Siemens SIMATIC S5 Manual page 106

Special case 2
If the appropriate limit switch is activated when the approach is started, the drive starts im-
mediately in the reference point direction.
Limit switch
v
o
-
VI
- V2
- v:
VI: Single step (25Hz)
V2: Start-stop frequency
V3: Reference speed
Fig. 4/9 Reference point approach with start at the reversal limit switch
Description of the Individual Operating Modes
3 0 1 2 3 0 1 2 3
I
Reference direction
Excitation pattern number
Limit switch s
1) Reference point with synchronization
2) Reference point without synchronization
s
s
4 - 1 3