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How to sense the invalid data or bad quality data to IEC 101 or 104 client ( SCADA ) when the CPU ( M340 or M580 ) doesn't communicates with the modbus slave devices

Published date: 20 August 2019


User wants to know if the NOR has lost communication with the devices, this should be communicated to the Master SCADA / Client.

Product Line:

BMXNOR0200 V1.7 IR10


Windows  7 Pro, Unity Pro V13


There is no direct method which will mark the data quality as bad or good before sending the data from BMXNOR0200 ( server ) to the Master SCADA ( Client ). However user must program its PLC in such a way that if there is communication break down between the CPU ( M340 or M580 ) and the modbus slave devices then the data which is fetched by the SCADA for that particular slave should be invalid or should be of bad quality. So to achieve this we need keep certain points in mind. 1. In the webpage of BMXNOR0200 module while configuring the data points make sure to select the option "Value with Quality" under the field " CPU Reg Mapping ". By doing this the data is created with the value and quality attribute. 2. Once the above correct selection is made the data mapping can be exported in *.xsy format. 3. This file can be imported back to unity pro and the two attribute "Value" and "Quality" for each data point ( IOA points ) can be seen in data editor of Unity Pro software. Now this Quality bit is 7th in number from LSB. So in general its the 7th bit of Quality word which is when "0" data is valid and when "1" data is invalid. So programmer can write a logic in the PLC program if the communication fails between the CPU and modbus device, Mark all the quality bit related to that modbus device variables to "1". So when this bits are sensed by SCADA, change the background color of the data field and declare as invalid data or communication break down to that particular modbus slave. The RTU conf and exported variable list from BMXNOR0200 module are attached for reference only and to understand the above concept.

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