Siemens SINAMICS S120 Commissioning Manual page 428

Appendix
A.6 Overview of measuring systems / encoders
Transfer the position value twice - only when supported by the encoder
Some manufacturers allow a position value to be transferred twice; this is called "ring shift"
or "fetch doubled". It detects transmission errors, although it extends the time taken to
transfer the position value. At least one fill bit is necessary between reading out the first time
and second time. You can also refer to the encoder data sheet for the number of fill bits. The
following example shows the use of fill bits:
1. Select "Double transfer" and enter a value for the fill bits (p0449).
Figure A-8
Gear ratio / measuring gearbox
Gearboxes or measuring gearboxes are relevant only for some motor types, e.g. for 1FW3
torque motors. The gear ratio is the ratio of encoder revolutions (p0432) to the number of
motor or load revolutions (p0433) and is also termed the transmission ratio.
This information is contained in the motor data sheet.
428
SSI encoder position value
Commissioning with Startdrive
Commissioning Manual, 11/2017, 6SL3097-4AA10-0BP1