Siemens SIMOTION Function Manual page 119

Figure 4-30
To indicate the reverse motion, the forw_back variable is set to false in an ST zoom-in
command.
Figure 4-31
TO Path Interpolation
Function Manual, 11/2010
Defining the return circular path
Set forw_back to false
Sample Project for the Path Interpolation
4.8 Programming the path interpolation in MCC
119