SIMATIC PCS 7 process control system

Configuration versions for failsafe systems
Failsafe
Single-channel configuration
AS 414F/
AS 417F
Failsafe and fault-tolerant
Configuration with a redundant
CPU and single-channel I/Os
AS 414FH/
AS 417FH
Configuration with a redundant
CPU and redundant I/Os
AS 414FH/
AS 417FH
PROFIBUS DP
ET 200M F modules
ET 200M ET 200M
IM 153
Disconnecting module
Design versions for failsafe systems
PROFIBUS DP
2 x
IM 153
Disconnecting
module
PROFIBUS DP
Disconnecting module,
redundant
F modules
redundant
Failsafe automation systems
The failsafe SIMATIC PCS 7 automation systems are available
in two design versions:
■ As single-channel AS 414F/AS 417F (with only one CPU)
■ As fault-tolerant AS 414FH/AS 417FH (with redundant
CPU)
The failsafe AS 414 F/FH and AS 417 F/FH automation systems
are able to process standard and safety functions on one system.
Mutual influencing is prevented in that the failsafe and
standard program components are strictly separated and that
the data exchange is carried out by special conversion blocks.
In association with the failsafe signal modules of the ET
200M/S distributed I/O system, failsafe automation systems
detect faults in the process as well as their own internal faults,
and automatically set the plant to a safe state when a fault is
detected.
The safety functions configured by the user by means of CFC
(Continuous Function Chart, see section on engineering) or
with the Safety Matrix are processed twice by completely redundant
command processing in different processor sections
of a CPU. Faults detected when subsequently comparing the
results do not lead to a CPU stop since the standard functions
continue to run without being influenced.
S7 F Systems with failsafe block library
The S7 F Systems engineering tool permits parameterization
of the AS CPU and the failsafe signal modules.
It supports configuration by means of functions for:
■ Comparison of failsafe programs
■ Recognition of changes in the failsafe program using the
checksum
■ Separation of standard and failsafe functions.
Access to the failsafe functions can be password-protected.
The failsafe block library integrated in S7 F Systems contains
predefined function blocks for generation of failsafe applications
with the CFC or the Safety Matrix based on it. The certified
failsafe blocks are extremely robust and intercept programming
errors such as division by zero or out-of-range
values. They save the necessity for performing diverse programming
tasks for detecting and reacting to errors.
Engineering of failsafe systems
Process safety 51