Communications Between Fault-Tolerant Systems And Pcs - Siemens SIMATIC S7-400H Manual

Communications
7.4.3

Communications between Fault-Tolerant Systems and PCs

Availability
When fault-tolerant systems are connected to a PC, the availability of the overall
system concentrates not only on the PCs (OS) and their data management but
also on data acquisition on the programmable logic controllers.
PCs are not fault-tolerant on account of their hardware and software
characteristics. They can be arranged in a redundant manner in a system,
however. The availability of this kind of PC (OS) system and its data management
is ensured by means of suitable software such as WinCC Redundancy.
Communications take place via fault-tolerant connections.
The "S7-REDCONNECT" software package is a requirement for fault-tolerant
communications on a PC. It makes it possible to connect a PC to an optical
network having a CP or to a redundant bus system having two CPs.
Configuring connections
No additional configuration of fault-tolerant communications is required at the PC
end. Connection configuration is taken care of by the STEP 7 project in the form of
an XDB file at the PC end.
You can find out how to use STEP 7 fault-tolerant S7 communications to integrate
a PC in your OS system in the WinCC documentation.
Redundancy
block diagram
Figure 7-6
Failure behavior
Double errors in the fault-tolerant system (i.e. CPUa1 and CPa2) and failure of the
PC will result in total failure of communications between the systems involved
(refer to Figure 7-6).
7-12
Fault-tolerant system a
CP
CPU
a1
a1
OLM OLM
Fault-tolerant system a
CPUa1
CPa1
CPUa2 CPa2
1-out-of-2 redundancy
Example of Redundancy with Fault-Tolerant System and Redundant Bus
System
S7-400H Programmable Controller Fault-Tolerant Systems
PC
CP
WinCC
1
server
OLM
System bus as opti-
cal two-fiber ring
Bus1
CP 1 PC
Bus2
A5E00068197-04