Siemens SINUMERIK 840D Function Manual page 293

If the machine operator releases the direction key, the machine axis is decelerated to zero
speed. Reference point approach is not aborted. Reference point approach is continued the
next time the direction key is pressed.
Referencing status
The referencing status of the machine axis is reset with the start of the reference point
approach:
DB31, ... DBX60.4 (referenced/synchronized 1)
DB31, ... DBX60.5 (referenced/synchronized 2)
DB21, ... DBX36.2 (all axes with obligatory reference point are referenced)
Distance-coded measuring systems
In distance-coded measuring systems, reference point approach can be started with any
traversing key.
Sequence
The machine operator or machine manufacturer (via the PLC user program) is responsible for
ensuring that the machine axes are referenced in the proper order.
● Machine operator
The machine axes must be started by the machine operator in the specified order.
● Machine manufacturer
The PLC user program of the machine manufacturer allows machine axes to be started only
in the proper order.
Simultaneous reference point approach of several machine axes
Several machine axes can be referenced simultaneously, depending on the control:
Completion of reference point approach
Acknowledgment that reference point approach of a machine axis has been successfully
completed is given by setting the referencing status:
DB31, ... DBX60.4 (referenced/synchronized 1)
DB31, ... DBX60.5 (referenced/synchronized 2)
Cancellation of reference point approach
In axis-specific reference point approach, the machine axis is traversed in the channel that was
assigned as the master channel of the machine axis.
MD30550 $MA_ AXCONF_ASSIGN_MASTER_CHAN
For aborting the reference point approach, either mode group reset or channel reset for the
master channel of the machine axis must be activated:
Axes and spindles
Function Manual, 06/2019, A5E47437747B AA
R1: Referencing
10.2 Axisspecific referencing
293