Siemens SINUMERIK 828D Function Manual page 325

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.
Programming code that scans $AA_FXS[] or a separate flag (here R1) in the condition will ensure that the
function is not activated more than once.
programming example (parts program fragment):
N10 R1=0
N20 IDS=1 WHENEVER ($R1 == 0 AND $AA_IW[AX3]>7) DO R1=1 FXS[AX1]=1
FXST[AX1] = 12
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 Functions
Function Manual, 09/2011, 6FC5397-0BP40-2BA0
; If X reaches a position greater
; 17mm FXS is activated
F1: Travel to fixed stop
6.4 Examples
325