QJ71C24N CH2 Echo back for MODBUS RTU Predefined Protocol

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I have some problem about QJ71C24N with Modbus RTU Predefined Protocol.

I have setting predefined protocol for QJ71C24N and use 485 wiring to modbus slave but when I start communication it returns CRC error

then I use Circuit trace to check communication that result as in attachment that there are some echo back from send command mix with response command from slave device

I think with these response cause crc error because there are some echo back in response data

I have setting echo back to prohibit but result are same.

How can I solve this problem?





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I have some more information that My PLC product information is not support disable echo back function as in picture below

If anybody have CPU please test about it to find that it is about PLC product information version.

Thank you



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I have solve it by I write echo back (1C2H) parameter to 1 for prohibit echo back on port RS-485

After disable echo back data communication is good as shown below.




Edited by Wasan

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