Siemens SINUMERIK 840D sl Programming Manual page 331

Mirroring is implemented in relation to the currently valid coordinate system set with G54 to
G57, G505 to G599.
NOTICE
No original frame
The MIRROR command resets all frame components of the previously activated
programmable frame.
AMIRROR X... Y... Z...
A mirror image, which is to be added to an existing transformation, is programmed with
AMIRROR. The currently set or last programmed coordinate system is used as the reference.
Deactivate mirroring
For all axes: MIRROR (without axis parameter)
All frame components of the previously programmed frame are reset.
NC programming
Programming Manual, 12/2019, 6FC5398-2EP40-0BA0
2.12 Coordinate transformations (frames)
Fundamentals
331