Product Overview
Fail-Safe Systems
1-8 A5E00085588-03
Compatibility of standard and fail-safe components in a programmable logic
controller
If you use a safety protector in the ET 200M, then you can operate fail-safe signal
modules with the S7-300 standard signal modules in an ET 200M even in safety
mode in SIL 3.
The safety protector protects the fail-safe signal modules from possible overvoltage
in the event of a fault. To do this, the fail-safe signal modules must be inserted in
the ET 200M configuration to the right of the safety protector, and all the standard
signal modules must be inserted to the left of the safety protector.
1.4 Hardware Components
An F System consists of hardware components that fulfill certain safety
requirements, such as:
• A CPU such as the CPU 417-4H with an F-Copy License
• F-I/Os
You can also expand the F System with standard components.
F-Capable CPUs
For S7 F/FH Systems, the CPU (e.g. the CPU 417-4 H as of V2.0) with an F-Copy
License is used either individually or as a fault-tolerant master/standby system.
The F-Copy License permits you to use the CPU as an F-CPU (i.e. to run a fail-
safe user program on it).
An F-capable CPU is a CPU that is approved for use in the S7 F/FH. It only
becomes an F-CPU if there is an F user program running on it. Otherwise, a
standard S7 program runs on the CPU. A combination of standard and F user
programs is possible because the safety-related data of the F user program is
protected from the influence of non-safety-related data. The CPU must be
configured as an F-CPU in this case as well.
Safety-relevant sections of the user program must be password-protected on the
CPU and in the ES/programming device against unauthorized access. In addition,
comprehensive self-tests run on the CPU. These ensure a high rate of fault
detection.
F-I/Os
The following F-I/Os are available:
For ET 200M:
• SM 326; DI 24 x 24 V DC; with Diagnostic Interrupt
• SM 326; DI 8 x NAMUR; with Diagnostic Interrupt
• SM 326; DO 10 x 24 V DC/2A, with Diagnostic Interrupt
• SM 336; AI 6 x 13Bit, with Diagnostic Interrupt
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