Siemens SINAMICS S120 Getting Started page 158

Performing basic parameterization
6.3 Drive axes
Multiturn resolution XIST_2 (p0421)
For multiturn encoders, the number of resolvable revolutions is displayed and set via the
resolution. With the number of revolutions, you also specify the measuring range (for
example, the travel path for a spindle). Typical values are, for example, 9 bits = 512
revolutions or 12 bits = 4096 revolutions.
The value of p0421 acts on p0483 (actual position value) and is required once only when the
encoder position (absolute position) is read at start-up.
Relationship between multiturn resolution and fine resolution
The encoder actual values transferred from the drive to the controller are limited to 32 bits. If,
for example, a standard multiturn encoder with a multiturn resolution of 12 bits (4096) and an
encoder resolution of 11 bits (2048) is used, the encoder actual value is reduced to only 32-
12-11=9 bits (512) for transferring the fine resolution.
If a higher fine resolution needs to be transferred in the encoder actual value, the multiturn
resolution of the encoder actual value must be reduced, which although it increases the
precision of the encoder, it also decreases the absolute measuring range of the encoder.
1. Enter here the fine resolution of the encoder used in bits. The pre-setting is 11 bits and is
sufficient for all Siemens motor encoders.
2. The multiturn resolution is set to 9 bits for all Siemens motor encoders and does not need
to be adjusted.
Should you nevertheless need a higher fine resolution, it is important to note that, in the case
of incremental encoders, the position values of the multiturn resolution still lie within one of
the quadrants (see graphic above). The following graphic shows the interaction between
multiturn information and fine resolution. Increasing the fine resolution moves the value of
the multiturn information to the left.
Figure 6-11
It is important that the multiturn information is still sufficient to record all revolutions which are
important for determining the position at start-up. If all values lie outside the quadrants,
uncontrolled movements of the axis can occur.
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Encoder actual values X_IST1
"Drive axis > Parameters > Basic parameterization > Actual value processing"
Getting Started, 12/2018, 6SL3097-5AG30-0BP0