Hello,

I recommend study MB_SLAVE in your TIA help or TIA system manual. Basically, DB in Slave station is only for Holding Register area, no Coils. In help it is good described, check addressing of different areas (Coils, Input Registers, Holding Registers). Simply your Master need basically ask in standard way (check f.ex. www.simplymodbus.ca), you don't need think about S7-1200 system, it will answer as you ask. S7-1200 has Coils as are defined on HW profile/cfg - Inputs, Outputs (DI/DO). Hope this is good start to your solution.

Update: maybe next hint about that Holding Register (DB in S7-1200). This area you need set/fill with data represented Holding Register. In case of type REAL f.ex., you need count with 2 registers occupation (if you have WORD f.ex as type in DB). This type I also recommend in case of different data types used in this Holding register DB.

Hello,

yes, first element of DB is 40001 register. Again, your Master need ask via standard way, no other better help. With Coils in DB I think is my fault because in some history I made this kind of <data interface> as trick to mix all expected data inside Holding register DB but pls keep in mind that this isn't standard way, Coils are defined simply as HW signals and need to be asked via standard Modbus FC for Colis - read or write. You simply can't acess to Holding Register because of other data type store. I think so much people like that trick and use that as simplest bypass of other MB functionality but pls remember, Modbus need to be implemented via it's defined standards, doing other not standard tricks is not good and correct way, simply we expect standards in this way and not user defined chnages to standards  

Dhafar

Hi again .. the communication Modbus  between labview (master) and s7 1200  succeded. Now i want to add a Sinamics V20 inverter  as 2nd Modbus slave. 

My question is can i use the S7-1200 as master and slave in the same time?

 Yes, but you need an additional CM and a second network.

Regards,
Kaulquappe

Dhafar

And in the program block, can i make all the networks (CONT language) in the same main OB ?

 yes