modbus tcp/ip write.

[Dide_]

I've got an iologik e2240 Moxa device and I'm using a Modbus protocol via TCP/IP to communicate with it. Using the NI Modbus Library, I have no problem with reading coils and registers but when it comes to writing any data to device, the MB_Ethernet_Master_Query.vi is returning an exception code 6 ( Busy, rejected message).

I got to know what Modbus is yesterday so I am a complete newbie.

Does anybody know why this exception occurs ?

[jyang72211]

06/0x06 Busy, Rejected Message Specialized use in conjunction with programming commands.
The server (of slave) is engaged in processing a long-duration
program command. The client (or master) should retransmit
the message later when the server (or slave) is free.

[Dide_]

I've founded explenation to this excepton code, but I didn't know why writing to registers caused this exception.

Finally after few hours of trying everything I've figured out that although some registers in this device are marked as a read/write, you can only read them (attempt to write them causes exception code "6").

🙂

[jyang72211]

Yeah, I think that what happened to me in the past as well.  That's why I only read/write holding registers.

[Dide_]

This happens also with holding registers on this device I'm using.