# SERCOS drive with position control in the CNC controller

## Position control with SERCOS

With SERCOS drives, position control generally takes place in the drive. Alternatively, the drive can operate in “velocity control” mode and position control then takes place in the CNC controller.

The following requirements must be met for position control in the CNC controller:

- The “velocity control” mode is enabled in the SERCOS drive.
- The set velocity is transferred to the drive (the telegram contains S-0-0036).
- The actual drive positions are transferred to the controller (the telegram contains S-0-0051, S-0-0053 or S-0-0386).
- CNC position control (CNC_POSITON_CONTROL) is selected for the axis mode (see P-AXIS-00320).

## Limitations of position control in the CNC

If position control takes place in the CNC controller, the following limitations exist compared to the “position control in drive” mode:

- No drive-controlled homing is possible. Instead, CNC-controlled homing is carried out.
- Currently, no zero pulse search is possible with CNC-controlled homing for SERCOS drives. Therefore, specify the axis parameter P-AXIS-00084 (homing_without_zero_pulse) as 1.
- No bus delays are considered to calculate the position lag (cf. P-AXIS-00191) .