Siemens SINUMERIK 840D sl Programming Manual page 987

Note
All workpiece counters are set to "0" when the control powers up with default values and can
be read and written independent of their activation.
Note
Channel-specific machine data can be used to control counter activation, counter reset timing
and the counting algorithm.
Note
Workpiece counting with user-defined M command
Machine data can be set so that the count pulses for the various workpiece counters are
triggered using user-defined M commands rather than the end of the program (M2/M30).
NC programming
Programming Manual, 12/2019, 6FC5398-2EP40-0BA0
Work preparation
3.22 Program runtime/part counter
987