Siemens SIMATIC S5 Manual page 106

Machine Data, Modes and Traversing Programs
Example D: The drive is positioned to the hardware end limit switch.
Forward
N H
A A
V
for
V
rev
Encoder's zero mark
Figure 5-17. Reference Point Approach in Example D
Start the reference point approach with "Start". The drive then executes the
following movements:
1. The IP 266 accelerates the axis in a reverse direction at the specified
acceleration rate. The drive is thus moved toward the reference point switch.
2. When it has reached reference speed 1, the drive moves at a constant speed.
3. When the edge of the signal from the reference point switch goes from 0 to 1,
the IP 266 decelerates the drive to reference speed 2.
4. An edge change from 1 to 0 in the signal from the reference point switch sets
an internal Enable signal. When this signal is set (the drive is moving at
reference speed 2), the IP 266 waits for the next zero mark pulse from the
encoder. A change in the zero mark signal from 0 to 1 sets the reference point.
The reference point coordinate specified in the machine data is assigned to this
position. At the same time, the IP 266 decelerates the drive to zero speed. The
actual value is acquired and displayed. When the drive is at zero speed, the
actual value is lower (i. e. more negative) than the reference point coordinate.
5-34
B
REF
R
V 2
R: Reference point
IP 266
A
H N
E E
s
V 1
EWA 4NEB 812 6057-02