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I/O configuration variants
4.2 Fail-safe operation
All of the components contribute to the functional safety of the system, in order, when a
dangerous event occurs, to put the system into a safe state or to keep it in a safe state.
Safety of fail-safe SIMATIC Safety Integrated systems
For SIMATIC Safety Integrated systems, the evaluation unit consists, for example, of fail-
safe single-channel CPUs and fail-safe dual-channel I/O modules. The fail-safe
communications take place via the safety-related PROFIsafe profile.
Functions of a fail-safe CPU
A fail-safe CPU has the following functions:
● Comprehensive self-tests and self-diagnostics check the fail-safe state of the CPU.
● Simultaneous execution of standard and safety programs on one CPU. When there are
changes to the standard user program, there are no unwanted effects on the safety
program.
Fail-safe I/O modules (F-modules)
F-modules have all of the required hardware and software components for safe processing
in accordance with the required safety class. This includes wire tests for short-circuit and
cross-circuit. You only program the user safety functions.
Safety-related input and output signals form the interface to the process. This enables, for
example, direct connection of single-channel and two-channel I/O signals from devices such
as EMERGENCY STOP buttons or light barriers.
Safety-related communication with PROFIsafe profile
PROFIsafe was the first communication standard according to the IEC 61508 safety
standard that permits both standard and safety-related communication on one bus line. This
not only results in an enormous savings potential with regard to cabling and part variety, but
also the advantage of retrofit ability.
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CPU 410-5H Process Automation/CPU 410 SMART
System Manual, 10/2013, A5E32631667-AA
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