HI Experts,

I have some work with S7-400 Fault tolerant CPU which needs to communicate to an external DCS via redundant modbus TCP-IP. Which module and licenses do I need to implement this perfectly?

Your quick help will be highly appreciated.

From Dubai.

On the other hand, if we say S7-400 with fault tolerant, does it mean that this is a redundant CPU system?

Thank you.

Hello lalabmi;

S7-400H Fault-Tolerant systems are designed as redundant configurations. You can examoine the specifications here:

S7-400H SIMATIC Fault-tolerant systems S7-400H

Siemens proposes libraries for Modbus TCP for S7-400 and S7-300 CPUs under the name "Open Modbus TCP". There are redundant variations of Open Modbus TCP for S7-400H systems, and you have to select between different licenses, for a pair of CP 443-1 or the integrated PN port of the CPUs.

More information here:

How do you establish a Modbus/TCP communication from a SIMATIC S7-300/S7-400 and where can you find further information?

Read more on versions of the redundant Open Modbus TCP licenses: 

What are the differences between Simati Modbus/TCP Redundant V1, V2 and CP Redundant?

Hope this helps,

Daniel Chartier