Siemens SIMATIC S5 Manual page 105

Description of the Individual Operating Modes
Special case 1
If the IP247 detects the precontact before reaching the hardware limit switch, the direction
is reversed at the end of the precontact.
"o"
Limit switch
V I
o
- VI
- V2
- V3
VI: Single step (25Hz)
V2: Start-stop frequency
V3: Reference speed
Fig. 4/8 Reference point approach with reversal at the BERO
4-12
3 0 1 2 3 0 1 2 3
I I I I I I
I
s .
Reference direction
Excitation pattern number
Limit switch s
1) Reference point with synchronization
2) Reference point without synchronization
s