From GpsWiki
Non-Volatile Memory (NVM) Reset
The PN-40 contains a small amount of non-volatile memory. The contents of NVM are saved even when the batteries are removed. NVM contains the almanac data which the unit uses to determine which satellites to use when trying to acquire a fix.
It should never be necessary to reset (erase) NVM. However, some users have reported that doing so after the update to the 2.5b3 firmware yields better WAAS behavior.
Erasing NVM removes almanac, ephemeris, and other satellite data. It does not affect the firmware, maps, or user data such as waypoints, tracks and routes.
Erasing NVM requires you to put the unit in Support Mode. WARNING: Using support mode without DeLorme Technical Support assistance may cause serious problems. Use Support Mode at your own risk.
To reset NVM:
- Turn the PN-40 off.
- While holding down Page and Menu, turn it back on.
- Once you see the dark blue warning screen, release the Power button first, then the Page and Menu buttons.
- Press Enter to acknowledge the warning and proceed to Support Mode.
- Scroll to System and press Enter.
- Scroll to NVM reset and press Enter.
- In response to the "Are you sure?" prompt, scroll to Yes and press Enter.
- Press Quit as many times as necessary to return to the first page.
- Scroll to Reboot and press Enter.
- Place the unit in full view of the sky in order to allow it to acquire a fix and download the almanac.
Because the unit has lost all almanac data, it will require a full sky search in order to acquire a fix. This may take some time. After you acquire a fix, plan on leaving the unit in full view of the sky for 20 minutes or so. This will allow the unit to acquire the full almanac (which requires at least 12.5 minutes).
