Remote Terminal PLC Module with Dual Port RAM
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Solution Overview
Problem
Typical software-type PLC functions in remote terminal devices used in industrial plants negatively affect process performance due to insufficient operation speed and memory, requiring costly high-level main modules to compensate.
Innovation Solution
A remote terminal device with an industrial VMEbus structure incorporating a PLC function module that uses dual port RAM and a PLC chip to perform control logic operations without altering the typical hardware data bus structure, ensuring efficient process performance and reducing hardware replacement burdens.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a software type PLC function is applied to a remote terminal device, then PLC control capability is provided, but process performance of the main processor deteriorates
Solution Approach 1:
The patent divides the remote terminal device into separate functional modules: a main module for data acquisition and control, and a dedicated PLC function module for logic processing. This segmentation allows the PLC function to be added without burdening the main processor, thus maintaining process performance while providing PLC control capability.
Solution Approach 2:
The patent introduces a dual port RAM as an intermediary between the main module and the PLC function module. This intermediary enables efficient data exchange through shared memory areas (input variable area and output variable area), allowing the PLC chip to perform logic operations independently while maintaining fast communication with the main module.
2Speed
If operation speed and memory margin are insufficient, then a high level main module is needed, but costs increase
Solution Approach 1:
The patent extracts the PLC logic processing function from the main module and places it in a separate PLC function module with its own dedicated PLC chip and memory. This extraction allows the main module to operate at full speed without the overhead of PLC software execution, while using a standard, cost-effective main module rather than requiring an expensive high-level module.
3Adaptability or versatility
If a PLC function module is added without changing the typical hardware data bus structure, then compatibility is maintained, but system complexity increases
Solution Approach 1:
The patent designs the PLC function module with a dual port RAM that can be accessed by both the main module and the PLC chip using the existing VMEbus data bus protocol. This universal interface approach allows the PLC function module to communicate with the main module through the typical hardware data bus structure without requiring changes to the bus architecture, thereby maintaining compatibility while adding functionality.
Data Source
AI summary
Provided is a remote terminal device having an industrial versa module eurocard bus (VMEbus) structure and including a main module that receives control logic information of a field device from an input/output module, and a programmable logic controller (PLC) function module that receives the control logic information from the main module, performs a logic corresponding to the control logic information, and outputs a result of the performed logic. The PLC function module includes a dual port RAM including a plurality of memory areas, and a PLC chip that reads the control logic information written on one of the plurality of memory areas, performs the logic corresponding to the read control logic information, and outputs the result of the performed logic to another one of the plurality of memory areas.