The ACR9030/9040 has the ability of having absolute feedback with Ethernet Powerlink (EPL) drives.
After EPLC ON upon initial power up, the ACR9030/9040 will query the EPL drive's absolute encoder position and will assign that as the axis's "EPLD Position" and "Actual Position" parameters.
The ACR90x0 will also allow you to use the AXIS RES command to override the absolute position information and set the position to anything that we desire. This may be required if the motor is at "machine zero" yet reads something other than zero. We can issue the "AXISn RES", where "n" is the axis number, to set this position to the zero position. We can alternately issue "AXISn RES m", where "n" is the axis number, to set this position to the "m" unit position.
If you want to remove this offset and reset the axis to the absolute feedback device's position, you will have to disable the axis and issue the "EPLD RES" command.
Example: The proper method for Axis 0 (a.k.a. "X", which uses EPLD0 as its position feedback device) would be as follows:
DRIVE OFF X
RES X : REM zero out all position counters, this is optional
DRIVE ON X
It is important that you disable the drive before issuing the EPLD RES command. Failure to do so will inject a potentially large position error and possibly damage equipment.