Siemens Sinumerik 840D sl Programming Manual page 599

Further Information
Position offset in the basic coordinate system
Using the system variable $AA_OFF[axis] motion can be superimposed on every axis in the
channel. It acts as a position offset in the basic coordinate system.
The position offset programmed in this way is overlaid immediately in the axis concerned,
whether the axis is being moved by the program or not.
Limit main run variable output:
It is possible to limit the absolute value to be corrected (main run variable output) to the value
saved in the setting data SD43350 $SA_AA_OFF_LIMIT.
The type of superimposition of the clearance is defined using machine data MD36750
$MA_AA_OFF_MODE:
Value
0
1
Using the system variable $AA_OFF_LIMIT[axis] it can be interrogated, dependent on the
direction, whether the correction value is within the limit range. The system variable can be
interrupted from synchronized actions and when a limit value is reached, can be used to e.g.
stop the axis or set an alarm.
0:
1
-1:
Job planning
Programming Manual, 02/2011, 6FC5398-2BP40-1BA0
Significance
Proportional evaluation
Integrating evaluation
Offset value not in range
Limit of offset value reached in the positive direction
Limit of offset value reached in the negative direction
Motion synchronous actions
10.4 Actions in synchronized actions
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