Siemens SINUMERIK 840D sl Programming Manual page 164

Geometry settings
8.1 Settable work offset (G54 to G57, G505 to G599, G53, G500, SUPA, G153)
Note
With the four available zero offsets, it is possible (e.g. for multiple machining) to
simultaneously describe four workpiece clampings and call them in the program.
Further settable zero offsets: G505 to G599
The command numbers G505 to G599 are available for further settable zero offsets.
Therefore, a total of 100 settable zero offsets can be created in the zero point memory via
machine data including the four preset zero offsets G54 to G57.
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Programming Manual, 09/2011, 6FC5398-1BP40-2BA0
Fundamentals