As-I Bus Configuration With Multiple F-Cm As-I Safety St Modules - Siemens SIMATIC ET 200SP Manual

Configuring

5.3 AS-i bus configuration with multiple F-CM AS-i Safety ST modules

5.3 AS-i bus configuration with multiple F-CM AS-i Safety ST modules
The F-CM AS-i Safety ST module generates an additional physical bus load on the AS-
i cable.
To avoid faults due to too low levels of the communication signals on the AS-i cable, the
entire bus load on the AS-i cable must not exceed a maximum value.
The following rules apply to the determination of the physical bus load on the AS-i cable:
Device type
Slave with A/B address
Slave with standard address
F-CM AS-i Safety ST module
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Maximum value as sum of all devices
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Determine the total bus load by adding the bus load values of the components connected to
the AS-i cable. You do not have to include the standard AS-i master and AS-i power supply
unit system components when calculating the bus load.
To avoid disturbances, the maximum bus load must not exceed the value 35.
The bus load value of the F-CM AS-i Safety ST module remains unchanged if switching
groups are activated in the F-CM AS-i Safety ST module for control of safe outputs. In other
words, the internally generated AS-i addresses do not influence the bus load value.
If you connect additional components, e.g., an MSS 3RK3 modular safety system, to the
AS-i cable, you must take into consideration the bus load values of these components. For
more detailed information, refer to the relevant manual.
When a repeater is used, this yields multiple cable segments for which the bus load can be
determined separately.
The following configuration examples result from the table:
● In a fully expanded AS-Interface network configuration (with 31 slaves with standard
address), you can install 1 F-CM AS-i Safety ST module.
● In an AS-Interface network configuration with 30 slaves with standard address, you can
install 2 F-CM AS-i Safety ST modules.
38
Bus load value
0.5
1.0
2.5
35.0
Fail-safe Module F‑CM AS‑i Safety ST (3RK7136‑6SC00‑0BC1)
Manual, 03/2017, A5E03957059020A/RS-AB/002