language program and the association table for determining a physical address for each of the variable names and the corresponding devices; generating the symbol table by the compiling and linking, the symbol table defining the determined physical address for each of the devices; and storing the symbol table in the memory of the programmable logic controller. A programmable logic controller executing the high-level language program and storing the symbol table is also provided.