The ACR9000 has the ability of having absolute feedback via the Synchronous Serial Interface (SSI) protocol.
Initially upon power up, the ACR9000 will query the information from the SSI encoder and will assign that as the motor's "actual position."
The ACR9000 will also allow you to use the AXIS RES command to override the SSI information and set the position to anything that we desire. This may be required if the motor is at "machine zero" yet it 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.
If you want to remove this offset and reset the axis to the SSI feedback device's position, you will have to disable the axis and issue the "ENC RES" command.
Example: The proper method for Axis 0 (a.k.a. "X", which uses ENC0 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 ENC RES command. Failure to do so will inject a potentially large position error and possibly damage equipment.