Hello,

no problem if only change that struct type, go offline, then to your DB definition and change type from INT to WORD. Recompile, download, make tests.

Modbus RTU in the S7-1X00 handles the data in WORD sizes. The communication is not worried what declaration type is used.. only that there are enough {bits} to record the information. That is why we use non-optimized DB structure.

Do not use "Data_block_1".Data.
Use the "Data_block_1"  as is, to have the system cover the whole DB.

Leave the INT declarations in the DB as it is now.
If you want to have "bits" later on, then best to declare WORD and extract individual bits from the declared WORD.

Does this work for you?
w

OK ! I understand . Tks :D

Hello,

you can also look to this topic:

write bits on MB_Slave

Look, in this conference are so many topics about your problem, you can simply click with mouse also to next page, history

if you want to use bits function in Modbus, you could use addresses that are not physically associated with your system since S7-1200 with bits functions address I and Q, that are just your inputs and outputs of PLC.

Let say

you have a CPU and 1 expansion 16I and 16O

You need to map MODBUS 16 input and 16 coils output starting from address 0

You could configure your CPU I/O physical address starting from I100.0 and Q100.0,

so, this let the Master ModBus address coils and inputs 0-15 without affects your physical system, using function 5-15

So... adjust your addresses physical and Modbus as your convenience.

To prevent unwanted write of ModBus Master to your physical Out, you could use this simple workaround, saving and restoring Q registers sourrounding MB_Slave FB.

https://support.industry.siemens.com/tf/it/en/posts/mb-slave-inibith-write-to-q-05-15-function/157038/?page=0&pageSize=10

Regards,

Luca