Siemens sinumerik 840D sl Function Manual page 244

Detailed description
2.1 Coupled motion
Tracking (DB31, ... DBX1.4)
Activation of tracking for an axis is done via the PLC program by setting the following
NC/PLC interface signals:
DB31, ... DBX2.1 = 0 (control system enable)
DB31, ... DBX1.4 == 1 (tracking mode)
When activating tracking mode for a coupled axis grouping, the specified NC/PLC interface
signals must be set simultaneously for all axes (master and slave axes) of the coupled axis
group.
If tracking mode is activated for the master axis only, a permanent offset results within the
coupling.
Whether and which axis is a leading or a following axis can be seen from the following
NC/PLC interface signals and system variables:
DB31, ... DBX99.0 (leading axis/spindel active)
DB31, ... DBX99.1 (following axis/spindel active)
$AA_COUP_ACT[axis identifier] (see: Status of coupling)
2.1.4 Status of coupling
The coupling status of an axis can be determined using the following system variables:
$AA_COUP_ACT[axis identifier]
Value
0
1, 2, 3
4
8
16
32
Note
Only one coupling mode may be active at any given time.
24
Description
No coupling active
Tangential tracking
Synchronous spindle coupling
Coupled motion active
Master value coupling
Following axis of electronic gearbox
Special functions: Axis Couplings and ESR (M3)
Function Manual, 11/2006, 6FC5397-2BP10-2BA0