Siemens SINUMERIK 840D Function Manual page 335

Release: NC START for "MDI" and "Overstore" modes
The enable of NC START for execution of part programs or part program blocks in the "MDI"
and "Overstore" modes with the state "Position restored" is performed via:
MD34110 $MA_REFP_CYCLE_NR ≠ -1 (axis sequence for channel-specific referencing)
MD20700 $MC_REFP_NC_START_LOCK = 2 (NC START lock without reference point)
NC/PLC interface signals
The restored actual position is not considered to be equivalent to an actual position after
reference point approach. Therefore, the state "Position restored" and not "Referenced/
synchronized" is displayed for the measuring system of the machine axis.
Actual position restored:
● DB31, ... DBX60.4/.5 = 0 (referenced/synchronized 1/2)
● DB31, ... DBX71.4/.5 = 1 (position restored, encoder 1/2)
Measuring system referenced:
● DB31, ... DBX60.4/.5 = 0 → 1 (referenced/synchronized 1/2)
● DB31, ... DBX71.4/.5 = 1 → 0 (position restored, encoder 1/2)
Note
The monitoring of the traversing range limits (software limit switches, working area
limitation, etc.) is already active in the "Position restored" state.
Boundary conditions
Spindles
If the encoder limit frequency is exceeded, a spindle is reset to the "Not referenced/
synchronized" state:
● DB31, ... DBX60.4/.5 = 1 → 0 (referenced/synchronized 1/2)
● DB31, ... DBX71.4/.5 = 1 → 0 (position restored, encoder 1/2)
Further information
Referencing with incremental measurement systems (Page 296)
Axes and spindles
Function Manual, 06/2019, A5E47437747B AA
10.10 Automatic restoration of the machine reference
R1: Referencing
335