Two-Fiber Ring And Bus System - Siemens SIMATIC S7-400H Manual

Redundancy
block diagram
Figure 8-9
Redundancy
block diagram
Figure 8-10
Response to failure

Two-fiber ring and bus system

Since standard S7 connections are used in this particular instance (the connection
terminates at the CPU of the subsystem, in this instance CPUa1), an error on the
fault-tolerant system – for example, CPUa1 or CPa1 – and an error on system b –
for example, CP b – both result in a complete failure of communication between
the systems involved (refer to Figures 8-9 and 8-10).
There are no differences specific to the bus system's response to failure.
Automation System S7-400H Fault-tolerant Systems
A5E00068197-07
Fault-tolerant system a
CP
CPU
a1
a1
OLM
OLM
Fault-tolerant
system a
CPUa1
CPa1
CPUa2 CPa2
Example of interconnected standard and fault-tolerant systems on a redundant
ring
Fault-tolerant system a
CPU CP
a1 a1
Fault-tolerant
system a
CPUa1
CPa1
CPUa2 CPa2
Example of interconnected standard and fault-tolerant systems on a redundant
bus system
Communication Functions
System b
CPU
CP
b
b
OLM
System bus as opti-
cal two-fiber ring
Connection
OLM/
System b
Bus1
CPb
CPUb
OLM/
Bus2
System b
CP
CPU CP
b2
b1 b1
System b
Connection
Bus 1
CPb1
CPUb1
CPb2
Bus 2
Bus 1
Bus 2
8-17