Siemens SIMATIC FM 353 Manual page 265

Synchronization
Creating the position reference between the internal FM position value and me-
chanical position of the axis.
Measured value synchronization
Irrespective of the approach direction, the synchronization point can be located on
the side of the lower or the higher actual position values in relation to the reference
point switch position. It is demarcated by the rising edge of a zero pulse or by the
reference point switch. This selection is made by the MD18 (together with the ap-
proach direction).
Example
Current-sourcing pattern
zero or zero pulse external
Measurement grid
With reference to the synchronization point, the reference point can be located on
the side of the lower or the higher position actual values. In the "reference point
approach" operating mode the machine axis additionally traverses this distance,
during its last phase of motion, once the synchronization point has been found.
Consequently, the axis halts the motion, in each instance, exactly on the reference
point.
Example
Variant 1
Variant 2
Measurement grid
RV − Reference point offset
FM 353 Stepper Drive Positioning Module
6ES7 353-1AH01-8BG0
RPS
Cyclical zero mark
RV +
RV −
Cyclical zero mark
Description of Functions
Axis direction +
Synchronization point
Axis direction +
Axis direction +
Synchronization point
Reference point
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