Siemens Sinumerik 840D sl Function Manual page 221

05.07
[RECEIVE]
...
Conv1=TXT MPF
Conv2=NCA SPF
Example:
DRILL_4711.TXT  DRILL_4711.MPF
MILL_4711.TXT  MILL_4711.MPF
DRILL_4811.NCA  DRILL_4811.SPF
MILL_4820.NCA  MILL_4820.SPF
If the files do not have any file extensions prior to the upload, they can only receive
one file extension in DNC, because it cannot be determined which file extension
was appended prior to the download.
Extract from machine configuration file:
[RECEIVE]
...
Conv1=- SPF
Example:
DRILL_4711  DRILL_4711.SPF
MILL_4711  MILL_4711.SPF
DRILL_4811  DRILL_4811.SPF
MILL_4820  MILL_4820.SPF
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Motion Control Information System DNC (FBDN) - 04/10 Edition
DNC Plant/DNC Cell (FBDN1)
10 Configuration
FBDN1/10-213