Siemens SIMATIC ET200SP Function Manual page 38

Circuit diagram example
4.4 TIA Portal configuration
In the 1oo2 evaluation, equivalent both inputs of the safe AS-i slave are occupied, either by
a 2-channel encoder or by two single-channel encoders. The two single-channel sensors then
belong together functionally as a pair, e.g. two position switches of one door monitoring. The
input signals are compared internally for equivalence. A discrepancy analysis is possible in the
1oo2 evaluation equivalent.
To suppress coupled-in interference or brief switching pulses, you can set an input delay for
each AS-i slave.
For fail-safe inputs, the discrepancy monitoring for equivalence is used to infer errors from
the time characteristic of two signals with the same functionality. If different levels for two
associated input signals are detected after the input delay time has expired, the discrepancy
analysis is started. A check is made to determine if the difference has disappeared after
expiration of an assignable time period, the so-called discrepancy time. If not, there is a
discrepancy error. Before reclosing, the signal value 0 must be present at both inputs.
The discrepancy behavior determines the value that is made available to the safety program
in the F-CPU during the discrepancy, i.e. while the discrepancy time is running. This
parameter is permanently set to "Provide 0 value".
Reintegration after discrepancy error: This parameter is permanently set to "Test 0 signal
necessary on both channels". A discrepancy error is not considered to be rectified until an
"OFF" signal is present again at both input channels. Reintegration of the PROFIsafe channel is
then possible.
The sequence monitoring monitors the sequence of the signals of the channel pair when
there is a signal change OFF >>> ON at the inputs of the safe AS-i slave.
If the Startup test parameter is activated, the value transferred to the safety program is kept
at the substitute value "0" until the connected sensor has been correctly actuated at least
once.
You can specify the start address of the process image in the "I/O addresses" tab of the
Properties dialog box of the F-CM AS-i Safety ST. Which actual bit in the safety program is
accessed, for example for a safe input slave, can be found in the "Input address" described
above.
The "I/O addresses" tab also appears in the Properties dialog box of the AS-i slaves. Taking the
example of the AS-i F adapter, a distinction is made between "Digital I/O" and "Safe inputs".
Under "Digital I/O", the data area of the communication is set with the AS-i master. This area
in the user program can be accessed e.g. for diagnostic purposes. Under "Safe inputs", the
same input bit as under the AS-i address in the Properties dialog box of the F-CM AS-i Safety
(see "Input address") is present. As described above, this bit is accessed in the safety program.
Emergency stop and pushbutton and toggle switch are in an enclosure together with the two
necessary AS-i slaves (a safety slave and a standard slave). The two installed slaves are
configured separately in the TIA Portal.
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Safety engineering with AS‑Interface in the SIMATIC ET 200SP, including typical circuit diagram
Function Manual, 08/2020, A5E44991382002A/RS-AB/002