Cut and paste from my AOM Hope it helps
CDI
When the FMS is selected as the navigation source on the PFD, the scale of the CDI
will be based on the displayed active RNP value. The two-dot full scale deflection
will always be equal to the RNP value displayed on the PFD.
Excessive Lateral Deviation
The FMS does not provide an indication to the crew of an excessive lateral (cross
track) deviation. Lateral deviation is not considered in the display of the RNP
integrity alert. It is the pilot’s responsibility to monitor lateral deviation, and take
appropriate action to ensure that the aircraft follows the flight plan with minimal error.
Integrity Alert
The steering sources required for each RNP type assume worst-case position
determination by the FMS. Regardless of the sensors in use, the RNP integrity alert
will always be provided at any time the current position determination mode of the
FMS does not yield satisfactory accuracy and integrity to satisfy the containment
requirements for the active RNP type.