Siemens SINUMERIK 840C - Manual (Page 864)

04.96 12 Functional Descriptions
12.11.2 ENDAT absolute encoder (SW 5.2 and higher)
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 absolute offset = - (2 * absmax)
99999999< absolute offset< absmax use NC MD 1808*, bit 1
99999999> absolute offset> absolute offset>absmax absolute offset+(2 *
absmax)
Example:
Assumptions:
Position controller resolution:
0.5 * 10 -4 mm
Spindle pitch: 10 mm
EQN 1325: 4096 revolutions
Maximum traversing range due to position controller resolution ± 2048 * 10 mm = ±20.48 m
1st step: Traversing range of encoder / 2 = 10.24 m > 9.99999999 m
2nd step: Divided again by 2 = 5.2 m < 9.99999999 m
If a value > 10.24 has been ascertained for the absolute offset, 20.48 m must be deducted
from this value.
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SINUMERIK 840C (IA)