Siemens SINUMERIK 840D Function Manual page 528

M3: Coupled axes
14.5 Generic coupling
Status of the coupling during synchronous operation
State
Not synchronized
"Coarse" synchronous operation
reached
"Fine" synchronous operation
reached
The status of the coupling for the synchronous operation can be read with the following system
variables:
System variable
$AA_SYNC [FAx]
Signal reaction
Synchronous operation signals themselves do not stop the involved axes, but can release them
via synchronized action or NC/PLC interface signals (see Section "R3: Extended stop and
retract (Page 615)").
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Description
Provided the synchronous operation difference is greater than the
threshold value for position "coarse" synchronous operation or
"coarse" speed synchronous operation, the coupled group is des‐
ignated as non-synchronous.
The synchronous operation difference has reached the threshold
value for "coarse" position synchronous operation or "coarse"
speed synchronous operation.
In case the actual value-based synchronous operation difference,
the following NC/PLC-interface signal is set:
DB31, ... DBX98.1 (coarse synchronous operation)
The synchronous operation difference has reached the threshold
value for "fine" position synchronous operation or "fine" speed syn‐
chronous operation.
In case the actual value-based synchronous operation difference,
the following NC/PLC-interface signal is set:
DB31, ... DBX98.0 (fine synchronous operation)
Meaning
State of the coupling
Value State
0 Not synchronized
1 "Coarse" synchronous operation reached
2 "Fine" synchronous operation reached
Axes and spindles
Function Manual, 06/2019, A5E47437747B AA