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How to Read and Write query in PLC by HMI (on software base)

NImesh Sharma

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I have trying to design communication interface with LG-New Master K Series 300S plc.
I have also refer Master-K series document.
But i can't found any proper documents for communication.
How to read register from PLC?
How to write register in PLC?
please suggest me any documents or query format for same.
I got query from HMI which is already connected with PLC.
This type of query format not explain in any documents.
please help me.

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  • MVP 2023

This appears to be a manual for an LG touchscreen.  You are correct - there's no details on the protocol. 

But they do mention something on page 22 about the "CPU Direct" connection, which tells me a proprietary LG protocol exists.

Tell us about your hardware - do you have an LG Master PLC and you're trying to come up with an HMI for it?  Or are you trying to decipher how it talks?  

I found this sales information on the Master-K:


I'm not sure what we can do to help here.

Joe T.


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hello sir,

Finally we solve our 80% problem by peakHMI software. we connect peakHMI with lg plc for read data but we have one more problem we require 7c as a BCC.

I attach one image file can you send bcc calculation in your terms in programing language(we required BCC in programing language).  please little more help.

Thanks for your support.

NImesh Sharma

PLC Replay.png

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