That you have to ask Siemens .....

Start a support request.

Take a look at this Topic, last post from user tb4450 at 9/8/2017 11:41 PM:

How achieve reading/writing logo8 variables/inputs/outputs and show on PC software using Modbus TCP Connection?

He wrote at the same problem.

frantam

Hello

port is Ok

adressing coil register in modbus protocol is fail

I don't wrote in my last post nothing from port. I wrote that a look of this post in the linked topic.

tb4450

i can confirm. accessing the logo8 as server over port 502 did not work. only port 510 worked.

even though port 502 is set here (see attachment).

and yes. also register numbers seem to be set off by 1.

e.g. logo8 register number 529 (AM1) should be written using register 528. otherwise you are going to write to AM2.

i am new to plc. is this a common issue?