Siemens SINUMERIK 840C Installation Instructions Manual page 864

04.96
It must be taken into account that all absolute values have the format± 99.999.999 input units:
In order to be able to enter a larger absolute offset, bit 1 must be set in NC MD 1808*. When
this bit is set, the absolute value of 99.999.999 must be deducted from the ascertained
absolute offset.
:
Example
Absolute offset = -100000010
Set NC MD 1808*, bit 1
Enter -11 in MD 396*
Calculating a correction value:
The smallest traversing range (absmax) of the encoder that is greater than 99999999 must be
calculated. This is done by continuous division of the maximum traversing range of the
encoder by 2.
Absolute offset> absmax
99999999< absolute offset<
99999999> absolute offset>
Example:
Assumptions:
Position controller resolution:
Spindle pitch:
EQN 1325:
Maximum traversing range due to position controller resolution ± 2048 * 10 mm = ±20.48 m
1st step: Traversing range of encoder / 2 =
2nd step: Divided again by 2
If a value > 10.24 has been ascertained for the absolute offset, 20.48 m must be deducted
from this value.
© Siemens AG 1992 All Rights Reserved
SINUMERIK 840C (IA)
12.11.2 ENDAT absolute encoder (SW 5.2 and higher)
absolute offset = - (2 * absmax)
absmax use NC MD 1808*, bit 1
absolute offset>absmax absolute offset+(2 *
absmax)
-4
0.5 * 10 mm
10 mm
4096 revolutions
10.24 m > 9.99999999 m
= 5.2 m < 9.99999999 m
6FC5197- AA50
12 Functional Descriptions
12–89