Siemens SINAMICS S120 Function Manual page 456

Function modules
8.7 Closed-loop position control
In the case of linear axes, the virtual multiturn resolution (p2721) is preset to the multiturn
resolution value of the encoder (p0421), which is extended by six bits, (max. 32
positive/negative overflows).
The setting for p2721 cannot be edited again afterwards.
Example: Multiturn encoder:
For a linear axis, the value for p2721 is set to 262144 for an encoder with p0421 = 4096.
That means, +/- 131072 encoder revolutions or load revolutions can be reproduced in this
way.
If, as a result of extension of the multiturn information, the displayable area of r2723 (32 bits)
is exceeded, the fine resolution (p0419) must be reduced accordingly.
Tolerance window (p2722)
After switching on, the difference between the stored position and the actual position is
determined and, depending on the result, the following is initiated:
Difference within the tolerance window -> the position is reproduced based on the current
actual encoder value.
Difference outside the tolerance window -> an appropriate fault (F07449) is output.
The tolerance window is preset to quarter of the encoder range and can be changed.
Note
The position can only be reproduced if, in the powered-down state, the encoder was moved
through less than half of the range that it can represent. For the standard EQN1325 encoder,
this is 2048 revolutions or half a revolution for singleturn encoders.
Note
The ratio stamped on the gear rating plate is often just a rounded-off value (e.g. 1:7.34). If,
for a rotary axis, it is not permissible to have any long-term drift, then the actual ratio of the
gearbox teeth must be requested from the gearbox manufacturer.
456
Function Manual, (FH1), 04/2014, 6SL3097-4AB00-0BP4
Drive functions