Siemens SINAMICS S120 Function Manual page 801

If encoder 1 (p0187) is switched over via DDS, then an MDS must also be switched over.
Note
Switching over between several encoders
In order to be able to switch between two or more encoders using the EDS switched
function, you must connect these encoders via various Sensor Modules or DRIVE-CLiQ
ports.
When using the same connection for several encoders, the same EDS and the same
encoder type must be used. In this case a switched on the analog side (e.g. of the SMC) is
recommended. A switched on the DRIVE-CLiQ side is, due to the permissible insertion
cycles and the longer times to establish DRIVE-CLiQ communication, only possible with
some restrictions.
If a motor is operated with motor encoder 1 and then later with motor encoder 2, two different
MDSs must be created with identical motor data.
One drive object can manage up to 16 encoder data sets. The number of encoder data sets
configured is specified in p0140.
When a drive data set is selected, the assigned encoder data sets are also selected.
Note
EDS switchover for safe motion monitoring
An encoder which is used for safety functions must not be switched over when a drive data
set (DDS) is switched over.
The safety functions check the safety-relevant encoder data for changes when data sets are
switched over. If a change is detected, fault F01670 is displayed with a fault value of 10,
which results in a non-acknowledgeable STOP A. The safety-relevant encoder data in the
various data sets must therefore be identical.
Drive functions
Function Manual, (FH1), 04/2014, 6SL3097-4AB00-0BP4
Basic information about the drive system
13.2 Data sets
801