Control Frame Queue Prioritization for Predictable Message Timing
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Solution Overview
Problem
In control devices like PLCs, message communication for data transmission is often delayed due to the high priority of IO refresh cycles, leading to unpredictable arrival times for data destined for transmission paths.
Innovation Solution
Implementing a high priority event queue management system that prioritizes communication frames related to IO refresh, ensuring timely processing and avoiding conflicts with normal event requests by suspending normal event processing until high priority requests are completed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If IO refresh is set with the highest priority to ensure timely data exchange, then processing speed and reliability of control operations are improved, but message communication for other data transmission is delayed and arrival time becomes unpredictable
Solution Approach 1:
The transmission path is segmented into multiple transmission queues (first transmission queue for high priority events, second transmission queue for normal events). This segmentation allows different types of data to be transmitted through different channels, ensuring that control operations maintain high priority while message communication can proceed without being blocked by high-priority traffic.
Solution Approach 2:
A queue management unit acts as an intermediary between event requests and the transmission path. This intermediary manages multiple transmission queues and determines the transmission order based on event priority, thereby mediating between the conflicting requirements of fast control operations and predictable message communication arrival times.
2Adaptability or versatility
If data is transmitted by message communication during periods other than IO refresh, then flexibility in data transmission is improved, but transmission delay occurs due to lower priority status
Solution Approach 1:
The transmission system is divided into multiple queues with different priority levels. High priority events (including IO refresh) use the first transmission queue, while normal message communication uses the second transmission queue. This segmentation ensures that message communication can operate flexibly during non-IO-refresh periods without being blocked by high-priority traffic, while still maintaining predictable transmission timing through queue management.
Solution Approach 2:
The queue management unit dynamically adjusts transmission priorities based on the type of event. When high priority events occur, they are transmitted immediately through the first queue. When only normal events are present, the second queue processes message communication requests, providing flexible adaptation to different transmission needs while maintaining overall system performance.
Data Source
Figure 1
Figure 2(A)~2(C)
Figure 3(A)
AI summary
Provided is a computation device that includes: a communication interface; a first transmission control means for sending, via a transmission path, a first communication frame at every prescribed cycle; a second transmission control means for sending a second communication frame in response to an arbitrary event request; and a priority management means. Upon receiving a request to issue a second event request from a second event issuance means, the priority management means waits for completion of the sending processing for a second communication frame corresponding to a first event request currently being processed by the second transmission control means, and then allows issuance of the second event request to the second event issuance means. The second transmission control means suspends subsequent processing of first event request following the first event request currently being processed until processing of the second event request is complete.