Modbus Over TCP/IP, DATA_EXCH Not Working for Code 05h (Write To Coil)

[ANF-Energy]

I am still new to M580 and getting Modbus over TCP/IP working. I got read register (code 03h) to work but cannot get write to coil (code 05h) using function block DATA_EXCH to work. Here are my code samples along with the M580 manual references I am using and the protection relay I am writing to a 1 bit register ("coil"), if someone can pinpoint the error:

[HAIBO]

You may try this demo DFB to send FC5 

[MatthewM]

Please check your data types and data packing.  I think your issue is that you need to re-pack the data correctly.  The Tx_Data array is INT, but the manual shows the structure as BYTE, WORD, BYTE.  You might be better off working in a raw data BYTE array to build up the query, and then use BYTE_AS_WORD and WORD_TO_INT to push into the Tx_Data array for EMIS.

PS - do you need to use the DATA_EXCH?  I think you would only use this if you expect a response form the device following the command.  The standard Modbus WRITE_VAR can also write to coils, and READ_VAR can read all Modbus types.