I need communicate by modbus 1 PLC s7-400 with any instruments in a red modbus. i going to have 72 node with different instruments.

 

Hello;

To implement Modbus RTU master functions on a S7-400 (assuming you want 2 distinct RS-485 networks to connect your 72 modbus slaves):
- a CP441-2 (6ES7 441-2AA0-0AA0)
- 2 x RS-485 sub-modules (6ES7 903-1AA00-0AA0)
- a Modbus master (6ES7 870-1AA00-0XA0)

Look at the following manual for more details and programming xamples:

http://support.automation.siemens.c...tion=cssearch&searchinprim=0&nodeid0=10805420

Hope this helps,
Daniel Chartier

 

There's a CP441-2 for a S7-400. It can work as Modbus RTU master. However you will need an additional config package and drivers for a Modbus master functionality as well as a dongle.

Regards,

Jacek Dobrowolski

 

Hi,

I have no idea about Modbus, but according to Siemens manual for Modbus master it might be slight problem to connect 72 slaves with CP441-2. They say that possible config is 2 x 32 slaves per CP441-2.

Regards,

Jacek Dobrowolski

 

I remember there used to be some problem with redundancy in the serial modbus communication with S7-400. It was not native build-in to the system. You had to do some programming jugglery.

Has this problem been addressed by Siemens and fixed? Would appreciate feedback.

 

Did you have a look at ProSoft Technology?
http://www.prosoft-technology.com
Go to Prolinx, Gateways

regards