Siemens SIMATIC S5 Manual page 89

IP 266
Also note that
• the software limit switches
• the reference point and
• the actual value
are recomputed when a zero offset is used. When you enter the data, remember
that all coordinates must be within the permissible range (refer to the following
example).
The zero offset values are available only to the programmable ZOs in traversing
programs (see Section 5.4). If you want to specify another zero offset, you must
use modes 12 and 15.
Example:
Table 5.3 contains absolute position values. The "Before" column shows the
positions that were current prior to a ZO. A relative zero offset of - 400 mm
renders the actual value, the software limit switches and the reference point
more positive by 400. As you can see in Table 5-3, this measure puts the software
end limit switch out of range.
Table 5-3. Coordinate Shift as Consequence of a Zero Offset
Software limit switch (start)
Software limit switch (end)
Reference point
Actual value
EWA 4NEB 812 6057-02
Machine Data, Modes and Traversing Programs
Coordinates in mm
Before
-
16000
32500
0
200
After
-
15600
32900
400
600
5-17