Configuration Variants For Fail-Safe Systems According To Availability Requirements - Siemens SIMATIC S7 System Manual

2.3 Configuration Variants for Fail-safe Systems According to Availability
2.3
Requirements
Options for Increasing Availability
To increase availability of an automation system and, thus, to prevent process failures due to
faults in the F-system, S7 F Systems fail-safe systems can be configured optionally as fault-
tolerant systems (S7 FH Systems). This increased availability can be achieved by
component redundancy (F-CPU, communication connections, and F-I/O).
For S7 F Systems, availability can be increased without fault-tolerant configuration. Fail-safe
signal modules (F-SMs) can be used redundantly in one ET 200M or in several ET 200Ms.
The following section includes a description of how to achieve increased availability through
redundancy of the F-CPU and F-I/O in S7 FH Systems.
Note
Availability of the fail-safe CPUs in S7 Distributed Safety and S7 F Systems cannot be
increased by using the "SW Redundancy" software package.
Configuration Options in Safety Mode
Fail-safe systems can be configured three different ways, as follows:
Table 2-1
Distributed
Systems
Systems
Typical configuration examples are presented below. A different level of availability of
process data is achieved for each configuration variant.
Additional Information about Increased Availability
Communication between F-CPUs in S7 FH Systems is described in the
CPU Communication
systems, refer to the
Safety Engineering in SIMATIC S7
System Manual, 04/2006, A5E00109529-05

2.3 Configuration Variants for Fail-safe Systems According to Availability Requirements

Configuration Options for Fail-safe Systems According to Availability
System Configuration
Option
Single-channel
S7 •
I/O
Safety
S7 F
S7 FH Single-channel
•
switched I/O
Redundant
•
switched I/O
section of this manual. For information about S7-400H fault-tolerant
Automation System S7-400H Fault-Tolerant Systems
Configurations and Help with Selection
Description
Single-channel and fail-safe (F-CPU and F-I/O
are not redundant)
Single-channel switched and fail-safe (F-CPU
is redundant, F-I/O is not redundant; in the
event of a fault, the system switches over to
the other F-CPU)
Multichannel and fail-safe (F-CPU, PROFIBUS
DP, and F-I/O are redundant)
Availability
Standard
availability
Increased
availability
Highest
availability
Safety-Related CPU-
manual.
2-9