Siemens SINUMERIK 840D Function Manual page 749

The spindle brakes from the calculated "braking point" with machine data:
MD35210 $MA_GEAR_STEP_POSCTRL_ACCEL
to the target position.
Spindle speed < Position-control activation speed
At the time identified by the braking start point calculation in phase 3, the spindle brakes to a
standstill with the acceleration configured in position control mode (MD35210
$MA_GEAR_STEP_POSCTRL_ACCEL).
Phase 4a:
When the SPOS command is activated the proximity of the end point is such that the spindle can
no longer be accelerated to the configured position-control activation speed (MD35300
$MA_SPIND_POSCTRL_VELO).
The spindle brakes to a standstill with the acceleration configured in position control mode
(MD35210 $MA_GEAR_STEP_POSCTRL_ACCEL).
Phase 5
Spindle speed > Position-control activation speed
Position control remains active and holds the spindle in the programmed position.
Note
The maximum encoder limit frequency of the spindle position actual-value encoder is
monitored by the control (it may be exceeded); in position control mode, the setpoint speed is
reduced to 90% of the measuring system limit speed.
The following NC/PLC interface signal is set:
DB31, ... DBX83.1 (programmed speed too high)
If "MS limit frequency exceeded" is still pending following a reduction in the setpoint speed, an
alarm is output.
Spindle speed < Position-control activation speed (Phase 5, 5a)
The spindle is stationary and it has reached the position. The position control is active and stops
the spindle in the programmed position.
If the distance between the spindle actual position and the programmed position (spindle
setpoint position) is less than the configured exact stop fine and coarse limits, the following NC/
PLC interface signals are set:
DB31, ... DBX60.7 (Position reached with coarse exact stop)
DB31, ... DBX60.7 (Position reached with fine exact stop)
The exact stop limits are defined with the machine data:
MD36010 $MA_STOP_LIMIT_FINE (exact stop fine)
Axes and spindles
Function Manual, 06/2019, A5E47437747B AA
S1: Spindles
18.2 Operating modes
749