Siemens Sinumerik 840D sl Programming Manual page 535

Create master value
As an option, master values can be generated with other self-programmed methods. The
master values generated in this way are written to and read from variables
- $AA_LEAD_SP
- $AA_LEAD_SV
Before you use these variables, the setting data $SA_LEAD_TYPE = 2 must be set.
Status of coupling
You can query the status of the coupling in the NC program with the following system
variable:
$AA_COUP_ACT[[axis]]
0: No coupling active
16: Master value coupling active
Status management for synchronized actions
Switching and coupling events are managed via real-time variables:
$AC_MARKER[i] = n
managed with:
i flag number
n status value
Job planning
Programming Manual, 02/2011, 6FC5398-2BP40-1BA0
9.3 Axial leading value coupling (LEADON, LEADOF)
Master value position
Master value velocity
Axis couplings
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