Siemens SIMATIC ET 200SP Manual page 77

Note
System behavior according to AS-i specification
If you connect a slave with duplicate address to the AS-i cable while the bus is operating, the
added slave is initially excluded from cyclic data communication and its LEDs indicate a
communication error. According to the specification, the AS-i master does not activate an
AS-i slave until its address is recognized as a new address on the bus, e.g., when a power-
up of the bus takes place. If the bus contains an active slave, no further automatic slave
activation occurs on the same address during operation, even if an additional slave with the
same address (duplicate address) is added.
However, manual activation of the the slave can be initiated via the command interface by
writing parameters to the slave address.
For physical reasons, the duplicate address detection function of the CM AS-i Master ST
cannot detect a duplicate address during cyclic data exchange in every configuration.
Therefore, like for any AS-i system, it is essential to ensure when assigning AS-i addresses
that each AS-i slave contains a unique AS-i address on the bus, e.g., by using addressing
device 3RK1904-32AB02.
The duplicate address detection function can assist in identifying inadvertent duplicate
addressing.
The duplicate address detection of the CM AS-i Master ST from firmware V1.1 and higher
has been optimized for an AS-i cable length up to 100 m without branches.
The duplicate address detection function of firmware V1.0 is designed for shorter cable
lengths.
The duplicate address detection function can be used in the specified and additional
configurations, but it cannot be guaranteed that duplicate addresses will be uniquely
detected in every case.
For configurations with an AS-i repeater, the duplicate address detection function does not
work due to the separation of the cable into multiple segments.
Enabling the duplicate address detection function
For the CM AS-i master ST with firmware V1.1 and higher, the duplicate address detection
function is activated in the configuration via HW Config or the GSD setting. After a start or
restart of the CM AS-i Master ST V1.1 and higher, the setting is accepted from HW Config or
the GSD setting.
For the CM AS-i master ST with firmware V1.0 and higher, the duplicate address detection
function is deactivated when the AS-i master is switched on and can be set by writing data
record DS 100, see Section "DS 100 Switch duplicate address detection on/off (Page 171)".
The activation status is saved in volatile memory of the AS-i master. After a startup or restart
of the CM AS-i Master ST V1.0, the duplicate address detection function must be activated
via the user program, if required.
AS-Interface master CM AS-i Master ST (3RK7137-6SA00-0BC1)
Manual, 07/2017, A5E02655262020A/RS-AD/004
Alarms, faults and system events
8.6 Duplicate address detection
77