Siemens SINUMERIK 840D sl Function Manual page 349

Sequence in case of a fault or abnormal termination
The NST DB31, ... DBX62.4 ("Activate travel to fixed stop") is reset.
Depending on the machine data:
MD37060 $MA_FIXED_STOP_ACKN_MASK
the acknowledgement of the PLC is awaited through resetting of the NST
DB 31, ... DBX3.1 ("Enable travel to fixed stop") is waited for.
The torque limitation is then canceled and a block change executed.
Deselection
The NC recognizes the function deselection via programming of the command FXS[x]=0.
Then an advance stop (STOPRE) is internally released, since it can't be forseen where the
axis will be after deselection.
The torque limitation and monitoring of the fixed stop monitoring window are canceled.
The NST DB31, ... DBX62.4 ("Activate travel to fixed stop") and DB31, ... DBX62.5 ("Fixed
stop reached") are reset.
Depending on the machine data:
MD37060 $MA_FIXED_STOP_ACKN_MASK
the acknowledgement of the PLC is awaited through resetting of the NST
DB 31, ... DBX3.1 ("Enable travel to fixed stop").and/or
DB 31, ... DBX1.1 ("Acknowledge fixed stop reached") is waited for.
The axis will then change to position control. The followup mode of the position setpoints is
ended and a synchronization to the new actual position is carried out.
A programmed traverse motion can then be executed. This motion must lead away from the
fixed stop or else the stop or even the machine may sustain damage.
A block change is executed after the target position has been reached.
Multiple selection
A selection may only be carried out once. If the function is called once more due to faulty
programming (FXS[Axis]=1) the alarm 20092 "Travel to fixed stop still active" is initiated.
Blockrelated synchronized actions
By programming a blockrelated synchronized action, travel to fixed stop can be connected
during an approach motion.
Programming example:
N10 G0 G90 X0 Y0
N20 WHEN $AA_IW[X]>17 DO FXS[X]=1
N30 G1 F200 X100 Y110
Basic logic functions: Travel to fixed stop (F1)
Function Manual, 11/2006, 6FC5397-0BP10-2BA0
2.1 General functionality
; If X reaches a position greater
; 17mm FXS is activated
Detailed Description
13