Cause : Memory Unit Detached comes when the memory unit was detached when the control unit was powered. Switch off the power to the control unit and reinstall the memory unit.

1. In case the memory unit was not actually removed when the fault occurred, check that the memory unit is properly inserted into its connector and its mounting screw is tight.
2. Reboot the control unit (using parameter 196.08 Control board boot) or by cycling power.