Siemens SIMATIC S7-400H - Page 242

Communication
14.5 Communication via S7 connections
S7-400H
242 System Manual, 03/2012, A5E00267695-11
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Figure 14-12 Example of connecting a fault-tolerant system to a single-channel third-party system
using PROFINET IO with system redundancy
Response to failure
Double errors in the fault-tolerant system (i.e. CPUa1 and IM153) and single errors in the
third-party system lead to a total failure of communication between the systems involved
(see previous figure).
The point-to-point CP can also be inserted centrally in "Fault-tolerant system a". However, in
this configuration even the failure of the CPU, for example, will cause a total failure of
communication.