Operating Principle Of The Safe As-I Outputs - Siemens SIMATIC ET 200SP Manual

Configuring
5.2 Safety-related communication with AS-Interface
5.2.2

Operating principle of the safe AS-i outputs

Safety-related communication for safe AS-i outputs also uses code sequences. However,
they have a different data structure compared to the code sequences of safe AS-i input
slaves. The code sequences for safe AS-i outputs do not have to be taught and transferred.
For the function of a safe AS-i output, you need the following components:
● A control unit
● An evaluation unit
Control unit
The control unit outputs safety-related IN or OUT control commands to the AS-i bus. The
control unit is integrated in the F-CM AS-i Safety ST module. The control unit assumes an
active position in the communication. It acts like an AS-i slave and has an AS-i address that
must be called by the AS-i master. The values in the output data of the AS-i master are not
relevant in this case. The F-CM AS-i Safety ST module inserts the safety-related control data
into the communication data.
Besides controlling the OFF state according to specification, a control unit can control up to
four different output switching states: F-OUT 1, F-OUT 2, F-OUT 3, and F-OUT 4. The
F-CM AS-i Safety ST module, however, makes available only the output switching state
F-OUT 1, i.e., The OFF and ON states are controlled.
In addition to the switching states, a control unit can send out two different auxiliary signals:
AUX1 and AUX2. You can use these auxiliary signals for error acknowledgement in the
evaluation unit. For technical reasons, the AUX1 and AUX2 signals are mapped in the safe
process image output. The auxiliary signals are not safety-related signals, however. During
control by the safety program, the F-CM AS-i Safety ST module sends a sequence from
each auxiliary signal one after the other on the AS-i bus. Up to 16 different control units can
be activated in the F-CM AS-i Safety ST module. The control units are managed in the
F-CM AS-i Safety ST module as switching group 0 to switching group 15.
If you want to use more than 16 different control units, you can plug two
F-CM AS-i Safety ST modules into the ET 200SP station.
Observe the information on the bus configuration in Section AS-i bus configuration with
multiple F-CM AS-i Safety ST modules (Page 38).
NOTICE
Uniqueness of the AS-i address on the AS-i bus
Carefully check the AS-i addresses for the control of the safe AS-i outputs. Ensure that the
assigned AS-i address exists only once on the AS-i bus. This is particularly important when
you are using multiple devices that can control safe AS-i outputs on the same AS-i bus. If
this is not observed, reliable shutdown of a safe output module is not guaranteed.
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Fail-safe Module F‑CM AS‑i Safety ST (3RK7136‑6SC00‑0BC1)
Manual, 03/2017, A5E03957059020A/RS-AB/002