I have already successfully connected the Idec PLC (FC6A) to the SMA inverter Sunny Tripower (STP 25TL). I have also connected the Open ModScan and Modbus Poll to the SMA inverter, both work perfectly. But PLC S7-1200 does not work. It occurs with the 8384 error code.

I referenced many ways to fix that error from many topics in this forum, but nothing worked.

Today is the year 2025. Has anybody been successful? Can you help me, pls?

The following post might be of use.
https://support.industry.siemens.com/forum/nl/en/posts/protocol-error-8384-modbus-tcp/203828

This error code indicates that the server returned the exception code 03. An exception code is something that the server will return if it cannot handle the action / data the master has requested or sent.

Here is the official text from the Modbus specification.

ILLEGAL DATA VALUE
A value contained in the query data field is not an allowable value for server. This indicates a fault in the structure of the remainder of a complex request, such as that the implied length is incorrect. It specifically does NOT mean that a data item submitted for storage in a register has a value outside the expectation of the application program, since the MODBUS protocol is unaware of the significance of any particular value of any particular register.

To help us determine what might be causing it, answer these questions. What are you trying to do? Read / writing? What data type? What address? Do you have a specification for the server device?

As mentioned in the linked post, it could be that you are trying to write floating point values and your number of registers is not a multiple of 2 or the start address is offset incorrectly. Floating point numbers are contained in 2 16-bit registers (as they are 32-bit data types). You must write each register pair to the first address that holds the floating point value. You could be trying to write the register pair starting at the second address of the floating point value.

It is difficult to say without a bit more information on the server device.

Smiffy.

I am trying to read the serial number on Modbus address 30005. The Modbus address, data type, and data format are shown in the attached file.

hpcvietnam

I am trying to read the serial number on Modbus address 30005.

Based on your logic screendump, you are attempting to read Holding register address 430005.

What you want to read is Input address register 30005 so change MB_DATA_ADDR to a simple 30005 value and you may be in businesses.  

hpcvietnam

Yes, I have already been put 430005 into MB_DATA_ADDR, but nothing worked at all.

 Change 430005 to 30005 please as per my previous post

New question published by U_10dcc3b0-14c1-4ee9-9c4b-ff40edaf6c80 is split to a separate thread with the subject Connecting and reading text 30775 from SMA does not work.

Best regards
Wit_Moderator