Star-Shaped Serial PLC Switch Module for High-Speed Communication
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Solution Overview
Problem
Existing programmable logic controllers (PLCs) of the building block type face limitations in communication speed due to bit skews, cross talks, and ground bounce in parallel bus methods, and are affected by the number of connected modules, while serial bus methods have signal degradation issues and bucket relay methods are prone to failure if one intermediate module is troubled.
Innovation Solution
A PLC with a switch module providing N-to-N switching between serial communication lines and dedicated serial communication lines connecting the CPU module and device modules, forming a star-shaped serial communication network, which avoids the issues of bit skews and ground bounce and maintains transmission capability regardless of the number of connected modules.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If parallel bus method is used for inter-module communication, then communication speed can be improved, but bit skews, cross talks, and ground bounce occur causing communication failures
Solution Approach 1:
The patent replaces the parallel bus communication method with a serial communication method using switching elements. Instead of transmitting multiple bits simultaneously through parallel lines (which causes bit skew, cross talk, and ground bounce), the system transmits data serially through dedicated communication lines with switching elements that route signals between the CPU module and device modules. This substitution eliminates the electromagnetic interference issues inherent in parallel communication while maintaining high-speed data exchange capability.
2Reliability
If serial bus method is used for inter-module communication, then bit skew and ground bounce are avoided, but signal degradation occurs
Solution Approach 1:
The patent segments the communication system into dedicated communication lines for each device module, with switching elements that can independently route signals. Instead of using a shared serial bus that all modules compete for (causing signal degradation), each module has its own dedicated serial communication path to the CPU module. This segmentation eliminates signal degradation from shared media while maintaining serial communication's immunity to bit skew and ground bounce.
3Device complexity
If bucket relay method is used for inter-module communication, then simple wiring is achieved, but communication fails if one intermediate module is troubled
Solution Approach 1:
The patent introduces switching elements as intermediaries between the CPU module and device modules. Instead of using device modules as relay points in a bucket relay configuration (where failure of one module breaks the entire communication chain), the switching elements act as dedicated intermediaries that can independently route communications. This allows the system to maintain communication reliability even if individual device modules fail, as the switching elements provide isolated communication paths.
4Adaptability or versatility
If number of connected modules is increased, then system capability is improved, but transmission capability is significantly affected in bus-based methods
Solution Approach 1:
The patent segments the communication architecture into independent communication paths from the CPU module to each device module through switching elements. When the number of connected modules is increased, each module maintains its own dedicated serial communication line, avoiding the signal degradation and speed reduction that occurs in bus-based methods where multiple modules share the same communication medium. This segmentation allows the system to scale without compromising transmission capability.
Data Source
AI summary
A PLC of building block type includes a switch module incorporating a switch part having N-to-N switch function between serial communication lines with a plurality of lines and a plurality of device modules individually incorporating device systems with various advanced-function device module characteristics. A CPU system having CPU functions of the PLC may be incorporated in the switch module, the switch module incorporating the CPU system and the plurality of device modules being connected together into a single body in a building block structure through module-connecting mechanisms. Dedicated serial communication lines each with a single line or a plurality of lines connect between the switch module incorporating the CPU system and each of the plurality of device modules such that a star-shaped serial communication network is formed with the switch module incorporating the CPU system as a central node and each of the plurality of device modules as a peripheral node.