PLC Data Setting Device for Safe Variable-Length Write
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Solution Overview
Problem
Conventional PLCs face challenges in safely rewriting large-size variable-length data due to limitations in industrial network frame sizes and the absence of fragmentation mechanisms, leading to potential malfunctions during data transmission and processing.
Innovation Solution
A method where a terminal code is written at the head of the data area, and subsequent data is written in segments, ensuring the area is recognized as empty until the final data is written, preventing unintended operations during the transition period.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If data is transmitted in divided frames to exceed maximum frame length, then larger variable size can be handled, but data integrity cannot be guaranteed without session management
Solution Approach 1:
The patent applies preliminary action by writing the terminal code at the head address of the data area before transmitting the divided data. This preliminary placement of the terminal code establishes a safe initial state that prevents PLC malfunction during the data writing process, allowing large variables to be transmitted without compromising data integrity.
2Ease of operation
If divided data is written sequentially with offset, then transmission is simplified, but PLC may malfunction during transition period with improper data
Solution Approach 1:
The patent applies preliminary anti-action by placing the terminal code at the head address before data transmission begins. This counteracts the potential harm of improper data appearing in the PLC memory during the transition period, preventing PLC malfunction while maintaining the simplicity of sequential data writing with offset.
Solution Approach 2:
By preliminarily writing the terminal code to establish a safe initial state, the patent prevents potential PLC malfunction during the data writing process. This preliminary action ensures that even if the PLC reads data during the transition period, it will not cause improper operations.
3Reliability
If terminal code is written at head address first, then data integrity is protected during transmission, but additional transmission frame is required
Solution Approach 1:
The patent applies beforehand cushioning by placing the terminal code at the head address before data transmission. This creates a protective buffer that ensures data integrity during the divided data transmission process. The additional transmission frame is a necessary cost to establish this protective mechanism that prevents PLC malfunction.
Data Source
AI summary
In one aspect of the present invention, data to be written is divided into a plurality of pieces of divided data of a maximum size or less to calculate an offset of each piece of divided data, a frame issuing an instruction to a PLC to write a predetermined terminal code in a head address of a data area is transmitted, a frame issuing an instruction to the PLC to write the divided data at a position of the corresponding offset from the head address of the data area with respect to the divided data except a head divided data is transmitted, and a frame issuing an instruction to the PLC to write the head divided data in the head address of the data area is transmitted.