Rockwell Automation 999 IMC S Class Compact Motion Controller (Cat. No. 4100-999-122) - Manual (Page 107)

Understanding IMC-S/23x Setups 5-27
Publication 999-122 - January 1997
The Unwind Reference value is entered in position units and can be a
positive or negative number up to 9 digits.
Enter the Unwind Reference Point and press ENTER.
Encoder Loss Detection
Each physical axis of the IMC-S/23x can be configured to detect loss
of the encoder feedback signal. The IMC-S/23x asks:
Toggle to YES and press ENTER to use encoder loss detection for this
axis. If encoder loss detection is enabled, an encoder loss fault occurs
under either of the following conditions:
5. Both of the differential signals for any encoder channel (A+ and A-,
B+ and B-, or Z+ and Z-) are at the same level (both high or both
low). Under normal operation, the differential signals are always at
opposite levels. The most common cause of this situation is a broken
wire between the encoder and the motion controller.
6. Loss of encoder power or encoder common to the motion controller
or the encoder.
If encoder loss detection is not desired for this axis, toggle to NO and
press ENTER to disable encoder loss detection.
Editing the Overtravel
Configuration For physical SERVO axes, after editing the conversion constant, the
IMC-S/23x asks
Toggle to YES and press ENTER to set up the overtravel configuration
for this axis.
Unwind Reference Point
(Position Units) = +0
Use Encoder Loss Detection? NO
Edit Overtravel Configuration? NO