PLC Message Processing Unit with Dual Filters
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Solution Overview
Problem
Conventional PLC systems are inefficient in processing messages due to the need for slaves to receive and analyze all messages from the master, leading to increased processing time and load as the number of slaves increases.
Innovation Solution
A message processing unit in the PLC system is introduced, comprising a first filter to identify broadcast messages and a second filter to determine if a message is destined for a specific slave, allowing only relevant messages to be processed by the processor, thereby reducing unnecessary message processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If slave modules receive and analyze all messages from the master module, then all messages are processed uniformly, but processing time and load increase as the number of slaves increases
Solution Approach 1:
The filter unit performs preliminary filtering of messages before they reach the processor. By pre-identifying broadcast messages and discarding irrelevant unicast messages, the system reduces the processing load on the processor without compromising the completeness of necessary message processing.
Solution Approach 2:
The message processing function is segmented into two distinct components: a filter unit for preliminary message screening and a processor for detailed message handling. This segmentation allows the filter to handle routine filtering tasks while the processor focuses on meaningful message processing, thereby reducing overall processing time.
2Reliability
If slave modules receive all messages from the master module, then no messages are lost, but the processing load increases with the number of slaves
Solution Approach 1:
The filter unit extracts and identifies broadcast messages from the message stream using a predefined filter value. By separating broadcast message handling from regular unicast message processing, the system ensures reliable delivery of broadcast messages while reducing the processing burden on slave modules for irrelevant messages.
3Device complexity
If a single filter is used to process all message types, then the filter structure is simple, but the filter cannot efficiently distinguish between broadcast and unicast messages
Solution Approach 1:
The filter unit is configured with specific local properties (filter value settings) that enable it to selectively identify broadcast messages based on their unique characteristics. This localized configuration allows the filter to efficiently distinguish between message types without requiring a complex multi-stage filtering structure.
Data Source
AI summary
Disclosed is a message processing unit provided in a PLC system including a master and a plurality of slaves. The message processing unit is provided to each of the slaves and includes a first filter configured to receive a message transmitted from the master and to determine whether the message is a broadcast message, a second filter configured to receive the message delivered from the first filter and to determine whether the message is a message-to-be-processed, and a processor configured to process the message he delivered from the first filter or the second filter.