Siemens SIMATIC ET 200S Installation And Operating Manual page 65

Warning
Safety-related activation of outputs of standard DO modules is not possible; rather, only
safety-related shutdown is possible. You must therefore take the following effects into
account:
In the worst case you must consider all possible faults of the standard DO modules and the
programs controlling them for which the faults cannot be found directly. For example, the
PM-E F pm DC24V PROFIsafe does not detect external short-circuits as per L+ at the
standard DO module outputs. All faults of the standard DO modules influence the process
via final controlling elements. The process must be made known to the F-CPU via sensors
and a suitable safety program.
The safety program must react in a safety-related and logically suitable fashion to unwanted
or potentially dangerous states in the process via the PM-E F pm DC24V PROFIsafe and
fail-safe output modules.
If you want to avoid the problems described above completely, we recommend that you use
P/M switching fail-safe electronic modules 4 F-DO DC24V/2A PROFIsafe with standard
ET 200S power modules (see
Table "Assignment of Power Modules to Electronic Modules/Motor Starters and Safety
Class"
Property of the safety-related shutdown of standard DO modules by the PM-E F pm DC24V
PROFIsafe:
With this cost-effective solution, when a fault is discovered in the process or on the PM-
E F pm DC24V PROFIsafe, there is a comprehensive and simultaneous shutdown of all
outputs involved.
Property of individual shutdown of F-modules with fail-safe outputs:
If a fault is discovered, the extent of the shutdown is kept to a minimum. It is also possible to
react to critical process states staggered over time or to perform safety-related shutdown of
individual outputs. This solution is expensive compared with the safety-related shutdown by
the PM-E F pm DC24V PROFIsafe.
ET 200S Distributed I/O System - Fail-Safe Modules
Hardware Installation and Operating Manual, 07/2005, A5E00103686-04
) instead of standard DO modules.
7.2 PM-E F pm DC24V PROFIsafe Power Module
"4 F-DO DC24V/2A PROFIsafe Digital Electronic Module "
Fail-Safe Modules
and
7-5