Map updates are pushed ever two months.  However, to ensure no loss of navigation ability while using the system, there is no automatic map update in DMD2.  You will be notified of map updates by the Map Layer icon on the "Map View" page displaying, in green, the number of available updates as a number.  To trigger the update, you must manually enter the "Map Layer", go to download maps, the respective region and selecting and updating each individual map.
A data connection is required for the map update.
Once you have started a map update, the map being updates is no longer available until the update is complete.